ESE's works engine tuner

[FastFred]

We outboarders commonly burn methanol, and we are free to try nitro and such other exotic (liquid only) fuels as we think our engines can be made to survive.

TeeZee would absolutely love to be able to use exotic fuels ... :yes:

[FastFred]

New member here, old Yank outboard racer, mostly 250cc Hydroplane, 45 years ago (and maybe again soon): I've laid out a welcome mat for those of you who got legislated out of GP bike racing, and who might be open to a form of racing that rewards pure 2-stroke horsepower. We outboarders commonly burn methanol, and we are free to try nitro and such other exotic (liquid only) fuels as we think our engines can be made to survive. (If anybody cares to hear a little more about it, go to the New Member section).

Below is a the link to the start of Smittys new member posts, they are well worth a look:-


Raced 250cc alky-burning Konigs and other oddities (Quincy, Anzani, Yamato) on hydroplanes and racing runabouts in the mid-60's thru mid-'70s. Still have some old gear, hope to get back on a racecourse and impede everyone else's progress sometime before I croak. My interest here is in 2-stroke engine tech.

[wobbly]

I searched all over the world for a good priced " real " Devcon,and was amazed that RS product 691-195 was as good a price as I could get.
RS is always silly prices but they have the stock usually,I ordered a couple of tubs and it took a few days to come from usa.
The putty doesnt slump much and can be smoothed over with a wet finger to look real nice without much grinding when set.
If you want to do port roof angles I sit the cylinder on a jig of some sort with the angle you want,warm the cylinder up, fill with Devcon and the temp makes
it slump slowly level at the correct angle.
Put a bit of tape over the bore so you can over fill slightly and then grind the roof angle and corner radius when its gone off.
At 80*C it goes hard in about 1/2 an hour.

[lodgernz]

Thanks for all your helpful replies re Devcon for transfer ports.
I'm sorry that I forgot to mention the the motor is water-cooled and the cylinders I am modifying are cast iron.
Does that make a difference to the choice of compound?

[husaberg]

Wobbly suggested I use Devcon to contour the roofs of transfer ports.
I see there are several Devcon "plastic steel" epoxies. I'd appreciate it if someone would point me at the best product for this application.

This is what I understand they used at Aprilia
http://www.sylmasta.com/acatalog/Creative_Kneadatite_Putties.html

There is also references from other contributors to what they use.

Reference to "Stucco Verde"
on Page 16, 28, and 30 of part 2 of the thread Interview with Mr Thiel and Overmars

[Grumph]

I searched all over the world for a good priced " real " Devcon,and was amazed that RS product 691-195 was as good a price as I could get.
RS is always silly prices but they have the stock usually,I ordered a couple of tubs and it took a few days to come from usa.
The putty doesnt slump much and can be smoothed over with a wet finger to look real nice without much grinding when set.
If you want to do port roof angles I sit the cylinder on a jig of some sort with the angle you want,warm the cylinder up, fill with Devcon and the temp makes
it slump slowly level at the correct angle.
Put a bit of tape over the bore so you can over fill slightly and then grind the roof angle and corner radius when its gone off.
At 80*C it goes hard in about 1/2 an hour.

The Loctite one is more liquid than devcon and can present problems getting it to stay where you want. I find a dam made of plasticene works well. Cast Iron...historically you'd bronze it. The right flux is available. I have used it to repair fins on Vintage stuff.

What surface prep do you do Wob ? As a minimum I bead blast. In 4T inlets I often insert a pin or screw to mould the filler around - but I'm paranoid about it coming loose....

[peewee]

This is what I understand they used at Aprilia
http://www.sylmasta.com/acatalog/Creative_Kneadatite_Putties.html

There is also references from other contributors to what they use.

Reference to "Stucco Verde"
on Page 16, 28, and 30 of part 2 of the thread Interview with Mr Thiel and Overmars

i believe thats the same stuff i posted on the previous page, just under a different label name. can find it all over ebay for dirt cheap

[husaberg]

i believe thats the same stuff i posted on the previous page, just under a different label name. can find it all over ebay for dirt cheap

No idea I just remember it being on pitlane....

[FastFred]

It is well known that having water flowing around the entire exhaust duct is advantageous. However, in situations where the duct has too large a volume is it on balance, better to reduce the volume with a Devcon in-fill and lose some cooling effect, or not?
Trevor

Links to posts where TeeZee talks about screwing and gluing with Belzona epoxy a plate into the exhaust port for an exhaust port dam. You will have to go to the original posts to see the pictures.


The glued and screwed in port floor dam held up OK and the dyno results were better.


Yes, high temp epoxy to seal the plate. I fastened the plate in with screws, the epoxy was mostly for sealing around the sides and under the plate.


Well at least its good to know I am on the right track but I sure would like to know if this is the limit or if I can take it closer to the top of the transfers.


The exhaust port dam is so easy to impliment it certainly would be worth while looking at it again some more in the near future.


And it improved when I put in the exhaust port


Thanks, but screw and glue looks like an easy repetable way of doing it.
The last one was held in place with a couple of screws, and that seemed to work OK.


292539

The good news is, that after 40 liters of fuel and hours on the dyno the exhaust port dam and Belzona epoxy are still there.

[TZ350]

Well that was Mt Welly, my little RG50 ran beautifully, I finished with two third placings in F5.

Nathaniel set a new F5 lap record of 30.249 which would be a very respectable time for F4 A grade.

Fine day, great organisation, friendly people what more could you want.

303907303908303911303912

Speedpros EFI bike was there, I think this is the first ever kit based home brew electronic fuel injected Bucket ever raced, sounded very nice on the track. When Speedpro started it in the pits, he simply pulled the back wheel by hand and it started right up, very impressive.

303923 303924

A couple of the 2T's that run in F4

[TZ350]

303941

I have been mulling over how to arrange air ducting for the Beast MKII to be known as Queen Anns Revenge.

Smitty has made some suggestions to me about using the area between the front number board and mudguard as an air duct. Today I went around the pits and had a look at some of the FXR setups.

303944303943303942

It looks like some of the FXR's have shaped front number boards that direct some of the air stream towards the oil radiator above the engine.

303939303940

The old Beast had a front number board that directed some air down towards the engine and my original GP125 had a duct under the number board that directed the air stream onto the head.

For Beast MKII I will develop the ducting ideas further and have air scoops and ducting on the engine itself too, like Kels number 38.

[chrisc]

Kel's KE125/RS125 air ducting from the 2014 Tokoroa GP. Also one of my favourite pit photos.

Click the photo for larger size

Link to the gallery here (https://www.flickr.com/photos/sonscc/sets/72157642282552865/)

https://farm8.staticflickr.com/7414/13122241145_1992cf2aa0_c.jpg (https://www.flickr.com/photos/sonscc/13122241145/sizes/o/)

Slightly closer photo:

https://farm8.staticflickr.com/7444/13122483384_52ac73aa70_c.jpg (https://www.flickr.com/photos/sonscc/13122483384/sizes/o/)

[F5 Dave]

Because I'm in it? I bet that's it.

[chrisc]

Because I'm in it? I bet that's it.

Close, but it's the matching racing stripe of Kel's hat, his t-shirt and the back of his leathers that make it.

[husaberg]

303941

I have been mulling over how to arrange air ducting for the Beast MKII.

Smitty has made some suggestions to me about using the area between the front number board and mudguard as an air duct. Today I went around the pits and had a look at some of the FXR setups.



It looks like some of the FXR's have shaped front number boards that direct some of the air stream towards the oil radiator above the engine.



The old Beast had a front number board that directed some air down towards the engine and my original GP125 had a duct under the number board that directed the air stream onto the head.

For Beast MKII I will develop the ducting ideas further and have air scoops and ducting on the engine itself too, like Kels number 38.
John Bradleys first book book pg225 on has some interesting stuff on ducting for air cooled bikes.
303993

[TZ350]

Thanks for the tip, looked for the book and found this:-

http://silodrome.com/moto-morini-bialbero/

303995

Great looking racer, and even better looking air duct for directing cooling air to the head.

[husaberg]

Thanks for the tip, looked for the book and found this:-

http://silodrome.com/moto-morini-bialbero/

303994303995303996

Great looking racer, and even better looking air duct for directing cooling air to the head.

And so so nearly stole the title from the Honda four.(Hailwood I think was on the Honda too)

[seattle smitty]

Question (my first of probably many here, until y'all get fed up with them):

Looking at some of the photos here, it appears that some are wrapping their pipes with thermal barrier wrappings, which I'll refer to generically as thermo-tape. Another way to thermally insulate an expansion chamber (with its large heat-radiating surface area) is with a ceramic coating. The best-known one of these in the states is done by a company called Jet-Hot. Jet Hot blasts your pipe with alumnum oxide, then coats the inside and double-coats the outside with their heat-barrier/reflectant. Contrast this with the usual high-temp flat black paint most of us have always used on our pipes, a treatment that probably increases heat loss.

As you all know already, the idea of the ceramic coating or the thermo tape is to retain temperature and acoustic wave energy. I have been googling the subject trying to find somebody who has done any semi-scientific (i.e. with a dyno) testing of these heat barriers. Specifically I'm wondering how much the heat barriers typically change the tune of the pipe. Do you end up cutting and shortening your pipe(s), or build entirely new pipes of a different length/shape/angles/etc. to accommodate the effects of reduced heat transfer? I find people asking each other these questions, but not getting much more than speculation, or seat-of-the-pants impressions from a ride around a kart track. I have seen in various hot-rodding and motor-racing forums that some of you Kiwis are on top of the tech. Does anyone know something more about this than a lot of us dumb Merkins with uninformed opinions?

[wobbly]

There is only two main reasons to be using thermal wrappings on 2T pipes.
The first as was done by Aprilia was to stop the radiated heat from getting at the crankcase/gearbox.
Then the second is to reduce the effect of cool air flowing over the pipe and lowering the wall temp.
This is also done by many race teams by having carbon shields over the exposed parts of the pipe hanging out in the breeze.
Another is mainly due to the second one, but as the pipe heat is retained by the wrapping - the effective tuned length is shortened
due to the increase in wave speed - and this can be used to increase the overev power.
But then this really indicates that the pipe is too long to start with.
Bikes like the RZ/RG500 need to have longer pipes on the rear cylinders, as there is no cooling air over them - unlike the bottom ones that
are cooled by air thru the fairing, but also by the air down the sides.
But as there is never a free lunch, the retained heat due to wrapping will maintain that heat over a much longer period and
this then also looses a heap of bottom end power as well.

An unwrapped or uncoated pipe will drop its wall temp quite rapidly on the overun into corners ( titanium does this even better ) and gives
a natural increase in lower end power when getting back on the gas.
All this is very hard to replicate on the dyno - except to say that I have tested several pipes on the dyno with air flowing over them, and the customer has subsequently had them coated
( usually for the visual effect only ) and then reported that the pipe had lost all its bottom end.
After being given stick for doing it wrong, they grit blasted the ceramic coating off the pipes and they responded exactly as originally designed.

Last issue is be aware that wrapping the header up near the flange is a very bad idea - it overheats the return plug of A/F sitting in the duct - and Mr Deto arrives quickly afterward.

[husaberg]

The Nascar style tape wrap allegedly causes TI pipes to rot extremely quickly when exposed to water.
Nascars used to wrap the pipes to stop heat transfer to ancillary accessories such as alternators etc rather than for any go faster factors.

We have covered the different pipe materials have different properties but this graph sticks in my mind.

[kel]

Close, but it's the matching racing stripe of Kel's hat, his t-shirt and the back of his leathers that make it.

The things that other people notice. Would seem I have a subconscious predilection for blue with white stripes :scratch:

The wrap starts 4 inches down the header pipe and is primarily there to shield heat from the crankcase, gearbox and the gearbox oil cooler :whistle: Did not notice any real change in power delivery on the dyno (bike has lost almost 1 hp but thats down to a lack of maintenance)
The ducting currently only comes as far forward as the triple clamp with sections cut out to allow the forks to turn. Eventually the number board will be molded and extended so there is a continous ducted path to the cyliner and head. Ideally the cylinder would be completely enclosed with the duct extending/exiting into the low pressure area behind, but the head is hard up against the RS frame rails so not possible. See the old NACA papers for design and test data.
Also to note is that the wheel guard has an upwards curve at the back (kick up) so the air is directed to the cylinder rather than being dragged down by the spinning wheel.
Motor was sand blasted and had a copper plate base gasket formed into a cylinder shroud.
Bike hasn't suffered heat stroke since these mods, but then it's only making 27hp.

[RomeuPT]

There is only two main reasons to be using thermal wrappings on 2T pipes.
The first as was done by Aprilia was to stop the radiated heat from getting at the crankcase/gearbox.
Then the second is to reduce the effect of cool air flowing over the pipe and lowering the wall temp.
This is also done by many race teams by having carbon shields over the exposed parts of the pipe hanging out in the breeze.
Another is mainly due to the second one, but as the pipe heat is retained by the wrapping - the effective tuned length is shortened
due to the increase in wave speed - and this can be used to increase the overev power.
But then this really indicates that the pipe is too long to start with.
Bikes like the RZ/RG500 need to have longer pipes on the rear cylinders, as there is no cooling air over them - unlike the bottom ones that
are cooled by air thru the fairing, but also by the air down the sides.
But as there is never a free lunch, the retained heat due to wrapping will maintain that heat over a much longer period and
this then also looses a heap of bottom end power as well.

An unwrapped or uncoated pipe will drop its wall temp quite rapidly on the overun into corners ( titanium does this even better ) and gives
a natural increase in lower end power when getting back on the gas.
All this is very hard to replicate on the dyno - except to say that I have tested several pipes on the dyno with air flowing over them, and the customer has subsequently had them coated
( usually for the visual effect only ) and then reported that the pipe had lost all its bottom end.
After being given stick for doing it wrong, they grit blasted the ceramic coating off the pipes and they responded exactly as originally designed.

Last issue is be aware that wrapping the header up near the flange is a very bad idea - it overheats the return plug of A/F sitting in the duct - and Mr Deto arrives quickly afterward.


Will this mean that doing an alloy or copper exhaust flange with cooling fins may increase some power? Or even most cylinders would benefit from a longer exhaust duct surrounded by water cooling?

Rule of thumb for the lenght of the duct seems a little more than the piston diameter, what can you say about this wob? Thanks :)

[wobbly]

Yes, cooling the flange certainly works a treat.I havnt tried it using fins etc, but have modified engines that allow access to water easily, back behind the flange face.
I have drilled pairs of holes directly from the flange face back into water, and then cut slots in the Ex flange and the cylinder flange face to cool down the spigot.
This has a remarkable affect, and if it was done properly like we see in the Jetski world that have water all around the duct right up to the flange
face, then the positive effect would be even more marked.
No I dont think having a "long " cooled duct is the go - we are simply trying to keep the slug of A/F in the area adjacent to the piston relatively cooled
down, so when its rammed back in at the last moment, we dont have hot gases combining with those above the piston and causing deto.
Coupled with this we are wanting to use as much energy in the expelled gases to be doing work in the pipe, not wasted heating up the radiator water system.

[speedpro]

Given the time the slug of gas is in the exhaust duct before it returns to the cylinder I'm curious just how much it is affected by a hotter or cooler duct/header. It seems there would be very little time available for the cool slug of fresh fuel and air to actually absorb any heat. Back to back tests is the obvious method to determine an actual benefit from cooling. Additional coolant circuits that could reduce the cylinder temp in general seem a more lilkely explanation to me

[TZ350]

I put together a bit of a photomontage of Neil’s many many projects i haven’t put them in order yet. One word describes Neil ...........Prolific

http://www.kiwibiker.co.nz/forums/album.php?albumid=4864

if you can't see the album don't blame me.

Its worth the visit ......

[Frits Overmars]

Also to note is that the wheel guard has an upwards curve at the back (kick up) so the air is directed to the cylinder rather than being dragged down by the spinning wheel.Is that wheel spinning backward? That would be very bad for the tire :confused: .

[kel]

Is that wheel spinning backward? That would be very bad for the tire. Or are you riding backward? That would be very bad for the other riders.

I realise it sounds completely counterintuitive, but you can't argue with the thermal images. Maybe the air flow was sticking to curve of the original wheel guard :scratch:

[Frits Overmars]

I put together a bit of a photomontage of Neil’s many many projects i haven’t put them in order yet.
One word describes Neil ...........Prolific http://www.kiwibiker.co.nz/forums/album.php?albumid=4864.

Its worth the visit ......Amen to that!

[seattle smitty]

Interesting to hear the effects that Wobbly saw with the thermo-wrap, and that seem not to have happened very noticeably in Kel's experience. Wobbly, one of the happy situations for outboard racer is the ease of making pipes and altering pipes. Currently most of the motorcycle-sized (125-1100cc) racing engines are opposed-twins or opposed-fours with the cylinders crosswise to the boat, carbs in front, expansion chambers pointing straight aft, supported with brackets. Not only far simpler to build than bike pipes, but we can incorporate sliding sections into them, typically a section about 4 1/2" long right back of the flange that bolts to the cylinder. Coming off a corner, with engine revs down, we have the pipes slid back to maximum length (they're cockpit-controlled, usually via a foot-pedal or a lever). As the boat gains speed heading down the straightaway and the revs come up, we pull the pipes forward, shortening them. Aren't you envious?!!

What's more, since we have a whole lake-full or river-full of water to put to use, we also have a push-button on the dash to spray some water into the pipes to make them act like they are even longer. Outboards have no transmission, and can always use some help getting the boat on-plane and accelerating up to where the pipes start to come in tune. So during that plane-off period we're injecting the water into the beginning of the diverging cone to slow the waves down and make a low-rpm pipe. Alky-burning outboards gradually started using expansion chambers from the early-'60s (other guys continued with open megaphones and often big percentages of nitro) and by the late-'60s were starting to get into slider-pipes, with the water injection coming into widespread use a little later.

So that's a long way of saying that where the thermo-wraps might cost you the bottom of your powerband, in outboards we are able to cheat our way around that to some extent.

Actually, with quite a few 2-stroke bikes you could build-in some adjustability like ours (and for all I know maybe some of you have tried this long-since). This would be by putting a sliding section in the fat, straight-sided section between the diverging cone and the baffle cone, something that the kart racers were doing by around 1970 or so (don't know if they still do it). The karters had a rule against this being driver-adjustable in the middle of a race, which is just as well (for them or you), but the sliding section meant the pipe was easy to adjust between heats, and you could get a lap-times comparison.

As to the inadvisability of using wrap on the first several inches of the pipe, something the snowmobile racers might have been the first to discover the hard way, I have been exchanging PMs with TZ350, who was trying ways to address an overheating problem (about 980 pages back; geez, I have a lot of reading to do!!). As I said to him, welding just one or two cooling fins on the first several inches of the front of the exhaust header pipe as it comes out of the flange could easily double the surface-area of the header-pipe for heat-shedding purposes, if that helps . . . .

[koba]

Thanks for all your helpful replies re Devcon for transfer ports.
I'm sorry that I forgot to mention the the motor is water-cooled and the cylinders I am modifying are cast iron.
Does that make a difference to the choice of compound?

I have a tub of the Steel Devcon if you want to use some.

[lodgernz]

I have a tub of the Steel Devcon if you want to use some.

Oh thanks Malcolm. I'll talk to you on Sunday at the track.

[wobbly]

Re the cooling of the spigot.
As we already know that wrapping a header will instantly cause deto from overheating the slug, then the heat uptake in that area for sure
has enough time to wreak havoc.
So by inference a cool duct would also have time to cause a positive effect.
But I well know assumptions are errors waiting to be revealed, so hard evidence is needed.
I just happen to have that, as I have been drilling holes and cutting slots into the flange faces of KZ2 castings the results are easily seen and repeatable.
On track the simple mod reduced the egt by around 30*C - a jet size spot on.
So now we run 1 jet leaner over the original dyno baseline weather corrected RAD, and can run all day at 640C with no deto.
Absolutely impossible previously.
The bulk cylinder water temp is the same as before at 45*C exit, but on the dyno it is now possible to touch the flange bolted to the cylinder,after a hard all
gear run up.
Previously it was way too hot to do this.
At the time I didnt recognise that I could have leaned it down on the dyno - and make more power, but on track the data log was immediately conclusive.

I am sceptical about cooling the header with heat radiating plate fins or whatever, as this would be detracting from the pipe heat energy available - BUT, it may be a workable
compromise if the duct cannot be kept cool enough - for whatever reason.

[Yow Ling]

So how far down the header does the mixture extend before being pushed back into the cylinder ?
A bit of an open ended question as different states of tune and different porting will have different outcomes.
Are we looking at 50mm past the flange or something else?

[wobbly]

It varies obviously but back in the days of being able to run leaded racegas, and nowdays in bikes only where Avgas is allowed
we see the white lead burn mark in the header from 50 to 100mm down the length.
So I would surmise that there is sufficient unburned,cool A/F mixture in that part of the header that is absorbing heat to the point
that the wall temp is low enough not to show any burn mark.
The dividing line is always VERY clear, a real start/stop line to the hot/cold areas of the header.

[Frits Overmars]

... one of the happy situations for outboard racer is the ease of making pipes and altering pipes. Currently most of the motorcycle-sized (125-1100cc) racing engines are opposed-twins or opposed-fours with the cylinders crosswise to the boat, carbs in front, expansion chambers pointing straight aft, supported with brackets. Not only far simpler to build than bike pipes, but we can incorporate sliding sections into them, typically a section about 4 1/2" long right back of the flange that bolts to the cylinder. Like so, Smitty :shifty: ?
304110


with quite a few 2-stroke bikes you could build-in some adjustability like ours. This would be by putting a sliding section in the fat, straight-sided section between the diverging cone and the baffle coneThere are several options in lengthening a pipe. You can move the end cone, or you can lengthen the header, like on the trombone pipe in the video below.

The gas pressure generates a force that is proportional to the cross section area of the moving part and proportional to the pressure difference at either side of that area. For a moving end cone this force can be up to 4 times larger than for a sliding header. That is one reason to go for the trombone system rather than the moving cone system.

The second reason: sealing. The circumferential gap that has to be sealed, is three times shorter for the trombone system. That means three times less leakage and three times less friction.

The third reason: say you wish to lengthen the total length of the pipe by 10 %. If you do it by moving the end cone, you will also enlarge the pipe volume by a little over 10 %.
But in a good pipe configuration the header length is about 1/3 of total pipe length, so in the trombone system, lengthening the pipe by 10 % will be done by lengthening the header by about 30 %. That gives a far greater variation in the pipe's Helmholtz frequency than a 10 % volume change.

It is true that the length percentages of all pipe components should be in a rather fixed relation to each other. Varying the lengths of all components by the same percentage would be the theoretical optimum, but that is not feasible.
Lengthening the belly will disturb the optimum relations, as will lengthening the header. So the pipe in its lengthened version will not be the optimum for the low resonance rpm dictated by the length. But it will be a hell of a lot better than using an exhaust power valve that spoils the 180° effective exhaust timing, necessary for true resonance.
And a pipe shortened beyond its optimum may not show the optimum length relations between its components either, but it will be a lot more effective in overrev than artificially raising the exhaust gas temperature by retarding the ignition, or by weakening the mixture strenght through closing a power jet, which has the disadvantage that not all inhaled air is used for combustion.

Trombone pipe: http://www.youtube.com/watch?v=0odVzSgufjk&feature=youtu.be

[husaberg]

Like so, Smitty :shifty: ?
304110

There are several options in lengthening a pipe. You can move the end cone, or you can lengthen the header, like on the trombone pipe in the video below.

The gas pressure generates a force that is proportional to the cross section area of the moving part and proportional to the pressure difference at either side of that area. For a moving end cone this force can be up to 4 times larger than for a sliding header. That is one reason to go for the trombone system rather than the moving cone system.

