ESE's works engine tuner

[jonny quest]

Very clever detective work TZ350 ;)

[TZ350]

very clever detective work tz350 ;)

:) .......

[wobbly]

Simply lifting the cylinder to get 115 on the transfers and 192 on the Ex means you will have shit loads of STA on both, but the thing will then be severely blowdown limited.
It may in fact make better power than what you have now - but such a STA mismatch will always mean narrowing of the useable power and probably even
more issues with big torque holes.
115 is what you would run on a full noise road racing setup, 192 is what a much lower power hot road bike might need - so the resulting power will always be compromised by the missing blowdown
that matches neither the transfers nor the Ex STA.
Just coz its easy dont mean its right - it aint.

[Grumph]

296833

Something I have just seen on the net. Valves dimpled on the head like a golf ball for better air flow over there surface, so clever I don't know why it had not been done before.

Well....I don't know....If it is that good why is the exhaust valve dimpled more than the inlet ? I look at where the dimples are on the inlet and wonder about turbulence at low lift...and how it may limit flow. I suspect the weight saving may be of more benefit then anything else.

Back to 2 strokes please.

[FastFred]

Just coz its easy dont mean its right - it aint.

You are sort of right but there is not enough information to make quick judgments as one would need to know the exhaust port shape/area to know the actual blowdown STA.

I am picking that they have half a clue about what they are doing and possibly think there was excessive blowdown with the standard setup and that by raising the barrel and RPM ceiling that what was excessive blowdown STA at lower rpm is suitably adequate for the higher rpm they are aiming for. So it could be they are tuning for the blowdown area they already have. And yes the spacer plate is easy but it also makes things easily reversible, so easy could be good if they are wrong.

Anyway I am sure there will be a dyno graph in due course.

[F5 Dave]

Well....I don't know....If it is that good why is the exhaust valve dimpled more than the inlet ? I look at where the dimples are on the inlet and wonder about turbulence at low lift...and how it may limit flow. I suspect the weight saving may be of more benefit then anything else.

Back to 2 strokes please.

Yeah I'd file that along with Rifled Banshee comustion chambers (can't find a pic & too lazy to search for more than 30sec).

[husaberg]

me i'm still trying to get my head around this...........
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=289240&stc=1&thumb=1&d=1383254774

Jess ...................

[Drew]

me i'm still trying to get my head around this...........
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=289240&stc=1&thumb=1&d=1383254774

Jess ...................

That makes sense to me. Once I figured out what 'squish' was, were I in to fucking about with 2 strokes I'd maybe even have given it a go.

[Grumph]

[QUOTE=Drew;That makes sense to me. Once I figured out what 'squish' was, were I in to fucking about with 2 strokes I'd maybe even have given it a go.[/QUOTE]

Do you really want to squirt wet mixture at the plug ? refer wobs post a few back about unburned mixture left in crevices and the probs it causes.

[Drew]

Do you really want to squirt wet mixture at the plug ? refer wobs post a few back about unburned mixture left in crevices and the probs it causes.

I wouldn't think it through that far. My mind would get stuck at 'turbulence' and the possibility of more.

[Frits Overmars]

296833Valves dimpled on the head like a golf ball for better air flowNo doubt the dimpling will do what it's supposed to do: promote cash flow :devil2: .

[jonny quest]

That's a pretty bold statement without having tried them yourself Frits. But again, this is not a 4 stroke thread, so I'm not going to get into a pissing match with anyone over this.

[Grumph]

That's a pretty bold statement without having tried them yourself Frits. But again, this is not a 4 stroke thread, so I'm not going to get into a pissing match with anyone over this.

Jonny - i see you've only eleven posts, so maybe you haven't worked out that on KB pissing matches are normal - and even encouraged....

By all means start another thread on this subject and let's be at it.....i've never tried dimpled valves either but my 4 stroke experience is at least as long as Frits 2 stroke experience - and i wouldn't give them house room.

[Frits Overmars]

That's a pretty bold statement without having tried them yourself Frits.It's pretty bold to state that I haven't tried dimples Jonny. How would you know?:p

[wobbly]

If you can make the assumption that "they " have 1/2 a clue about what they are doing, then I can also make the assumption the original manufacturer
also had 1/2 a clue as well.
If so then the original timings of 90* and 121* by their very nature would produce a small ( though not necessarily correctly matched ) blowdown STA.
Then by simply lifting the cylinder , the transfers suddenly become suitable for a full noise road racing setup,but that small blowdown number remains relatively the same.

Its very similar thinking to lengthening and shortening a pipe by chopping or sleeving the header.
Sure the tuned length is being affected, and the engine may in fact respond to this change favourably, but if you fail to realise that having a header say 28% or 36%
of the tuned length will invariably produce huge holes in the torque curve - due to the incorrect positioning of the diffuser - then that for sure indicates only 1/2 a clue is present
and the result is exactly as deserved.

[wobbly]

To prove my point about the pipes, here is a dyno graph of a pipe designed using TSR for a 490 Banshee.
The rpm was some 1500 down , so of course they cut the header, oh dear even less power.
I redesigned the pipe ( with exactly the same length as the shortened version ) and it suddenly seems to work a little better.
Amazing eh.

[wobbly]

Golf balls with dimples fly further due to the fact they create turbulent flow in the boundary layer.
This turbulence close to the surface pulls the laminar flow in the direction of travel into a smaller area behind the ball in flight, thus reducing the overall drag.
Simply dimpling a valve will for sure create the disturbed flow conditions on the surface, but a valve isnt round, so the effect of reducing the disturbed area
behind the valve head doesnt exist - no free lunch.
If this did actually work then you can be sure all the Nascar and V8 Supercars and F1 valves would have this simple mod - sorry they dont.
Same as grooving the squish band, an Indian guy patented the idea years ago, and if it was so damn good then any one of the big manufacturers would have bought the rights.
Yamaha paid a fortune to the sly old fox Dr Erlich for his patented offset combustion chamber, they used it once in the TZ 250 G model, and as we know all that did was deto its tits off
due to insane MSV on one side and none on the other - no free lunch again.

[jonny quest]

Who said a Nascar team isn't running them... and a few factory MX teams. .. and a factory US Super bike team?

Highest velocity point is at low lift. SATOP did some computer modeling. ..honestly I don't know if it's a true laminar situation, or fuel atomization scenario. In a 250cc MX bike typically .3-.4 HP gain. I'll take that any day.

[husaberg]

Sounds a bit ranti tanti so your point is exactly.

I think what he is trying to say is take a holistic approach to what you are doing.
For instance if you run your changes in a sim, but use the header shorten by 25mm and then do the same sim, but shorten the mid section by 25mm. pipe length the same, Yet results different.........

As for the valves Jonny mmm................I will sit on the Fence but i do note...
I see they are Ti.......so likely lighter, seem to have a different shape than std ( Frits would appreciate their shape :shifty:)......... and might even rock up the comp a bit too..(underneath) they might have a new set of seats to go with them, and then sit a little more proud too? plus have a better seat than those which they replaced............
Were the dyno results carried out with the same valves pre and post dimpling?
pipes very pretty though......

One other bit that maybe Frits won't even know is the odd set ups Nascar have to bend arround their rules, which result in engines with rather odd quirks, Huge comp (like 18;1) and tiny ports with 100mm bores turbulent heads with extreme intake velocity........(like the speed of sound)

[jonny quest]

Yes, A B A B testing numerous times.

I've never had luck shortening a header after a good length was found. .. like Wobbly has said, 31-33%. Always error on long side.

The end of diffuser has shown to always be the biggest influence on power for me. 1/8" long or short would always make or break a pipe for me. That was always more influential than anything. If you had a pipe that worked pretty well. .. but wanted a bit more rev.... take length from mid section.

If you wanted to lengthen pipe adding to header usually worked well for a quick first attempt. But shortening it at header...almost always hurt to many other variables if it was in the ballpark

[2T Institute]

296833

Something I have just seen on the net. Valves dimpled on the head like a golf ball for better air flow over there surface, so clever I don't know why it had not been done before.

Looks like your a victim of a bit of ASTROTURFING via a trail of bread crumbs from the Williams MotoWerx website :scooter:

http://en.wikipedia.org/wiki/Astroturfing

[wobbly]

Well im involved in building a full house classic Triumph engine for a customer ( though I hate compressors with a passion ) and have been discussing valve/port geometry with several friends who build engines
at Hendrick ( Nascar Chevy ) Roush ( Nascar Ford ) Yamaha MotoGP and Mecedes F1 so I know none of the TOP engines in those fields have valve dimples.
It for sure would seem that the idea could do " something " but the golf ball analogy doesnt cut it - so if it really does make power in a true back to back,then
some other effect is in play.

The point I was making about cutting or sleeving headers to do a dyno test, is that simply doing that and trying to analyse the results is completely pointless
if you havnt measured the pipes beforehand to see what the original design intent was.
If the header is short to start with, and you then shorten it more, the tuned length may be perfect, but the negative effect from the now silly short header length
will overpower any of the good effects of the overall length.
Conversely if the header was short and you lengthened it, the power increase may be mainly due to now having a " correct " % of header - though the pipe length may be completely wrong for the port timing.
Im just trying to help those with as you say " 1/2 a clue " get a bit closer to the full clue - and if I dont help with this then who the hell is.

[FastFred]

Your explanation makes sense of Fixers dyno graphs. It will be interesting to see a post from TZ with a new (after modification) dyno graph explaining their reasoning for the cylinder plate approach. But it may be a bit of a wait as I hear they have had a woopsie with the dyno computer and need a replacement copy of the Dynojet software so they can commission a replacement computer.

[F5 Dave]

. .
Im just trying to help those with as you say " 1/2 a clue " get a bit closer to the full clue - and if I dont help with this then who the hell is.
Not Santa Claus, - he’s a Rotary partisan

yeah we appreciate it Wob.

[jasonu]

Who said a Nascar team isn't running them... and a few factory MX teams. .. and a factory US Super bike team?
.

But are they the WINNING teams???

[Grumph]

Well im involved in building a full house classic Triumph engine for a customer ( though I hate compressors with a passion ) and have been discussing valve/port geometry with several friends who build engines
at Hendrick ( Nascar Chevy ) Roush ( Nascar Ford ) Yamaha MotoGP and Mecedes F1 so I know none of the TOP engines in those fields have valve dimples.
It for sure would seem that the idea could do " something " but the golf ball analogy doesnt cut it - so if it really does make power in a true back to back,then
some other effect is in play.


You have my sympathy Wob....been there with triumphs.....they're very sensitive to the shape of the back of the valve, in case you hadn't heard. Also don't forget to tell the customer that, even though you've installed the best available valves and guides - and he's paid for them - they will require replacement in quite a short time. In NZ with limited racing, probably two seasons....

[wobbly]

Yea I got 6mm stem titanium Kibblewhite valves with beehive springs ( minus dimples sadly ) and the other Banman will be doing cams/seats for me , but i expect very little -
so disappointment is minimised.
Just amazed that everywhere I go I get such a litany of negativism to my " modern " approach.
Why do you want a 90* crank, why do you want a Nicasil bore, why do you want Methanol, why do you need DLC thin wall small ends,what do you want special Carrillo long rods for and of course
why the hell do you need 500 thou lift on the inlet - the fact no one else has done it, just means they dont know shit about discharge coefficients and the complete
normality of pulling valves 30 % of their diameter off the seat.
All the reasons, as I have explained in blunt detail to all these wankers, is they are completely the reason British motorcycle industry is firmly down the dunny.

[F5 Dave]

Ah c'mon. . .Bit of time on the drill press we'll have those dimpled for you. Hell we'll even dimple the valve springs just to help out.

[Grumph]

Yea I got 6mm stem titanium Kibblewhite valves with beehive springs ( minus dimples sadly ) and the other Banman will be doing cams/seats for me , but i expect very little -
so disappointment is minimised.
Just amazed that everywhere I go I get such a litany of negativism to my " modern " approach.
Why do you want a 90* crank, why do you want a Nicasil bore, why do you want Methanol, why do you need DLC thin wall small ends,what do you want special Carrillo long rods for and of course
why the hell do you need 500 thou lift on the inlet - the fact no one else has done it, just means they dont know shit about discharge coefficients and the complete
normality of pulling valves 30 % of their diameter off the seat.
All the reasons, as I have explained in blunt detail to all these wankers, is they are completely the reason British motorcycle industry is firmly down the dunny.