The second reason: sealing. The circumferential gap that has to be sealed, is three times shorter for the trombone system. That means three times less leakage and three times less friction.

The third reason: say you wish to lengthen the total length of the pipe by 10 %. If you do it by moving the end cone, you will also enlarge the pipe volume by a little over 10 %.
But in a good pipe configuration the header length is about 1/3 of total pipe length, so in the trombone system, lengthening the pipe by 10 % will be done by lengthening the header by about 30 %. That gives a far greater variation in the pipe's Helmholtz frequency than a 10 % volume change.

It is true that the length percentages of all pipe components should be in a rather fixed relation to each other. Varying the lengths of all components by the same percentage would be the theoretical optimum, but that is not feasible.
Lengthening the belly will disturb the optimum relations, as will lengthening the header. So the pipe in its lengthened version will not be the optimum for the low resonance rpm dictated by the length. But it will be a hell of a lot better than using an exhaust power valve that spoils the 180° effective exhaust timing, necessary for true resonance.
And a pipe shortened beyond its optimum may not show the optimum length relations between its components either, but it will be a lot more effective in overrev than artificially raising the exhaust gas temperature by retarding the ignition, or by weakening the mixture strenght through closing a power jet, which has the disadvantage that not all inhaled air is used for combustion.

Trombone pipe: http://www.youtube.com/watch?v=0odVzSgufjk&feature=youtu.be

This graph sticks in my mind.
Can't find it..............
it had three beautiful overlapping curves.
Later.......he does and posts it below

I had to search for this but this was pretty profound, I along with plenty of others had our thinking a little back to front.

You have to stay within certain length percentage limits for all elements of the exhaust system; you cannot make one part a lot longer or shorter in relation to the others without losing power somewhere.
It is best to concentrate on getting all dimensions correct for maximum power. In the high gears you don't ride low revs and in the low gears you'll have enough low-down power left to pull a wheelie or spin out the rear wheel (I'm not talking about buckets though, so you might want to reconsider your case).
If you have a decent setup for angle*areas, pipe, carburation and ignition, the necessary overrev potential will come naturally; no need to sacrifice maximum power in order to make it rev a little higher.



Something to think about while the rest of the family occupy themselves with buying, boiling, painting, hiding, searching, finding and eating easter eggs: a couple of recent videos from the Dutch 50 cc scene.
http://www.youtube.com/watch?v=mvV4xbFKs0g&feature=relmfu
http://youtu.be/0odVzSgufjk


It was designed and built by Richard Maas http://www.adriaanmeeuwsen.nl/team-pagina.html. Hopefully we will see it in action next monday.
And if I were you, I would make it go shorter with rpm :whistle:.



More news from Richard Maas. Did his trombone pipe give the desired results? O yes. At 10,000 rpm it gives 4 HP more than the same engine with a fixed pipe. It runs over 17,000 rpm without the need for a powerjet and with a fixed ignition timing. It is miles better than an engine with an exhaust power valve. And the mapping of pipe length, ignition timing and powerjet pulse width has yet to be carried out. Maybe the powerjet can disappear altogether.
Only problem so far: the piece of pipe that is fixed to the cylinder, is shrouded by the pipe that slides over it, so it gets very hot. Too hot for the Viton O-ring that is taking care of sealing. Any bright ideas, anyone?

[TZ350]

It's pouring rain here in Seattle (aka Swamptown), a good day to sit at the keyboard and try to learn from y'all. So . . .

When I do a search here, as for "torroidal heads," I invariably am directed to several 2-stoke threads with ten thousand posts apiece, and no further suggestions as to which pages have the subject term. So I'll just ask here, and know that I HAVE tried to search first:wacko:

You might find these search tips useful.


Some may find this useful. Rather than use the site search which usually fails, use Google so to search this site use an ordinary search phrase and after it add

site:www.kiwibiker.co.nz (http://www.kiwibiker.co.nz/)

for example

Frits priceless site:www.kiwibiker.co.nz (http://www.kiwibiker.co.nz/)
or
Frits pisa site:www.kiwibiker.co.nz (http://www.kiwibiker.co.nz/)

the same will work for other sites with the appropriate site address

Mick


Here's some help on searching in these forums.

Top right hand corner of the screen, click 'advanced search'
Click the blue box 'search single content type' at the top.
Scroll down and select the forum area to buckets which is right near the bottom of the list.
Scroll down and select the dot next to 'posts' in the criteria called 'show result as'.

304439304438304437

THREAD IMAGES
Another handy tip is under thread tools (near the top of this page) click view thread images. Very! Helpful on the ESE thread


Another way to filter the wheat from the chaff is to click on the user name of the person and either view attachments by user or forum posts.

Page 1020 links list to go here:- :soon:

304286

Hedge trimming, Isle of Man style.

Photos taken of the glory days at the IOM 61-67 http://mikepollitt.weebly.com/1960s-iom-tt-pictures.html

Hondas Golden era:- http://www.hondatwins.net/forums/8-pictures-videos/20301-motorcycle-story-golden-years-19.html

Chris posted some 2T Hydroplane video, you will have to follow the link back to his original post to see them.


304290
Cable operated adjustable header on the hydroplane.
And 2T Hydroplanes In action

Seattle Smitty ... reposted here because I think they make such interesting reading, as they are written by someone who was into all out boat racing with 2T's in the 60's and I don't want them to be lost as they give a glimpse of clever people working away in their sheds pushing the boundaries of what is possible with a no holds barred racing two stroke motor.


Raced 250cc alky-burning Konigs and other oddities (Quincy, Anzani, Yamato) on hydroplanes and racing runabouts in the mid-60's thru mid-'70s. Still have some old gear, hope to get back on a racecourse and impede everyone else's progress sometime before I croak. My interest here is in 2-stroke engine tech.


Since few if any of y'all are boat guys, let me tell you a little about this. Over the decades, outboards have usually been one or two generations behind the current 2-stroke design and practices in motorcycling, esp GP racing in Europe. The outboard racing I'm talking about is jocularly referred to as "PRO," i.e., Professional Outboard Racing as practiced by the APBA (American Power Boat Assn.) or the USTS (United States Title Series), a tiny, amateur, in-crowd hobby-sport. This sort of outboard racing is not to be confused with Formula One tunnel-boats powered by big V-6 factory production racemotors, usually built by Mercury or OMC complete with starters and full cowlings, burning gasoline and often racing for actual money. By contrast, the PRO category of racing that I'm talking about uses motorcycle-sized engines (125, 175, 250, 350, 500, 700, and 1100cc displacement) completely stripped down, with unmuffled pipes and burning real racing fuels, powering hydroplanes and racing runabouts. I should say that some of the best of this sort of racing is done in Europe, up to 500cc, and in fact all of the most up-to-date racemotors we use now are coming out of Europe, mainly Italy.


My tentative understanding, based on very sketchy input, is that nothing resembling our PRO racing is being done in NZ or Oz, though there apparently was some stock outboard racing done many decades ago, and some tunnel-boat racing. That's too bad for those of you who are real far-gone 2-stroke lovers. Like you, the 2-stroke crowd in North America grieves for the loss of 2-stroke GP motorcycle racing (and the bikes didn't even get to burn fancy fuels). There's something of a 2-stroke comeback in motocross, so I hear, yet even with sleds (snowmobiles) the 4-strokes are always preferred by and often favored by the authorities-in-charge. PRO outboard racing is nearly the last arena for the most fanatical 2-stroke tuners and modifiers. The only real limits, within a given displacement, is no bottled fuels or oxidizers (nitrous is out), and no supercharging (other than that done via expansion chambers or intake tract tuning). The advantages of PRO outboard racing for our kind is that first, the 4-strokes are always going to be too heavy and especially too top-heavy to work well, and second, the 4-strokes wouldn't get any kind of traction advantage as they can on a motorcycle roadrace course. A modern racing propeller (generally 3 or 4, sometimes 5-blade) is not only quite efficient, but it HOOKS UP to the water all of the power you can find in the engine.


(Hope this will get a few of you old 2-stroke bike racers excited).


--Smitty



When I started racing Stock Outboards forty-five years ago, the engines for all of those classes (250/322/500/700cc) were Mercury factory racemotors, meaning production engine powerheads on short towerhousings with small, low-drag, direct-drive lower units and light flywheels. No modifications allowed. I believe that these small stock Mercury engines were what got raced Down Under, long ago. Most outboard racers here start out in the stockers, learn to read the water, to make starts against a clock, and to race. The competition is close and the speeds are not insane, and many race drivers (as opposed to tuners, men with shop skills, and 2-stroke tech enthusiasts) prefer to stay with the Stocks. Some of the old crossflow Mercurys of the '50s and early '60s still are enthusiastically raced, no longer in the Stock or PRO categories, but in a semi-modified category, burning gasoline and running open megaphones. Moreover, there have been a runabout and a hydro class for old twin-opposed cast-iron block motors first raced in the 1930s. These Antique C (500cc) classes burn methanol and nitro, are run by themselves at PRO races, and limited to the original open-exhaust configuration of eighty years ago. Old alky racers who keep at it often end up in the Antique C boats because they aren't too fast, make good sounds, and are raced by men who have been pals for life.


Crossflow 2-strokes actually were a pretty good design for small, low revving outboards. I have a 1956 5 1/2hp Johnson that is as smooth a motor for trolling hour after hour for salmon as anything built today.


(EDIT) ellipsis, when you get around to doing something with that Anzani, if you're interested I can impart a ton of obscure and otherwise useless info on that engine.



Thanks all for getting me into the 21st century (well, I guess; so far I think that overall the late-'50s/early-'60s were the best of times, at least in this part of this country).


I've been slowly working through the ten thousand pages of those threads, bliss for 2-stroke lovers. Looks like a couple of posters were near or right at the top of 2-stroke GP racing in its heyday (is "kel" who I think he might be??). Any possibility one of them would lower himself enough to take PM questions from an outboard racer on applying modern tech to our lower-tech engines?


Again, I think fellows like them, or any far-gone 2-stroker who lives to carve on ports and roll cones for pipes would have a blast working on engines with almost no limits to modifications or fuel. Actually, two such men, both Italians, have got into outboards, and are manufacturing the first up-to-date racemotors our little sport has seen in a long time. Giuseppe Rossi, a many-times European champion outboard racer, builds the GRM 125/175/250/350/500cc engines which are winning most of the races in those classes here and in Europe. Carlo Verona, who I understand has done contract work for some of the motorcycle factory teams, makes the VRP engines that are fully competitive with the GRMs. A slightly sad consequence of the competition between these two well-informed men is that their engines are so good out-of-the-box that ordinary outboard racers know they aren't knowledgeable enough to improve on them, which used to be half the fun of PRO outboard racing. However, there are still possibilities for getting an edge . . . heh, heh, heh.



Very slowly plodding through it due to time constraints.


Need another term, what is a "spigot"? Is that the intake tract from the carb, or is it the venturi in the carb, or what?


I'm not far into the thing, still reading 5 year old posts, but wondering how "TZ350" made out with his experiments on cylinder cooling. I've always thought that the front wheel of any motorcycle is a terrible obstruction to engine cooling, and that big ugly air ducts would be the solution (for air-cooled barrels anyway). I Also think you can help the situation a bit by welding some cooling fins to the first several inches of the exhaust header-pipe, right after the monting flange. As we all know, the megaphone section of the expansion chamber draws some fresh air/fuel charge some distance into it, and this is then crammed back into the cylinder at exhaust-closing by the positive return wave from the baffle cone (in Seattle, in the first days of expansion chambers, we boatracers called them "bounce-pipes.). This column of air/fuel picks up heat while it is in the exhaust tract; I'm guessing it would pick up less of this heat if the header-pipe had cooling fins.


I did this, welded some cooling fins to the header pipes, on my '76 Yamah RD400C when I made a new exhaust system. But I did no before-and-after testing of that feature in isolation. I don't race it, and ride it like an old lady (I'm old, I never raced bikes, only boats, and I don't mind a splash but don't want to crash), so can't tell you anything about the practical effect of the fins, sorry.


Actually, there is some evidence seemingly supporting my idea, from the sled (snowmobile) racers (who have some interesting 2-stroke tech, if you want to check that out). When the pipes on a sled get hit by a big load of snow, they cool off, the wave-speed slows, and they go out-of-tune until the snow melts off. Same thing can happen with racing outboards. The sled guys sought to prevent this by wrapping their pipes with thermal-insulating wraps. They soon found that it was best to leave the first several inches of the header-pipe uncovered, no thermo-tape, because of what I'm talking about, an over-heated slug of air-fuel getting shoved back into the cylinder.



Since I came into this in the middle of things, I don't know what kind of thing you are racing (roadracing? motocross?). Are you restricted as to octane?


I still think you should try any/all of the other things before putting water in your fuel. This is sort of basic, so don't be offended if you've done this long ago, but have you got the squish-height down to near the minimum recommended by the experts on your particular engine? That's very important. If you still get detonation with minimum squish (and have ruled out too much ignition advance), don't ever try to reduce compression by means of shimming up the head with a thicker gasket or whatever. Once you get a squish-height that's tight but never lets the piston actually touch the head, leave it alone, and if you have to reduce compression, do it by taking material out of the combustion chamber pocket. A little drop in compression won't hurt performance noticeably, but increasing the squish-height will tend to worsen detonation, even if it reduces compression at the same time. I learned about squish from a couple of smart engineers who raced outboards in the Sixties; this was at least fifteen years before the motor-racing magazines first began talking about it; today it's almost a buzz-word.


Is there some anomalous glitch in your ignition that makes it over-advance in some circumstances? Remember, the better the cylinder-filling (usually at peak torque), the less spark advance is needed to light the fire at the right time, as long as it keeps up with rpm.


How about fabricating a lightweight, custom-looking air-scoop atop the front fender or in whatever fairing you might have, and duct that air to right above the exhaust port exit?


Some guys look at big old air-cooled aircraft engines, and observe the finely-machined, closely packed cooling fins, and think their bike should have that. But the cowling of those engines, of all air-cooled engines, is a hard-won science that was needed to make those closely-packed fins shed heat. An aircraft cowling is built to pressurize the air to make it run between the fins. High velocity ram-air comes in the front of the cowling, is slowed as it comes into a higher-volume area, converting velocity to pressure, and is closely ducted to make sure it gets between the cooling fins. By contrast, a motorcycle has a few big fins that are just radiators of heat to turbulent air that passes in random, ever-changing eddies, mostly over the tops of the fins. A few of the bike makers (Suzuki, for one, with their old two-stroke 550) made what were supposedly ram-air ducts over the top of the head, and they might have helped a little, but how do you get any real ram-air effect when there's a front tire shoving the air to either side and making it wildly turbulent? So bike motors can't be like airplane motors without good control of the airflow (which we don't want to do because really effective air-ducting would hide our pretty engines, right?).




(I CAN'T TELL WHETHER THIS PM IS ACTUALLY GETTING SENT TO YOU . . . .????)


Yes yes five times :-)


Dang, I was afraid of that.

As to water, I know some of the real old-time outboard racers tried small amounts of it, but this was in combination with the methanol-based fuel they used. In the Thirties, outboard racing in the US was at least a semi-professional sport, and on the amateur (I think) side there was even an inter-collegiate outboard racing circuit. I don't think there was any Stock racing then, and modified engines running fuel blends was the rule. Methanol base with about 12:1 to 16:1 castor oil lubricant. Additives included acetone, toluol, gasoline, nitromethane, benzol, . . . and in one blend I read about, 5% water as an anti-detonant. Kind of funny that nowdays guys are very concerned about their methanol absorbing moisture. But water is only useful if you have a detonation problem that you can fix in any other way, and it does cost some power. That's why guys who put water injection systems in their gasoline-fueled cars sometimes mix the water half-an-half with methanol, which restores most of the lost power. If this is in a racing context, however, class rules may prohibit the methanol. Some people have the idea that water injection gives you a steam engine, which sounds like an advantage. But any push from the steam doesn't match the power lost from the cooling of the burn by the water. So unless you have detonation you can't fix, or you are so close to the ragged edge than you want the water for insurance against going over the edge, I think water is a last resort. The old outboarders who use the 5% water were doing it so that their engines would live under big loads (20-40%) of nitro without melting off the big piston dome deflectors in their crossflow engines. And the highly-developed aircraft piston engines of WW2 and the Fifties had water-alky ADI (Anti-Detonation Injection) systems that only cut in at high manifold pressures only used on take-off or in combat.




Hi again Smitty


I quoted one of your posts here:- http://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1130778618#post1130778618


Rob


Hard to see whether anybody else thought much of the idea, but I'm interested to see that you think it might have merit.


Fellows are talking there about polishing piston crowns (to considerably reduce surface area, as detectable on a microscopic level), something some of us were doing in outboard racing forty-five years ago, and about ceramic coating the pistons for the same reason but with greater effect.


But then they talk about polishing or coating the exhaust port and passage. I'm not so sure about that idea, partly for the reason I want a finned exhaust header: to keep from heating the portion of the new air/fuel charge that gets that far. I want the exhaust port and passage to be transferring heat as fast as it can to the cooling fins or water jacketing immediately behind the port. Polishing or coating the port drastically reduces the heat transfer to the outside, and that's the hottest part of the engine, and often the area where you get pistons sticking and melting, so I wouldn't want anything that impedes heat transferring out to the outside.


On my old outboard racemotors I always reworked the factory water inlet arrangement (these engines got water from the lake rammed in the front of the lower unit, no water pump) to get the water-in streams flowing across the metal directly behind each exhaust port, with the intent of scrubbing off steam-bubbles as they formed.


Besides adding fins to the exhaust header, AND devising an air-duct or two (surely the best fix) that will blast air directly at the cooling fins on the cylinder and the exh. header, I would also be looking at the various "black-body" coatings that claim to increase heat transfer from the surface of the fins to the air.


This last might only provide a marginal increase in heat transfer, but then most advances come from incremental improvements. You Kiwis probably are familiar with the old "Hundred Pound Rule of Motor Racing," which states, "There's no place you can take a hundred pounds out of the car. But there might be a hundred places you can take out one pound." A goofy little fix like my cooling fins on header pipes won't make much difference in isolation, but three or four such little fixes might add up to something worthwhile.


Gosh, Rob, you quoted me and made me somebody; flattering! I was just going to be a lurker for a while, and not barge into a long-running thread. But I don't mind you quoting me if you think I actually say something of any value, LOL.


(I CAN'T TELL WHETHER THIS PM IS ACTUALLY GETTING SENT TO YOU . . . .????)



Thanks for the photos, looks like you guys are having a blast! Unfortunately, I can't make out how the ducts run on bike #38. But I did notice some of the bikes had their number plates set so close to the top of the fender as to completely block any airflow between the forks. That area would seem to me to be the FIRST place to think airflow. Rules permitting, rather than have an absolutely flat number plate, I'd want to roll the outer edges back, at least the lower edge, and continue that rolled lower edge with some sheetmetal that takes the airflow through the forks and then diverts it down toward the engine.


Suppose the rules require a 10" by 10" absolutely flat number plate. Obviously the edges of that flat plate create lots of turbulence (and drag). The fix is to add four rolled pieces of sheetmetal to the four edges, each having a radius of one-quarter of the width of the flat plate, in this case 2 1/2". So even though your number plate is now 15" wide, and still has a 10" flat plate in the middle, it's now has a lot less drag . . . especially if you can continue some of your rolled edges farter back as far as you can to make a classic aerodynamic teardrop. Any time you have to drag a big box shape through the air (in my case, the box on my outboard racing trailer), radiusing the outer 1/4 of the front of the box (or as near as you can get to that) takes care of the aerodynamics of the front of the box. Of course, it's a lot more trouble to build than a plain square box, LOL.


A '76 Yamaha RD400C like I have came with a little plastic vanity cover over the lower fork clamp/steering thing (I think it's called a triple clamp)(I know little about bikes). This cover had no function, and I didn't like the sharp lower edge which hung into the area where the air comes through the forks above the fender. So I got rid of it, and then made a sheetmetal replacement that's intended to carry air smoothly under the triple clamp and then get it going about 40 degrees downhill. Whether it actually does so I can't say, and it's only a start in the direction of what you'd want for racing. Probably it mostly has been just a source of comments and speculation, over the years.


I still like a big air-scoop built into the top of the fender. Big issue there is adding a bunch of unsprung weight. Wait, I gotta go back to the photos and see if you get to remove the fender; back in a sec. . . .





Back; okay, some of you retain the front fender, some don't. If this is optional, maybe you can fabricate whatever you like, and make something very functional. And if you make it of carbon fiber, lightweight. You could bolt it on to the fork brace like the fender bolts on, or avoid any unsprung weight at all by hanging it from that lower triple clamp. Let's see, that would still follow the steering, so if you wanted to avoid that, you could suspend it from the frame, immediately behind the steering head.
Again, I know zip about bikes, and probably I have said little of nothing that you haven't considered long ago. Well, it has been fun for me to think about!

[TZ350]

Welcome to the piston side.
Below you will find brands such as:
Barikit, Kitaco, Wiseco, Pro-X, Polini, Mahle and others.
I stocks normally pistons that you see below.
, there are other pistons in stock,
which can be a bit odd sizes etc..
If you can not find what you are looking for, write and ask,
so we'll see if I can help you!

304145

http://www.pvlsverige.se/vrm/kolvar/kolvar.html

[husaberg]

Welcome to the piston side.
Below you will find brands such as:
Barikit, Kitaco, Wiseco, Pro-X, Polini, Mahle and others.
I stocks normally pistons that you see below.
, there are other pistons in stock,
which can be a bit odd sizes etc..
If you can not find what you are looking for, write and ask,
so we'll see if I can help you!

304145

http://www.pvlsverige.se/vrm/kolvar/kolvar.html

Rolffe is the Mad Swede who did the Debri cylindered MB50 with a disk valve.
What happened to the piston rod spreadsheet Brent was going to do.:innocent:
this site is a great one in particular as it gives the oclock position of the ring pegs'.

[jonny quest]

Frits, instead of Viton... piston rings.

Might want to look into shock piston seals... like those on newer dirtbikes. Don't know what they're made of, but pretty amazing stuff.

[wobbly]

What would work well I am sure would be a multi groove labyrinth.
You would need a parallel section, maybe a thin sleeve over the header.
I am still amazed every time I rebuild a crank that 4 small grooves over a shaft works as well as a lip seal with no contact at all.

[husaberg]

What would work well I am sure would be a multi groove labyrinth.
You would need a parallel section, maybe a thin sleeve over the header.
I am still amazed every time I rebuild a crank that 4 small grooves over a shaft works as well as a lip seal with no contact at all.

its a puzzle that one............:whistle:

[ken seeber]

I think Wobbly's on the case here. I was thinking of a circlip style groove towards the end of the female tube. Into this groove would be a metal seal, one suitable type being the multi strand retaining rings (see www.spirolox.com ). Alternatively, an oversize piston ring could be fitted into an undersize steel sleeve such that its end overlapped and its inside diameter was less than the outside diameter of the male header tube. This would be then annealed in this position (oxy or propane flame up the guts), such that when removed it would be a light fit over the header. Then it would be gapped to suit. Not sure about the assembly into the groove though. In either case, the header would need to have its outer edge chamfered to allow easy(ier) assembly.

Downsides are more friction, but with possibly improved sealing and less oily "weeping".

Wobbly's labyrinth is much simpler though with zero friction.

[husaberg]

I think Wobbly's on the case here. I was thinking of a circlip style groove towards the end of the female tube. Into this groove would be a metal seal, one suitable type being the multi strand retaining rings (see www.spirolox.com ). Alternatively, an oversize piston ring could be fitted into an undersize steel sleeve such that its end overlapped and its inside diameter was less than the outside diameter of the male header tube. This would be then annealed in this position (oxy or propane flame up the guts), such that when removed it would be a light fit over the header. Then it would be gapped to suit. Not sure about the assembly into the groove though. In either case, the header would need to have its outer edge chamfered to allow easy(ier) assembly.

Downsides are more friction, but with possibly improved sealing and less oily "weeping".

Wobbly's labyrinth is much simpler though with zero friction.

Hey guys go back to the original posts.........
http://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner/page474?p=1130298456#post1130298456

[Frits Overmars]

Hey guys go back to the original posts.........
http://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner/page474?p=1130298456#post1130298456
You said it, Husa. Those posts are 30 months old and the sealing issues have been fully solved since then. But thanks for the tips anyway.

[RAW]

You said it, Husa. Those posts are 30 months old and the sealing issues have been fully solved since then. But thanks for the tips anyway.

Success Frits, congratulations, any hints for the rest of us mere mortals on sealing.

[chrisc]

I couldn't find the actual solution when going back but I might be blind.
I was going to suggest water cooling the spigot after reading recent discussion about cooling the first bit of the header.

Frits, where can we find more information/pictures/videos of that trombone set up? EDIT: Answered my own question: http://www.adriaanmeeuwsen.nl/team-pagina.html

Cable operated adjustable header on the hydroplane


https://www.youtube.com/watch?v=hOYvFgGqjUg

In action


https://www.youtube.com/watch?v=q7iDQ_OevP0


I did some searches on this variable header that Kel found a while back and found some more information:


How about a variable exhaust header. This one allows 25mm adjustment

241299
241300

Google translate says "a new control to include inflammation of RTD and the like" Thanks Google.

304171304172304173

"HE-YES. VARIO EXHAUST

Making an expansion outlet is no sinecure. Let there be no doubt that it is a very complicated matter. Indeed, there are very many things that influence the final form and the result. It comes down to the fact that you're never done with it. Even in an advanced stage is often called a small improvement. Even at the major racing teams are still minor changes. This involves literally millimeters. To even approach the matter differently, we at He-Ja R & D at us engrossed in fabricating a vario outlet. Here's a design Henk hunter that is operated by a servo motor. This includes whether a new control in RTD, including inflammation and the like. This kit is "Not for Sale" and only for their own use and testing. The whole is fit to a He-Ja type B kit for more bottem power.'s vario outlet work in a way that at low speed, the length of the entire exhaust route is longer than 25 mm at a speed above 11,500. therefore, may be a result of engine speeds with the same adjustment."

From: http://www.he-ja.nl/news.htm

[husaberg]

I couldn't find the actual solution when going back but I might be blind.
I was going to suggest water cooling the spigot after reading recent discussion about cooling the first bit of the header.

Frits, where can we find more information/pictures/videos of that trombone set up?

Not Frits but Carbon ring from memory relayed i think via Raw from another forum maybe the british 50 site?

Anyway this is worth a look even if it has some silly halftime valve thingies.
http://thekneeslider.com/jlsp305-300cc-5-cylinder-honda-by-jean-luc-borgetto/

http://www.youtube.com/watch?v=6HSBeMPOdJ0
Homemade Honda 5

[TZ350]

Links to some Ruapuna B track and 2014 BOB video


This thread needs more good stuff, so untill somebody posts some video, here is one we made earlier



Video from yesterdays F4 cup, filmed from GPR bike no 11



Here is the first 15min of the BOB , Riding with Mr BucketRacer

[husaberg]

The late model SA500 had shields but a cutaway slot allowing A/F to be "flung" upwards from crank rotation.
The latest TM125 kart engines have exactly the same idea.
I will have one apart soon so will pic this, as according to my info from Maxter its worth at least a Hp in 40ish.
Yes the cranks were Hirth assembled.
Funny how the SA case has a striking resemblance to this model.
304297

Shields and a cut away slot, a bit like this?
302867

Things are moving along, ports only need a couple of degrees onthe exhaust , and 1 degree on the a and b ports so getting a bit closer
302868


Here is the sideways slot on a TM125KZ10B
304298

Here is the front tunnel.
The crank spins forward as normal, so the ramps over the crank shield the intake flow from the turbulent boundary around the wheels.
The rear slot lets "flow" from around the crank up under the piston.
Mr Thiel tried the shields on the Aprilia and found some power as well, but dont know if the sideways slot was tested at the time.

I found this pic from another angle whilst looking for something else.
Must be a different model?
304300

[TZ350]

I so much enjoyed the BOB last year it broke my heart to have to miss this year, and so I am so definitely going to be there with my new bike next year.

304307

Needed to trim the cylinder head heat sink, I don't have a mill so got the trusty old skill saw out.

304308 304309

Does a good job too.

304310

Head fits great.

304306

Thanks to Gigglebuttons help, the main engine mounts are all sorted.

Now I can get onto doing the thing I like most, engine building!

304311

When the motor is all together we will fit a head mount too.

I am so looking forward to getting to ride the Beast at the BOB next year.

[cotswold]

Experimetal DMF engine made by EMOTracing is ready for running.
Faeturing a 6 speed casette gearbox ,dry clutch ,rotary inlet.
And a experimental 90 degree turned cilinder layout.
The inlet is opposite to the exhaust ,which points out to the left side of the engine.

[F5 Dave]

Links to some Ruapuna B track and 2014 BOB video

Links aren't currently working? They are on the BOB thread. Orange bike buggering off near the start is my MB100, sadly my inability to actually win is another story.

[TZ350]

304346

Chambers 13.6 rwhp RG50 with pumper carb and KX80 ignition.

Chambers enjoys taking an intuitive approach to developing his motors and he seems to do pretty well with it.

304344

Blue line 74% Ex port width, Green line 82%.

I have always thought you can get away with more exhaust port width on a 50 than the bigger engines.

Now bringing a bit of science to the party.

As a rule of thumb, a bridged eyebrow exhaust port flows 85% of a single exhaust port of the same area.

So you would expect a well shaped single exhaust at 85% to flow as much as the widest (100%) of eyebrow ports.

The depth of ring to diameter ratio seems to favor the 50's. So I plan on exploring how far we can get with a single exhaust port RG50 because I think that there is little practical advantage to be had with a multi window exhaust port on these small cylinders if you can get away with running extra wide single exhaust ports.

304345

Blue line is JonnyBalistics aftermarket Aprilia 50 cylinder with eyebrow exhaust ports, Green is the RG.

I recon we will get more out of the RG when we play with the reed inlet and re shape the reed valve duct and barrel around the inlet area, currently it is stock, as are the transfer ducts/windows/roof angles (but transfer timing has been altered with a spacer plate).

[peewee]

As a rule of thumb, an eyebrow exhaust port flows 80% of a single exhaust port of the same area.

.

what do you meen eyebrow exh ? never really heard that term before

[TZ350]

what do you meen eyebrow exh ? never really heard that term before

Maybe I have used the wrong term, should I have called them T ports?

304361

RGV250 eyebrow or T ports? with power valves.

[lodgernz]

Maybe I have used the wrong term, should I have called them T ports?

304361

RGV250 eyebrow or T ports? with power valves.

...or without power valves, still a T-port. I think the main criteria is that the port has a central divider.

[peewee]

yes i know what a T port is. aka bridged exh. :laugh:

[seattle smitty]

Haven't been able to get online at all for a week, which is probably just as well since I got over-exposed here by the kindly intent of TZ350:sleep: Anyhow, to Mr. Overmars, my observation that some bikers could introduce a measure of adjustability into their expansion chambers via an adjustable baffle cone was offered only because it doesn't appear to me that moving the entire pipe, trombone-fashion, is a practical option on many bikes. But thanks for your little treatise on the subject, which I'll be reading carefully. Also, thanks for the photo of the Rossi outboard (note that it is sitting on the bottom of the towerhousing; when ready to race, there's a small streamlined lower unit bolted under the towerhousing, with a propshaft and steering skeg). I barely know enough about computers to do THIS, and haven't yet learned how to post photos.

My unscientific intuition about leakage problems in pipes with sliding sections is that if the fit-ups are reasonably close and craftsmanlike, leakage tends to be minimalized by the fact that the inner sliding element gets very hot and expands towards, maybe against, an outer sliding element that is exposed to the air and shedding heat, therefore somewhat cooler. On my own pipes, long ago, I sprayed an approx. 0.1mm thick coating of a heat-cured molydisulfide (Kal-Gard)(now called KG Industries) on the sliding section. This was to take up a little of the tolerance, and to give a good anti-grab surface. If only I hadn't been such a mediocre driver . . . .

We always used to joke about "speed secrets" (sometimes we only pretended we were joking, while secretly we were on full alert). Here's one for my new Kiwi friends (who probably know all about it). That moly coating I spoke of (spray it on meticulously clean parts with an air-brush, let dry, bake at 300F for an hour) works well inside rotary valve cases. Shhhhh!!!

Chrisc, about the outboard racing videos you linked, I've known the father of the racer featured in the first video for maybe forty years. He (the dad) owns a Kawasaki 500 triple that was water-jacketed and turned on-end for outboard racing that many years ago, and I occasionally pester him to put it together and run it. As to the second video, a "World" championship in our sport is run under European rules, which among other things mandate a "jetty start," in which all boats are started at the shore of the lake and start racing from that point. Personally, that doesn't appeal to me at all. American rules, at a "National" championship, call for a flying start against a giant clock sitting at the edge of the beach on the start/finish line, counting down the last minute, the idea being to hit the line at full speed a micro-second after the clock hits zero. When all twelve boats happen to get it right and come down line-abreast and flat-out, it's a wonderful sight; when they all get to the first turn in a pack, well, some folks are going to get seriously hosed!! On some hot summer day, put on your swimming trunks and your full-face helmet, go out in the backyard and have your wife or kids aim the garden hose straight at your face. Note that your vision is limited to a few intermittent and badly obscured glimpses, when you can see anything at all. This is pretty much what you get to see if you are mid-pack or back through the first turn. Unfortunately, I got to see a lot of this in my racing days.

(EDIT) I don't want anyone misled on my "speed secret" above. The coating can helpful particularly where you have a rather flexible rotary valve disc. As far as power improvement from friction reduction, probably not detectable. A lot of the drag may be from the oil on the cases and disc, and I don't know that the moly surface "wets" any better or worse than bare aluminum.

[husaberg]

what do you meen eyebrow exh ? never really heard that term before


Maybe I have used the wrong term, should I have called them T ports?



RGV250 eyebrow or T ports? with power valves.


...or without power valves, still a T-port. I think the main criteria is that the port has a central divider.

Blame Mr Bell rather than it being a quirk of the kiwi vernacular. I must say it always looked like eyebrows to me.:blip:

[Frits Overmars]

..to Mr. Overmars, my observation that some bikers could introduce a measure of adjustability into their expansion chambers via an adjustable baffle cone was offered only because it doesn't appear to me that moving the entire pipe, trombone-fashion, is a practical option on many bikes.Right you are. But note that Mr. Overmars was my beloved father; just Frits is fine by me.


I barely know enough about computers to do THIS, and haven't yet learned how to post photos.Right again. It seems like every forum has its own particular way of picture-posting, and Kiwibiker is very particular. It took me quite a while to get the hang of it and I'm sure I haven't discovered all finesses yet.


That moly coating I spoke of (spray it on meticulously clean parts with an air-brush, let dry, bake at 300F for an hour) works well inside rotary valve cases. Shhhhh!!!A couple of years ago we were temporarily sharing a four-stroke tuner's workshop. He molycoated the pistons of his Superbike and Supersport machines and he swore by it. So we tried it on a two-stroke piston. After one dyno-run, there was hardly a trace of the stuff left to be found. So we never tried it again on anything.


On some hot summer day, put on your swimming trunks and your full-face helmet, go out in the backyard and have your wife or kids aim the garden hose straight at your face. Note that your vision is limited to a few intermittent and badly obscured glimpses, when you can see anything at all. This is pretty much what you get to see if you are mid-pack or back through the first turn. Unfortunately, I got to see a lot of this in my racing days.Reminds me of a friend's description of the best way to imitate ocean-sailing: stand under a shower and throw away hundred-dollar bills as fast as you can.

[seattle smitty]

That's interesting that your coating attempt didn't hold up, because the coating we put on our pistons, which have to live with fuels that are hard on many materials, hold up very well. I got onto this moly dry-lube process in 1966 when talking with the father of a kid with whom I had been a Boy Scout. The dad was a Boeing engineer and lubricants specialist, had been with Shell Oil for years before hiring on with Boeing. He gave me a Boeing Materials Spec and a mil-spec (IIRC it was mil-L-8987), and directed me to the local company that did all of this work for Boeing (I forget what components). So I had them do my pistons, carburetor slides, and other stuff for a few years until finding out about Kal-Gard, which by the mid-'70s was running half-page color ads in Cycle magazine with their line of DIY dry lubes. That was the heyday of 2-stroke club-level roadracing, with a thousand mad amateur tuners grinding ports with their Foredom flex-shaft grinders, for better or worse, but loving it. By the mid-'80s the heyday of the home-modified roadracers was disappearing, and Kal-Gard dropped the ads and returned to servicing the gunsmiths who had been their original customers. Then the company changed hands, and as I said, the remnant is called KG Industries.

Usual practice (and it does take some practicing, with no-good pistons and parts) is to try to lay a coat roughly 0.05mm (0.002" which is what I'm used to) on the piston skirt (I mask off the ring groove). The EXTREMELY CLEAN piston is warmed up enough to drive off any moisture, then allowed to cool to a little hotter than room temp. I set the piston in the middle of an old phonograph turntable, set at low speed, and build the coating with an air-brush. As stated, after the coating has flash-dried and set up a little bit, I put the part in a small portable oven set for 300F (checked with an oven thermometer), and bake it for an hour. In the assembled engine, about the first half-thousandth (let's see, .010mm) is immediately burnished off, but then the remainder of the coating holds up for a long time. When it does wear down, the piston gets re-coated.

For a short time, long ago, I became a sort of guru for a little crowd of owners of old Nortons and Triumphs and Enfields. I was in a bike shop when one of them mentioned how his Amal carbs, which were rigidly-mounted, would wear their slides, resulting in rough idling. I offered to build up his slides with a coating that would tend to resist further wear. The guy was so happy with the result that for a little while his buddies were calling me for the same service. That surely will have been the only time in my life that I'll ever be any sort of "guru"!!

[lodgernz]

Very interesting Smitty. Thanks for your input.
Can you be more specific about which KG product is the MoS2 lubricant that you bake?

[wobbly]

During testing of pistons for the BSL we had endless trouble getting small batches made, with the small shape changes needed.
When we finally got it right we wore our last couple of sets out , after doing some 300+ laps when testing at Sepang.
They actually rattled on the overun into corners.
HPC coatings in Auckland applied a Moly based baked on coating, that they said would get us back running till replacements arrived.
The coating was thick enough that when first put together there was ZERO bore clearance.
I was super nervous about Steve Briggs being thrown down the road at Puke when running it in, but after a few laps he gave it death with no issues at all.
It did around 30 laps that day, and after pulling it down there was no sign of scuffing or the coating wearing away.
I put one piston into the single cylinder dyno engine that night, and it made just over 1.5Hp more in 56 repeatably.
Cheap method to retrieve worn pistons, and for sure the coating lasted well.

[peewee]

the brilliant team of engineers at wiseco put a coating on some of them pistons. doesnt seem to last very long then you have 2x the piston clearance. armorglide is the name but im sure its just some type of moly. your better off to remove it before hand or avoid it all together

[fatbastd]

I concur with what Wobbly said - the HPC coating is very effective and I have used it in a number of applications to (marginally) reste piston/bore clearance where the old piston was sound but undersize, correct errors where restores have been bored/honed just that little too big and as anti-eizure protection. I have found the coating to wear a touch, but ant-sozure protection has been excellent - have never seized a coated piston (and (insert preferred divine entity) knows I've tried..)

[Gigglebutton]

During testing of pistons for the BSL we had endless trouble getting small batches made, with the small shape changes needed.
When we finally got it right we wore our last couple of sets out , after doing some 300+ laps when testing at Sepang.
They actually rattled on the overun into corners.
HPC coatings in Auckland applied a Moly based baked on coating, that they said would get us back running till replacements arrived.
The coating was thick enough that when first put together there was ZERO bore clearance.
I was super nervous about Steve Briggs being thrown down the road at Puke when running it in, but after a few laps he gave it death with no issues at all.
It did around 30 laps that day, and after pulling it down there was no sign of scuffing or the coating wearing away.
I put one piston into the single cylinder dyno engine that night, and it made just over 1.5Hp more in 56 repeatably.
Cheap method to retrieve worn pistons, and for sure the coating lasted well.

Some thing like this Wob :)

[seattle smitty]

lodgernz, the product I used is called "Gun-Kote." When Kal-Gard was selling a lot of it to racers, they relabeled it as Piston-Kote and Gear-Kote, but someone in the company told me it was all the same. They did have a coating you could apply to cooling fins that was supposed to increase heat transfer to the air, but I don't know anything about it. I also don't know whether anybody at the successor company can give first-hand info about the old days. I just went to the KG Industries website and see that they also sell a PTFE coating, which is new to me. I would tend to worry more about that coating bonding well to pistons skirts, but maybe it's fine.

The Gun-Kote used to come in spray-cans, but you don't use much at a time, so the can would probably lose its pressurization on the shelf before you got full use of it. So buy it in a non-spray quart can, stir it and shake it, and apply it with an airbrush or one of the modern paint sprayguns, whatever will lay down a fine spray. Find an old phonograph turntable before us old folk, who remember what the hell they are, all expire.:facepalm:

Be obsessive about prepping the parts, and keeping your oily fingers off them before coating. Get 'em hot and sweat out the oils as best you can. If you have access to a shop that does hot vapor degreasing, so much the better. Blast the skirts for further cleaning and to create a surface that has some "tooth." Don't clean pistons with glass bead blasting; various piston ring companies have put out service bulletins warning auto machine shops against this common practice. Bits of glass will impinge themselves in the aluminum surface, which you can actually see with an optical comparator. FWIW, never glass-bead an aluminum part to get it clean for welding, either, unless you follow up by removing a little of the blasted surface with a rotary-file, or you could drive your welder batty.

Instead of glass bead, blast the parts with soda or salt or possibly walnut shell (don't know how that would work out for this purpose). Right before I'm going to coat the parts, I apply some welder's aluminum etching acid, then wash it off. As stated, I then heat the part just enough to drive out any moisture. That's too hot to coat, so I let it cool toward room temperature. I want it warm, not hot, when I shoot it. Since I've been handling the part, while it is cooling down from driving off the moisture I give it a quick wipe with a lint-free rag that has some acetone on it. By the time I turn on the turntable and pull the trigger on the airbrush, that part is as clean and surface-prepped as I can make it in my home shop setting.

Oh, one other thing I do is set the can of Gun-Kote in a pan of hot water to warm up the contents so it sprays better. I find this to be a good technique to use when spray-painting of any kind; warm up the can of paint, especially spray-can paint.

This is a long description, but it makes the job sound a lot worse than it is; it's really not very much trouble.

Once you have the stuff to do this coating, and have done it once, you'll find various odd uses for it. I once had a Datsun 510 station wagon and two dead L-16 engines. Each motor had piston damage, and I kept one piston out of each because one was a perfect textbook example of detonation (sharp-edged hole in the crown) and the other of pre-ignition (melted hole). They were such perfect examples that I ended up giving them to the local high school shop class last year. Anyway, between the two engines there were four undamaged pistons. I cleaned them and had the local machine shop knurl the skirts (an ancient technique from my father's time for re-using old worn pistons). Then I applied a thick (0.1mm) coating of Gun-Kote. I checked out both blocks, chose the one that was least worn, took the ridge out of the cylinders and honed them. New rings, gaskets, etc., came out with a rebuilt engine for about US$200. Sold the car, which has run and run for the buyer. I wouldn't build an engine for a keeper-car that way, but it pleased me to be able to get the car fixed up so cheaply.

(EDIT) On bottom of the last post at the bottom of page 1019, Frits gave us a link to a video of a trombone pipe. Take a look at the sliding sections moving open and closed: that is a good example of a place that you could apply the moly dry-lube coating (to take up some of the space between the sliding elements while having good low-friction qualities . . . ).

(another EDIT) If you screw up the coating of the skirt (with runs, for example), you'll have to get the coating blasted off before you try again. This should answer doubts about how tough this coating is . . . .

[Grumph]

Hot vapour degreasing = trychlorethylene bath. powdercoaters who can do work to ISO standard will have one of these.

Dangerously toxic so don't try this at home.

F5Dave - next time you're trying to weld cases, try getting them degreased at a friendly powdercoater.

[wobbly]

Yep, Giggle I have seen those pistons before somewhere.
Nice idea having the squish band angled with a flat top.
Must have been a clever bastard that designed them.

[seattle smitty]

It's pouring rain here in Seattle (aka Swamptown), a good day to sit at the keyboard and try to learn from y'all. So . . .

When I do a search here, as for "torroidal heads," I invariably am directed to several 2-stoke threads with ten thousand posts apiece, and no further suggestions as to which pages have the subject term. So I'll just ask here, and know that I HAVE tried to search first:wacko:


What about those torroidal heads? Do they always work better (restricting my questions to high performance 2-strokes here)? Is this because they get the plug electrode closer to the piston crown or what? Should I assume they are generally used with modern-style fairly narrow squishbands?

Related question: A lot of times, a spark plug of a given heat range and electrode configuration can be had in both 14mm and 18mm types, or at least this used to be true in the '70s. Would it not be better always to opt for the 18mm plug, given that the additional volume around the electrode should give the A/F mixture a little better access to the spark, and a lower misfire rate? Dr. Christopher Jacobs, an ignition expert of some years ago said that even with the best of the available igniton systems and conditions there would always be a percentage of misfires, and the idea was to minimize these so far as possible. Did any of the top engine builders ever test 18mm vs. 14mm plugs of the same heat range?

[chrisc]

Here's some help on searching in these forums.

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Click the blue box 'search single content type' at the top.
Scroll down and select the forum area to buckets which is right near the bottom of the list.
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304439304438304437

THREAD IMAGES
Another handy tip is under thread tools (near the top of this page) click view thread images. Very! Helpful on the ESE thread

[senso]

For some reason I always looked to those coatings as a marketing gimmick/wankery, all of them will just disappear when touched with wet hands(my experience is just with wossner, vertex and mitaka pistons, and some namuras that will loose the coating even inside the paper box from scratching).

[wobbly]

The coatings as used by Wossner/Vertex are purely designed as a "run in " coating.
The Moly coating as done by HPC is specifically formulated as a permanent slippy surface treatment.
They use it in Nascar, and have been told that it last longer than the pistons are used for = around 800 miles at 8,000 rpm.

Re proper Toroidal head shapes.
Bottom line is that the only real confirmed testing I know of, is that Jan developed the very flat topped wide bathtub at Aprilia with a domed piston.
I have done a huge amount of testing with flat topped pistons and the Toroid wins easily.
Yes getting the pug tip down into the path of the squish induced turbulence with its high speed flame front must be part of the deal.
The flat roof chamber with the dome probably has the same effect as that generated by the toroid and a flat top.
But as it stands there are plenty of very fast engines running domes and toroids.
One 125 kart World Champ tuner in Europe builds domes with toroids and the tech people finally agreed to allow it, as his engines must be ccd
with the cylinder sitting at a specific angle to allow the entrapped air out of the chamber.
He would not go to all that hassle if the toroid wasnt an advantage in those seriously deto prone KZ2 engines.
Its has been deemed illegal here in NZ, otherwise I would be doing it.
The squish MSV number is irrelevant to the discussion re the chamber shape - except to say that a theoretical 38M/Sec works on damn near everything.
This then becomes irrelevant also, when you run the piston/head clearance right at the limit of contact ( as you should be ) just past peak rpm - as zero
clearance would generate insane MSV numbers.
Having the theoretically correct setup in a 125 means you should be down at 0.65mm with a 50% SAR, but this has been found to possibly limit the peak overev
depending upon the fuel and atmospherics, and opening up the gap to 0.75mm solves that issue at 14500 if needs be..