How the hell do you get .500 lift without reducing flywheel dia for cam clearance - or changing the rocker geometry ? While both are possible, and i don't doubt that much lift would work, the rocker geometry is such that valve and guide life will be short...even shorter than usual.
Built a 6T road motor for my brother years back with aftermarket long alloy rods. 680cc single carb,late bonnie lobe center figures - and on vintage club runs it would shut down any other Triumphs - even 750's.
it's questions like this that make the weslake heads so attractive. i'm looking forward to seeing it run though.

[wobbly]

The 90* crank has a much smaller - lighter - flywheel ( made by EdG in Canada ) so cam crunch isnt an issue.
Using a T120 ally cylinder means the block height is short for a T140 - 830cc , and then some idiot put long rods in as well, so the cylinder has to
be sat on a plate even with extra material left on the CNC machined case deck.
The cams have been welded ( for the 90* offset ) and rough ground to .550" for clearance checking, and the brass tappet blocks have been moved up
and modified to suit - I spent alot of time trying to invent roller followers for it, but simply not enough room.
The rocker ratio has been changed ( in a mockup ) but that may not be needed once Kelford Kevin nails down the LCA and thus tdc overlap needed from
the flowbench numbers.

[wobbly]

I can hear the snickers now of the detractors when it turns up with a two into one + three step headers + anti reversion cans off
the FF1600 like I did for Evans.

[F5 Dave]

And Jonny, just so not to seem rude, we do poke some jest around here, but we're always keen to hear other ideas. It broadens our experience base with other more experienced members expanding our knowledge.

but you can keep your steenking tappets and cams and other bedevilry:oi-grr:

[Frits Overmars]

Why do you want a 90* crank, why do you want a Nicasil bore, why do you want Methanol?Why indeed? The Bonneville I once borrowed backfired and burned quite happily on regular fuel :rolleyes:

[kel]

Using Kels laptop to write this. We are down at the Taupo Car Clubs meet for classic cars, drift cars, racing trucks side cars and Hyosung bikes. Only four Hyosungs and four Buckets in the RR clase though. Kels bike is running great and he has placed first in each race so far after having to start of the back of the grid because he forgot to run a transponder in qualifying. Great weather lots of people, carpark full of very interesting stuff like the twin turbo monster Detroit two stroke Diesel truck engine, phenomenal noise when its in full flight. TeeZee.

[Grumph]

Why indeed? The Bonneville I once borrowed backfired and burned quite happily on regular fuel :rolleyes:

yeah, but there's no fun in being able to see the flames,Frits....Methanol fires come as a nice surprise when you can't see them...

[wobbly]

Aircooled motors simply love the huge latent heat of Methanol, the performance on Jungle Juice can approach that of a water cooled setup
with little or no heat soak power loss.
And as I have chosen the highest com pistons available for a 650, plus Nascar type gapless rings, I end up with near 15:1 compression at 830cc - needing twin plugs
to combat the completely shit chamber shape.
But then, using a 4 channel Ignitech and no dumb waste spark I get to dump a shit load of ignition power into the rich mixtures.
ENOUGH of this 4 stroke bullshit.

[koba]

ENOUGH of this 4 stroke bullshit.

Still interested to see how that one goes.

But yes, back to proper engines; I got mine running on the Ignitech today, hopefully in time for the 2 day Kaitoke Club Champs next weekend.
At this stage I'm on battery power, it's cool that I can get it running on a battery while I work out the alternator circuit.

As much as I've consistently stated that I HATE the idea of running total loss I'm becoming tempted to see how it runs with just a plate to trigger the pulse coil, that's loosing a lot (possibly too much?) flywheel mass.

Still have to find time to get the head off and tidied up this week.
At Roy's Hill I had clipped the head because it wasn't centred correctly, I've since changed it to a lapped spigot fit and also shaved a wee bit off the top to get the port timing right for the pipe, annoyingly I did this in a rush and after I'd taken it out of the lathe I noticed I'd left a ridge in it, too much to carefully take off by hand.

[TZ350]

... But yes, back to proper engines;

297018 297019

If we are talking 2-strokes, here is a real mans 2T inter cooled 40 psi roots supercharger feed by twin turbos and yes this 2T has poppet valves. The intercooler, fuel system, engine and transmission including the diff all had there own fan cooled radiators.

297020

[peewee]

for the 2t tuners. if you have a engine your not familiar with what method would you use to establish decent port timings ? would 192/130 (original is 180/124) be good place to start or keep transfers alittle lower ? its T style exh

[F5 Dave]

You first have to do some soul searching before you ask any questions.

What's its intended porpoise?
What revs do you think the piston & rings will survive?
same for crank?
What sort of spread and what peak power revs?
How often do you want to/afford rebuilding it?

[peewee]

You first have to do some soul searching before you ask any questions.

What's its intended porpoise?
What revs do you think the piston & rings will survive?
same for crank?
What sort of spread and what peak power revs?
How often do you want to/afford rebuilding it?




thnx for response. intended purpose is max power. rebuilding more often than normal is no problem

[wobbly]

The only way to establish the port timings is to use the STA numbers generated in a CAD program of some sort.
But as I explained before, running the transfers up at 130* would in most cases indicate you are looking to make 50Hp and go to 14,000
in a 125 cylinder with plenty of port width.
In that case 192 is a wild mismatch, no matter what the Ex geometry is, as the Blowdown STA will be tiny in comparison to the transfers ability.
This would mean far too low port velocity in the transfer ducts,where the port then looses coherence of the scavenging streams, and short circuiting kills the power dead - especially
if you somehow manage to get a well designed pipe that will suck like hell around BDC.
Then,not to mention we are fighting the huge residual pressure sitting above the transfers as they open - killing even more the flow velocity, due to the restricted Blowdown STA.

[peewee]

i hear what your sayin. if im starting at 180/124 should i just widen the trans as much as i can, raise exh alittle and widen it then test and see what happens ?

i do have engmod2t but its a bugger puttin in all the info. plus i havent used it enough to decipher the output info

[jasonu]

i hear what your sayin. if im starting at 180/124 should i just widen the trans as much as i can, raise exh alittle and widen it then test and see what happens ?

i do have engmod2t but its a bugger puttin in all the info. plus i havent used it enough to decipher the output info

How about just give it a go. Start conservative and experiment from there. Try not to make too many changes at one time as you will never know what made your project better (or worse). Right or wrong I used to stick to one change at a time.

[wobbly]

In EngMod all you gotta do is enter the basic engine bore/stroke etc and then the Ex and transfer data, and the front page gives you the STA info.
Tells you in a few minutes all the answers you will ever need.

[TZ350]

http://www.kiwibiker.co.nz/forums/showthread.php/153656-Chris-Bucket-photo-thread-Bandwidth-warning/page18

297035 Taupo ... Kel was fastest in qualifying and won the next 5 races but towards the end was having to cope with a slipping clutch and needed to nurse the engine by running around with as little throttle as possible. In the sixth race and on the second to last corner before the flag and another win the bike sized and dumped him.

From Frits and Wobs explanations of our experience with the old Beast running really well in practice but failing in the warm up laps at Wellington. We learnt that with a two stroke, to avoid detonation, our full on ignition timing needed to be retarded when the throttle is closed a little bit. So after that we ran a TPS with our digital ignitions.

This time Kel thinks it is just like when the Aprilia riders were doing burnouts and wrecking their engines, high revs and little throttle.

With high rpm and hardly any throttle there is insufficient blow down happening and the hot combustion gases left in the cylinder were backtracking down the transfer ducts over heating the motor and any incoming fresh air/fuel causing detonation and eventually a seizure.

Its counter intuitive I know, but Kels air cooled engine held together at wide open throttle going hard out all day long but just like at Wellington the engine failed when it was being driven in a gentler manner. We will know more for sure, when Kel pulls it down.

[richban]

http://www.kiwibiker.co.nz/forums/showthread.php/153656-Chris-Bucket-photo-thread-Bandwidth-warning/page18

297035 Taupo ... Kel was fastest in qualifying and won the next 5 races but towards the end was having to cope with a slipping clutch and needed to nurse the engine by running around with as little throttle as possible. In the sixth race and on the second to last corner before the flag and another win the bike sized and dumped him.

From Frits and Wobs explanations of our experience with the old Beast running really well in practice but failing in the warm up laps at Wellington. We learnt that with a two stroke, to avoid detonation, our full on ignition timing needed to be retarded when the throttle is closed a little bit. So after that we ran a TPS with our digital ignitions.

This time Kel thinks it is just like when the Aprilia riders were doing burnouts and wrecking their engines, high revs and little throttle.

With high rpm and hardly any throttle there is insufficient blow down happening and the hot combustion gases left in the cylinder were backtracking down the transfer ducts over heating the motor and any incoming fresh air/fuel causing detonation and eventually a seizure.

Its counter intuitive I know, but Kels air cooled engine held together at wide open throttle going hard out all day long but just like at Wellington the engine failed when it was being driven in a gentler manner. We will know more for sure, when he pulls it down.


.....EGT?.......
So good when they are working well. Mine on the 300.

297036

[TZ350]

.....EGT?.......
So good when they are working well. Mine on the 300.

297036

That is a neat looking EGT gauge, do they have ones that show EGT and CHT? With deto the head gets hotter and the pipe cooler than optimum.

[RomeuPT]

Hi everbody.

Been watching daily this thread, still amazes me, how much info and experiences I see here.

Been testing a dif head in my CRM 125 engine with the RS cylinder.

11cc got better than the previous I had 10.5cc head.

I think I am gonna to try a 11,6cc head. The ideia is to take one 10cc head that I have with bronze deto ring, it got's around 8mm squish with the radius that get inside the chamber, So I am thinking to get around 6,5mm squish, leave a sharp edge, make a 12mm offset chamber from plug and get a dome height of 9,8 instead of 10mm or more than the actual chamber. This then makes possible to achieve the 11,6cc volume.
But, will the 6,5mm squish be to low, and kills power? That's my doubt, and so what should be done to a bathtub type chamber to keep the squish at arounfd 50% and leave a desirable height? An almost rectangle chape? There is the drawing below of what I am thinking to try.

Thanks

[richban]

That is a neat looking EGT gauge, do they have ones that show EGT and CHT? With deto the head gets hotter and the pipe cooler than optimum.

Nah just these style I think. I will be running the det gauge as well next meeting. Hooked to ignitech. NIce and eazy to read when shit is happening fast.

[peewee]

anyone tried one of these ? i was gonna give it a go mostly for the rpm function but if you have single cylinder you can have rpm and water temp or egt displayed seperate on each screen

http://www.kosonorthamerica.com/koso/shop/egt-temps/new-dual-egt-with-rpm-amp-water-temperature-7/

[F5 Dave]

Ooooh. That's my tyre & petrol budget for the whole year's racing & I'm including driving to the events:laugh:

[Yow Ling]

Ooooh. That's my tyre & petrol budget for the whole year's racing & I'm including driving to the events:laugh:

Dont you get Racing for family's tax credit?

[Bert]

That is a neat looking EGT gauge, do they have ones that show EGT and CHT? With deto the head gets hotter and the pipe cooler than optimum.


Nah just these style I think. I will be running the det gauge as well next meeting. Hooked to ignitech. NIce and eazy to read when shit is happening fast.

One could use the twin gauge and replace one of the j/k thermocouple with a suitable one for the CHT.

:msn-wink:

KOSO gauge,why spend that much on a LCD... Which you have to try and read.
Much easier to see the analogue gauge and catch the needle flicker into the danger zone.

[wobbly]

Romeu what fuel are you running - and I assume by your 6,5 you really mean 0.65mm squish.
When you are running big volumes like you are talking the plug is way too far from the piston and you need to change to a toroid.

[fixer]

Woo hoo! ... The Team ESE dyno is up and running again after some ... er ... minor computer issues. So we put the RS50 Aprilia back on and experimented with a couple of different adaptors in the exhaust header. The result ... 130hp at just over 6000rpm! Can't wait to get it on the track.

297049

[speedpro]

That's not bad for a 50

[chrisc]

That's not bad for a 50

Only 2,600hp per litre. Definitely room for improvement though. I hear those 50s can go out to 3,000 hp per litre :Pokey:

[TZ350]

297049

Woo hoo! ... The Team ESE dyno is up and running again after some ... er ... minor computer issues.

Yep there is the proof Wob, 130hp,

Just by lifting the barrel, and a bit of guess work you can do wonders with a 50, easy as .... :laugh:

Seriously its great to have the dyno sort of working again, and its a big thanks to Fixer for his efforts and the donation of a suitable computer. Now at least we are back to being able to tell if something has made an improvement or not.

We will get the proper config file from DynoJet soon and it should all be back to normal.

[RomeuPT]

Romeu what fuel are you running - and I assume by your 6,5 you really mean 0.65mm squish.
When you are running big volumes like you are talking the plug is way too far from the piston and you need to change to a toroid.

Thank's for the reply.

Fuel, unleaded petrol 98 (portuguese) :D

I mean the squish band, 8mm is right at 50%. 6,5mm is less, I am not sure if is really important to keep around the 50% squish band for power production.

This is using a Domed top piston.

Before I knew the toroid was for flat tops I tried a stock Honda RS 125 toroid, totally losed power, mostly peak, I even tried to change the curve of the ignitech and checked the plug but didn't go any better.

Thanks.

[TZ350]

297052

http://www.quincylooperracing.us/subpage99.html

Konig Factory Tour.

[wobbly]

Romeu
What is the dome radius, or dome height of your piston.
I will do a sketch of a toroid for you to suit 98 pump and the domed piston..

[RomeuPT]

Romeu
What is the dome radius, or dome height of your piston.
I will do a sketch of a toroid for you to suit 98 pump and the domed piston..

2mm.

I am using a rs piston at the moment, with 0.8 ring. I think is an ART piston. other domed piston I use are the same, 2mm.

thanks

[wobbly]

Running 98 pump I would go to 13.8 : 1 and no more - this would give you 9.7cc combustion vol or 11.9cc to the top of the plug
with a 10 range plug.
The 17mm shown is the thread length for the plug to ensure the tip protrudes into the chamber.

[RomeuPT]

Running 98 pump I would go to 13.8 : 1 and no more - this would give you 9.7cc combustion vol or 11.9cc to the top of the plug
with a 10 range plug.
The 17mm shown is the thread length for the plug to ensure the tip protrudes into the chamber.


Thanks.

I believe you are giving the best advice. I got to try it sooner or later.

I am confused because using the Honda toroid (I think it is around 11,2cc) I lost big power, using the 10cc hemi head (That I am thinking to cut) I lose a litlee peak and a lot overrev. The 10.5cc bathtub does everthing good, and now the 11cc seemed to improve peak/overrev. That's is why my ideia was to go even lower cc with a bathtub design..

To remenber the engine specs besides the cylinder and head are:

- Ignitech DCCDI-P 15/16º at 12500
- 800 mm pipes.
- vforce 2 for cr 125 with hand made straight flange for 38 carb
- Mik TMX 38, no filter, big hand made air box

[wobbly]

If you are running 800mm pipe then you should also be running 200* Ex - is this the case ?
There are two types of Luyten cylinders, one for the 835mm "customer" pipes and the other for the "A" kit 800mm type.
The A kit setup is designed to be run with completely different ignition curve and powerjet switching as it runs to 14,000 +
the customer setup is 1000 revs short of that.
Here is a dyno sheet showng a very good customer RS125 with one of my pipes, a full factory A Kit setup, and the same setup with my pipe ( Blue )
all showing rear wheel Hp.

[TZ350]

.

All the Hot action at Taupo. https://flic.kr/p/nx7zvN

[RomeuPT]

If you are running 800mm pipe then you should also be running 200* Ex - is this the case ?
There are two types of Luyten cylinders, one for the 835mm "customer" pipes and the other for the "A" kit 800mm type.
The A kit setup is designed to be run with completely different ignition curve and powerjet switching as it runs to 14,000 +
the customer setup is 1000 revs short of that.
Here is a dyno sheet showng a very good customer RS125 with one of my pipes, a full factory A Kit setup, and the same setup with my pipe ( Blue )
all showing rear wheel Hp.

almost 50 rwhp is brutal :eek5:

I am running 198º exhaust. With a 96 RS NX cylinder.

Squish is around 0.8mm. The transfer timing is stock, but gives around 136 main, 133/132 second and rear port. I know, lowering the cylinder and raise the exhaust to 200º to get similiar to a A kit.
I don't want to keep spendig much more on this project, I am starting a banshee project after this, just thinking to find a head that works better for what I want, play around with what I got and leave the engine like it is.

The green line on the dyno is with a 835mm pipe?

I feel that my engine does peak around 13000 rather than 12500, because of that I have been advancing the ignitech slowly each time, and is getting better. Without a dyno I don't go much far.... :/

Thanks for your time.

[wobbly]

The green line is a "stock" RS125 with 195* Ex and 835 pipe and powerjet switched at 12200.
The kit setup has 200* and 800 pipe with powerjet switched at 12800.
I wonder if your 98 pump fuel is alot better than what we have here, as 10.2cc is the absolute limit running LL100 Avgas ( any less and it limits overev ) But using 98 with that head would
destroy our engines in seconds.

[RomeuPT]

The green line is a "stock" RS125 with 195* Ex and 835 pipe and powerjet switched at 12200.
The kit setup has 200* and 800 pipe with powerjet switched at 12800.
I wonder if your 98 pump fuel is alot better than what we have here, as 10.2cc is the absolute limit running LL100 Avgas ( any less and it limits overev ) But using 98 with that head would
destroy our engines in seconds.

Wheel, I did a couple of banshee pipes for a friend from Lisbon that tunes banshee's in his free time, told me that our pump fuel is bullshit, and he can only use with the 98 what the americans use with their 91 :/. So many times he uses avgas etc when drag racing. More tuners have talked about the problem, but talking may be just that.

Maybe one more reason for me to try a little lower compression.

[ken seeber]

Wobbly,

I have attached a pic of an LKE KZ head insert. Its design and damage leads to a few questions:

1. The squish area is very low at 32% (44.5 inside diameter of band), it has a strange radius return just inside the squish band and the actual bowl is relatively flat topped. Other KZ engines are similar. This is in contrast to the sketch you did a few days ago of the toroidal shape. Is there something different required to karts over bikes or is this the latest good thing?

2. Compression volume. Typically "as supplied" KZ engines are well over the minimum CC method of measurement used in Oz, possibly by around 1.5 CC or so. Given that, there are the options to reduce the volume. One being to just face the original insert, sticking with the shape. The next is goingto a totally new toroidal design (along the lines of your sketch), but the trade off here is that the volume in thetoroid above the bottom face of theplug boss will capture air during the measuring, thereby giving a lower CC reading than is actually the case, minimizing the possible CC reduction. However, it might turn out better to have a good shape with a larger volume than a CC measurement that is on the minimum allowed. Hope this makes sense. The other option is just to do nothing because there might be nothing to be gained and for the question below

3. Detonation damage. The majority of this is above the B & C ports, not the exhaust side. The piston was similarly damaged. This damage is not unique to just this engine. One would think that the piston crown adjacent to the exhaust would be hotter, thereby making that side more susceptible to detonation. One thought is that above the exhaust there might be end gas which might slow down the combustion rate in this area, hence less damage. However the opposite may be the case. It might also be that the volume is small enough such that it would be unwise to reduce the CCs further, given the 98 octane fuel requirement.

Thanks

Ken

[ken seeber]

here it is

[F5 Dave]

That is queer, you usually see damage either direct centre of piston or ex port edge taking off the sharp edge of the crown. It would be interesting to know what revs & throttle position with a det sensor & data logger to see when it is happening beyond normal running of a racebike perhaps? (I don't even know if this engine is fixed gear or not) With the insert and the sealing arrangement if there was a leak at some point in that area? There is a shiny area & a dull one so we can ignore the garks I guess?

Interested to see what Wob thinks, I'm just cluelessly speeling filling in time

[wobbly]

A very easy question to answer.
The KZ2 ignition is virtually a straight line, thus the static you set it to is what you get.
Thus the pipes are very short to enable the engine to rev 14000 + as the ignition timing is way too advanced at high rpm to dump heat into the pipe
as would normally be the case with any sort of digital or simple analogue retarding setup.
In these engines we are fighting this excessive advance all the time, and many factors must be looked at to get a good working setup that wont detonate
but of course make the best power.
Biggest issue is that the end gases trapped in the squishband will deto the instant you run a little lean, or have too much static wound in.
The key to understanding whats going on is to realise why it always happens opposite the Ex.
This is due to the direction of rotation, as the piston rocks over TDC the inlet side is momentarily the closest to the head.
I have tried all the many combinations of cc, squish and chamber shape and as im in a good mood I will give you some of the detail.
Get the chamber down to 13.2cc thus leaving a little for safety sake with Tech officers not so clever at using a burrette, this pumps up the power needed at 9000
to get off the mostly 2nd gear slowest hairpins.
The minimum squish at the bore edge can be no less than 1.3mm, with the band tapering away from the piston at least another 0.2mm.
It must have a sharp edge into the bowl, and cut away the roof ( as well as making it as flat - bathtub - as you can ) so that the plug is just legally below this surface.
You must run a R7376-10 fine wire plug and NOT a resistor cap.
Every engine is different and the combination of 13.2cc and the static timing is what will give the balance between mid power punch and straight out rev on ability.
I have run anything from 1.1 to 1.7mm, and the only way to determine what is best,is to ensure always to jet it so it never exceeds 620*C and run it on a dyno to see what it likes.
Track testing to do this is very hard on gear, and thus even more expensive than getting onto a dyno.
The problem with the testing is to keep the jetting under control, and look at the data/talk to the driver to see what is the best tradeoff between having good bottom
combined with plenty of revon.
The relationship is almost linear - as you wind in advance the mid pumps up - and the overev drops.
Trick is to only do short runs, and always use a bendy torch every run to watch the inlet squish side of the piston to see the shiny surface "just" starting to turn grey.
I will take a pic in the morning of Hamiltons national title winning engines piston that is on my dyno now.
That is absolutely on the edge,after running the qual,heats and final.
You will NOT get away with a toroid in NZ - I understand that a tuner in Europe is doing this, and wants his engines held on some super critical angle
to check the cc, but yes I have asked and no its not permitted here - makes no odds to me anyway as we kicked the World Cup winning Savard TecSav engines arse - toroid or no toroid I dont know.

[ken seeber]

Jeez Wobbly, I'm glad you were/are in a good mood.

Lots of usful info for the dudes over here, inc myself, to get our minds around.

So, if we ask you more questions , you'll be in a good mood more often. Everyone wins !!

However, I won't go as far as demonstrating a " 125 Aircooled with 24mm carb making 30 Hp at 10500", despie the rewards.

Cheers

Ken

[marsheng]

Ok this is way out there, but we spend hours getting into those tiny little transfer ports with all sorts of tools to get the right shapes.

What if we bored out the cylinder 10 or so mm and made new aly sleeve to fit inside. That way we could do all the porting on the aly sleeve possibly complete with cast iron liner then drop the whole lot back into the barrel. The top of the sleeve can have a ridge on it to stop it falling through and the bottom could be welded to the to the barrel bottom to keep it all strong.

As most barrels are quite porous the new solid aly sleeve would probably help quite a lot with heat transfer. The only issue that I can see is the exhaust bridge being '2' parts.

Comments ?
'

[wobbly]

Been there done that - forget having an ally sleeve AND a cast one, too many disruptions to the heat path.
As you say, big overbore, cut the sleeve, press it in and then weld it in at the top for the best heat transfer in the hottest area, and weld the transfer ducts
to the sleeve for retention.
Then get it plated.
I believe you have to use 6061 ally and special rods if the weld is to be covered by the Nicasil.

[marsheng]

Sounds an interesting option. Do you weld the transfer port dividers ? Will be hard to get in there.

Not sure if you heard, my Maico Barrel expired, started to split around a base bolt hole. Did 6 or so laps.

Cheers Wallace

[peewee]

hey wobbly or anyone else. ive seen what happens with insufficient blowdown. is there such a thing as too much blowdown ?

[wobbly]

Its not so much the issue of too much blowdown per se in an engine spec.
The real issue is how did the excess blowdown for the planned Hp/rpm actually occur.
Using a CAD program it is easy to see a mismatch between the STA numbers for any combination of port area and timing.
If for example we see really big numbers for the EX and Bl STA but a mismatched small Tr STA then the performance will be transfer limited - and we wont see the power as the BL STA would predict..
Go the other way and we can have big Tr STA and big Bl STA, and this in fact may not be an issue, as in many cases having the TR and Bl correct, but an undersize Ex STA
will just mean that a clever person has filled in the EX floor and the bottom corner rads to reduce short circuiting.
This scenario will perform as per the correct BL and TR STA numbers predict.
What I was going on about the other day was to point out that taking a cylinder with low Tr and low Ex timings and simply jacking it up, will for sure give a useful improvement.
Simply due to the better timing numbers suited to alot more performance, but having huge 130* transfers and a relatively low 192* Ex points to the engine then being BL STA limited.
Drop the cylinder and grind up the Ex to get all 3 STA numbers complementing each other,and more power than the simple jack up scenario is a given.
Here are the STA numbers for an Athena 50 - one with the cylinder jacked up, the other with the same transfers but the Ex ground up to match.