[TZ350]

It's pouring rain here in Seattle (aka Swamptown), a good day to sit at the keyboard and try to learn from y'all. So . . .

When I do a search here, as for "torroidal heads," I invariably am directed to several 2-stoke threads with ten thousand posts apiece, and no further suggestions as to which pages have the subject term. So I'll just ask here, and know that I HAVE tried to search first:wacko:

You might find these search tips useful.


Some may find this useful. Rather than use the site search which usually fails, use Google so to search this site use an ordinary search phrase and after it add

site:www.kiwibiker.co.nz (http://www.kiwibiker.co.nz)

for example

Frits priceless site:www.kiwibiker.co.nz (http://www.kiwibiker.co.nz)
or
Frits pisa site:www.kiwibiker.co.nz (http://www.kiwibiker.co.nz)

the same will work for other sites with the appropriate site address

Mick


Here's some help on searching in these forums.

Top right hand corner of the screen, click 'advanced search'
Click the blue box 'search single content type' at the top.
Scroll down and select the forum area to buckets which is right near the bottom of the list.
Scroll down and select the dot next to 'posts' in the criteria called 'show result as'.

304439304438304437

THREAD IMAGES
Another handy tip is under thread tools (near the top of this page) click view thread images. Very! Helpful on the ESE thread

[husaberg]

You might find these search tips useful.

Another way to filter the wheat from the chaff is to click on the user name of the person and either view attachments by user or forum posts.

[peewee]

hey wobbly in engmod is the Yam12 scavenging model the one i need to use for a banshee cylinder ? it appears to be the closest match from what i can see

[wobbly]

A stock Banshee is closest to Yam1, as that porting was a very a good system for a road bike in its day.
A well modified one with the axial angles reversed and a lot of epoxy becomes Yam 14.

[Frits Overmars]

Here's some help on searching in these forums.

Top right hand corner of the screen, click 'advanced search'
Click the blue box 'search single content type' at the top.
Scroll down and select the forum area to buckets which is right near the bottom of the list.
Scroll down and select the dot next to 'posts' in the criteria called 'show result as'.

Another handy tip is under thread tools (near the top of this page) click view thread images. Very! Helpful on the ESE threadThanks Chris. I didn't know that.
I played a little with it and amongst other things found this link for seattle smitty:
http://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1129962543&highlight=toroidal#post1129962543

Smitty, I think that first we need to establish what a toroidal head really is.
For Wobbly it is a head whereby the center zone, containing the plug thread, bulges down towards to the piston.
I have a slightly different definition. For me a toroidal head is a shape whereby the center of the combustion dome is off-center from the cylinder bore center line.
That can lead to Wobblies shape; it can also give a head shape whereby the center zone around the plug thread is flat instead of bulging down.
I haven't considered 18 mm plugs; I'd even like to step away from 14 mm plugs and use 10 mm plugs like KTM is doing. And I'd prefer to use surface-gap plugs (no empty volume inside the plug at all). These 'conceiled' (from the viewpoint of the scavenging stream) volumes provoke detonation.

[Frits Overmars]

Here's some help on searching in these forums.

Top right hand corner of the screen, click 'advanced search'
Click the blue box 'search single content type' at the top.
Scroll down and select the forum area to buckets which is right near the bottom of the list.
Scroll down and select the dot next to 'posts' in the criteria called 'show result as'.

Another handy tip is under thread tools (near the top of this page) click view thread images. Very! Helpful on the ESE threadThanks Chris. I didn't know that.
I played a little with it and amongst other things found this link for seattle smitty:
http://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1129962543&highlight=toroidal#post1129962543

Smitty, I think that first we need to establish what a toroidal head really is.

For Wobbly it is a head whereby the center zone, containing the plug thread, bulges down towards to the piston.
I have a slightly different definition. For me a toroidal head is a shape whereby the center of the combustion dome is off-center from the cylinder bore center line.
That can lead to Wobblies shape; it can also give a head shape whereby the center zone around the plug thread is flat instead of bulging down.

I haven't considered 18 mm plugs; I'd even like to step away from 14 mm plugs and use 10 mm plugs like KTM is doing. And I'd prefer to use surface-gap plugs (no empty volume inside the plug at all). These 'conceiled' (from the viewpoint of the scavenging stream) volumes provoke detonation.


the additional volume around the electrode should give the A/F mixture a little better access to the spark, and a lower misfire rate.True, and the best way to create a big volume around the electrodes is to move them to the center of the combustion chamber. I used plugs with an extra-long thread (meant to be used with sensor rings). I ground away the part of the thread that intruded into the combustion chamber, leaving just some support for the mass electrode. So the spark was right in the middel of everything. It worked, especially on the overrev.


Christopher Jacobs, an ignition expert of some years ago said that even with the best of the available igniton systems and conditions there would always be a percentage of misfires, and the idea was to minimize these so far as possible.True again.

[seattle smitty]

Do you see what I'm trying to say about the 18mm plugs having more space around the center electrode for the A/F charge to swirl around? Since all of the related events are happening in an extremely short time, I'd think this would give a slight advantage.

HOWEVER, after I left the computer yesterday, it occurred to me that you biker guys probably don't ever run the recessed-gap plugs that outboard racers often use when we run more exotic fuels than gasoline. In Champion, these would be L87R or L84R, for example, the suffix designating the recessed side-electrode. This is what is in MY mind when the subject is racing spark plugs. But since nobody would run this sort of plug if he didn't have to, and since you don't have to when burning gasoline, I asked a question that is probably of no interest here. :facepalm:

Anyway, the combustion chamber shapes (and piston crown shapes) are more interesting. If you follow the car-racers' discussions of ports that impart swirl and tumble to the intake charge, you'll notice that (for them or us) the piston still has a long way to go, half a stroke, after the swirly, tumbling intake charge gets shut off. The question becomes, first, just how much is the increasingly-compressed mixture STILL swirling/tumbling as the piston approaches TDC and squashes the charge down into a tiny space? And second, how much and what kind of turbulence is imparted into the now-highly-compressed charge by the squishband? And third, can that be improved upon, and how?

My elderly brain is failing to recall an old, obscure bit of terminology trivia. I expect you all are aware of the experimental squishband grooves of the famous/infamous Mr. Sommender Singh in India. His ideas (and remember he started as a 2-stroke motorcycle racer) are a wonderful source of speculation, though only a few engine-builders with real credibility have tried the grooves . . . with varied results, of course. Anyway, as with a lot of new ideas, somewhat similar things had been tried long before Singh's grooves. The old term that I can't remember was something like, "fire-slots" or "fire-channels" or some-such, and I first saw them in the mid-late-Sixties when OMC (Outboard Marine Corp., maker of Evinrude and Johnson outboards) came out with their first loop-scavenged engine, a 55hp triple. The heads on that motor had wide squishbands, a curious (and cast, not machined) fez-shaped combustion pocket, and two of the "fire-slots" in opposite sides of the squishband and pointed at an angle to the centrally-located sparkplug to impart a last-instant swirl. Just what Singh wants to do.

The next iteration of the OMC triple soon followed, as the engine went in stages from 55 to 60 to 65 to 70hp. Boost ports were added (enormous boost ports, as big as the two tranfers), and the weird combustion pocket and fire-slots were replaced by a simpler, machined hemispherical combustion pocket. Maybe they learned something in the dyno cells, or maybe the new head was just simpler to turn out, with a lower scrap rate.

You know where this is going.:yawn: Have any of you done any good tests with Singh's grooves? My first reaction on hearing about them was skeptical, but then I thought, well, we think we want that final-instant turbulence from the squish, so why sneer at somebody's new idea on enhancing that effect? I'm going to try it myself sometime next spring. I have an obsolete, homebrewed racemotor that wouldn't be competitive today, but can serve as a fine dyno-mule. This is a '73 Yamaha 125cc 56X50 motocross engine with the cooling fins mostly milled off and water-jacketed, and turned on end to make an outboard. I have a couple of extra homemade heads, and can fiddle with grooves or whatever else. I wouldn't expect anything dramatic; it just seems like a fun thing to try.

What I'd really like to try is multi-plug heads. All the Top Fuel dragsters are using 3-plug heads, and if you fly you know that a little airplane engine always drops rpm when you switch from BOTH mags to either one singly. Again, there are undoubtedly more productive uses of one's time when searching for another couple of 2-stroke horsepower. But the weird stuff is FUN.

(You crazed Kiwi 2-stroke tinkerers really ought to think about outboard racing, where the rules are nearly wide-open, you can convert any piston motorcycle engine, and you can use any fuel concoction you want. Yowzah!!!)

[Frits Overmars]

If you follow the car-racers' discussions of ports that impart swirl and tumble to the intake charge, you'll notice that (for them or us) the piston still has a long way to go, half a stroke, after the swirly, tumbling intake charge gets shut off. The question becomes, first, just how much is the increasingly-compressed mixture STILL swirling/tumbling as the piston approaches TDC and squashes the charge down into a tiny space? And second, how much and what kind of turbulence is imparted into the now-highly-compressed charge by the squishband? And third, can that be improved upon, and how? To get swirl in a four-stroke cylinder you need an asymmetrical inlet duct. But that means less flow, so you'll hardly find any swirl in a powerful four-valve engine.

Tumble is a different matter. It comes naturally with high-flowing downdraught inlet ducts, it is augmented when the piston concentrates the tumbling charge in an ever-tighter space (like a ballerina, doing a pirouette, will spin faster when she brings her arms above her head). And in the final phase of compression the tumble is enhanced by the squish.
Not that there is much squishband in a four-stroke; the valves occupy most of the head area, leaving relatively narrow fore-and-aft squish areas, mainly at the exhaust side. But the charge getting squeezed from between the piston and that squish area has just the right direction to enhance the tumble.

Four-strokes need all the mixture movement they can get at that final stage of compression in order to get anything like a decent combustion; the combustion volume is shaped like a wet pancake. No wonder last year's Formula 1-engines needed an ignition advance of up to 60° at full throttle, and even more at part-throttle.
(This year's F-1 engines don't rev, and sound like lawn mowers. Before the present rules were accepted, F-1 bos Bernie Ecclestone was warned that a low-revving six-pot turbo would not produce an attractive sound. Now he's complaining to the engine builders. What does he expect them to do? Change the laws of physics?)

[seattle smitty]

So the swirl speeds up approaching TDC, shoulda thought of that; what's that called, conservation of angular momentum or something, I'm just a dumb welder with a useless liberal arts degree. Thanks for that, Frits, although you didn't specifically address Singh and his groovy heads or multiple plugs. As to swirl in a 4-valve car engine, David Vizard did an interesting experiment in a Mitsubishi four that he built for a drag racer, with asymmetrical valve sizes specifically intended to impart swirl. Part of his intent was to keep the normal tumbling charge from tumbling right out of the exhaust ports given a wild camshaft. Google "vizard poly-quad head" to read about it.

Well now maybe I don't see it yet. Since 2-stroke loop scavenging imparts tumble, rather than swirl, what is THAT charge doing as the piston gets up to TDC? Does the tumble velocity increase in the same manner as the spin/swirl, even though the shape of the vessel in which it is tumbling is good for swirl but not so good for tumble? The puff from the squishband (assume we have the usual centrally located combustion pocket) would NOT be in a swirl, right? So then the question again would be: would a swirl at that instant be of value, and would some grooves in the squishband, aimed NOT straight at the plug but at a small angle, impart a swirl?

[Grumph]

Smitty - do you remember Torquemaster spark plugs ? long reach surface gap plugs with the last of the threads machined off and used in short reach heads....Idea was to get the spark source well into the chamber.
The reviews were a bit hit and miss as i remember - it worked well in some engines but not others. I'd assume how well they worked depended on how bad the swirl and squish worked in a particular motor.

[Flettner]

seattle smitty, thank you, I enjoy reading your posts. Most interseting, any pictures?

[Yow Ling]

Maybe this will help a bit


https://www.youtube.com/watch?v=3F_0PvbKo44

[peewee]

i have to think grooves on crankshafts dont work. if they did why wasnt there any on the rsa125 ? surely jan thiel would of used them if it was of some value





i dont recall jan or frits recomending everyone try grooves on the combustion chamber either. leads me to believe they have little or no value. i thought a mirror polished piston top and combustion chamber was the way to go ? i been thinking of trying it.

[seattle smitty]

Grumph, I never even heard of those plugs. Mercury outboards introduced the first surface gap plugs I know of in the late '60s along with a CD ignition. The tech rep would demonstrate the new system at the dealerships by dipping a surface gap plug into a can of grease, then showing how it would keep sparking. Yet while lots of racers immediately adopted the CD ignition (anything had to be better than Lucas magnetos!), almost no one I know used the new style plugs.

Flettner, I'm too old and tech-challenged to post pix. I should learn. I could show you guys some fairly oddball engines.

Yow Ling, I never knew you could fuel an engine with tomato paste. Interesting video, though I wish I could slow it down.

Pee Wee, X2 on mirror-polishing piston tops, something motor racers have done since the Thirties as maybe the best thing you could do for a piston until ceramic coatings came along (another interesting subject). Not clear on your statement about crankshaft grooves. I'm referring to putting grooves in the squishband. Google "Sommender Singh grooves;" quite a few people think Singh is a crank, maybe that's what you referred to . . .

[TZ350]

Flettner, I'm too old and tech-challenged to post pix. I should learn. I could show you guys some fairly oddball engines.

I would love to see the oddball engines...... :D

The basic steps are, Start a Post or Reply and then select:-

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[speedpro]

Little end bearings. For the same inner diameter and width is there any reason to use either a 18mmOD or 19mmOD bearing? I'm looking at 2 similar rods but with different diameter little end eyes. Bearings are readily available for both sizes. Obviously the bearing for the 18mmOD has smaller diameter rollers than the 19mmOD

[TZ350]

I know there are some aftermarket rods with small L/End eyes that suit the TZ350's and the little end brg breaks up after a while, something that does not happen with the original sized L/E brg.

[Frits Overmars]

I'm just a dumb welder with a useless liberal arts degree.You're a free thinker. What more could anyone wish for? Yeah, more education, and that goes for all of us. No matter how much we have studied, there will come a time when we reach the borders of our knowledge and we'll have to stop calculating and start guessing. I got rather good at guessing :msn-wink:.

you didn't specifically address Singh and his groovy heads or multiple plugs.Groovy heads make me think of a rasta-band rather than a combustion chamber. All of the mixture in the combustion chamber should be concentrated in one easily-accessible (for the flame) volume. Any other shape will bring about unburned mixture and/or detonation.
The first time I laid eyes on a grooved Singh-style head, my reaction was: "shouldn't cooling fins be on the outside of a cylinder head rather than on the inside?"

Multiple plugs are a good thing. But just how good, depends on the shape of the chamber, on the number of millijoules your ignition system can throw at those plugs,
and on the position of the original plug. Aprilia-experiments learned that twin plugs produced the same maximum power, revved a bit higher and required 3° less ignition advance than the original single plug. The engine also sounded a bit nicer, which makes me think of yesterday's Christopher Jacobs quote.


Since 2-stroke loop scavenging imparts tumble, rather than swirl, what is THAT charge doing as the piston gets up to TDC? Does the tumble velocity increase in the same manner as the spin/swirl, even though the shape of the vessel in which it is tumbling is good for swirl but not so good for tumble? The puff from the squishband (assume we have the usual centrally located combustion pocket) would NOT be in a swirl, right? So then the question again would be: would a swirl at that instant be of value, and would some grooves in the squishband, aimed NOT straight at the plug but at a small angle, impart a swirl?Loop scavenging imparts tumble, not swirl. It would produce swirl only if the right/left symmetry of the transfer ports was faulty. And you don't want swirl;
you don't even want tumble while the scavenging is still going on, because it would mean mixing the fresh charge with the spent gases instead of expelling those.
The scavenging video posted above by Yow Ling, nicely shows this (assuming the CFD simulation was correct, which would mean that the scavenging of the engine in that video was far from perfect).
Tumble is inevitable in a loop-scavenged engine, but what tumble there is, will be messed up by the squish action near TDC, which is much, much stronger.

Tangential grooves would impart a swirl; they would also cause a pressure loss in the squish area (like grooved tires on a wet track let the water escape from between the contact areas). So no grooves for me.

[seattle smitty]

. So no grooves for me.

Well, I have to try it, Frits; costs nothing but time (but then time is always the biggest hangup!!!!). I'll have a pal help me post a photo.

I'm going to back off for a while; I've been hogging this thread for several days to where the long-time members can hardly get a word in. But let me ask one more thing:

Looking at the references roadracers make, I take it that Aprilia's last GP engines were and are the peak of 2-stroke development so far, and that Jan Thiel is the ranking expert. Elsewhere there is a page or two of observations by Thiel, which included the number of dyno experiments he got to run every month at Aprilia. Wonderful!!

Anyway, I'd like to know if the factory still sells parts for those 125s. Cylinders, heads, crankshaft assemblies, pistons, . . . the powerhead parts I'd need to build a couple of outboards, a 125 single and a 250 opposed-twin. Obviously I'd be fabricating the crankcase, adapting the powerhead to vertical operation, etc.. Since the factory racing operation is shut down, was/is there a production version for privateers, and does the factory still support the owners of those machines?

I'd also like to acquire similarly high-tech parts to build a 175 opposed-twin (the 250s having gotten too fast for this old man to race himself). Half of 175 is 87.5cc. So far as I can tell, there's no roadracing class close to that displacement, but I think there is a motocross class for kids at about 80cc (true?). If there's a well-designed and currently-available cylinder with a bore in the range of 45 to 48mm, I'd like to hear about it . . .

I really appreciate all the helpful and friendly input.:niceone:

--Smitty

[Frits Overmars]

I take it that Aprilia's last GP engines were and are the peak of 2-stroke development so far, and that Jan Thiel is the ranking expert.You could say that, Smitty. Jans machines won 26 FIM Constructor World Championship titles and riders using them won 300 GPs and 25 Rider World Championship titles. No one else comes close.


I'd like to know if the factory still sells parts for those 125s....Since the factory racing operation is shut down, was/is there a production version for privateers, and does the factory still support the owners of those machines? I can't say; I always kept as far away from commercial things as I possibly could. And so did Jan. But a friend of ours, Thijs Hessels, produces his own parts for Aprilia racers (with a little input from Jan) and his cylinders are as good as the works RSA cylinders (hesselsfijnmechanica@versatel.nl).
Another option is to take a look at the various people who build 250 cc tandem-twin engines for superkarts: DEA, FPE, PVP, BRC, etc.
They all based their products on the Aprilia RSA.


I think there is a motocross class for kids at about 80cc (true?). If there's a well-designed and currently-available cylinder with a bore in the range of 45 to 48mm, I'd like to hear about it KTM builds motocross machines with 65 cc (bore x stroke = 45 x 40,8 mm) and 85 cc (bore x stroke 47 x 48,95 mm). Those cylinders are not bad.

[Yow Ling]

Smitty, all the Japanese manufacturers make 85cc motoX bikes with oversize pistons available up to +2mm, some of the cylinders are Cast iron bores some Nicasil, our rules prevent us from using them in Buckets, The 85 cc engines are around 22hp

[Frits Overmars]

I'm going to back off for a while; I've been hogging this thread for several days to where the long-time members can hardly get a word in.I think you are an asset, Smitty. But in case you really want to cool it here for a while, you might want to spend some time at
http://www.pit-lane.biz/t117p246-gp125-caracteristiques-aprilia-rsa

[Sketchy_Racer]

our rules prevent SOME of us from using them in Buckets

Except cheaters, cheaters use 85s ;)

[Yow Ling]

Except cheaters, cheaters use 85s ;)
Doesnt bother me !

[TZ350]

85's .... Hmmmm unrestricted 85's .... a proper unrestricted anything goes 85cc developers class ... yes please ... :D

[Flettner]

Smitty, yes, post pictures of odd ball engines please.

[peewee]

do any of you guys have experience with these things that go inside the carb bore, either before or after the slide ? is it just rubbish with a splash of snake oil ? i have hard time believing it does anything good. heres the description

The Quad-Flow Torque Wing has vertical and horizontal air flow stabilizers which increase air flow, air velocity, and fuel atomization, thereby increasing performance. This easy to install device gives a big increase in bottom-end and mid-range torque and performance. It delivers a great bang for the buck! Increases air flow, velocity, and fuel atomization Big increase to bottom-end & mid-range performance Increased torque enables pulling a taller gear Improved throttle response Allows leaner jetting which results in increased fuel mileage Laser cut stainless steel Quick & easy to install Made in the U.S.A.

[TZ350]

I have a hard time believing it does anything good. here is the description.

The Quad-Flow Torque Wing has vertical and horizontal air flow stabilizers which increase air flow, air velocity, and fuel atomization, thereby increasing performance. Big increase to bottom-end & mid-range performance Increased torque enables pulling a taller gear.

This is where a back to back dyno test would be very interesting. I would be happy to help if anyone has one to try.

[peewee]

heres one that installs upstream of the carb. yes if anyone has one to test that would be nice to see some results




The air box is connected to the throttle by the air boot. The typical boot is inefficient in routing the air stream as it snakes around the frame and shock before reaching the throttle valve. The irregular shape of the boot produces unsteady and erratic air flow – turbulence. The result is compromised power delivery.

The FMF SNAP™ divides the air passage within the boot into quadrants to increase air velocity by directing the air stream and reducing turbulence.

With improved air flow to the throttle valve, you will experience crisper and immediate throttle response, as well as a boost in the low to mid-range torque.

Installing the SNAP™ is as easy as installing an air filter in most cases and requires no jetting or fuel changes. Drop it in the air boot and feel an immediate difference at the first crack of the throttle with a healthier pull off the bottom. The FMF SNAP™ is bolt on performance!
• Better Throttle Response and More Torque
• Easy Installation
• No Fuel or Jetting Changes Required
• Patent Pending

[2T Institute]

heres one that installs upstream of the carb. yes if anyone has one to test that would be nice to see some results




The air box is connected to the throttle by the air boot. The typical boot is inefficient in routing the air stream as it snakes around the frame and shock before reaching the throttle valve. The irregular shape of the boot produces unsteady and erratic air flow – turbulence. The result is compromised power delivery.

The FMF SNAP™ divides the air passage within the boot into quadrants to increase air velocity by directing the air stream and reducing turbulence.

With improved air flow to the throttle valve, you will experience crisper and immediate throttle response, as well as a boost in the low to mid-range torque.

Installing the SNAP™ is as easy as installing an air filter in most cases and requires no jetting or fuel changes. Drop it in the air boot and feel an immediate difference at the first crack of the throttle with a healthier pull off the bottom. The FMF SNAP™ is bolt on performance!
• Better Throttle Response and More Torque
• Easy Installation
• No Fuel or Jetting Changes Required
• Patent Pending

If it boosts low end torque then it would be just as easy to put a dyno graph on the PR blurb as it would be to put some drawing ?

[TZ350]

I had a bit of a Google for dyno graphs. Looking around I realized that a dyno run is usually done at wide open throttle and that something designed to improve mid throttle response needs to be tested at several part throttle settings. A full throttle run would probably not do it justice.