[wobbly]

And here is the pic of the TM125 piston.
This has done 3 hard days testing, qualifying, 3 heats and a 25 lap final.
When you are this close to the edge one thing many dont realise is the following.
Always buy fresh fuel from the most popular gas station in town, that has regular tank topups.
NEVER leave fuel sitting overnight in the kart tank and use it the next day, and dont buy 20L at a time and only use 1/2 of it
during a test day, then use the other 1/2 the next day, with the fuel sitting in a 1/2 empty container overnight.
When you open a tin and hear the " whisssh " of pressure escaping the lid, all that "vapour pressure " is exactly that.
The light front ends of the fuel that are easy to emulsify as a fine mist and burn efficiently in the chamber, have all collected as vapour pressure in the can, or escaped out of the kart tank into thin air.
What is left is denatured ,crap, low octain, slow burning piston killing deto juice.
When heavy, large drops of fuel with little or no light fractions enter the combustion process, alot of this isnt burned, the molecule collections are simply to big to consume in time.
This shows as a "rich " mixture, so of course we lean that sucker down to get some temp into the pipe and bugger, it detoed its tits off.
Nothing to do with the jetting or the timing, its bad fuel from simply being left overnight in a tin or tank.

[peewee]

wobbly you might get a chuckle from this one. its alittle lopp sided but i didnt know any better at the time. one of the problems i had was the cylinder casting was pretty thin at aux exh ports which limited how large they could be (ill probly cut the side of the cylinder off and weld them next time). with a lack of exh area i tried to compensate by raising the main exh which threw the blowdown out of wack. ive got another cylinder so i can give it another go. ill fiddle with engmod and try to get the numbers looking alittle better for next time. im not sure what more i can do with the reed cage. i cut out some of the dividers which increased the tip area by 10mm (if i recall correct) which was equivalent to adding another petal.

http://i1081.photobucket.com/albums/j357/doddledo/IMG_20140517_213651_zps85656dcd.jpg

[pete376403]

And here is the pic of the TM125 piston.
This has done 3 hard days testing, qualifying, 3 heats and a 25 lap final.
When you are this close to the edge one thing many dont realise is the following.
Always buy fresh fuel from the most popular gas station in town, that has regular tank topups.
NEVER leave fuel sitting overnight in the kart tank and use it the next day, and dont buy 20L at a time and only use 1/2 of it
during a test day, then use the other 1/2 the next day, with the fuel sitting in a 1/2 empty container overnight.
When you open a tin and hear the " whisssh " of pressure escaping the lid, all that "vapour pressure " is exactly that.
The light front ends of the fuel that are easy to emulsify as a fine mist and burn efficiently in the chamber, have all collected as vapour pressure in the can, or escaped out of the kart tank into thin air.
What is left is denatured ,crap, low octain, slow burning piston killing deto juice.
When heavy, large drops of fuel with little or no light fractions enter the combustion process, alot of this isnt burned, the molecule collections are simply to big to consume in time.
This shows as a "rich " mixture, so of course we lean that sucker down to get some temp into the pipe and bugger, it detoed its tits off.
Nothing to do with the jetting or the timing, its bad fuel from simply being left overnight in a tin or tank.

The markings in the top of the piston (makers name, size, etc) "look" like little dimples/pinpricks with sharp edges. If they are, would that have any effect on detonation?

[F5 Dave]

And here is the pic of the TM125 piston.
This has done 3 hard days testing, qualifying, 3 heats and a 25 lap final.
When you are this close to the edge one thing many dont realise is the following.
Always buy fresh fuel from the most popular gas station in town, that has regular tank topups.
NEVER leave fuel sitting overnight in the kart tank and use it the next day, and dont buy 20L at a time and only use 1/2 of it
during a test day, then use the other 1/2 the next day, with the fuel sitting in a 1/2 empty container overnight.
When you open a tin and hear the " whisssh " of pressure escaping the lid, all that "vapour pressure " is exactly that.
The light front ends of the fuel that are easy to emulsify as a fine mist and burn efficiently in the chamber, have all collected as vapour pressure in the can, or escaped out of the kart tank into thin air.
What is left is denatured ,crap, low octain, slow burning piston killing deto juice.
When heavy, large drops of fuel with little or no light fractions enter the combustion process, alot of this isnt burned, the molecule collections are simply to big to consume in time.
This shows as a "rich " mixture, so of course we lean that sucker down to get some temp into the pipe and bugger, it detoed its tits off.
Nothing to do with the jetting or the timing, its bad fuel from simply being left overnight in a tin or tank.
Over night? I'm not one to challenge you. But if it's in a tin it's surely better preserved than in a vented gas station tank. I just asked my in house refueling expert and gas stations are filled twice a week for high use outlets. Kart tanks are plastic so breath. Or are you saying that mixed gas is affected worse?

[F5 Dave]

Ok here's a question. Kart guys seem to like to start their karts on the stands then rev them. From cold- Revvvv. Brake
Revvvvv. Brake. RREEEEVVVV brake.

What do they think they are doing? They don't seem to be warming them up. They can't be tuning them as they are not to temperature and not under load. What do they think they are doing?

Other concerning thing is the spinning wheels at waist height would take you apart if you walked into them.

[Kickaha]

Ok here's a question. Kart guys seem to like to start their karts on the stands then rev them. From cold- Revvvv. Brake
Revvvvv. Brake. RREEEEVVVV brake.
Used to be confined to the KT100 guys, dunno if the Rotax Max guys do to and used to annoy the crap out me parked beside someone doing it

Oh yeah, fucked if I know why they do it

[Yow Ling]

Ok here's a question. Kart guys seem to like to start their karts on the stands then rev them. From cold- Revvvv. Brake
Revvvvv. Brake. RREEEEVVVV brake.

What do they think they are doing? They don't seem to be warming them up. They can't be tuning them as they are not to temperature and not under load. What do they think they are doing?

Other concerning thing is the spinning wheels at waist height would take you apart if you walked into them.

Maybe they testing the brakes?

[TZ350]

Page 940-A

Fixers Cylinder and Pipe and some very insightful advice from Wobbly.



My beloved Aprilia RS50 acquired a new Doppler Vortex 50cc kit recently. I bought it because I liked the look of the wide bridged exhaust port and the wide and (I believe) nicely-angled transfer ports. It's advertised as a road kit so it (as I have discovered) has relatively mild port timing.

There's a video showing the inside of the kit here: https://www.youtube.com/watch?v=mUeeycpkpc8 .


The standard Aprilia top end with some exhaust port mods made a bit over 11hp on the ESE dyno. So we put her back on the dyno and, lo and behold, with the Doppler kit she was making just under 10hp with a dip in the power band the size of the Grand Canyon.

But ... we took advantage of the large number of exhaust pipes to be found in the ESE workshop to see if a different pipe might conjure up another pony or two.

297164

So the Conti pipe (which had been largely responsible for an earlier increase from 5hp to 8hp) came off and another pipe went on. Still a large dip in the power band, but substantially more power. Back up to just over 11hp. This pipe was a bit large and only fitted a couple of mm into the barrel. So we shaved a bit off the OD so it would fit in better.

It was probably about 10-12mm shorter when properly fitted, and was a disaster. Back down to just over 10hp. What?? Okay ... so we tried a different pipe. The result was MUCH better. Nearly 12hp with a much nicer looking power curve.

And then for the hell of it, we tried the original Conti pipe with a shorter adaptor between the pipe and the barrel (probably by about 12-15mm). Based on our previous experience of a longer pipe being better, I bet that this shorter adaptor would make things worse. WRONG!!! There was still a chunky dip in the power band, but it was back up to nearly 12hp.

The moral of the story ... the proof is in the dyno! Below centre is a photo of the 5 dyno charts. You can see the range of different results obtained from 3 different pipes, with two of them tried twice each with shorter or longer adaptors. The maximum power varies by around 20 percent, but 4 out of 5 have a similar dip. One doesn't. This is very promising.

297166 297165

The photo on the left illustrates the huge difference that just having a 10mm or so longer adaptor between the pipe and the barrel can make. The photo second from right shows the two adaptors.

So on went the degree wheel and some considered measurements were taken with the result being that we're going to raise the barrel a bit with a spacer, machine the head to fit it into the top of the cylinder. Tweak the squish band and stick her back on the dyno. More exhaust port duration is apparently what is required here.

Two-strokes and dynos ... a match made in, well, if not Heaven, then at least Wonderland. Tim


Simply lifting the cylinder to get 115 on the transfers and 192 on the Ex means you will have shit loads of STA on both, but the thing will then be severely blowdown limited.

It may in fact make better power than what you have now - but such a STA mismatch will always mean narrowing of the useable power and probably even
more issues with big torque holes.

115 is what you would run on a full noise road racing setup, 192 is what a much lower power hot road bike might need - so the resulting power will always be compromised by the missing blowdown
that matches neither the transfers nor the Ex STA.


I am picking that they think there may be excessive blowdown with the standard setup and that by raising the barrel and RPM ceiling that what was excessive blowdown STA at lower rpm is suitably adequate for the higher rpm they are aiming for.

Take a look at the Exhaust port here:- https://www.youtube.com/watch?v=mUeeycpkpc8

So it could be they are tuning for the blowdown area they already have. Yes the spacer plate is easy but it also makes things easily reversible.


If so then the original timings of 90* and 121* by their very nature would produce a small ( though not necessarily correctly matched ) blowdown STA.

Then by simply lifting the cylinder , the transfers suddenly become suitable for a full noise road racing setup, but that small blowdown number remains relatively the same.

Its very similar thinking to lengthening and shortening a pipe by chopping or sleeving the header.

Sure the tuned length is being affected, and the engine may in fact respond to this change favourably, but if you fail to realise that having a header say 28% or 36% of the tuned length will invariably produce huge holes in the torque curve - due to the incorrect positioning of the diffuser.



To prove my point about the pipes, here is a dyno graph of a pipe designed using TSR for a 490 Banshee.

297167

The rpm was some 1500 down , so of course they cut the header, oh dear even less power.
I redesigned the pipe ( with exactly the same length as the shortened version ) and it suddenly seems to work a little better.



The point I was making about cutting or sleeving headers to do a dyno test, is that simply doing that and trying to analyse the results is completely pointless if you have not measured the pipes beforehand to see what the original design intent was.

If the header is short to start with, and you then shorten it more, the tuned length may be perfect, but the negative effect from the now silly short header length will overpower any of the good effects of the overall length.

Conversely if the header was short and you lengthened it, the power increase may be mainly due to now having a " correct " % of header - though the pipe length may be completely wrong for the port timing.


Your explanation makes sense of Fixers dyno graphs. It will be interesting to see a post from TZ with a new (after modification) dyno graph explaining their reasoning for the cylinder plate approach. But it may be a bit of a wait as I hear they have had a woopsie with the dyno computer and need a replacement copy of the Dynojet software so they can commission a replacement computer.


The only way to establish the port timings is to use the STA numbers generated in a CAD program of some sort.

But as I explained before, running the transfers up at 130* would in most cases indicate you are looking to make 50Hp and go to 14,000 in a 125 cylinder with plenty of port width.

In that case 192 is a wild mismatch, no matter what the Ex geometry is, as the Blowdown STA will be tiny in comparison to the transfers ability.

This would mean far too low port velocity in the transfer ducts,where the port then looses coherence of the scavenging streams, and short circuiting kills the power dead – especially if you somehow manage to get a well designed pipe that will suck like hell around BDC.

Then, not to mention we are fighting the huge residual pressure sitting above the transfers as they open - killing even more the flow velocity, due to the restricted Blowdown STA.


I hear what your saying. if I am starting at 180/124 should I just widen the trans as much as I can, raise exh a little and widen it then test and see what happens ?

I do have engmod2t but its a bugger putting in all the info. plus I have not used it enough to decipher the output info


In EngMod all you gotta do is enter the basic engine bore/stroke etc and then the Ex and transfer data, and the front page gives you the STA info.
Tells you in a few minutes all the answers you will ever need.


hey wobbly or anyone else. I have seen what happens with insufficient blowdown. is there such a thing as too much blowdown ?


Its not so much the issue of too much blowdown per se in an engine spec. The real issue is how did the excess blowdown for the planned Hp/rpm actually occur.

Using a CAD program it is easy to see a mismatch between the STA numbers for any combination of port area and timing.

If for example we see really big numbers for the EX and Bl STA but a mismatched small Tr STA then the performance will be transfer limited - and we wont see the power as the BL STA would predict..

Go the other way and we can have big Tr STA and big Bl STA, and this in fact may not be an issue, as in many cases having the TR and Bl correct.