[F5 Dave]

I'm rather partial to those turbo spinner fans to put at the end of your exhaust they used to advertise in the 80s. That's where the next performance increase in 2 strokes comes from but it is being repressed by Honda as they have too much investment in the fore stroke IC engine.

A conspiracy:drool:

How about if the smoothed the intake of your cornflakes in the morning if it could improve the outflow of your waste products before you left the house. Result.

[Grumph]

do any of you guys have experience with these things that go inside the carb bore, either before or after the slide ? is it just rubbish with a splash of snake oil ? i have hard time believing it does anything good. heres the description

i don't see any dimples on it - room for improvement or just the next model "improved" version ?

[TZ350]

I'm rather partial to those turbo spinner fans to put at the end of your exhaust they used to advertise in the 80s. That's where the next performance increase in 2 strokes comes from but it is being repressed by Honda as they have too much investment in the four stroke IC engine.

:oi-grr: .... I can see you are not a true believer ......

[Frits Overmars]

Installing the SNAP™ is as easy as installing an air filter. Drop it in the air boot and feel an immediate difference at the first crack of the throttle.
• Easy Installation
• Patent PendingDropping a bath towel in the air boot will do the same. Patent pending.

[cotswold]

just took a look at the lads Frits mentioned.

http://www.he-ja.nl/2007-RS125-intro.htm

[seattle smitty]

Smitty, all the Japanese manufacturers make 85cc motoX bikes with oversize pistons available up to +2mm, some of the cylinders are Cast iron bores some Nicasil, our rules prevent us from using them in Buckets, The 85 cc engines are around 22hp

What I probably have to do is find a forum for the dads who set up these little bikes for their kids to race, in hopes that they can lead me to an engine-builder or two who specialize in this sub-specialty. My guess is that all these engines have pretty mild port timing from the factory, and probably smaller ports than I'd want for all-out horsepower. My hope would be to have some experienced tuner who has "seen it all" give an opinion as to which cylinder has the biggest, best shaped ports to start with, port timing being fairly easy to alter, but port shape/aiming/etc. being not so easy, especially in those tiny bores. Since Frits has already suggested KTM, I'd check that out first.

Currently (unless something has come along that I haven't heard of yet), the 175cc twin-opposed production racing outboards from GRM and VRP are derived from their other classes of engines, with the result that they are quite over-square. I got accustomed to square and long-stroke, long-rod engines long ago, and over the years watched the fashions change back and forth, but would prefer a somewhat long-stroke 175 (as you can see from my asking about 45 to 48mm bore cylinders). The engines built by those two Italian companies are very well-made and up-to-date, and a great improvement over anything we outboarders have ever had available to us, and we are very grateful to Mr. Rossi and Mr. Verona. (EDIT)(My info was out of date, as I've learned that at least one of the Italian makers has a "square" 175cc twin. Nevertheless, I'd still rather come up with something unique).

The trouble is, they are good enough that nearly all of the PRO racers nowdays just use the engines as they come from the factories, whereas the mark of alky outboard racing used to be that you had to do a lot of your own beefing up and hopping up (or get someone to do it for you). The idea of "checkbook boatracing" doesn't appeal to me at all. To me, there's an important distinction to be made between "racers" and mere "drivers." That distinction is ultimately the long hours a racer spends in his home shop, measuring and calculating and grinding and welding and turning and milling and wrenching, when the "mere drivers" are out on a golf course, or whatever it is that that sort of person does. I guess I just don't relate well to men who never get dirt under their fingernails.

So "turn-key" racing has no appeal to me whatever, and I like a site like this because I can see that many of you feel this way as well. For myself, I want to see if I can build something that nobody else in the pits has ever seen or thought of, and if it will keep up with or beat the un-modified new factory motors, so much the better.

[seattle smitty]

Did I miss something here, were you also doing engine development at Aprilia, Frits??

[peewee]

theres some ktm mx forums that have sections discussing the 65 and 85 engines but i wouldnt bother asking any technical questions. most of those members barely know how to change clutch plates, let alone how to properly modify the cylinder

[Frits Overmars]

Did I miss something here, were you also doing engine development at Aprilia, Frits??Jan Thiel did all the hard work at Aprilia. Until he retired, I performed thermodynamic and gasdynamic calculations for him, and I also tried to think along with him about various two-stroke developments. I've explained it a bit more extensively in that Pit-Lane link I posted the other day:
http://www.pit-lane.biz/t117p246-gp125-all-that-you-wanted-to-know-on-aprilia-rsa-125-and-more-by-mr-jan-thiel-and-mr-frits-overmars-part-1-locked

If you start reading there, even if you only read the english texts, you'll be occupied for the rest of the year. So Merry Christmas and a Happy New Year :msn-wink:.

[Frits Overmars]

... My guess is that all these engines have pretty mild port timing from the factory, and probably smaller ports than I'd want for all-out horsepower.... Since Frits has already suggested KTM, I'd check that out first.The KTM 85SX already has decent transfers; all you need to do is set their timing at 130°, widen the auxiliary exhaust ports and raise them from their standard 174° to 188°. The central exhaust port already is 194°.

[TZ350]

do any of you guys have experience with these things that go inside the carb bore, either before or after the slide ? is it just rubbish with a splash of snake oil ? The Quad-Flow Torque Wing has vertical and horizontal air flow stabilizers which increase air flow.

Hi Peewee, there seems to be as many people who rush to rubbish a new idea without critical thought as embrace it, either way its a "Faith Based" assumption, if their opinion is not based on measured fact.

Humans have two great attributes, Faith and the ability to make Intuitive leaps.

And to make consistent advances, after the intuitive leap the objective needs to be measured empirically, and the real (sometimes difficult) trick can be in devising procedures to measure something in a way that reflects its intended improvement, ie its no good measuring a device that improves quarter to mid throttle response at WOT on a dyno.

In my efforts to find better ways of flowing air through a 24mm carb I found various flow straighteners helped a lot.

304560

The best that was tested for outright bulk flow was this 24mm venturi insert pressed into the back of a 38mm carb. I think it worked by the body of the carb straightening up the air column before it entered the 24mm venturi.

I also found that air flow into the engine actually had to be a problem before I could improve it. As extra flow on the bench did not necessarily mean extra power on the dyno if something else in the system was really the bottleneck.

I inadvertently demonstrated strengthening the strongest link in the chain did not make the chain any stronger.

I had to find the weakest link and that is harder than you think. Because it might not be as obvious (or interesting to fix) as insufficient blowdown STA but as simple as poor fuel atomisation or any one of the 101 other seemingly little things.

In the quest for improved performance I think everything is worth a look, I would love to test those flow straighteners.

[richban]

I took the bike out for a test yesterday at a MotoTT track day in group one. A great day out and loads of track time.

I made a new plastic mount for the EGT but its still getting interference form somewhere. I will go over the wiring and insulate the lot and also make sure it does not pass to close to plugs etc.

So, new heads with proper squish and power valves all working. Oh and a real 15 degrees advance at peak. Woohoo it just keeps getting better. I am going to lower the shift light rpm as I think its just dropping out of the happy place at 11700 I will pull it down to 11500.

Quite good fun chasing the big bikes.



<iframe width="560" height="315" src="//www.youtube.com/embed/60sUymSTaoA?list=UUzagK2vhzjvKtWJ9cYZRuDA" frameborder="0" allowfullscreen></iframe>

[TZ350]

EGT its still getting interference form somewhere. I will go over the wiring and insulate the lot and also make sure it does not pass to close to plugs etc.

Great Vid Rich.

If your picking up AC or Radio frequency interference try shunting it to earth with a small capacitor.

[richban]

Great Vid Rich.

If your picking up AC or Radio frequency interference try shunting it to earth with a small capacitor.

Sounds worth a try for sure. When I take it of the bike on the dyno and hold it in my hand it is as smooth as silk and dose not go over 1100F.

[peewee]

Hi Peewee, there seems to be as many people who rush to rubbish a new idea without critical thought as embrace it, either way its a "Faith Based" assumption, if their opinion is not based on measured fact.

Humans have two great attributes, Faith and the ability to make Intuitive leaps.

And to make consistent advances, after the intuitive leap the objective needs to be measured empirically, and the real (sometimes difficult) trick can be in devising procedures to measure something in a way that reflects its intended improvement, ie its no good measuring a device that improves quarter to mid throttle response at WOT on a dyno.

In my efforts to find better ways of flowing air through a 24mm carb I found various flow straighteners helped a lot.

The best that was tested for outright bulk flow was this 24mm venturi insert pressed into the back of a 38mm carb. I think it worked by the body of the carb straightening up the air column before it entered the 24mm venturi.

I also found that air flow into the engine actually had to be a problem before I could improve it. As extra flow on the bench did not necessarily mean extra power on the dyno if something else in the system was really the bottleneck.

I inadvertently demonstrated strengthening the strongest link in the chain did not make the chain any stronger.

I had to find the weakest link and that is harder than you think. Because it might not be as obvious (or interesting to fix) as insufficient blowdown STA but as simple as poor fuel atomisation or 101 other seemingly little things.

In the quest for improved performance I think everything is worth a look, I would love to test those flow straighteners.

i agree. everything is worth a look. i didnt see any talk or photos of any winged gadgets around here so i figured maybe you guys had already found them to be useless. $100 is alot of money for a $2 piece of laser cut stainless steel but if it does what it claims then maybe there is a free lunch after all :laugh:

[husaberg]

The wings and the blades etc yes they might even have positive effect...... but is the effect they have on say drivability the result of poor factory jetting etc......... I know not the answer but if the F1 and moto gp and gp bikes don't have them I do wonder why.
I also get suspicious of gains that are not backed up by dyno charts.
I posted a few pics ages ago asking if anyone knew of them or had tested them I go no answers then.
I think the ones I asked were power blade and power wings.

[seattle smitty]

Jan Thiel did all the hard work at Aprilia. Until he retired, I performed thermodynamic and gasdynamic calculations for him, and I also tried to think along with him about various two-stroke developments. I've explained it a bit more extensively in that Pit-Lane link I posted the other day:
http://www.pit-lane.biz/t117p246-gp125-all-that-you-wanted-to-know-on-aprilia-rsa-125-and-more-by-mr-jan-thiel-and-mr-frits-overmars-part-1-locked

If you start reading there, even if you only read the english texts, you'll be occupied for the rest of the year. So Merry Christmas and a Happy New Year :msn-wink:.


Good heavens, Frits, you are handing me my engine on a silver platter! I'd never have asked you for actual port timing, just general questions, figuring it's my place to cut-and-try. Very much appreciated, understanding that it has taken you many years to be able to state such figures with confidence. I'm still shaking my head at your generosity; Merry Christmas indeed!! One way or another, I'll supply photos of the build.

After I asked about your Aprilia connection, I did go to the first link to Pit Lane and read for a while (the English). Thanks for that lead. I also looked up a couple of your countrymen who have continuing Aprilia parts projects. I'm finding that, coming from outboard racing, and that decades ago, my awareness of what's happening in the wider world of 2-strokes has been a lot more restricted and insular than i'd guessed. I knew that GP roadracing was a big deal in Europe, but in my searching (the subject was fuels in this case) I have come on to little in-crowds of guys building custom-chassied, fuel-burning, drag-racing ATVs (quads) and others drag-racing equally wild snowmobiles.

You being a thermodynamics man, I've got some questions I'm dying to ask on that subject, but as I said, I don't want to become a pest here so I'll save that for down the road.

Thanks again!

(EDIT) Two old but serviceable hydroplanes are to be delivered to me in two days. The best boats in our sort of boatracing have been coming from Europe, but in the last couple of years, some American builders have started producing their versions. One of these builders is Mike Schmidt, whom I see has posted to this thread. Mike, along with his sons, is among the very top outboard racers today, many times a winner and national champion in the 250 and 350cc classes. He is an engineer and a very good guy, and if ever my own personal old-age racing program justifies the expense I'll be ordering one of his new-tech hydros.

[TZ350]

... i didnt see any talk or photos of any winged gadgets around here so i figured maybe you guys had already found them to be useless.


The wings and the blades etc yes they might even have positive effect...... but is the effect they have on say drivability the result of poor factory jetting etc......... I know not the answer but if the F1 and moto gp and gp bikes don't have them I do wonder why.

Possibly different riding conditions, and bike setups like you say. The wings might suit Trail and MX more than outright RR with its all or nothing WOT conditions.

[husaberg]

Possibly different riding conditions, and bike setups like you say. The wings might suit Trail and MX more than outright RR with its all or nothing WOT conditions.

I trolled the net found this no idea what it says or means as it bloody blurry as well.
304582

[alfiestewart78]

why not just get a really big aircooled head off say a MZ250 weld up the combustion chamber and machine one that suits your engine. i think you are really going to struggle with the fan thing . I was looking at a fan at work today that would probably do the job but it was 1.1KW 3 phase. Think how big the fan at the dyno is and thats just for short runs.

[TZ350]

Think how big the fan at the dyno is and thats just for short runs.

Yes the dyno fans are big but they need to throw a lot of air some distance. My plan is ducted air and possibly a battery powered leaf blower.

304628

https://www.ryobitools.com/outdoor/products/details/580

Suitable Leaf blowers range from 150 to 300 cubic feet of air per minute.

This is where I am a little unsure but I think 1m3 of air absorbs about the same amount of heat as 1L of water for 1 deg C temperature rise. How many litres of water a minute pass around the cooling system of a Honda RS125? probably not even a 50.

Its all about carrying waste heat away quickly and sure water gets into very small areas around the combustion chamber, we just have to think of clever ways of doing that with air.

One idea is to have a number of 3/8" copper tubes running through the critical parts of the head and blowing cooling air through them. The beauty of this is that the length of warmed copper tube will expose a greater surface area to the cooling air than the head could by itself.

304626

The fan could force feed air through a group of pipes stacked together like this. The pipes could then be routed to where cooling is needed.

[husaberg]

Yes the dyno fans are big but they need to throw a lot of air some distance. My plan is ducted air and possibly a battery powered leaf blower.

Suitable Leaf blowers range from 150m3 to 300m3 of air per minute.

This is where I am a little unsure but I think 1m3 of air absorbs about the same amount of heat as 1L of water for 1 deg C temperature rise. How many litres of water a minute pass around the cooling system of a Honda RS125? probably not even a 50.

Its all about carrying waste heat away quickly and sure water gets into very small areas around the combustion chamber, we just have to think of clever ways of doing that with air.

One idea is to have a number of 3/8" copper tubes running through the critical parts of the head and blowing cooling air through them. The beauty of this is that the length of warmed copper tube will expose a greater surface area to the air than the head by itself.


The fan could force feed air through a group of pipes stacked together like this. The the pipes could then be routed to where cooling is needed.

70 litres per minute rings a bell for the RSA
http://www.pit-lane.biz/t3173p80-gp125-all-that-you-wanted-to-know-on-aprilia-rsa-125-and-more-by-mr-jan-thiel-and-mr-frits-overmars-part-2-locked

Later oh hell no golly

Compare two cooling systems, A and B. In system B the water flows three times as fast and picks up only half the amount of heat per liter, compared to system A.
Then system B removes 50% more heat than system A! And provided your piston clearance is OK, you just cannot have too much cooling. In the Aprilia RSA125 the water pump circulates 160 liter per minute. That is 3 liter per HP per minute!

Nowadays we have a fine solution for avoiding corrosion; it's called plastic. Saves weight too.

I don't know exactly how the NZ dollar is doing, but that sum will probably buy you two of these:
http://www.hvg-engineering.com/index.php?action=article&group_id=10000015&aid=127&lang=NL
160 liters per minute

[TZ350]

.

304627

While looking for info on Honda RS125 cooling systems I found this handy little gem on setting up RS125's and how to get the best out of a small race bike. Also a RAD air chart for setting up carbs.

[TZ350]

70 litres per minute rings a bell for the RSA
http://www.pit-lane.biz/t3173p80-gp125-all-that-you-wanted-to-know-on-aprilia-rsa-125-and-more-by-mr-jan-thiel-and-mr-frits-overmars-part-2-locked

Later oh hell no golly


Aprilia RSA125 the water pump circulates 160 liter per minute. That is 3 liter per HP per minute!

Thanks Husa, thats what I need, a handy rule of thumb to work to.

I am aiming for 40hp so 120m3 a min of air, sounds possible with a leaf blower combined with conventional air cooling. With the leaf blower for the critical areas.

[TZ350]

Specific heat explained:- http://www.iun.edu/~cpanhd/C101webnotes/matter-and-energy/specificheat.html

Turns out that the specific heat of air is a quarter that of water.
So 300+m3 of air is required, well still doeable but getting difficult.... :scratch:

[husaberg]

Specific heat explained:- http://www.iun.edu/~cpanhd/C101webnotes/matter-and-energy/specificheat.html

Turns out that the specific heat of air is a quarter that of water.
So 300+m3 of air is required, well still doeable but getting difficult.... :scratch:

Scooters use engine driven fans and shrouds just saying........ kiss

[Muciek]

Maybe snowmobile fans? They are big and move a lot of air (talking from what I have seen here when I was repairing sleds).

[TZ350]

Scooters use engine driven fans and shrouds just saying........ kiss

Yes and it allows them to get away with quite small fin areas for their power output. Because the power absorbed by a fan goes up by the square of its speed ie double the speed = four times the power required to drive the fan. To keep it simple and the power absorbed to a minimum I prefer the idea of a constant speed electric fan to the variable power drain (and output) of a fan attached to the crank.

[husaberg]

Yes and it allows them to get away with quite small fin areas for their power output. Because the power absorbed by a fan goes up by the square of its speed ie double the speed = four times the power required to drive the fan. To keep it simple and the power absorbed to a minimum I prefer the idea of a constant speed electric fan to the variable power drain (and output) of a fan attached to the crank.

Granted but..... wouldn't the electric power to power the electric fan also need to be generated or carried. I would also propose the engine power loss to drive a engine driven fan would be nullified when compared the power loss caused by thermal overload power losses as it is at present.

Then again I am no physicist...........

[TZ350]

Granted but..... wouldn't the electric power to power the electric fan also need to be generated or carried. I would also propose the engine power loss to drive a engine driven fan would be nullified when compared the power loss caused by thermal overload power losses as it is at present. Then again I am no physicist...........

Struggling to get my head around it to, all this talk about m3 of air required, for instance I don't see 300m3/min of air squeesing through a typical RS125 radiator, do you? Thinking 300m3, I have obviously got something wrong.

The specific heat talks about how much heat is required to raise something 1 deg C, well I guess there must be a reasonable difference between radiator inlet and outlet temp.

So, say the air temperature gets raised 20deg C as it passes through the radiator, then 1m3 of air raised 20 deg C = 20m3 raised 1 deg C.

So when I was thinking 300 m3 of air to do the job, I really only need 30/20 = 1.5m3 of air if its temperature is raised 20 deg as it passes through the cooling system.

Intuitively, we only need the same amount of air that passes through a Honda RS125 radiator to pass through the air cooling system and it will carry away the same amount of waste heat if its discharge temperature has been raised to the same level as it would have been passing through the RS radiator.

The trick is to effectively apply the air cooling to the essential parts like the combustion chamber shell and the underside of the exhaust duct.

[Yow Ling]

Yes the dyno fans are big but they need to throw a lot of air some distance. My plan is ducted air and possibly a battery powered leaf blower.

304628

https://www.ryobitools.com/outdoor/products/details/580

Suitable Leaf blowers range from 150 to 300 cubic feet of air per minute.



energy/specificheat.html[/URL]

Turns out that the specific heat of air is a quarter that of water.
So 300+m3 of air is required, well still doeable but getting difficult.... :scratch:[/QUOTE]


if 300m3 of air is required then 300 x 35(cfm per m3) = 10500 cfm or about 35 300cfm leaf blowers , might be more convenient to run a duct back to the pits

[TZ350]

Granted but..... wouldn't the electric power to power the electric fan also need to be generated.

True but the drain on the motor would be constant as the fan speed would be constant.

I have a small generator, and after the ignition and EFI it has about 5 amps to spare.

[husaberg]

True but the drain on the motor would be constant as the fan speed would be constant.

I have a small generator, and after the ignition and EFI it has about 5 amps to spare.

5 amps drain at 12 volts equal 60 watts which has to be drawn from somewhere.
re the rad, the air does have to flow through it it just has to be exposed to it. Air is pretty abundant.

I found this remember how big a fan is on a bus
http://johnmaherracing.com/tech-talk/how-much-power-to-drive-the-cooling-fan/

flex fan blades also fatten as speed rises....... so as the they flatten the power consumption curve required to drive it lessens.
either way I think I like water

[TZ350]

... if 300m3 of air is required then 300 x 35(cfm per m3) = 10500 cfm or about 35 300cfm leaf blowers , might be more convenient to run a duct back to the pits

Yes you're right, I don't think towing a trailer would be all that easy, so it needs to be a big fan running off three phase power back in the pits. The ducting would not be a problem unless I actually pass someone, which is a bit of an unlikely event on a normal day.

35 leaf blowers!!! clearly something wrong with my initial assumption of the volume of air required. Because that much air does not pass through a Honda RS125 radiator or even a turbocharged Mac trucks radiator.

[TZ350]

5 amps drain at 12 volts equal 60 watts which has to be drawn from somewhere.

True but the power drain on the motor does not increase by the square of engine speed like it would with a crank driven fan.


I found this remember how big a fan is on a bus
http://johnmaherracing.com/tech-talk/how-much-power-to-drive-the-cooling-fan/


Interesting about the bus tests.

An alternative is to use a Turbocharger to blow air through selected ducts in the head and cylinder.

304630

A side benefit of a turbo would be using the waste gate for varying the expansion chambers internal pressure like Frits moving gate.

304629

[wobbly]

Been away testing/racing again and missed a few days on here.
The real world testing I have done with carb inserts is restricted to big VM round slide Mikuni carbs as we are forced to
use in pre82 Classic bike racing.
The company that makes the cheese cutter cross piece to fit in the front of the carb also make a plastic UFO thing that fits into the bottom of the slide.
The huge increase in flow velocity over the pilot circuit from the slide insert required dropping the jet from a 65 down to a 32.5.
All i can say is that with the 38mm round slide Mikuni as fitted to a TZ350, when both of the items are fitted to the carb and the tuning is corrected
the old piston port engine has gained near on 1000 rpm of useable bottom end power and now easily wheelstands the first 3 gears out of every slow corner.
It would never do that previously , and has a night and day effect on throttle response on track.
Again it enabled a 71 year old to kick arse with the young guns whether they were on a TZ or a Pantah, no snake oil - the inserts work.

[husaberg]

True but the power drain on the motor does not increase by the square of engine speed like it would with a crank driven fan.

neither does a well designed cooling fan though either.. look how little the huge I assume vw fan consumes.........

[TZ350]

do any of you guys have experience with these things that go inside the carb bore, either before or after the slide ? is it just rubbish with a splash of snake oil ? The Quad-Flow Torque Wing has vertical and horizontal air flow stabilizers which increase air flow.

Hi Peewee, In the quest for improved performance I think everything is worth a look, I would love to test those flow straighteners.


The real world testing I have done with carb inserts is restricted to big VM round slide Mikuni carbs as we are forced to use in pre82 Classic bike racing.

The company that makes the cheese cutter cross piece to fit in the front of the carb also make a plastic UFO thing that fits into the bottom of the slide.

The huge increase in flow velocity over the pilot circuit from the slide insert required dropping the jet from a 65 down to a 32.5.

All i can say is that with the 38mm round slide Mikuni as fitted to a TZ350, when both of the items are fitted to the carb and the tuning is corrected the old piston port engine has gained near on 1000 rpm of useable bottom end power and now easily wheelstands the first 3 gears out of every slow corner.