But an under size Ex STA will just mean that a clever person has filled in the EX floor and the bottom corner rads to reduce short circuiting. This scenario will perform as per the correct BL and TR STA numbers predict.

What I was going on about the other day was to point out that taking a cylinder with low Tr and low Ex timings and simply jacking it up, will for sure give a useful improvement.

Simply due to the better timing numbers suited to alot more performance, but having huge 130* transfers and a relatively low 192* Ex points to the engine then being BL STA limited.

Drop the cylinder and grind up the Ex to get all 3 STA numbers complementing each other, and more power than the simple jack up scenario is a given.

297168 297169

Here are the STA numbers for an Athena 50 - one with the cylinder jacked up, the other with the same transfers but the Ex ground up to match.

[TZ350]

Page 940-B



Woo hoo! ... The Team ESE dyno is up and running again after some ... er ... minor computer issues. So we put the RS50 Aprilia back on and experimented with a couple of different adaptors in the exhaust header.

297170

The result ... 130hp at just over 6000rpm! Can't wait to get it on the track.

Seriously its great to have the dyno sort of working again, and its a big thanks to Fixer for his efforts and the donation of a suitable computer. Now at least we are back to being able to tell if something has made an improvement or not.

We will get the proper config file from DynoJet soon and it should all be back to normal.


What I was going on about the other day was to point out that taking a cylinder with low Tr and low Ex timings and simply jacking it up, will for sure give a useful improvement.

Simply due to the better timing numbers suited to a lot more performance, but having huge 130* transfers and a relatively low 192* Ex points to the engine then being BL STA limited.

Because the dyno software thinks its looking at a 2000hp setup not our 200hp one the hp is way over stated but I think the rpm and shape of the curve are realistic.

297171

Well, just like Wobbly predicted we might by simply jacking the cylinder up, we did get what looks like a useful improvement and the dip is no where as bad as it was, but its no where ideal. Interestingly the best run now is with a pipe that was the worst of the 5 pipes we tried before.

We are exploring this cylinder in reversible steps so the next move in following Wobs advice is to increase the blow down STA and we are going to try and do this by Devconning the top of the transfers so they open a little later.

[TZ350]

Page 490-C



Rear cylinder wall in red, as I understand it. Could you offer a potential interpretation as to why this did not offer any gains?

297657


Answers are easy to "get " when you know the effects of the mods.

Cutting away the rear tang support at the base of the cylinder means that the flow thru the reeds then smashes directly onto a flat surface - the piston.

This may seem counter intuitive, in that most people think ( wrong ) that when the piston rises it creates a depression that opens the reeds and it is this that causes inflow into
the case.

The rising piston may make a piston port lawnmower operate, but the vast majority of bulk flow in a race 2T is caused by the pipes diffuser depression, around BDC - when the piston is very much in the way.
This negative pressure ratio at the Ex port is then communicated to the reeds via the transfer ducts , creating flow when the piston is at BDC - exactly opposite to the theoretical scenario.

Secondly - many , in fact most modern engines have the same sharp edge scenario as is shown in the pic of the Honda transfer entry, at the bore. But be aware - Mr Thiel is no idiot, and the Aprilia ( and all my engines ) have a LARGE ball nose radius where the duct meets the bore edge.

This is one of the ideas that last weekend won the National Kart title for KZ2 - 125 against the very best World Cup winning engines tuned at enormous expense in Europe by a French dude called Savard.

We kicked arse - making the pass for the lead by simply having more power down the shoot, and better chassis setup to drive away on better tyres.

Transfer duct length is a very tricky area, in that most times when you shorten this, in effect you are reducing the duct volume, AND reducing the area ratio between entry and exit. This I believe has more effect than the actual "tuned" duct length has.


The other small point I thought of later was that the drop down rear piston support tang, if shaped well also helps to deflect the reed flow sideways toward the transfer duct entry area, and not allow most of it to migrate straight forward and hide under the piston.

I should temper my comments about reed flow at BDC somewhat in that when you watch the tip lift and case depression curves in EngMod you see that the case going negative and the inlet going positive, if tuned correctly opens the reeds very quickly and soon after BDC, thus initiating flow into the case when the piston is still hanging around " in the way ".

But again I emphasize it isn’t the rising piston that creates the inflow in a race engine.


So, as fuel passes inside the open reed cage there should not meet a very big case entry or the flow velocity is lowered too much, then the fuel should go in the easier path to sit under transfer ducts. Is this right?


The amount of inlet flow capability varies from motor to motor with cylinder reed setups.

But I know for example in the RZ400 I had to make the Boyesen ports in the CPI cylinder twice as big and then use a Blaster type piston full of big holes to get sufficient inlet STA to support over 100 Crank Hp.

That engine ended up making 96 RWHP and held up over 90 at 12,000 so when pushing the limits on a cylinder reed you have to use everything available.

297658

Here is a pic of the Blaster pistons in 66mm bore, next to stock Blaster and RZ ,I had Wossner make them for the RZ and the TZ400. Been reliable to over 500Km hard racing so far.


Re the reed flow - yes keeping the reed box duct volume small helps keep the velocity high and in all late model engines you can see the progressively smaller entry volume being redesigned year by year.

I have thought about making a pair of curved vertical guides in the reed box that would direct the flow from the outer reed petals ( in a 6 petal reed ) toward the transfer duct entries.

The center petals then dumping flow onto the big end slot for lube - not had a suitable project yet to try this yet.


So what are your thoughts on making the cases as wide as possible on a case Reed motor? This NSR500 has the case Reed width almost as wide as the transfer ducts in the cases.

I have a cr125 that I'm doing and debating on how wide I should make the case Reed width entering the crankcase, and ultimately into the transfer ducts in crankcase


From what I have seen by various factories the development seems to have been toward reducing the area/volume in front of the reed tips as much as possible - at the expense of what you would think was a "good " flow regime.

But along with that the Italians are lifting the duct floor higher and higher with it sloping upward and transitioning into the flywheel covers, just leaving a slot for lube.

This has also coincided with angling the carb upward, removing any bend in the inlet tract.

That has also given festerers like me endless fun with reed configurations - no longer do we need to bias the flow with differing stiffness and or backups on the top/bottom to counteract the manifold bends deleterious effect on flow.



Has anyone tried adding transfer ports under the exhaust port?
Yes and No ... tried an exhaust port dam, seemed to work OK, as for the transfers under the exhaust port itself, good idea but from memory Frits reported that Jan Theil had tried it without success.

Follow the link trail to read about Ex port floor dams and extra transfer ports there.


Most of us cut the squish angle of our heads on the lathe. With a domed piston which is a radius... the squish angle is slightly mismatched being a straight angle. Any performance benefit to CNC the head squish to match piston dome?


There was one guy in Czech republic who tuned a moped engine to get he's degree at university.

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And he did this kind of test, here are the results Blue line piston angle same as head angle and red line domed piston and straight angle head and 2nd picture modified piston to get same angle as head.


The squish following the piston shape by using CNC is even more important if you are pushing the limits with around 50% SAR and very tight clearance.

297661

This also works together with the sharp edge into the bowl, and I suspect that if the tests shown were done with all this in mind the difference in performance would have been even greater.


Yamaha paid a fortune to the sly old fox Dr Erlich for his patented offset combustion chamber, they used it once in the TZ 250 G model, and as we know all that did was deto its tits off due to insane MSV on one side and none on the other.



http://killacycleracing.com/about-us/eva-hakansson/

KillaJoule is the world’s fastest electric sidecar motorcycle with a top speed of 216 mph (348 km/h) so far.
Builder, owner and driver is Eva Håkansson.
KillaJoule is really eco-activism in disguise. The only purpose of this 19 ft., 400 HP, sleek, sexy motorcycle is to show that eco-friendly doesn’t mean slow and boring.

And then there is the 8 second drag bike.

http://media.killacycleracing.com/2013/06/KillaCycle_Woodburn_no_color_for_slider.jpg

You will have to go and have a poke around the sight if you wan't to know more.

http://killacycleracing.com/about-us/eva-hakansson/

[chrisc]

Page 490-A

490? You've gone back in time Rob!

http://www.motorcyclenews.com/upload/208827/images/Nicolas%20Terol.jpg

[husaberg]

Page 490-C

https://lh4.googleusercontent.com/-7FsnF4-pAfE/UrfrhfGrYnI/AAAAAAAAyf0/1yo2v0Jrd1A/w900/dyslexia.jpg

[TZ350]

490? You've gone back in time Rob!

Back to the Future ....... fwk..:blank: ...... anyway the links list from the last 10-20 pages is to go there when I have compiled it.

[Grumph]

Ok here's a question. Kart guys seem to like to start their karts on the stands then rev them. From cold- Revvvv. Brake
Revvvvv. Brake. RREEEEVVVV brake.

What do they think they are doing? They don't seem to be warming them up. They can't be tuning them as they are not to temperature and not under load. What do they think they are doing?

Other concerning thing is the spinning wheels at waist height would take you apart if you walked into them.

If you want to warm up a kart with either direct drive or a centrifugal clutch, holding at a constant rpm is hard - and hard on chain etc.
Varying the speed - bringing it back down with the brake - is actually the best way to do it. But yeah, noisy and irritating.
Old guys' factoid for you dave - post WW2 preselector gearboxes were still in use for roadracing cars. The only way to warm them up - and you had to otherwise they developed clutch slip etc - was to start the car and put it up on jackstands then run it at a fast idle in gear for 10 - 15 minutes. Noisy, dangerous, hell yes. still done by ERA owners in vintage racing too.

[wobbly]

Re the fuel flashing off all its good light front ends.
Next time you go to a gas station have a look around and somewhere you will see several pipes stacked up in a row that are often over 6M high
with a U bend on top so the outlet faces down.
These are the tank breather pipes, and the pressure head created in the tank by this high exit vent is there to contain the vapour pressure of the fuel.
When you have a 1/2 empty 20L container of petrol, within several hours the light chemicals in the fuel will flash off and create the vapour pressure you always
have when opening a drum - this "good stuff " instantly dissipates to atmosphere as soon as you open the tin, and the more times you do it, the worse the fuel gets.
With fuel sitting in a kart tank, and a direct vent to atmosphere as you must have, the vapour pressure exits to atmosphere continuously, so overnight is plenty long enough to ruin the
already suspect pump gas.
The effect is much worse now that lead has been taken out, and all manner of really bad shit has been put back in to lift the octain to 98 especially.
The number of times I have seen mainly KZ2 but also KT100 and Rotax engines detoed to death by this effect is just amazing - but hey what do I know after all these years at the track and dozens of
National/World No1 plates .
The higher the tune/bmep the worse the effect you see from low octain fuel with low vapour pressure, so alot of racers get away with it, alot of the time - but with fresh fuel you can always rely
on your baseline tuning settings, without that assurance you have no chance against the guys really on the ball.

[wobbly]

PS - the only reason you need to rev/brake a kart on the stand is to circulate the water and get the cylinder/radiator up to temp.
This is usually an issue as they only get 1 lap of warmup, but the other side of the coin is that the things go best when cold, so all they really need
is enough to get say 35* into the water.
There are plenty of wqnkers that make us all deaf in the pit for no reason at all.

[wobbly]

Last point about the markings on the KZ2 piston.
Frits pointed out that Aprilia brighly polished the piston to reflect combustion heat so I tried this on a KZ2.
I also tried using a clear ceramic coating ( often used by cheaters in KT100 ) and found that both helped to save the piston
if deto started to eat away the squish.
But no matter what I did it would always then start eating the head.
Once I understood what not to do, deto went away and it became easy to tune to the edge with egt and a magnifying scope that usb plugs into a laptop.

[F5 Dave]

Re the fuel flashing off all its good light front ends.
Next time you go to a gas station have a look around and somewhere you will see several pipes stacked up in a row that are often over 6M high
with a U bend on top so the outlet faces down.
These are the tank breather pipes, and the pressure head created in the tank by this high exit vent is there to contain the vapour pressure of the fuel.
. . .

ok thanks I'm going to have to think about this for a while.


I've been using Av for years now and the airport is miles away so I get a couple of 20l at a time which lasts me several meetings on the bucket. I've never noticed any affect that I could put my finger on in dyno tests with new fuel, but I'll keep it in mind.

[F5 Dave]

PS - the only reason you need to rev/brake a kart on the stand is to circulate the water and get the cylinder/radiator up to temp.
This is usually an issue as they only get 1 lap of warmup, but the other side of the coin is that the things go best when cold, so all they really need
is enough to get say 35* into the water.
There are plenty of wqnkers that make us all deaf in the pit for no reason at all.

We mainly see this on KTs & it doesn't seem to be before the race, just at random times.