It would never do that previously , and has a night and day effect on throttle response on track.
Again it enabled a 71 year old to kick arse with the young guns whether they were on a TZ or a Pantah,

no snake oil - the inserts work.

There you go Peewee ......

[190mech]

I feel a proper cooling duct system would help greatly,Look at the old NACA files,L4I11d and No.1092.These deal with large radial aircraft engines that run very cool at high power settings with careful duct work,,just food for thought....

[peewee]

like husaberg said, why do we not see dividers in the rsa125 inlet track ? perhaps they can work well in engines with inferior intake designs.

[Yow Ling]

like husaberg said, why do we not see dividers in the rsa125 inlet track ? perhaps they can work well in engines with inferior intake designs.

Maybe they work in engines where the riders ride part throttle much of the time, which probably isnt an RSA125, they look like they reduce some of the turbulence caused by the partially opened slide. From what I have read here RSA does not like partial throttle openings and causes it to detonate and run badly

[TZ350]

I feel a proper cooling duct system would help greatly. Look at the old NACA files,L4I11d and No.1092 - food for thought....

Found and downloaded it, thanks.

[wobbly]

The experience with the VM round slides has no relevance whatsoever to a RSA125.
Thats like looking for some similarity in a Nascar tunnel ram to a ITB intake on a MotoGP bike.
Apart from the fact that the tract length differs by a factor of 2 and the RSA has a flat slide with no severe flow disruption at the sides or under the slide cutaway , even loosely comparing
a rotary valve inlet with timings of 140/90 to a piston port with 98/98 timing is an exercise in blind futility.
The RSA has a digital ignition with a shit load of mid advance and a powervalve to boost mid response - the TZ350 has neither , so an exercise in improving the old engines
efficiency is bound to have a dramatic effect in the main area of deficiency for a big carb on a piston port intake, part throttle response - as it is so crap to begin with.

[husaberg]

The experience with the VM round slides has no relevance whatsoever to a RSA125.
Thats like looking for some similarity in a Nascar tunnel ram to a ITB intake on a MotoGP bike.
Apart from the fact that the tract length differs by a factor of 2 and the RSA has a flat slide with no severe flow disruption at the sides or under the slide cutaway , even loosely comparing
a rotary valve inlet with timings of 140/90 to a piston port with 98/98 timing is an exercise in blind futility.
The RSA has a digital ignition with a shit load of mid advance and a powervalve to boost mid response - the TZ350 has neither , so an exercise in improving the old engines
efficiency is bound to have a dramatic effect in the main area of deficiency for a big carb on a piston port intake, part throttle response - as it is so crap to begin with.

Can you post a pic what the ufo filler under the slide looks like Wob?

[Ocean1]

neither does a well designed cooling fan though either.. look how little the huge I assume vw fan consumes.........

VW has an extremely sophisticated method of correcting the exponential power requirements of the fan so that it closely matches just the required air flow for cooling.

The vee belt slips.

[Frits Overmars]

The best boats in our sort of boatracing have been coming from Europe, but in the last couple of years, some American builders have started producing their versions.So apparently have some youngsters in Thailand (where Jan Thiel happens to live nowadays :rolleyes:): http://www.youtube.com/watch?v=ybpdNcMPs8s

[wobbly]

http://www.thunderproducts.com/u_f_o.htm

The marketing bullshit with the parts like UFO and Quad Torque Wing are the products of a very fertile imagination but in the case of the old VM round
slide carb the improvements are repeatable and for sure worth having - where you are forced to use them due to tech regs.
There may be cases where the flow disruption of the stainless X insert may offset any gain in response, but in a TZ350 this isnt a limiting factor.
I thought about this seriously after doing the TZ400 with 40mm HV Lectron flat slides ( period legal in Pre 82 ).
This setup had such superior throttle response on the dyno, when compared to the shitty Bwwraap Bwwraap stumbling against any applied load, of the VMs, even when tuned as well as possible.

[adegnes]

First of all I want to say thanks for all the great info in this thread!
First time posting here, but I've been lurking for a while.
I'm from Norway and I enjoy fiddling with small two strokes.

Currently I'm building 50cc rotary valve single variated engine, and I have a few questions I thought maybe you could help me out with.
This is a shameless thread-jack, so please let me know if I should start a new thread.

Questions:
1. In the attached picture you can see how I cut the transfers and the inlet. I aimed the inlet upwards a bit, my thought was that the incoming charge would kind of jump the crank webs. Should I just remove the "kicker" and aim straight in, and focus more on flow "around" the webs?

2. I'm planning to run on e-85, when building a pipe after Frits' FOS concept, whats a good starting point number for speed of sound? Lower speed than for pump gas I suppose?

Thanks!


304698

[TZ350]

Your questions about the inlet are interesting, I would like to know too.


Currently I'm building 50cc rotary valve single variated engine
304698

Please keep posting pictures and reports as your build progresses.

[Frits Overmars]

I aimed the inlet upwards a bit, my thought was that the incoming charge would kind of jump the crank webs. Should I just remove the "kicker" and aim straight in, and focus more on flow "around" the webs?It's hard to tell from just one picture, but I get the impression that you aimed the inlet upwards more than just a bit.
Put a piston in a cylinder at BDC; then put that cylinder on your crank case and look through the inlet hole. Chances are that the piston is right in the way of the flow path, so you may want to lower that path. Remember that the flow must be able to reach the opposite transfers. If you need a 'kicker' at all, the crank web bevel will do that for you.


I'm planning to run on e-85, when building a pipe after Frits' FOS concept, whats a good starting point number for speed of sound? Lower speed than for pump gas I suppose?I haven't used E85 yet; you could be right. You'll just have to find out by trying.

[husaberg]

http://www.thunderproducts.com/u_f_o.htm

The marketing bullshit with the parts like UFO and Quad Torque Wing are the products of a very fertile imagination but in the case of the old VM round
slide carb the improvements are repeatable and for sure worth having - where you are forced to use them due to tech regs.
There may be cases where the flow disruption of the stainless X insert may offset any gain in response, but in a TZ350 this isnt a limiting factor.
I thought about this seriously after doing the TZ400 with 40mm HV Lectron flat slides ( period legal in Pre 82 ).
This setup had such superior throttle response on the dyno, when compared to the shitty Bwwraap Bwwraap stumbling against any applied load, of the VMs, even when tuned as well as possible.

Looking at that pic made me think of something Cameron wrote that Ev Kanemoto (I think) had been told about the slide cut away on some GP bike by one of the Japanese techs.
it went along the lines of "FFS don't touch that cutaway" it took us 2 months to get just right..........

[adegnes]

Your questions about the inlet are interesting, I would like to know too.

Please keep posting pictures and reports as your build progresses.

Will do, and thanks for the fast reply and warm welcome!



It's hard to tell from just one picture, but I get the impression that you aimed the inlet upwards more than just a bit.
Put a piston in a cylinder at BDC; then put that cylinder on your crank case and look through the inlet hole. Chances are that the piston is right in the way of the flow path, so you may want to lower that path. Remember that the flow must be able to reach the opposite transfers. If you need a 'kicker' at all, the crank web bevel will do that for you.

I haven't used E85 yet; you could be right. You'll just have to find out by trying.

Thanks for your fast reply to! My phone is running out of juice, I'll post when I come home.

[seattle smitty]

About ten pages back, I offered up a "speed secret" (heat-cured moly coating on the inside of rotary valve cases). I did this somewhat tongue-in-cheek, but later thought this might not have been clear and that someone might take the idea too seriously and then be disappointed if they didn't see a tire-shredding power increase (or any power increase). So I went back and edited it.

An old friend of mine, Bob Wartinger, who has been racing outboards with great success since we were both in college in the mid-'60s, has a fine judgement on the supposed "speed secrets" we all simultaneously laugh at and covet. Of the ones that actually work at all, the vast majority come under Bob's category of,

"Well, it can sometimes help a little . . . but it won't make up for a bad start."

[jonny quest]

I had a half hearted attempt at running E85 on a 4 stroke.... it makes power. From what i remember it likes 7:1 instead of 14:1 air to fuel. One peculiar thing about that fuel, even though it made more bottom end power... it wasn't crisp and snappy down low. But again. .. i didn't spend a ton of time getting jetting just right. On a 250cc 4strk single it was 2hp better than 93 pump

[adegnes]

It's hard to tell from just one picture, but I get the impression that you aimed the inlet upwards more than just a bit.
Put a piston in a cylinder at BDC; then put that cylinder on your crank case and look through the inlet hole. Chances are that the piston is right in the way of the flow path, so you may want to lower that path. Remember that the flow must be able to reach the opposite transfers. If you need a 'kicker' at all, the crank web bevel will do that for you.

Yep, more like quite a bit, or a fair bit... And as you have predicted flow is aimed straight at the piston. Out with the kicker.


I haven't used E85 yet; you could be right. You'll just have to find out by trying.

Try I will!

[adegnes]

Forgot the picture...
Is shaping the intake so the valve opens the whole side at once good practice, or should I keep it as is(just mached to how the hole is shaped on the valve cover)
I've never built anything rotary valve before...

304702

[Frits Overmars]

I had a half hearted attempt at running E85 on a 4 stroke....From what i remember it likes 7:1 instead of 14:1 air to fuel. Here are some numbers to help you on your way.
We need 14,7 kg air to burn 1 kg petrol. We call this the stoichiometric ratio. A mixture with this air-fuel ratio is also called "Lambda=1". But for maximum power we make the mixture a bit richer: Lambda=0,86 is best for power. That means: 1 kg petrol for every 12,64 kg of inhaled air.

The stoichiometric ratio for ethanol is 8,4. E85 fuel is 85% ethanol and 15% petrol. Completely burning one kg of the stuff would require 0,85 x 8,4 kg air + 0,15 x 14,7 kg air = 9,345 kg air in total, so its stoiciometric ratio is 9,345.
And since we want power, we go for Lambda=0,86 again, so we feed the engine 1 kg of E85 for every 8,04 kg of inhaled air.
Conclusion: E85 needs 1,57 x the amount of petrol.

[Frits Overmars]

Is shaping the intake so the valve opens the whole side at once good practice, or should I keep it as is(just mached to how the hole is shaped on the valve cover) I've never built anything rotary valve before...I seem to remember that Martijn Stehouwer posted a rotary-building-manual on www.emotracing.nl.

[adegnes]

I seem to remember that Martijn Stehouwer posted a rotary-building-manual on www.emotracing.nl.

Great! Thanks!

[Flettner]

Something odd happens with ethanol, at approx 70 degrees C ( engine temp ) you will need to up the ratio a little, make it richer.
I have had no end of trouble with my air cooled twostroke, carburetored, You will get a few laps in then suddenly the engine goes lean. Or you set the engine up rich and suffer for the first few laps. Thats one of the reasons I run EFI, there is a temp graph for changing the fueling as temp changes. I run E90, you will need a small petrol squirter to start the engine on cold days, ethanol doesn't light up as well as straight petrol. You will use more compression, a high squish head is important also I think.

[seattle smitty]

So apparently have some youngsters in Thailand (where Jan Thiel happens to live nowadays :rolleyes:): http://www.youtube.com/watch?v=ybpdNcMPs8s

I rode on a couple of the Thai klong-boats in 1970, but I don't think they were being formally raced then as they are now. Having the props spinning out at the end of a gimble-mounted eight-foot shaft would certainly put a damper on competing drivers wanting to get close enough to be "trading paint;" it could become a Thai version of "Texas Chainsaw Massacre."

Actually, in the US northwest we have had a similar thing going on for something over fifty years: "Indian war canoes." Back in the days when we were racing fuel-burning crossflow Mercury engines with open megaphone exhaust on hydros and runabouts, members of one of the coastal indian tribes procured some of the two-cylinder, 322cc Mercs, and mounted them on the dugout canoes that they were already building (as a hobby). They modified the canoes by scabbing on a flat area at the back of the boat for planning purposes. Whether the canoes already were flat-bottomed when this experiment began, I don't know. If they started with round-bottom canoes, they would have learned the inadvisability of that on their first test-run. Even with the flat bottom, they are canoes, very long and very narrow, and quite tricky to drive when on-plane. In our local club races, the indian "war" canoes showed up and ran as a special event, and were very popular with everyone. All these years later, the same tribe and maybe other tribes on the Washington State coast, are still racing the canoes, though they haven't come to our outboard races in a long time. Nowdays, instead of the open-pipe Mercurys, they use engines that come from Japanese pari-mutuel outboard racing, which is another zany (but very profitable!!) form of boatracing.

[wobbly]

One thing I learned from playing with the KZ2 and 125 open kart engines is that having a "bend" of any sort in the intake tract
seriously affects power.
Now this relates to reed engines and I suspect that much of the effect is to do with flow bias thru the petals as we have spent countless hours
trying differing petals and backup stiffness to try and find the best flowing combinations.
But now the intakes are dead square to the flow path thru the reeds and no power is to be had with differing petals, but the overall stiffness and backup configuration
is even more critical.

In the CPI Cheetah cylinders, having the reed 5mm offset to one side in the reed box is a loss of around 5Hp, simply due to the asymmetric flow into the transfer tunnel entries.

Many years ago though I built a Rotax 256 with CNC valve covers that angled the carbs upward 10* on the manifolds and from memory
that simple change was worth 3 Hp in mid 70s by simply angling the flow slightly before it hit the chamfered edge of the flywheel.
When working at ZipKarts I tried a back to back test on Hines brand new engines for his SuperKart title shot ,by grinding the inlet port with straight angled sides ( but with quite big top corner radi ).
That made several Hp more, and we kept the idea on the qualifying engine only as the case began to wear quickly.
I figured this was due simply to the increased STA of the port - as the engine made better power with 2mm bigger carbs ( it didnt previously ) but they lost too much mid power to use on track.
Then I wasted 2 weeks trying a huge number of rotary valve leading/trailing edge angles/curves - nothing I did made any better power, but I read a while ago
than Jan made the comment that an angled leading edge helped reduce wear around the port - no mention of any power advantage I am aware of.

[adegnes]

One thing I learned from playing with the KZ2 and 125 open kart engines is that having a "bend" of any sort in the intake tract
seriously affects power.
Now this relates to reed engines and I suspect that much of the effect is to do with flow bias thru the petals as we have spent countless hours
trying differing petals and backup stiffness to try and find the best flowing combinations.
But now the intakes are dead square to the flow path thru the reeds and no power is to be had with differing petals, but the overall stiffness and backup configuration
is even more critical.

In the CPI Cheetah cylinders, having the reed 5mm offset to one side in the reed box is a loss of around 5Hp, simply due to the asymmetric flow into the transfer tunnel entries.

Many years ago though I built a Rotax 256 with CNC valve covers that angled the carbs upward 10* on the manifolds and from memory
that simple change was worth 3 Hp in mid 70s by simply angling the flow slightly before it hit the chamfered edge of the flywheel.

Good info! I'll reduce my intake angle from more than a bit angled to just a tiny bit.

[adegnes]

I seem to remember that Martijn Stehouwer posted a rotary-building-manual on www.emotracing.nl.

Link wont work for me. Tried looking around at a few of the other EMOT sites but no luck...

[Frits Overmars]

Link wont work for me. Tried looking around at a few of the other EMOT sites but no luck...Here's something that will work: http://www.emotracing.com/rotary-inlet-making.html
But I thought that somewhere there was also a written how-to. Can't find it though. Maybe you should write Martijn an email; he is extremely helpful.

[lodgernz]

Link wont work for me. Tried looking around at a few of the other EMOT sites but no luck...

There is a page on converting engines to RV, but it's about EMOT doing it for you, rather than you doing it yourself.
There are some bits you can buy from him though.

[SwePatrick]

I had a half hearted attempt at running E85 on a 4 stroke.... it makes power. From what i remember it likes 7:1 instead of 14:1 air to fuel. One peculiar thing about that fuel, even though it made more bottom end power... it wasn't crisp and snappy down low. But again. .. i didn't spend a ton of time getting jetting just right. On a 250cc 4strk single it was 2hp better than 93 pump

Just about 30% more than petrol is correct. :)

[adegnes]

Heres some pics of this contraption of mine, if anyone's interested.

It's a Peugeot Spx 103, a bit modified.

Stock bike
304725

Naked
304726

With fairing
304727

Previous version of the engine
304734

New engine in progress, went from this:
304735

To this:
304736
In two evenings with a dremel, without the aid of beer, a feat I'm quite proud of.

[adegnes]

More pics of new engine.

304737
304738

Just a mockup, but it will be mounted "upside down" with a straight exhaust.
304739

[husaberg]

There is a page on converting engines to RV, but it's about EMOT doing it for you, rather than you doing it yourself.
There are some bits you can buy from him though.

Roffe site has them listed as well and on one of the threads the euro or britsh 50cc racing ones he details a few conversions.
Including for the MB50/derbi /rotary valve/
he sells the bits as well.
http://www.vrm.se/
like everyone else it seems hes on Facebook as well.........

[adegnes]

Roffe site has them listed as well and on one of the threads the euro or britsh 50cc racing ones he details a few conversions.
Including for the MB50/derbi /rotary valve/
he sells the bits as well.
http://www.vrm.se/
like everyone else it seems hes on Facebook as well.........

I appreciate you all trying to help me out here, but I'm not really looking for info on how to do a conversion, I may have worded myself incorectly. I'm just wondering what to go for; a roundish port or one wider at the top. I marked it in the picture.
304702

[husaberg]

I appreciate you all trying to help me out here, but I'm not really looking for info on how to do a conversion, I may have worded myself incorectly. I'm just wondering what to go for; a roundish port or one wider at the top. I marked in the picture.
304702

I got that don't worry I was just added in the Roffe stuff cause I hope to get commission...lol
Fits or jan I think discussed the shape on pitlane probably part one or part two.

Also this is Jan of FB

"Jan Thiel" If you use the same diameter for the inlet hole as the carburetor you would need a very big disc diameter, so usually the inlet duct is oval. So it is usually a compromise of available room and carburetor diameter, also thinking about friction...........

...........Later the disc diameter was enlarged to 123, later 126, because of the flow loss the 120mm disc caused......

I understand these inlet ports are ok.......:shifty:
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[adegnes]

No problem!
I'll see if I can find it!

[husaberg]

No problem!
I'll see if I can find it!

I have a few crankcase and RSW pics and others here.......
http://www.kiwibiker.co.nz/forums/album.php?albumid=4862

http://www.kiwibiker.co.nz/forums/album.php?albumid=4839

[adegnes]

I have a few crankcase and RSW pics and others here.......
http://www.kiwibiker.co.nz/forums/album.php?albumid=4862

http://www.kiwibiker.co.nz/forums/album.php?albumid=4839

Thanks!
Seems like roundish is the way to go.
Am I right in concluding that with the same timing, even though a port with a wider top will open more of it's area early and keep more area open for longer, the better flow and consistent shape from carb trough the intake of a round one is to prefer?

[adegnes]

Another question:
The bike I'm building is single variated, variator on the crank fixed pulley on a jackshaft with chain drive to the wheel on the opposite side.
The whole engine moves towards the fixed pulley when it variates. The engine mount allows for some axial movement, to keep the pulleys aligned during variation. Now to the question; with the variator doing it's thing, force is applied both axialy and radialy, is floating the crank a bad idea? Both crank bearings are press fit on the crank in stock form.

[Frits Overmars]

The bike I'm building is single variated, variator on the crank fixed pulley on a jackshaft with chain drive to the wheel on the opposite side. The whole engine moves towards the fixed pulley when it variates. The engine mount allows for some axial movement, to keep the pulleys aligned during variation. Now to the question; with the variator doing it's thing, force is applied both axialy and radialy, is floating the crank a bad idea? Both crank bearings are press fit on the crank in stock form.Yes floating the crank, normally desirable, is a bad idea in this case. Or rather, the single variator is a bad idea (it's French, you know...)

[adegnes]

Yes floating the crank, normally desirable, is a bad idea in this case. Or rather, the single variator is a bad idea (it's French, you know...)

Thanks!
Yep, not exactly an ideal solution... But it has one advantage over dual variated - you can easily gain some manual control over it with a foot lever.

[Frits Overmars]

Yep, not exactly an ideal solution... But it has one advantage over dual variated - you can easily gain some manual control over it with a foot lever.It sounds like you're in the market for a real vintage bike; you'll have manual control over mixture strength and ignition advance too.
By the way, doesn't 'manual' mean: by hand? I'd love to see you reach down and adjust the gearing coming out of every corner :devil2:.

[adegnes]

It sounds like you're in the market for a real vintage bike; you'll have manual control over mixture strength and ignition advance too.
By the way, doesn't 'manual' mean: by hand? I'd love to see you reach down and adjust the gearing coming out of every corner :devil2:.

Footual?
Yeah, no it's more like this is what I've got, and I enjoy having fun modifiyng it, most of all the learning part of it.

[adegnes]

Yes floating the crank, normally desirable, is a bad idea in this case. Or rather, the single variator is a bad idea (it's French, you know...)

How about floating just the bearing on the opposite side of the variator, a good compromise, or still bad?

[wobbly]

In many engines floating one side, with a roller or relieving the journal is all that is possible as the drive gear
is held between the bearing and a locknut.
Floating one side allows the crank freedom of movement as the case/bearings heat, up so works fine.

I think that the rotary valve port shape with a wider top and straighter sides is an advantage where the vertical height is limited
by the valve diameter, as it gains area needed to correct the STA.
But rule 1A in any situation is to make the width as narrow as you can,this reduced "port angle " if you like means the valve spends less time
partially covering the port and disrupting flow for the same open/close timings.
Angling the carb will help flow as well by straightening out the duct.

[adegnes]

In many engines floating one side, with a roller or relieving the journal is all that is possible as the drive gear
is held between the bearing and a locknut.
Floating one side allows the crank freedom of movement as the case/bearings heat, up so works fine.

I think that the rotary valve port shape with a wider top and straighter sides is an advantage where the vertical height is limited
by the valve diameter, as it gains area needed to correct the STA.
But rule 1A in any situation is to make the width as narrow as you can,this reduced "port angle " if you like means the valve spends less time
partially covering the port and disrupting flow for the same open/close timings.
Angling the carb will help flow as well by straightening out the duct.

Thanks! I'm maxed out heightwise, so the wider top might be a good idea then.

[AndreasL]

Halfway through the thread for the second time.
So much information at such hi level. Great!

I'm "stuck" with a very old design, 50cc moped engine, (Single exhaust, 2 crap transfers and piston port inlet.), I will have a go at improving it with the information gained here.

So for a start I'm planing to use the rule of thumb of 90% ex port duct, minimal squish clearance, around 190/130 ex/tr etc etc. Trying to keep it simple. It will be difficult enough anyway.

What I have tried to find is some baseline info like the above for how to direct the transfers when only having one per side.

I also would appreciate any thoughts about piston port timing. I have come across all between 140-200* and I guess this is as old as the piston port it self.

I have been able to balance my STA:s in EngMod and get some (to good) results using the "low and wide" rute and pipes based on Frits formulas, but I feel I need some better knowledge/rough guidelines before I continue.

Thanks in advance.

/Andreas

[TZ350]

Page 130 links list to go here ...

Racing at Greymouth

You will have to follow the link back to the original post to find the Video link, well worth a look to see Team GPR in action.


Last of Scott's Greymouth vids. Got the one view only of the third race.


Masterblaster in the wet, and it gets wetter...


Race two. Greymouth, Scott's bike leading the way, almost all the way...


Here's that first race again, this time looking back at a wet Greymouth. Getting wetter as the race goes on!


Greymouth racing 2014. First F4 race looking forward from Scotty's bike.


Pretty amazing times there , you and Dennis would have been in top 5 in P82

GPR engines 1st and 2nd. Good work


http://www.mylaps.com/en/events/1092929


http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=304779&d=1414657825

Quite cool that they sand blast all the road markings (white and yellow lines) pre-event to ensure some grip in case of rain.