[wobbly]

The problem with the KT100 is that the jetting you use on the track is way too lean in the bottom to use when the engine is cold
and being push started.
Those good drivers/tuners can wind out the bottom needle for the first lap ,then take it back in correctly when the cylinder/pipe is up to temp.
But thrashing it in the pits to heat it up is another way for those not so skilled on the needles.

[RomeuPT]

Re the fuel flashing off all its good light front ends.
Next time you go to a gas station have a look around and somewhere you will see several pipes stacked up in a row that are often over 6M high
with a U bend on top so the outlet faces down.
These are the tank breather pipes, and the pressure head created in the tank by this high exit vent is there to contain the vapour pressure of the fuel.
When you have a 1/2 empty 20L container of petrol, within several hours the light chemicals in the fuel will flash off and create the vapour pressure you always
have when opening a drum - this "good stuff " instantly dissipates to atmosphere as soon as you open the tin, and the more times you do it, the worse the fuel gets.
With fuel sitting in a kart tank, and a direct vent to atmosphere as you must have, the vapour pressure exits to atmosphere continuously, so overnight is plenty long enough to ruin the
already suspect pump gas.
The effect is much worse now that lead has been taken out, and all manner of really bad shit has been put back in to lift the octain to 98 especially.
The number of times I have seen mainly KZ2 but also KT100 and Rotax engines detoed to death by this effect is just amazing - but hey what do I know after all these years at the track and dozens of
National/World No1 plates .
The higher the tune/bmep the worse the effect you see from low octain fuel with low vapour pressure, so alot of racers get away with it, alot of the time - but with fresh fuel you can always rely
on your baseline tuning settings, without that assurance you have no chance against the guys really on the ball.

Nice to read this kind of info.

A good tank respirator, should link the top of the tank end then go down with a rubber tube below the tank? mine enters the ram air box.

Do this type of respirator keep the "good stuff"?

Thanks

[fixer]

So the RS50 has now had it's barrel raised by 1.5mm or so. The result as mentioned by TZ350 is that the pipe that seemed to be the best performing pre-barrel-lift is now the worst pipe post-barrel-lift. However, the beauty of this situation is that the pipe that was the worst before is now the best. And it's the pipe I actually own. Brilliant!

Pre-lift, the power looked pretty gruesome. It's the worst one in the photo below. Just under 10hp max with a massive dip in the middle. A curve that would make a bactrian camel's mother proud:
297179

Post lift, and with a slightly different adaptor in the exhaust header and a little adjusting of the ignition timing, the power looks much nicer:
297180

Of course, we have no idea how much power is actually being made due to our on-going dyno computer issues. However, having had a play at Edgecumbe kart track on Sunday, I'm feeling rather optimistic. Unfortunately, the last time I was at Edgecumbe was about 8 years ago on a minimoto, so I really have no reference point. So in the absence of any actual dyno numbers, I'm going to have to rely on a dry meeting at Mt Wellington next weekend and some lap times to work out if it is as good as it looks and feels.

[2T Institute]

A superbike team here was pinged for running illegal fuel (not 98 PULP) they provided samples of the fuel, evidence of wher/when it was purchased etc etc. The samples showed their fuel was not doctored but just very fresh fuel from a very busy servo on the Tullamarine freeway a mere stones throw from the Shell refinery.

[wobbly]

Dead right that Avgas isnt so prone to causing issues with vapour pressure loss - this is simply due to the fact that the lead
content that has so much effect on the deto resistance,does not flash off to atmosphere.
Running the vent hose from a tank down lower than the fuel level, or into an airbox, simply means the flash off runs up, then down
and out to fresh air.
No free lunch.

[Ocean1]

Running the vent hose from a tank down lower than the fuel level, or into an airbox, simply means the flash off runs up, then down
and out to fresh air.
No free lunch.

A lot, (most?) of modern cars have PRV/vacuum break valves built into the tank caps.

As a fix it's not free but it's nearly so.

[RAW]

Wobbly, the KT100, With the piston at bdc if I had a hole in the piston aligned with the inlet port how do you think this may effect things

[F5 Dave]

I'm assuming the tech inspector would disqualify you (having seen them in action at last Kart meet, but without knowing kart rules), but also shake his head.

[F5 Dave]

Dead right that Avgas isnt so prone to causing issues with vapour pressure loss - this is simply due to the fact that the lead
content that has so much effect on the deto resistance,does not flash off to atmosphere.
Running the vent hose from a tank down lower than the fuel level, or into an airbox, simply means the flash off runs up, then down
and out to fresh air.
No free lunch.

ok, something to be careful with my dirtbike which slurps 95 (I avoid 98 due to unknown Ethanol inclusion) but its not near any BMEP limits, but it does drag through sand & whatnot from time to time.

[Drew]

Running the vent hose from a tank down lower than the fuel level, or into an airbox, simply means the flash off runs up, then down
and out to fresh air.
No free lunch.How does that differ, from what the tank vents do at the petrol station?

[Yow Ling]

How does that differ, from what the tank vents do at the petrol station?

At the petrol station the tank is underground so probably at a lower temp so maybe less vapour
the surface area of the petrol at the station is probably quite small in relation to the total volume of petrol in the tank so more light fractions are more likley to stay in the petrol.

do the tank vents in the petrol station let in more air than vapour out ?

[wobbly]

Petrols vary widely but the RVP ( Ried Vapour Pressure ) can be upward of 9psi - thats the pressure you hear escaping when you open the drum lid.
Having the tank vent 6M up in the air creates a gas head of pressure above the fuel in the gas station tank.
The RVP climbs in the tank as the fuel evaporates until equilibrium is reached, and the rising column of gas in the vent tube continually keeps the tank under its own pressure.
A vent tube only a few inches above a kart tank does nothing.
Here is a good description of RVP and its effect.


" Now that I have the equipment to test fuel's RVP and it's relative "freshness" I have been testing almost every racer's fuel, and now am thinking about what is actually going on in everyone's combustion chambers. RVP readings indicate the presence of the fuel's "front ends" which are the first to initiate vaporization. Front (or "light") ends are critical to initiate and create fuel vaporization especially in low temperature (air and engine) engines! Remember--fuel will not burn until it vaporizes. Unvaporized fuel only displaces O2 in the combustion chambers and can short out spark plug electrodes. The misfire we hear when people "warm up" or "clean out" their race engines is a combo of lean net mixtures in the combustion chambers and unvaporized globs of fuel shorting out the plugs!


The AMA motorcycle flatrack pros say that they must now use spec fuel--Sunoco Supreme which is supposed to have RVP of 8.0psi, and sold to the racers in "sealed" 5 gallon pails. Connecticut AMA pro #2 Kenny Coolbeth was here with RLJ racing (Ron Jewell of Holley, NY) recently preparing for Daytona with a new modded Honda 450 (Ron Jewell never was able to get Kenny's Kaw 450s to quite match his 63+ hp Honda mods, so Kenny wisely jumped ship). His sealed pail of Supreme's measured RVP was only about 4psi instead of the published 8psi meaning that half of the front ends had escaped into the atmosphere between refinery and the pail! Sunoco tells me they do not put fuel in drums or pails, they only ship rail and truck tankers to wholesalers, and after that it's beyond their control. Once again we needed close to 12/1 A/F (wideband out the muffler) to make max HP at those high revs instead of the 13/1 that is most common with flattrackers who use higher RVP fuel. So surely more of the stale Supreme is going through Kenny's intake and combustion chamber in globule-form and ultimately vaporizing in the exhaust pipe.


So, if someone is tuned spot-on with his RVP pump gas blend at 13/1 out the pipe, then splurges for some of that expensive Supreme that he sees Kenny C pouring into his tank, his bike will probably slow down from suddenly being way too lean in the combustion chamber. "Over-Octaned" is the commonly offered, but incorrect explanation for the HP loss.


Lower than published RVP is very common--the last test I did on some VP Import fuel for a turbo two-stroke measured ZERO psi meaning it was DOA in a sealed pail. Yes, we were able to use it, but we were careful to have the engine smoking-hot (engine heat helps vaporize the stale fuel) and A/F in the conservative 11.5/1 range--staying far away of the 13/1 max HP A/F ratio".

[koba]

I'm not keeping up, they were running leaner by exhaust reading to run richer in the blast pot?

[Grumph]

thanks for that wob...it explains a few things i'd already worked out empirically.

One further question though - Injection..... i've had a lot of experience with methanol in carbs - and fresh fuel with absolute minimum water content is vital for best results.

When a speedway motor is injected, because of the better vaporisation of the fuel, fuel condition becomes less imprtant. the water content becomes pretty well irrelevant as the pressure through the nozzles will vaporise it anyway...

Do you have any experience yet that may indicate injection on 2 strokes could make the fuel condition less sensitive ?

[F5 Dave]

And this is starting to answer the question I posted pages back about what was happening with my dirt bike that it often would run dreadful until it had passed through the gearbox then would run sweet. Yet 2stroke drag bikes run cold.

I was wondering about the physics of why.

Of course the dirt bike has old gas in it. Even some residue in the bowl, but has to use old gas and worst effect is when it is cold. Once the engine is hot the fuel will vapourise better.

[TZ350]

While I wait for the new dyno software so I can get back to the EFI project I thought I may as well make some progress on my Air Cooled RGV250 cylinder project. A good 30+ hp Suzuki GP125 with a power valve, ATAC chamber, 30mm Trombone and variable stinger venture and EFI of course. If I can get the water to stay mixed with the fuel (H2O fuel additive for combustion control) things could get very interesting, maybe high 30's.

297197

The 8mm plate gets bolted to the crankcase and the RGV cylinder and heat sink bolts to the 8mm plate.

297198

Some of the heat sink fins will be milled away so the cylinder can nestle down inside the heat sink and be mounted directly onto some copper covering the 8mm plate. The 2mm copper sheet that transfers heat from under the cylinder will also be sandwiched between the 8mm plate and heat sink. The cylinder sits on this copper sheet and the copper distributes the cylinders heat out all over the under side of the bottom heat sink.

297199 297200 297201

A Wobbly designed Toroid combustion chamber will be machined into the block of 6061 alloy and another heat sink on top of that. The water jacket of the cylinder will be filled with copper chips and high conductivity thermal epoxy. Copper will be used to transfer heat away from the head and cylinder and particularly the area under the exhaust port duct to the outer (cooler) edges of the heat sinks. The heat sinks were salvaged from big old VSD drives.

[wobbly]

"I'm not keeping up, they were running leaner by exhaust reading to run richer in the blast pot?"

NO - when globs of fuel do not vaporise, they pass thru the engine unburned and this gives rich readings on both egt and Lambda.
If this situation is " fixed " by the tuner jetting down, we then get a chemically lean condition in the combustion space but this then reads as "normal " for
best power at say 13:1.
This is what happens to the KZ2 engines that regularly deto the piston and head to death,when crap fuel is being used with what the driver thinks are safe jets.
In the quoted article, they kept the bad fuel under control by not going leaner than 12:1,this saved the engine, but made alot less power.

[wobbly]

Fuel vaporisation is very good with a carb such as the Lectron, and for years it has been seen that these carbs are way less sensitive to A/F ratio than your average VM round slide Mikuni for example.
If you read the marketing blurb by SmartCarbs, they are telling us that the fine mist from that carb is way better than that we get from what we would regard as normal injection.
But running super high pressures and or air over fuel as we see in Etec etc may ameliorate this , dunno.

[WilDun]

Fuel vaporisation is very good with a carb such as the Lectron, and for years it has been seen that these carbs are way less sensitive to A/F ratio than your average VM round slide Mikuni for example.
If you read the marketing blurb by SmartCarbs, they are telling us that the fine mist from that carb is way better than that we get from what we would regard as normal injection.


Not really up with the play here, but will ask a question anyway, so here goes! - will that "fine mist" remain a fine mist when it passes through the curves of the transfer passages? - is it possible that it could be "centrifuged" into droplets again before it reaches the cylinder?

[F5 Dave]

I typed this before but lost it. I've been following the SC progress on the GasGas forum. They've had manufacturing issues & delays on the cast versions. Some have had luck, but others not so much fun. & much adoo with one-type-fits-all needles needing tiny iterations to get them in ballpark - seemingly with people in Auss having different fuel & thus different requirements.

Makes me wonder how they will last long term with tiny amounts of wear, will they be like early Dynojet kits which ripped out.

Hope they do sort it, it does promise so much. Ironically the renewed talk has other bolting up Lectrons & getting good results.