BOB ... battle of the Buckets.


This thread needs more good stuff, so untill somebody posts some video, here one we made earlier


https://www.youtube.com/watch?v=6KgogC_sMJc


Video from yesterdays F4 cup, filmed from GPR bike no 11


Anyway here is the first 15min of the BOB , Riding with Mr BucketRacer


http://www.youtube.com/watch?v=N5z5hhIWYFo

[husaberg]

Halfway through the thread for the second time.
So much information at such hi level. Great!

I'm "stuck" with a very old design, 50cc moped engine, (Single exhaust, 2 crap transfers and piston port inlet.), I will have a go at improving it with the information gained here.

So for a start I'm planing to use the rule of thumb of 90% ex port duct, minimal squish clearance, around 190/130 ex/tr etc etc. Trying to keep it simple. It will be difficult enough anyway.

What I have tried to find is some baseline info like the above for how to direct the transfers when only having one per side.

I also would appreciate any thoughts about piston port timing. I have come across all between 140-200* and I guess this is as old as the piston port it self.

I have been able to balance my STA:s in EngMod and get some (to good) results using the "low and wide" rute and pipes based on Frits formulas, but I feel I need some better knowledge/rough guidelines before I continue.

Thanks in advance.

/Andreas

Both Frits and Wob have given out very good pipe designs
Here (Later)
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=303424&d=1413021861

[TZ350]

Heres some pics of this contraption of mine, if anyone's interested.

It's a Peugeot Spx 103, a bit modified. Naked

304726

Previous version of the engine

304734


I like your bike ... :D


New engine in progress, went from this:

304735

To this:

304736

In two evenings with a dremel, without the aid of beer, a feat I'm quite proud of.

I know how hard that is, I had to use a die grinder with carbide bit, took me most of a week to make the fins and cut the transfers out.

304773 304774

12mm alloy base adapter plate to mount the cylinder and under cylinder copper cooling fins.

Ventilated the cases a bit so will bog them up with Devcon F aluminum putty. Std practice on our other motors.

[wobbly]

A pair of transfers is a nightmare.
I did an old 390 aircooled Husky and the only way to get any power at all was to reliner and divide the HUGE transfer pair in two.
And for sure you cannot even think about using Frits or my design styles for what is essentially a lawnmower due to the pipe overscavenging
the transfer system.
This means that at BDC a good diffuser ( read fat ) will create so much negative pressure ratio, most of the uncontrolled transfer streams will do a U turn and exit the cylinder.
When it comes to the piston port, the only approach I can see is to create a port as wide as you want, then use as little timing as is needed to match the STA
to the blowdown and transfer numbers.
These small size pistons can easily go 80% of bore with the Exhaust, so the limiting issue is going to be how much transfer you can create.
My first guess would be 60* back and 30* up, that at least will create some sort of loop effect for you.
Is it possible to get a reed into the inlet, then a boost port can be added and this works well, going all the way back to Kaden et al.

[AndreasL]

Thanks Husa.

I have tried some of that the last couple of days just to get to grips with "what effect what" of the pipe. Not easy and takes a lot of time. But interesting.

I feel that I would like to have the engine modeled a bit better in EngMod before starting to play around more with the pipes. Thus the question about transfers and inlet.

I know its its a interacting process but think I need to do first things first. :)

[AndreasL]

See that Wobbly posted an answer while I was writing the one above.

Thanks Wobbly, that was the kind of information I was looking for. :drinknsin
Will increase my trans angles from ~22° to ~30° and see what happens.

And as you say, trying tapered headers and fat bellys at this low timing and bad scavagening engine has not given the results I first thought it would. Why "slim and shallow" seems better makes more sense now.

For the inlet I have done exactly like you suggest and will continue on that route. Look at the STA:s and follow what the numbers say.
Really glad I got EngMod. Without a decent sim, one is totally lost! Now I'm still loost...but at a higher level. :pinch:

So far i have used Yam12 for the transfers since I have almost no inner radius etc. All other models seems to be "to good" for my engine.

I have actually looked at how to build a case reed. But that is a long way ahead, making inserts and welding the cases etc etc. But can be done relativly easy. Need to get engine number one running first though. :brick:

Realise I might need to clearify my self when I stated " the rule of thumb of 90% ex port duct" in my initial post.
I refered to a exhaust exit duct/header area of 90% of the effective ex cylinder port area. Just to avoid any misconception.

Getting the ex port to 80% of cylinder bore might be tricky with the to close cylinder bolts and lack of material before hitting air. And as you say Wobs, getting enough transfer in to match the exhaust and blowdown capabilities wont happen without a boost port and reed I think.

Sorry if posting to long, I will try to keep it shorter in the future.

[seattle smitty]

Andreas, I hope you don't succeed in keeping it shorter, because I have many dusty boxes of disassembled old, crude, low-tech racing outboard motors from decades ago, with their two big transfers and skinny boost port, much like your engine, and I am here to listen to ways I might upgrade these old beasts as best I can. If I wanted to crack wise, a little, I could say I feel your pain, but in fact I think this kind of thing is a lot of fun. Especially fun when you don't have to guess at everything, but can get some general direction from an old hand like Wobbly.

[AndreasL]

seattle smitty, thanks for the support.

You are spot on except for the big transfers. On mine everything is tiny. :)
But still I might be able/have to get some inner radius in there for a better attached flow.
The transfer enter/exit ratio is also a bit high so this will be improved as well with some epoxy added.

I agree about the fun in playing with old out of date engines, (in)famous for being impossible to get ANY power from. Apply some modern technology and great ideas from the likes of Wobbly and Frits and it will be really interesting to see what results one can get. If I am able to transfer what the theory and simulations say in to practice with good enough quality.

Have to take a closer look at the flying boats you race. Sounds fun and very hard at the body. :)

[F5 Dave]

Which kind of begs the question; with so much to gain & considering the amount of crankcase work you have done; is it possible to carve another transfer behind the primaries? Even a drill hole up with a bore in has to be a better starting point.

Pictures show a Derbi GPR50 head grafted on?

[seattle smitty]

One thing I should have said, Andreas, is that neither of us should ask Frits for advice on this old junk we're fooling with. He has stated that he has no personal interest in thirty year old 2-stroke tech, which you can easily understand. It would be like asking Colin Chapman how to hop up your flathead Ford. Frits directed me to the French "Pit Lane" site, and if you go there and work your way through the archived tech threads (I'll need to do this multiple times, taking copious notes), pretty much everything you need to know is there. When the tech masters like Wobbly offer us a tip or two in our efforts to make a silk purse from a sow's ear, we're lucky, and really shouldn't expect such favors. WE have to figure stuff out.

[TZ350]

So far i have used Yam12 for the transfers since I have almost no inner radius etc. All other models seems to be "to good" for my engine.

Getting enough transfer in to match the exhaust and blowdown capabilities wont happen without a boost port and reed I think.


Yes I found that with EngMod too, and used Yam12. I would have liked a lower performance port simulation that more closely matched the poor port ducts I was working with on the GP cylinder.

304983304982

Using a drill press might be rough, but it was very effective at opening up the rear ports, I highly recommend it.

[Frits Overmars]

neither of us should ask Frits for advice on this old junk we're fooling with.... It would be like asking Colin Chapman how to hop up your flathead Ford.I like the comparison, although I feel much more alive and kickin' than old Colin does nowadays.
Of course I've been asked by classic-racing friends to take a look at their bikes. But it is usually frustrating; there's no material where you need it, you're not allowed to do what you deem necessary, and if you finally happen to generate some more power, the cooling system can't cope with it, so the bike seizes and I get the blame.
So no, thanks.


Using a drill press might be rough, but it was very effective at opening up the rear ports, I highly recommend it.That's the way I attacked my first moped cylinder about a century ago :msn-wink:.

[AndreasL]

One thing I should have said, Andreas, is that neither of us should ask Frits for advice on this old junk we're fooling with. He has stated that he has no personal interest in thirty year old 2-stroke tech, which you can easily understand. It would be like asking Colin Chapman how to hop up your flathead Ford. Frits directed me to the French "Pit Lane" site, and if you go there and work your way through the archived tech threads (I'll need to do this multiple times, taking copious notes), pretty much everything you need to know is there. When the tech masters like Wobbly offer us a tip or two in our efforts to make a silk purse from a sow's ear, we're lucky, and really shouldn't expect such favors. WE have to figure stuff out.

Totally agree smitty and as you say, fully understandable.
Thats why I try to post as general as possible so as many as possible can gain from the knowlage the gurus so kindly share with us. :)
So I'm more then happy that Wobbly gave me some directions to try out as a start and why this might be good. The rest is up to us.

Have read the RSA threads at Pit Lane but hear I need to lurk around some more. Thanks!


I like the compartison, although I feel much more alive and kickin' than old Colin does nowadays.
Of course I've been asked by classic-racing friends to take a look at their bikes. But it is usually frustrating; there's no material where you need it, you're not allowed to do what you deem necessary, and if you finally happen to generate some more power, the cooling system can't cope with it, so the bike seizes and I get the blame.
So no, thanks.

Not half the man in "my disipline of motorsport" compared to you Frits. Still people sometimes asks for advice etc etc. So I think I know what you mean.
No blame on you when I blow my engine. ;)

One small question though if I may... :innocent:
Since I use a "thermally unsound" engine I'm interested in how to approach the stinger/venturi in your baseline pipe calculations.
Fit a waterpump?
Or make the stinger the dimension sugested but without the venturi part?
EngMod tells me that the venturi gives some nice gains, but probably at the cost of the engine. (We have been warned!)
Guess that "Max Unburnt Zone Temp" and "Cylinder Temp" is the ones to look out for when trying different dimensions?
This baseline calcs have been very usfull to get me going so I owe you a couple of truckloads of :drinknsin

TeeZee, yes, something bad enough to feel comfortable its as bad as our own hacks would be nice. LOL

Thanks all for posting!

[Frits Overmars]

Since I use a "thermally unsound" engine I'm interested in how to approach the stinger/venturi in your baseline pipe calculations. Fit a waterpump?Waterpump? From the description of your engine I gathered that it would be cast-iron and aircooled. But if it's watercooled, by all means fit a pump.
And as Wobbly pointed out, match the angle.areas for blowdown and transfer, and do not try to run higher revs than the blowdown is good for, otherwise spent gases entering the transfer ducts will rapidly overheat the cylinder.
Stinger-venturi: I can't give you a size. Just start big and work your way down, carefully watching the temperature. You may ruin a piston anyway, but you will get the experience.


This baseline calcs have been very usfull to get me going! Glad to hear it; that was exactly my intention when I published them. Mission accomplished.

[TZ350]

304983304982

Using a drill press might be rough, but it was very effective at opening up the rear ports, I highly recommend it.


That's the way I attacked my first moped cylinder about a century ago :msn-wink:.

304984

Team ESE bringing you yesterdays technology today ..... :laugh:

[seattle smitty]

Andreas, I have a '73 Yamaha 125 MX cylinder, bought new that year to turn into a racing outboard motor. Since we have a whole lake full of cool water that we can ram (usually not pump) into our engines, we actualy are able to over-cool some engines, as bikers and karters cannot. One of the decisions to make was how to shape the waterjacketing that would surround the cylinder after I milled off the air-cooling fins. You have what's left of an upper and a lower fin to form the outer edges of the waterjacket, which you creat by shaping a piece of 6061 sheet aluminum that wraps around these two stubs of fins, TIG-welded. That's pretty straightforward and obvious. What is less so is the stubs of the in-between fins; when you ran your milling cutter around the cylinder, cutting away the fins, what's left of them are all the same length because of your straight-sided miling cutter. Now, what do you do with these in-between fins? Of course you make notches or holes or whatever to get the water to flow through all of them . . . but do you really want them at all? These mostly milled-off fins still provide a whole lot of surface area in a water-cooled context. My thinking was that they would be TOO effective, given that steady supply of cool water a boatracer has, so I took a grinder and rotary file and removed most of those intermediate fins. I did leave them alone in the area around and above the exhaust port; in fact, on all my outboards I set up the water inlet(s) so as to flow the coolest water over the exhaust port area FIRST to scrub away steam bubbles.

Or I should say, that's the way I USED TO do it; haven't done any of this in decades. But I'm giving it all one more shot.

But if you do decide to convert to a water cooled system, you don't have a lake full of cool water, but a closed system of limited capacity which will get pretty warm. So in your case, you might need plenty of surface area left inside your waterjacketing.

When some of us outboarders were fooling around with this, all with early '70s piston-port or reed induction Yamahas, somebody cast up some water-cooled heads that we all used (though I also made a couple of heads from billet). It was soon found that you could get enough cooling to run the engine hard by cooling either the head alone or the cylinder alone; you didn't have to cool both. My feeling was that the cylinder is where the piston sticks, and the head is where the power is made, so if I'm only cooling one, it will be the cylinder. I could have used my water-cooled cylinder with the factory aircooled head . . . except that we were burning methanol, and felt that to take full advantage of that fuel we wanted a tighter combustion chamber. I started trying to weld up a factory head, but maybe it had a bunch of zinc in the alloy because I made a mess of the job. But again, in YOUR case, I think you'd want to make a water-cooled head AND cylinder, if you go that direction at all.

Compare notes with TZ350, who is experimenting with ducts and baffles for his air-cooled machine. Of course, his is a racer; ducting won't help if you get stuck in a traffic crawl. I still like my idea (pride of authorship?) of welding some fins on the header pipe of the exhaust to add surface area and cool the slug of A/F that is drawn out into the header until it is shoved back into the cylinder with the reflected wave. It was pointed out that this could cost a little power by cooling the exhaust gases. Maybe so, but you can't win a race if you don't finish. I'm thinking that the header needs this minor amount of cooling, while the rest of the pipe, downstream from the header, should be insulated with a ceramic coating. The large-diameter areas of an expansion chamber are surely where the major heat loss occurs.

[Grumph]

Stinger/Venturi size - I can't give you a size guidance either but I can tell you that going down in .5mm increments shows improvement very quickly. It shows on the plug very quickly too. Once judgement shows you may have gone too far - and if you've been lucky/experienced enough to catch it before damage is done...Then very much smaller increments of size come in.
Without a dyno or instrumentation going smaller than the last safe .5mm step is not worth it.

[AndreasL]

Thanks Frits.

Sorry for confuce you with the water.
Its all cast iron and aircoold here.
Thought the correct answer to ALL questions about aircoold engines was "Get it watercoold!" ;)

As for a fixed number for the stinger I understand that cant be given. I will watch my temps trying different venturis.

Realise I need to find some more information regarding how to quantify blowdown (STA?) in relationship to rpm to have a better feeling for when its running out of steam. Probably this can easily be seen in EngMod when knowing what to look for. More to study. Nice! :2thumbsup

[wobbly]

Once you have a well functioning sim of your engine and have run the Turbulent Entrainment model for your combustion Wiebe parameters
the data feedback from TubMax is super accurate.
Getting the advance and stinger dimensions on the money to have this figure sitting on mid 900*C without WARNING - DETO - WILL ROBINSON screaming at you from the screen.
It is good enough to take those numbers direct to the dyno in the knowledge it wil not explode as long as you are watching the instrumentation religiously.
But - there are some very old guidelines that still work remarkably well today.
Take as an example the RG50 T port cylinder I am working on at present.
It has a 75% duct exit area at the flange = 24mm oval area.
Take 0.58 of this diameter and we have 14mm, what is in the sim right now - 13.7mm with 18Hp at the crank.
Thankyou Kevin Cameron.

[peewee]

hey guys i thought maybe this was discussed somewhere before but i dont remember. if you were to make a inline twin with reed block in the front of the case and turn the cylinders backwards, would it be best to have the crankshaft also spin in reverse so the rod and crankwheels are going the same direction as inlet flow or would it make much difference which direction the crank rotates ?

if the top of the crankshaft was shielded (just a slot for the rod), would that make any difference in which direction is best for crankshaft rotation ?

[AndreasL]

Looking through my own notes from 28th of October (Yes, 5 days ago) I find the following recommendation posted by Frits:
"Blowdown: 8.72*mm^2/cc_tot/1000 rpm" :facepalm: <--- Me

But I must have got something wrong here or its just that the numbers are derived from the RSA and therefore not realistic to reach with a old engine?
Or maybe I have misunderstood it all together. Not the first time...

Thanks Wobbly, I really appreciate it.
Have not come to run turbulent yet but hope to get there soon.

EDIT: Sorry all others making post regarding watercooling and stingers. I did miss it somehow.
Watercooling, either the way smitty sugest (I have seen pictures of an old cylinder like mine having this treatment done in the 70:s), or going modern. But dont think this will ever happen due to a lot of reasons.

BUT after visiting a friends house last night and listening to a watercoold Stage6 R/T fitted to his old Zundapp I am tempted for something as brutal. I can only say WOW. 75cc, custom 44mm crank from Roffe (With the Derbi/Honda you know) and a tell tale reading of 15007rpm from the last outing around the block. Super low exhaust duration (167° when run 39mm stroke/85mm rod IIRC) and pulls from ~1rpm. Yes, STA is what counts but still its hard for me to understand how to get the needed blowdown etc with such low timing. A lot of users having hade great result with that one on all kinds of engines. If I had the time I would try to do a sim to see if its realistic or his tacho is reading way off. But nothing for Buckets I guess since its marked "Racing". Sorry for the detour.

[wobbly]

Running the crank backward will loose power in the gears needed to correct the rotation - more I would guess than any created by having
the "correct" flow rotation.
Having the flow running with the flywheel direction of spin is worth power but then so is shielding the intake flow from the wheels
when an "exit slot " is cut to radially direct the little boundary layer movement there is,up under the piston.

[peewee]

Running the crank backward will loose power in the gears needed to correct the rotation - more I would guess than any created by having
the "correct" flow rotation.
Having the flow running with the flywheel direction of spin is worth power but then so is shielding the intake flow from the wheels
when an "exit slot " is cut to radially direct the little boundary layer movement there is,up under the piston.

im not sure what your saying. if the reed blocks were mounted at the front of the cases, cylinders turned backwards, sheilded crankshaft wheels with slot for the rod, then i should be just fine with a standard forward spinning crankshaft ? thnx for the help by the way :niceone:

[F5 Dave]

. . .

BUT after visiting a friends house last night and listening to a watercoold Stage6 R/T fitted to his old Zundapp I am tempted for something as brutal. I can only say WOW. 75cc, custom 44mm crank from Roffe (With the Derbi/Honda you know) and a tell tale reading of 15007rpm from the last outing around the block. Super low exhaust duration (167° when run 39mm stroke/85mm rod IIRC) and pulls from ~1rpm. Yes, STA is what counts but still its hard for me to understand how to get the needed blowdown etc with such low timing. A lot of users having hade great result with that one on all kinds of engines. If I had the time I would try to do a sim to see if its realistic or his tacho is reading way off. . ..
yeah a mate used to claim he saw 17,000. most cheapo ones are crazy at high revs and lose the plot by several thousand rpm.

[AndreasL]

yeah a mate used to claim he saw 17,000. most cheapo ones are crazy at high revs and lose the plot by several thousand rpm.

This was a KOSO one. Popular with the scooterkids but dont know for sure how accurate they are.
15krpm sounds high for this engine even if its full off nice bits. Anyway, it runs great trying to throw its rider of even in 5th gear.

[seattle smitty]

If one of "the many reasons" for not converting your cylinder is that it's cast iron, you could still mill the cooling fins down and braze the sheet steel wrapper to the periphery of the upper and lower fins to complete your water jacket. Actually, you only are milling down probably the top four fins; any fins below that are left alone. The first of those fins you left alone serves as the lower wall of the water jacket. At least, that's how I did it.

And don't paint over your brazed joints; you want to make sure everybody sees these weird homemade mods!! And then when you go for a ride on your scooter, wear a pair of those party glasses with the eyes in them that blink open/closed/open as you nod your head up and down, oh and mount a model airplane propeller on top of your helmet, spinning in the breeze . . . . Scooter riders and recumbent bicycle riders should be natural collegues.

[wobbly]

What you describe is exactly how KZ2 kart engines are laid out.
By reversing the crank rotation in this configuration you will get more power - been there tested that by Mr Thiel.
But to use this layout for a twin in a bike you will need to have an extra gearset, usually arranged as the balance shaft ( KTM250 GP)
between the crank and clutch - goodbye to more than the extra power from crank rotation.

[F5 Dave]

For sure if you are allowed to wc the bike this will make a big step in power consistency and even outright power. Ugly still works. This is my Ally barrel (ignore the torque plates) but I've seen iron ones done. I use a yacht galley pump at present which is absolutely feeble but is so much better than nothing it will stay till other projects are worked on first.

[peewee]

What you describe is exactly how KZ2 kart engines are laid out.
By reversing the crank rotation in this configuration you will get more power - been there tested that by Mr Thiel.
But to use this layout for a twin in a bike you will need to have an extra gearset, usually arranged as the balance shaft ( KTM250 GP)
between the crank and clutch - goodbye to more than the extra power from crank rotation.


so go with a forward spinning crankshaft is what your saying

i got the idea after looking more at the banshee. why not make some new rearranged cases and use proper cylinders. to hell with them straight up cramped transfers :first:

[speedpro]

I watercooled my AC50 cast iron cylinder a long time ago. After I removed all the fins except the very top one it was machined round and then extended by sitting it upside down on fire bricks and building up the top with braze. This was than machined down to match the diameter of the base and a suitable piece of tube brazed on. I had a small radiator made from a piece of Ford TX5 radiator. I had to fully tape it up front and back in the wet to try and get it to warmup. My old sidecar was bought with a watercooled cylinder only. When I tried to sort out the tuning it started destroying pistons. I had the head machined down and waterjacketed and the problems went away.

I watercooled the cylinder on my AC50 for the same reasons you describe - keeping the cylinder cool and dimensionally stable. I think this was a mistake. I should have cooled the head if I was only going to do one part, though ideally both. I thought at the time it would be good to leave the head hot so it didn't absorb heat and lose power. There was a lot of other things not right with that motor so it never really became a problem.

All the heat is generated in the head though it makes it's way to other places, mainly the exhaust. The lower part of the cylinder has transfer ducts so the water never gets near the bore. The upper part is clamped to the head so could dissipate heat into the water in the head.

[Drew]

Running the crank backward will loose power in the gears needed to correct the rotation - more I would guess than any created by having
the "correct" flow rotation.
Having the flow running with the flywheel direction of spin is worth power but then so is shielding the intake flow from the wheels
when an "exit slot " is cut to radially direct the little boundary layer movement there is,up under the piston.Just do what Husaberg (the bike manufacturer) did, turn the motor 180 and flip it upside down. Though, they did it with a four stroke for Christ only knows what reason.

[husaberg]

Just do what Husaberg (the bike manufacturer) did, turn the motor 180 and flip it upside down. Though, they did it with a four stroke for Christ only knows what reason.

Mass centralisation..........The Two stroke doesn't need it though.
I myself install my on own the garage floor, then do nothing with them:innocent:

[Drew]

Mass centralisation..........The Two stroke doesn't need it though.
I myself install my on own the garage floor, then do nothing with them:innocent:Really? Why not just stack the gearbox to get the crank further back?

[seattle smitty]

Dave, you have a really high-volume water jacket there; my notion was to keep the volume small and go for faster-moving water . . .

[husaberg]

Really? Why not just stack the gearbox to get the crank further back?
Plus it looks dambitching...........but that was the reason they gave.........

or was it.