[wobbly]

To answer the two questions, yes fuel mist will drop out of suspension and become raw fuel sitting on the walls of the ducts.
Conventional wisdom tells us that in a 4T this can be minimised by making the inlet port walls surface finish equivalent to 180 grit wet and dry.
Now this is interesting as in most cast 2T transfer ducts end up being around this number - and so called " beautifully " cast ones and those polished up by
expert tuners end up way smoother - loosing power in the process.

The other question around the SmartCarb fuel needle issues.
I told them right at the beginning that the only way to enable fine tuning of the carbs - especially when on a twin Banshee for example, was to run a powerjet with very small jet increments as Lectron
did with great success very early on.
But they are /were so enamoured with their own cleverness re the insensitivity of the carb thus not needing to be fine tuned, I was ignored.
The possibility was / is there to finely emulsify the powerjet fuel using the so called AdjustaJet principal of having a variable air bleed into the powerjet suction circuit but sadly
some horses dont even like water.
Those carbs do work supremely well, but seems for now the only way to get fine tuning is to be fucking about sanding the needle tips with a digital micrometer in the other hand.

[Frits Overmars]

...when globs of fuel do not vaporise, they pass thru the engine unburned and this gives rich readings on both egt and Lambda.I don't get this, Wob. When fuel passes through the engine unburned, the oxygen in the A/F-mixture will pass through the engine unused.
That should give high (= lean) Lambda readings, shouldn't it?

[fixer]

The ESE boys might have only half a clue, but it's a good half. And they have a functioning dyno now. With the addition of a small aluminium plate to raise the barrel, a small mod to the exhaust manifold and a little fiddling with the ignition timing, my Aprilia RS50 with it's Conti pipe and Doppler top end has gone from 10hp to 13.6hp. Woo hoo! Evidence below:

297225

[wobbly]

Sorry Frits I gave the wrong impression with that statement, but as per the article I quoted above ( from Dynotech Magazine a superb mine of info on 2T testing )
"unvapourised fuel only displaces O2 in the combustion space " so we do have excess fuel dropping the egt and if the engine is then leaned down
it will deto due to the actual lean condition in the chamber.
But if using Lambda we cannot run fuel that has low amounts of light front ends at the "normal " best power ratio of 13:1 as the unburned droplets contribute nothing to the combustion process.
So the actual " burning " A/F ratio in the chamber is in effect lean.
As in the Dynotech example they gave they had to run under 12:1 or the engine would have been destroyed by deto in an instant, when running the new fuel with zero RVP.

[wobbly]

And as for the 1/2 clue guys I have obviously offended at ESE ( not my intention at all ) I strongly disagree with the idea of taking a 2T cylinder
with very average timing figures, trying a bunch of pipes " just to see what happens " then jack the cylinder up and retry the pipes.
As I did say, lifting the cylinder MAY give an improved result, and who knows what pipe would then work with that combination.
But the bottom line still remains for me is that IF the cylinder had been measured, the result put into a CAD program and the timings/STA numbers matched correctly
you would then KNOW what the result " should " be with a specific pipe - and be able to move forward knowing its for sure not the ports causing big holes or power loss.
The end result you have now is for sure better than what you had, but if it was done " properly " I also know for sure way more power is still on the table.
Look at how much power is able to be extracted from that Athena 50 cylinder with matched STA numbers - if I then stuck some random pipe onto that setup
and it made 7 Hp less at the crank ( ie about what yours is doing now ) I would be looking seriously at the pipe , as I know the porting is correct.
Surely that approach is a better way of getting a really good result - maybe I am wrong again?

[TZ350]

And as for the 1/2 clue guys I have obviously offended at ESE ( not my intention at all )

No .. not offended but of course you can expect a ribbing for being so blunt...... :laugh::bleh:


The end result you have now is for sure better than what you had, but if it was done " properly " I also know for sure way more power is still on the table.

We are absolutely sure your right and this makes Fixer and his bike a great test subject to demonstrate that, as he is a very good rider with a bike he is developing in progressive steps.

Its great that Fixer is posting all the details of his work complete with dyno graphs of his progress and its all happening quite quickly (in Bucket terms).

He is currently running second in F5 and has a realistic shot at first so we know he will ride the wheels of the thing on the track, and so along with the development progress we will get real on track racing performance feedback too.

Currently with cut and try and a few good guesses its at 13.5 rear wheel hp and a 3.5k rpm spread of power, hopefully Fixer will keep working on it and we will get to see how it all unfolds and where Fixer gets to with this tuning project of the after market 50cc road bike 2T cylinder as it progresses from the usual starting place of cut and try to doing it "properly" by bringing ever more science to the party.

Wob, we value your input, maybe this is the year we see NZ's first documented 18rwhp F5 2T.

[wobbly]

I was dreaming late last night ( about 2Ts - what else ) and thought thru the statement that Frits was questioning ( a complement to a very skilled bullshit detector that man I must say ).
Maybe the logic of " unvapourised fuel only displaces O2 in the combustion process " leads to the Ex gas then also being low in O2 so the Lambda reads rich ?
I dont know to what extent ie what % of O2 can be displaced by fuel that is never burnt, and if that level is then sufficient to affect the Lambda reading.
That then leads me to the question - wouldn't a continuously misfiring engine read rich on the Lambda, and isnt that then the same end result as unburnt fuel droplets passing thru an engine?
This is too early in the morning for this - I need strong coffee.

[Grumph]

If oxygen makes up 20% of the atmosphere then in theory, 20% of the volume of unburned fuel equals the amount of oxygen displaced...

But you'd expect a lower proportion of oxy in the end gases anyway - so maybe the effect is bigger than at first appears.

maybe i need something stronger too.....

[wax]

Wobbly are you saying you think the lectron is the better carb size for size ??

[wobbly]

I have done the tests on a Superflow and the so called HV Lectrons will outflow a size for size Mikuni or Kehin easily , and ,as say a 38mm HV has a 34mm venturi
behind the slide it acts like a much smaller carb at 1/2 throttle.
In Europe I know they are using 30mm Lectrons on 50cc race engines with great success.
The SmartCarb does not have a venturi, but has an egg shaped bore at the slide that probably does the same thing.
They also have an aux venturi above the top of the entry trumpet, that is connected to the bowl air space - and it is this that gives the carb its auto adaption to air density,be it weather or altitude.
This for sure works a treat, with no jetting change when climbing Pikes Peak - but at the moment they do seem to be having endless trouble getting the things into the ball park at sea level.
At this stage Lectron do have a huge range of incremental needles to suit any application and also have a powerjet with very fine flow sizing that makes fine tuning a twin super easy.
I have just got a 30mm SmartCarb here for a Giggle project , so if someone with 1/2 a clue wants to do some testing im sure we could arrange something.

[wax]

I have done the tests on a Superflow and the so called HV Lectrons will outflow a size for size Mikuni or Kehin easily , and ,as say a 38mm HV has a 34mm venturi
behind the slide it acts like a much smaller carb at 1/2 throttle.
In Europe I know they are using 30mm Lectrons on 50cc race engines with great success.
The SmartCarb does not have a venturi, but has an egg shaped bore at the slide that probably does the same thing.
They also have an aux venturi above the top of the entry trumpet, that is connected to the bowl air space - and it is this that gives the carb its auto adaption to air density,be it weather or altitude.
This for sure works a treat, with no jetting change when climbing Pikes Peak - but at the moment they do seem to be having endless trouble getting the things into the ball park at sea level.
At this stage Lectron do have a huge range of incremental needles to suit any application and also have a powerjet with very fine flow sizing that makes fine tuning a twin super easy.
I have just got a 30mm SmartCarb here for a Giggle project , so if someone with 1/2 a clue wants to do some testing im sure we could arrange something.

I would love to take you up on that I have an 86cc ported scooter engine i have just finished building. Its a shame I am in australia, some say i have not even 1/2 a clue so best i sit this one out lol
Thanks for the information I am deciding if to try a lectron or to stick with my 28mm pwk on my new 86cc engine

[wobbly]

Here is a link to DynoTech,that mentions stale fuel as well.
I have been using the copper tube deto detector into my dyno headphones for years, so as im in a good mood again today here is the detail
on how to do it and why.

http://www.dynotechresearch.com/blog/archives.asp?chosenMonth=4&chosenYear=2013#294

Nowdays, I like to use the Czech deto box running into the dyno data logger, so i can see at a glance where the deto occurred exactly.

[wax]

Sounds good now if only i could adapt that to my helmet, then again I would most likley be listening so much I would crash.
thanks for the link

[husaberg]

http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=297278&d=1400751403

Variable pipe lengths with length or temps


Cagiva ran a system in the "lil Jon" days which extended the header pipe with a hydraulic actuation at huge pressure (1500psi) the pump allowed the header pipe to lengthen along the lines of 20mm extra or minus length .I guess they shorten the header length in operation. If I can be bothered I have pics somewhere.
Of course the Honda water injection based system was much simpler.QUOTE]


[QUOTE=Frits Overmars;1130191442]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.



Re adjustable pipes
I know Cagiva ran a Hydraulic system and I think electric is to slow and to thirsty for power.
I also know that Cagiva ran the power valve (YAMAHA Style I guess) and Atac valve on the Randy Mamola bike.

249692

I planed at a later stage to use a Greeves (woolley) style labryrinth seals with piston rings to seal the pipes.

My idea was compressed air. Easily rechargeable light nice and simple, super fast and a little goes along way.
I planed to run the Water injection the same way and use excess air in the pipes to reheat it them.
maybe a little fuel if there wasn't enough in the pipes to work it what do you think. I also envisaged using air/electric to trigger the Atac


Bimota did that once: they built a pressurized thin-wall tubular frame with a manometer, so you could scientifically establish when the frame had developed a crack.
Going electric on the movable pipes is not too bad either. I was talking about a Yam TZ500 four cylinder sidecar engine, but for a single the electricity consumption will not be all that much. Here are some pictures to wet your appetite:
249693249703249694

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.


Compressed air is rechargeable and simple. I am not so sure about 'light and going a long way'. You might want to do a rough calculation on how much volume at what pressure you consume each time the pipe is moved. That could force you to use a bigger air bottle than you had planned...
A CO2-cartridge could be your way out: I estimate its energy density to be about a hundredfold better than air. Or, what I would do in Holland: use LPG (liquified petroleum gas, or autogas). I don't know whether you guys use the stuff in NZ, but I can get it at every street corner; the pressure is about 8 bar and being liquid its energy density (just talking about the pressure, not about what happens when you light it) is much better than that of compressed air.





Saving that for pulling the slippery pipe.

Frits Overmars

A powervalve does not really give you real resonance power; it just prevents the pipe pulses from completely messing up the power curve at low revs. I expect a sliding pipe will make more low-down power.

http://www.pit-lane.biz/t1666p15-technique-rossigrm-2strokes-boat-engine?highlight=twin+rotary



If you are using an Ignitech then by adding an RZ or R1 powervalve servo means you can program any position you like into a moving slide or rotary "timing changer" - easy.
Having a movable "slide" in behind the closing edge of a rotary valve, pushed/pulled into position by servo cables, would be easy and reliable. Get on with it.


I was just pointing out that the idea of using water, great as it may be in theory, and on a dyno when looking for bottom end, it "works" just fine.
But in a controlled test to see if its was useful, it failed, as the systems effect had to be reduced so much that any gain in bottom end was still offset by a loss in the top end.
As Burgess said, when the effect was useful, it took too long to reheat the pipes.
My thoughts, from the testing I did with a PV and ATAC operated separately ( instead of combined together as many MX engines have now) is that this works real well with no down sides at all,and is easy to implement.



OK, here is some info on how to utilise the servo option on the Ignitech.
The servo has 5 wires, two are 12V +/- and the other 3 are the servo feedback positioning pot.
Always wire the two functions on separate plugs. Once you have the servo connected to the blade or whatever, disconnect the servo motor power plug.
Then on the screen you will have a readout for the servo position, as mV or as a % if using the RACE box.
I have never used the % option so here is how to program the mV setup. Drive the servo to the travel limit ( in, or down or whatever) by gripping the servo wheel with vise grips.
Cycle it back and forth a few times to get an accurate position that takes up any small slack in the cables.
Note down the "servo measured" value on the screen. Then wind the servo around to the opposite limit, note this value down.
Then in the servo screen you can enter the two values of fully up, and fully down, with an rpm span between them.
Use a few of the extra points in between, so you can, if needed, force a non linear movement with rpm ie not a straight line.
Hit program, turn off the ECU, turn it on again, and it will cycle up and down,as it has been programmed.
You can check the up and down positions and compare the "servo measured" to the "servo desired" on screen, in real time.
The hysteresis should be set usually at around 100mV, less will speed up the response, but go too low and the servo will "hunt" around the values programmed.
The RZ servos are all getting old and shagged - the newer R1 servo is mechanically very similar but uses a special molded in plug - I have the right ones to match.
The R6 and ZXR ones are not as well made, the shaft isnt supported at both ends properly.
Here is a sample wiring setup and a PV curve, set to start opening at 7200 and full open at 9000, with about 1V of span between.
You could use this to rotate a spool like an RZ, a blade like a flat PV or even the 1/2 throttle plate if you wanted to.