In the following release, Husaberg explains the benefits derived from its new, 2009 engine redesign that lays the cylinder down at a 70 ° angle. Notable among those is the raising, and moving rearward, of the crank rotation to place the principal gyroscopic effect closest to the center of gravity (CG). This should make the bike feel lighter and change direction more easily.
70° CYLINDER ANGLE
A shallow cylinder angle of 70° enables the crankshaft to be repositioned more than 100 mm higher and approx. 160 mm further back, which moves the crankshaft’s rotating masses closer to the motorcycle’s centre of gravity.

In this position, the gyroscopic forces generated by the rotating crankshaft have the lowest possible leverage effect on the bike, which results in exceptionally easy handling for a four-stroke, single-cylinder.

The favourable side-effects of the lifted engine are a reduced overall width and notably improved ground clearance – an enormous advantage in narrow, rocky terrain.
http://www.motorcycledaily.com/wp-content/uploads/2007/11/110907middle.jpg

[Grumph]

I still think someone at husaberg was fooling around with photoshop - and thought "why not".....Then went looking for reasons why.

[husaberg]

I still think someone at husaberg was fooling around with photoshop - and thought "why not".....Then went looking for reasons why.

Took the buggars years to get the kick start on the proper side then they go and get rid of it..........

[Bert]

Plus it looks dambitching...........

http://www.motorcycledaily.com/wp-content/uploads/2007/11/110907middle.jpg


I still think someone at husaberg was fooling around with photoshop - and thought "why not".....Then went looking for reasons why.

It would be interesting to see the FMEA or stress modelling on the internals esp. The gearbox.

[husaberg]

It would be interesting to see the FMEA or stress modelling on the internals esp. The gearbox.

The gearbox and pretty much all the engine is generic KTM, or to be more precise what KTM sell as KTM which was derived from Husaberg in the first place.........
Those who I know who have one say they feel like a 250 to steer, but I understand they feel "funny" in the air......

[Ocean1]

Those who I know who have one say they feel like a 250 to steer, but I understand they feel "funny" in the air......

These feel like a BMX to steer: 305023

Dunno about the air thing though, I'm not allowed to do that shit.

[Frits Overmars]

...I set up the water inlet(s) so as to flow the coolest water over the exhaust port area FIRST to scrub away steam bubbles.That is the main reason for keeping the water jacket fairly tight around the cylinder: you want high coolant flow velocities.
Compare a recent watercooled 50 cc cylinder with for example a classic watercooled Kreidler racing kit; you could keep goldfish in those.


Dave, you have a really high-volume water jacket there; my notion was to keep the volume small and go for faster-moving water . . .Smitty, how did you manage to read my above post before I even posted it?


I still like my idea (pride of authorship?) of welding some fins on the header pipe of the exhaust to add surface area and cool the slug of A/F that is drawn out into the header until it is shoved back into the cylinder with the reflected wave.Sometimes it pays to mince words, if only to help you paint a clearer picture in your mind of what is actually going on.
You don't cool that slug of fresh mixture in the exhaust duct; you just try to prevent it from heating up even more.


I'm thinking that the header needs this minor amount of cooling, while the rest of the pipe, downstream from the header, should be insulated with a ceramic coating.Yes.


The large-diameter areas of an expansion chamber are surely where the major heat loss occurs.No.
In those areas the ratio between cross flow area and pipe wall surface is such that a lesser percentage of the gas even touches the wall. To say it simple: the gas in the middle keeps warm. Also, by the time the gas gets to this large-diameter area, it has expanded a lot, so its density, including its thermal energy density, is lower.
Simple test: Gentlemen, start your engines and keep touching the header, the belly and the end cone. The header wil be the first to hurt your hand, followed by the end cone, and finally the belly.



...a watercoold Stage6 R/T... Super low exhaust duration (167°).That Stage 6 R/T cylinder was designed by a friend of mine and he deliberately kept that exhaust way too low, because, as he said: "Everybody is going to grind it higher anyway. And this way they will have a decent result and praise our Stage 6-stuff instead of first ruining it and then bad-mouthing it".
Try giving it 194° exhaust timing and report back. Then build a longer pipe (or just put a distance piece between cylinder and pipe), so even with the long exhaust timing the maximum power will be developed below 14.000 rpm, and report back again.

[speedpro]

I've checked my MB100 engine and the slug of air clearly makes it about 60mm down the port and just into the flange

[AndreasL]

Good fun to see all this homemade LC cylinders.
To be a bit clearer about "the reasons" not to LC, the main two things is lack of time (I try to be realistic here. Not my strong part normally.) and that it would be nice if it was not to obvious that a lot of things was VERY modified.
Ideas of how to hide/camouflage a radiator on a simple 1957 moped is most appreciated. ;) So in reality its just really bad excuses for not doing it...

Cooling only the head I have seen one guy doing to this specific engine with great success as well. (He made a billet one and runs it thermosiphon)
Thanks for all the good advice. I will have it in mind.

Frits,
You have a really clever frind I hear. I think his analysis of the real world is spot on.
Getting the owner of the bike to take it appart may be a bit hard. Not that hes not capable, but it runs so d**n good I think he vill leave it as is.
A great pitty, but I will tell him what you suggested.
Get a R/T or a 50SX for my old excuse for an engine is out of the question im affraid. 40x40 cylinder studs and every thing tiny tiny...not the best to start with. I will pause the old hat rant now Frits before you :yawn:

305036

[seattle smitty]

Hide the radiator, Andreas? Why?? Wear it with pride!! Or hide it the way it's done on cars, with a grille. Last night I saw a 1958 Edsel; now THERE's a grille for you!!

More seriously, does anyone know of a surface treatment (for Andreas' cylinder and head) that promotes heat dissipation? I think it was in the early Fifties that the Germans found that if they painted their cooling fins silver they had to increase the fin area by nearly 30% to get the same heat dissipation as they had got with black paint (flat black? gloss black? the article didn't say). Is there something better than ordinary high-temp black paint for this?

Meanwhile, Prof. Frits, yes that was very sloppy writing on my part (about "cooling" the slug of air/fuel, and about forgetting the relationship of surface area to volume as volume increases). One of the few useful things you can get out of a Liberal Arts major is the habit of editing your own work. The best profs insist on VERY careful editing, and each and every spelling error, typo, or grammar gaffe after the first one costs you one letter grade on your paper, before they start grading it on content.

(Here's a funny thing; my awareness of the relationship of volume to surface area, and surface cooling, originally came to me from reading about evolutionary zoology, you know, mice with (relatively) lots of surface and elephants with much less).

Has anyone had a ceramic coating applied to the interior of an expansion chamber? Does carbon stick to it and build up, as it does on un-coated pipes?

[Frits Overmars]

Meanwhile, Prof. Frits, yes that was very sloppy writing on my part (about "cooling" the slug of air/fuel, and about forgetting the relationship of surface area to volume as volume increases). One of the few useful things you can get out of a Liberal Arts major is the habit of editing your own work. The best profs insist on VERY careful editing, and each and every spelling error, typo, or grammar gaffe after the first one costs you one letter grade on your paper, before they start grading it on content. I don't care about spelling errors and typos, let alone grammar. After all I'm a Dutchie trying to get by with English here and struggling with German on an other forum.
I merely wanted to point out that formulating correctly will help you think straight.


Has anyone had a ceramic coating applied to the interior of an expansion chamber? Does carbon stick to it and build up, as it does on un-coated pipes?Yep, well, sort of. I've seen pipes getting treated internally with enamel and I'm not sure if that qualifies as ceramic or rather as glass.
I expect that there will be less build-up because the inner surface is smooth and possibly hot enough to burn off the carbon.

[seattle smitty]

Understood, sir! And thinking straight would be a novel experience for me.

Wobbly, I have a question for the pipes ace. A MOTORCYCLE question, for a change:

I hope you will explain this to me, because I have never got a response to this question anywhere else.

In the early Sixties, I was racing a 250cc Konig inline two-cylinder alky-burning outboard. The factory pipes in those days (and I still have them) look laughably crude and ineffective next to the modern-looking fat expansion chambers of several years later (our Seattle-area boatracers' term for expansion chambers in those days was "bounce-pipes"). Anyway, these early-generation chambers had a single-angle, very shallow angle diverging cone, which terminated in a nearly flat baffle (with a long, largish-diameter stinger). There was no parallel section at all. As you can imagine, with that almost flat baffle there was no doubt about where the pipe "came in." Of course, the poor little engine only made about 37hp max, so it didn't exactly jerk the wheel out of your grip.

By 1976, the year my Yamaha RD400C was built, those skinny pipes with their flat baffles were long-gone from racing, . . . but if you looked inside the chrome-plated shell of one of the RD400's factory exhausts, you found a pipe that was just like those ancient racing pipes: a single-angle shallow megaphone capped with a very flat baffle "cone." Yamaha, by 1976, knew a whole lot about pipes. Why did they pick that one (other than the fact that, being real skinny, it wouldn't likely be dragged on the ground much by ordinary riders)?? Was it because they wanted the rider to get a charge out of feeling the pipe come in (the flat baffle), without the power coming on so hard that the front wheel would loop over his head (the shallow diverging cone)?

I never have ridden the bike much, even after upgrading the shocks and other fixes usually applied to RDs. But the chrome shells over the factory pipes look pretty bad, so I thought I might weld up some new and possibly better pipes. I don't want any of the aftermarket pipes, because they are specifically "performance" oriented, whereas I am an old man who mostly just wants to go putt-putt down the road, seeing the sights. An old, garden-variety 4-stroke twin would be far more appropriate for my riding, but I'm a 2-stroke guy for better or worse.

So my notion was to come up with a pipe of the modern style, but a lot less hyper. A two or three-angle diffuser, but shallow angles, so that the center section of the pipe might be an inch and a half smaller in diameter than a pipe you would build for a wild young rider. AND this pipe would have a long, mild-angle baffle cone, one that specifically does NOT come on with a bang. I haven't worked it out on paper, but this pipe might not even have a straight section in the middle.

This is the pipe I would have, in my ignorance, supposed that Yamaha might have selected for the RD. Would you explain to me where my thinking is wrong here?

(P.S.-- Rather than making two pipes of this variety, I'll first try just one, coming out of a short-coupled 2-into-1 header. This has been very common in outboard racing; doesn't cost a whole lot of power, and does save weight that works against you when you throw the boat into a turn).

I am very eager to hear your answer!!!

[wobbly]

I did not know what was inside the Yamaha pipes of that period ( I simply took them off ) but I do know the history and dynamics of the same type of system in karting that was called a "plate pipe ".
This was used in direct drive applications starting early on with chainsaw derived engines, and later with the early versions of Yamaha KT100.
In this scenario what is needed is a wide flat torque band, with very low peak Hp number.
The instant you try to create anything like decent power the air cooled system becomes thermally limited and the engine suddenly power fades and detoes to death.

The shallow diffuser does not create much negative pressure ratio around BDC, thus does not overscavenge the poorly configured transfers.
In the chainsaw engine these were simply drillings in from the side with capping plugs pressed in to cover the holes.
The kart pipes did have a long parallel body that also formed a resonant chamber that suppressed noise ( high frequency ) but at a set point ( variable for differing tracks )
was a flat " reflector " plate.
This distance down the pipe of the plate would be the mean reflection point of a real rear cone setup.
Being a flat plate it did not have the effect that a convergent cone would have - that is a long duration ,low amplitude return wave that by its very nature has a detrimental effect
on power each side of the tuned length rpm, due to that long duration return pulse being incorrectly timed.
At low rpm most of the long return pulse is way too early, at high rpm most of the long pulse is way too late.

A simple flat flat plate returns a very short duration "ping " if you like that has limited effect, even at its tuned length due to its super low duration - and each side of the tuned rpm it has even less effect
than that you would see from a cone.
This system gives exactly what the direct drive kart engine, and the Konig needed to get out of turns at low rpm, but then also the ineffectiveness of the tuned length also allowed the engine
to rev well past its natural peak power rpm.

Lastly you mention a big stinger.
This is exactly the same scenario as we use in very fast jetski engines.
Again, to reduce the effectiveness of the pipes tuned length at low rpm we kill the pipes efficiency by dropping the system pressure with a big stinger.
This again reduces the amplitude of the wrongly timed reverse pulse - and the engine makes more power down low.
As it comes into tune we then dump water into the stinger with a solenoid controlled valve - thus the system pressure gradually rises back to the point where
it would be with a correctly sized bleed off pipe size.
The big stinger in the Konig and the Yamaha, would also reduce the flat plates tuned length effectiveness.

Kart engines later made much more power over an even wider band with a rear cone full of holes, surrounded by the main body or muffler.
When that volume behind the cone resonates with the forcing frequency of the port timing, the holes almost disappear.
This system called a Vevey pipe has an even wider, higher torque band above and below the natural tuned length than a flat plate or a "proper" cone could hope to achieve.
This is due to having 4 parallel systems that can be tuned to have different effects, the TL, the number of bleed holes and their position, plus the tuned volume behind the cone and the diffuser length.

[F5 Dave]

Dave, you have a really high-volume water jacket there; my notion was to keep the volume small and go for faster-moving water . . .

Actually I don't but it looks that way (esp the photo angle). The 'through' studs make the barrel square. The jacket is 10mm at most except around the ex where it is shorter but deeper to make about the same x section.

[seattle smitty]

Dave, the observation you quote from G. Jennings at the bottom of the post applies all too well to my own intuition . . . .

Wobbly, I remember those early kart engines (McCullough, West Bend, Homelite, Power Products), pretty sad designs by later standards, yet as I recall it, karting in this country was never bigger or more enthusiastic than in those days, the early to mid-'60s. One of the small side-benefits for a few of us outboard racers was the work the karters did with Tillotson in getting kits to convert those little pumper carburetors for use with alcohol, and they came up with some imaginative reed block designs as well. Later, as I mentioned elsewhere, when the karters started using more modern looking expansion chambers on their Italian and Japanese engines, some of them had sliding baffle-cones, adjustable in the pits (they couldn't easily slide the entire pipe, as outboarders can).

I understand the part about the shallow diffuser, though I had not related it to the tiny Mac ports, which makes sense. But my RD has far better ports for a pipe to draw through, as you have no doubt proved to many RD-owning customers. You also suggest that one of the constraints on the factory in designing a pipe for a production street bike is that it has to be extremely reliable, and not ever operate anywhere near the onset of detonation. That also makes their choice of that pipe seem more reasonable, as does the reason I thought of, ground clearance.

But I still don't quite grasp the reasoning on the flat baffle. Everything else on the pipe gives a wide, flat powerband, as you'd want (or anyway, as I want) in a street-only bike. But the flat baffle has a narrow effective range. I would have guessed that a long-duration baffle (i.e., a long-taper cone) would go well with a long-duration diffuser. But I'll read your answer a few more times, and maybe I'll see it. I've been reading a ton of info from the Aprilia designers on another site, and there have been a few assertions by them that only made sense to me after I had gone back days later, read them again, and again, and finally had my "Aha" moment of clarity.

Anyway (hoping my description was reasonably clear), what's your reaction to my basic idea for a new, mild pipe for my RD? I'll build in some adjustability of lengths for testing, then finish-weld to whatever configuration seems to work best (or least badly!!). I'll put a somewhat bigger diameter stinger than you'd use for racing, to keep the piston cool. And it will be muffled. I don't know why I didn't finish this thing long ago, because I made the header and cut out and rolled some of the cones. And I did a pipe like this, as single pipe, for another guy with a little RD125 basket case bike. He seemed to like the result, but he had never ridden the bike with the stock pipes, and had even less riding experience than I do, so his opinion didn't carry much weight (his pal did the jetting and retiming for him).

A couple of things on this job: I have to do a little engine work anyway, so I'll get the squish down to about .85mm to avert any detonation. I'll keep the little factory carbs, though I might try using just one, with a 2-into-1 intake, for simplicity and an easy-going wide powerband.

I won't be inviting any other RD owners to look at my alterations; they'd denounce me as a pussy, and have no more to do with me!!

(EDIT) So far, googling gets me nothing on Vevey pipes. I'd like to see a photo or drawing, maybe it's something I can use. Got a link?

[AndreasL]

Smitty, will be interesting to see what you come up with.

I'm in no way an expert (as you already know) but I would try to get a little tighter on the squish.
0.7 can't be a problem with the kind of revs you will be using?
One carb might sound simpler at first and might work perfect for your application.
But doesn't it get a bit complexed in a 2t twin with the intake pulses from one cylinder mess up the jetting? I don't know, that's why I ask. Old 2t cars did run single carb 2/3 cylinder engines when thinking about it. Hmmm

For me I have always looked at one throttle per barrel as a great plus. But nothing more then car related 4 strokes to base that opinion on.

[seattle smitty]

Google "konig 4-cylinder," the Images section, and see no end of weird configurations. Dieter Konig built engines both for outboard and sidecar racing. He also built some motors for ultralight aircraft, eventually was killed in one.

[wobbly]

The problem with a long slow angle rear cone is that it returns a pulse ( though of low amplitude ) over a very wide band.
Thus in effect it "affects " the engine even more when well outside the tuning range of the mean reflection point than a shorter steeper design.
Taking this concept to the extreme, a flat plate "works" over a super narrow range ( and even then its not that effective due to the super short duration period )
and does virtually nothing outside the TL rpm.
Here is a pic of a "Vevey" type pipe as modelled in EngMod, and this system works supremely well in exactly the scenario you are looking at.
I made several for Yamaha fan cooled engines used in small aircraft, with a 2:1 header - tuned to just 6000 rpm.
They need a very wide torque curve to enable them to spool the prop up, and then overev when needed.
A very similar end use to pushing a prop thru water, and having trouble reaching planing speed.
Also a pic of the drone pipe as I called it - with a nice stainless racebike pipe for comparison.

[F5 Dave]

Google "konig 4-cylinder," the Images section, and see no end of weird configurations. Dieter Konig built engines both for outboard and sidecar racing. He also built some motors for ultralight aircraft, eventually was killed in one.

Google Kim Newcomb; an employee at Konig who put one in a GP bike. . eventually was killed on one.

ps you'll doubtlessly have to machine the chamber as it will be too small when squish correct. 2-1 carb will have a long manifold. Some kits exist for Banshees but diff to early RD & why?

[AndreasL]

1kg of red Vinamold arrived today. Will last for every possible duct I will ever want to mould.
Will be interesting to see how bad especially the transfers are.

[wobbly]

The RD stud pattern went back to first R5 twin and was used on all subsequent RD versions - ending in the 400 that had an identical case but bigger flywheel diameter
to take the 62 stroke..
The Banshee is based on the RZ - stud pattern is completely different.
The RD400 stock head has super low compression, dropping the squish to even 0.7 will still be safe as houses on unleaded, trouble is the squish angle is
all wrong so this needs to be corrected as well to do it properly.

[husaberg]

(EDIT) So far, googling gets me nothing on Vevey pipes. I'd like to see a photo or drawing, maybe it's something I can use. Got a link?

They get a mention in the bellbook can't remember what though.....

[peewee]

1kg of red Vinamold arrived today. Will last for every possible duct I will ever want to mould.
Will be interesting to see how bad especially the transfers are.

hey i just ordered some also. hope to see it by friday. 2kg but maybe i only needed 1kg. oh well i guess ill have plenty of extra if i need it :headbang:

since i never used vinamold before, what type of oil or grease do you apply to the duct wall so the vinamold can be removed easily ?

[seattle smitty]

The problem with a long slow angle rear cone is that it returns a pulse ( though of low amplitude ) over a very wide band..

Okay. And that would seem to match the effect of the long, skinny, low-angle diffuser cone. Both ends of the pipe have a long duration, low amplitude effect. Which would seem like the right thing for a very broad range, moderate power street motor. Why have one end of the pipe with a mild effect, and the other end with an on-off switch effect?

Wobbly, have you ever encountered anyone who wanted a "mild" RD, for commuting and just tooling around? I never have seen this idea offered up anywhere. Everybody else wants a rocket.

About the Vevey pipe: Was Vevey a brand name, a pipe manufacturer, or just the name of the person who came up with a baffle cone with lots of holes? It's hard to tell from googling (and BTW, Bell referred to it, but had no pix or drawings). More important to me, since you say it's a good deal for my purposes, are there any guidelines to making one? Your drawing appears to be of a rather short, somewhat steep-angle cone, with (my guess) 12mm holes all over the aft 2/3 of the cone. It looks like a good thing from the standpoint of noise reduction even before one comes up with a silencer.


Dave, I knew about the motorcycles, and omitted mention of them because there were few, whereas Konigs were used in sidecars for a long time, as I understand. Another German bike racer, Helmut Fath, built his own engine with a similar layout, and had some good runs. After Konig was killed, all the racing parts and tooling were bought by someone in the Czech Republic, and new and (I hear) improved versions of the 500 and 700cc fours are being sold under the name Konny.

[seattle smitty]

Question for anybody, have you seen a good discussion of the property of "over-rev" in the power curve as applied to 2-stroke engine and pipe design for motorcycle applications? In my ignorance (you know, dumb welder with useless liberal arts degree:violin::violin:), my notion is that this is NOT a useful property for racing outboard motors. My assumption is that one picks a prop that loads the engine to stay at the power peak. If the boat takes a bounce and the prop comes out of the water, I don't want the engine winding to the moon, I want a rev-limiter, or an engine and pipe with a rev-limiting effect, a relatively long power curve (because I have no transmission), BUT one that drops like a rock after passing peak power rpm . . . .

Well, don't I ?????

Where has over-rev been talked about at length? I want to know (I think)(??) how to "design it OUT." In other words, IF I do not need this particular property, maybe I can make design tweaks to improve other characteristics of the engine/pipe combo slightly, at the expense of a property that bikers need but my outboards don't.

(EDIT-EDIT-EDIT) WHOA, there, Wobbly, you've been holding out on me!! I just got to page 350 of this mega-thread and see that you have done pipe work for Rossi/GRM engines. For the factory, for somebody in Europe, for somebody Here??? Anyway, talk to me!!

[chrisc]

(EDIT-EDIT-EDIT) WHOA, there, Wobbly, you've been holding out on me!! I just got to page 350 of this mega-thread and see that you have done pipe work for Rossi/GRM engines. For the factory, for somebody in Europe, for somebody Here??? Anyway, talk to me!!

Welcome to the ESE thread :corn:

[dark art]

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Okay. And that would seem to match the effect of the long, skinny, low-angle diffuser cone. Both ends of the pipe have a long duration, low amplitude effect. Which would seem like the right thing for a very broad range, moderate power street motor. Why have one end of the pipe with a mild effect, and the other end with an on-off switch effect?

From my experience, rather low for instance, a pipe with good ressonance will produce high torque figures at the ressonant speed. As Wobbly as described in over-rev and low rpm will be inferior to one pipe not so ressonant. The more ported the cylinder is, the higher the initial pulse from exhaust port down to the pipe and the more ressonant the system becomes. But the higher the dips in torque be as well.

The ressonant speed may be low rpm or high rpm for good power peak. Even inside the "powerband", or "in-the-pipe" you can move the torque peak around. If eventually the torque peak is right after the "pipe-hit" you get a hard hit followed by loads of over-rev and little power. For me this is a engine that is not a pleasure to drive, either more in high cc bikes, due the hard hitting power-band. But it sures lift the front weel easy...
That is what very shallow diffuser angles tend to do...

Now, if you eventually design a pipe that kills ressonace deliberately, the torque peak is not so high, but anywhere from 0 rpm to the peak the torque area will be superior. If the engine allow correct breathing, even in over-rev will have more power... Actually I´ve saw systems like Wobbly described, the vevey system, to get more peak power than a poorly designed, true ressonant, system. Usually there is a very flat, predicatable and wide torque curve. Is usually more easy to get the carburation right as well, without any flat spots.

Does the flat plate in the pipe has some big bleed holes? If yes, the flat plate becames a natural "ressonance killer".

Does that make any sense?