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:.


:niceone::niceone:
I'm impressed with how it slips all nice and steady!

Frits, may I ask, wouldn't it affect the 1st pressure wave in the diffuser, when fully inserted? -in a way to have a measurable impact on pipe effects I mean


You may. It will affect all the waves in the pipe. And it does have a measurable impact on pipe effects :2thumbsup .
But I suspect you are referring to the header intruding into the diffuser. It doesn't. Even in the shortest position everything is smooth inside the pipe.


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?

I came upon this today.

Slippy exhaust pipes
Why they're so difficult to pull, and how to fix it...
There has recently been a thread on the Mailing List in regards to the amount of effort required to "pull" the typical slippy (adjustable) exhaust pipe that is common in many road racing classes.
Well... A bit over 20 years ago, I had the same frustration, and I'll explain what I found, and how I solved the problem.
The image below show's an approximation of a "typical" slippy exhaust pipe. I have not shown the outlet hole in the "can"... (and a number of other things are missing as well), but this will serve the purpose for now. The moveable rear (convergent) cone is shown in its "out" position by the blue lines... and in it's fully "in" position by the green lines. The thick magenta line is a rough representation of the cable which pulls the rear cone/stinger assembly.
http://www.muller.net/mullermachine/docs/exhaust1.gif
OK... here's the problem in a nutshell: The amount of effort required to "pull" the rear cone is directly proportional to the difference in pressure between the front and back sides of the moveable cone. (There's some other minor things like friction, but they're insignificant compared to the pressure differential).
Since the the rear cone (at its big end) does not fit the large center section perfectly, some "pressure" leaks by the outside of the cone into the area behind the cone. If the outer rear cone (the one that supports the stinger) has too much clearance on the stinger (where I wrote "Here's the problem"), then the pressure behind the rear cone can "bleed" into the can (which has lower pressure than the inside of the exhaust pipe). This results in a pressure differential between the front (engine) side of the rear cone, and the back side.
THAT is what you are pulling "against" when you try to pull in your slippy pipe.

Now here's how I fixed the problem...
Years ago, Hartman Engineering made some very nice spun "outer" rear cones especially for slippy pipes. I started with one of those. They were made with a very large hole on the small end. (Oh... the other thing that was really nice about those Hartman cones is that they were very short. This allowed you to get the weld to the center section a long ways away from where the adjustable cone would be sliding.... which made it easier to keep the center section nice and round).
I made an insert for the small end of this cone (shown in red in the drawing below). This "insert" had a bit of a "bell-mouthed" shape to the inside diameter. I did this so that I could run a very tight fit to the stinger, without the stinger "binding" due to any misalignment that might exist. I also took the stinger material (before welding it to the cone) and had it hard-chromed, and then ground the outside diameter. This made it perfectly straight and round, as well as giving me a super fine finish that would resist any sort of galling or seizing. I gave the insert about .005 clearance on the stinger (as I recall).
How did it work?
Too well. At the time I was running Open class. Due to the power, Open engines were notorious for being almost impossible to pull the exhaust pipe for the full race (an hour long at the time). My first time on the track with this pipe was a complete surprise. The very first left-hand sweeper I went through, the rear cone went all the way in by itself, just from cornering force! The pipe was actually far too easy to pull. My solution was to experiment with "vent" holes into the can. With the clearance that I had given the stinger in my "support sleeve"... as well as the fit of the large end of the cone in the center section of the pipe... I ended up running a 3/16" diameter "bleed hole" from the outer rear cone (the short steep one in the drawing below) into the can. This gave just about the perfect "feel" in my case. I could operate the pipe handle with one finger... yet there was enough pressure on the cone to move it back out fairly quickly when I let go of the handle.
http://www.muller.net/mullermachine/docs/exhaust2.gif
You may not care to build your own slippy pipe... and we're seeing less and less classes where slippys are allowed... but hopefully this might help some of you that still run them.
Just remember: the effort required to pull the rear cone is directly related to the pressure differential on the front and back sides of the moveable cone. Anything you can do to prevent leakage around the stinger and into the can will make the pipe easier to operate... up to the point (I discovered) where it's too easy.



There are several options in lengthening a pipe. You can move the end cone, like on the above drawing, or you can lengthen the header, like on the trombone pipe.
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: 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 result in 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.


Slippy exhaust pipes

I was having a quick look at some old posts and re-discovered this from F5 Dave about adjustable length expansion chambers. It has to be a good idea, if it could be automated to work by itself even better. Now how to fit it onto my bike?????????????

From an Add for a RC Car exhaust:- The precisely engineered components of the Power Exhaust System use the unique exhaust pressure characteristics of 2-stroke motors to dynamically adjust the tuned length of the exhaust system. This is why Power Exhaust Systems can achieve maximum performance over a much wider RPM range than is possible with a fixed pipe. Changing of the tuned length is accomplished by the movement of the internal Tuned Assembly within the Power Exhaust Body.

While traditional tuned pipes focus on only one RPM range for maximum effect, the Power Exhaust System can boost performance throughout the entire RPM range. It’s (possibly) the world’s only tuned pipe that dynamically adjusts its tuned length during use.

"Tuned length" refers to the total combined length of the exhaust header and tuned pipe from the face of the piston to the end point of the convergent cone. This is the factor that is generally calculated first in pipe design. The tuned length is a function of certain fixed engine parameters and more significantly, a target RPM for maximum performance. Of course, a designer can only choose one target RPM. One RPM equals one best-tuned length. For a maximum benefit over a greater range of RPM you must change the tuned length.

F5 Daves might be better because only the rear cone moves but the RC Car pipe shows how it could be automated.

Pic-1 from F5 Daves post

Pics-2 to 4 is how RC Cars do it.

.


.

"Tuned length" refers to the total combined length of the exhaust header and tuned pipe from the face of the piston to some point on the convergent cone. This is the factor that is generally calculated first in pipe design.

Danger Danger Danger There are two common ways that the term "Tuned Length" is used. Some people think tuned length is measured to the end of the convergent cone others measure tuned length to the mean reflective point half way along the cone. Thats half way along the complete cone with its pointy bit still on the end.

When talking about/compairing/calculating tuned lengths you need to know how the "Tuned Length" is being defined. Its an important difference, about 50-80mm or 1,000 to 1,500 RPM and can completly confuse your tuning efforts.

I am indebted to Thomas for pointing this out to me.

He also says that the sum of all the individual stages (cones) in Pic-1 should more correctly be called the overall length, and the overall length is most certinaly not the tuned length given by most/all formulas that you see for calculating the tuned length of an expansion chamber.

Most/all formulas for tuned length based on time and the speed of sound give a value for the length from the piston face to the mean reflective point of the convergent cone (Pic-2) and this is correctly called the "Tuned Length" because this is the mean distance/time the pressure wave travels out and back in the pipe.

Pic-1 Tuned Length. "tuned length measured to the end of the cone"

Pic-2 Tuned Length. "tuned length measured to the mean reflective point of the cone"

Pic-1 is wrong and Pic-2 is right as the "Tuned Length" is the mean distance/time the pressure wave travels out and back in the pipe.
[QUOTE=speedpro;1129291137]It's been done before in bucket racing, Peter Steadman. The end cone was slid back and forth by a servo, possibly a central locking solenoid. It had a cable pulling it in each direction. Remember Peter's bike has the stinger exiting from the centre section. I'm not sure why it wasn't persisted with. His bike was pretty quick without it so maybe it just wasn't worth the added complexity.


I had a bit of a quick squizzy at The effects of crankcase volume on the delivery ratio:-
http://www.edj.net/2stroke/jennings/...ase_volume.pdf (The effects of crankcase volume on the delivery ratio:- http://www.edj.net/2stroke/jennings/...ase_volume.pdf) & must admit I'd never heard of the test engines. Then noticed they spin out to the dizzy heights of 4500rpm at best. One can imagine that the pressures involved are not proportional compared to time areas due to gas flow at up to 3x the revs.

ok here's one to send people down the garden path with a nice but difficult idea
http://www.muller.net/mullermachine/docs/slippy1.html

Borut makes Zeeltronics stuff for mainly RGV, NSR etc but could be possible to adapt to a bucket but you'd have to talk to him, you need 3 boxes to get programmable & will cost a site more than 100 euro. (I have a setup on my 500).

Pipe design elements relating to variable with pipes


If I were to explain pipe design I would need to write a book,but in general things are pretty straight forward in relation to the % values.
End of header is always 31 to 33% and end of diffuser is always 62 to 68%.
To see the effect of a silly long header, you can watch the pressure ratio at the Ex port, and thus the effect this has on the depression in the cylinder.
We are looking for the lowest and widest negative ratio we can get around bdc when the transfers are fully open.
A long header delays the beginning of the depression too late in the cycle, when in the power band.
In a race 2T we are always fighting power range Vs peak power.
Shorter diffusers create steeper angles,thus greater wave amplitude, but this narrows the effective band width.
So - in general the best compromise is around 66%.



The % I quoted for header means that portion of the length from piston to rear cone end.
Its from the piston to the beginning of the diffuser, what happens in between isnt relevant.
Unless of course you use a small Ex duct and a bigger header, that makes more power.
And of course same for the diffuser end, that is simply 66% of the length from the piston to the end of the rear cone.
Frits Overmars

A powervalve does not really give you real resonance power; it just prevents the pipe pulses from completely messing up the power curve at low revs. I expect a sliding pipe will make more low-down power.

http://www.pit-lane.biz/t1666p15-technique-rossigrm-2strokes-boat-engine?highlight=twin+rotary[/QUOTE



Imagine the valve passes 60 cc of fuel per minute, but the engine only needs 30 cc. How would you go about that? You could open the valve for 30 seconds and then shut it, but by that time the engine may have drowned.
Open it for one second, close it during one second, open it for one second, sounds more sensible, doesn't it? That is why I quoted the valve's frequency: 13 Hz.
That means it can open and close up to 13 times per second. This again means it could open for 1/13 of a second and close the rest of the second, or open for 12/13 of a second and close during 1/13 s, or everything in between. And of course it can stay completely open or closed; enough possibilities to govern the mixture.

The ignition timing does not have to be changed when you use an electronic power jet. But both the ignition timing and the powerjet timing are means of influencing the exhaust gas temperature. A late ignition and/or a lean mixture both cause a higher EGT, so you can match the exhaust resonance frequency to a rising engine rpm.
And if you have that power jet available, the ignition does not have to do it all by itself anymore, so you can search for a timing that gives a better overall result.



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.

[husaberg]

Oh i missed this one Frits

Water injection into exhaust pipes in order to lower the exhaust gas temperature and thus the system's resonating frequency has been tried over and over. It works, but it does nothing to protect the engine from detonation.
Therefore I wanted to inject water into the combustion chamber, exchanging temperature for steam pressure. I even had a water reservoir designed around the exhaust tail pipe in order to heat the water to just below its boiling point before it was injected.
I also tried to hit the piston crown with the injected water but a steam cushion would form, preventing most of the water from wetting the piston crown. Breaking through that steam cushion would require a huge (for that era) pressure and a very thin water jet, or the engine would drown. I could not get it realized back then (in 1992, when I was working for Rumi) so there are no test bench data.

[Frits Overmars]

I was dreaming late last night ( about 2Ts - what else ) and thought thru the statement that Frits was questioning ( a complement to a very skilled bullshit detector that man I must say ).
Maybe the logic of " unvapourised fuel only displaces O2 in the combustion process " leads to the Ex gas then also being low in O2 so the Lambda reads rich ?
I dont know to what extent ie what % of O2 can be displaced by fuel that is never burnt, and if that level is then sufficient to affect the Lambda reading.
That then leads me to the question - wouldn't a continuously misfiring engine read rich on the Lambda, and isnt that then the same end result as unburnt fuel droplets passing thru an engine?
This is too early in the morning for this - I need strong coffee.I hope you had that coffee, Wob. And as you are ten hours ahead of me, I suspect you are sipping something tastier by now.
First let's look at the 'logic' of unvaporized fuel displacing O2. The fuel is carried into the combustion chamber by the air; air and fuel are in there together and there's no way that the air could be forced away by unvaporized fuel droplets.
Unvaporized droplets won't be doing much forcing anyway because the volume of an unvaporized droplet is about a thousandfold smaller than the volume of a vaporized droplet.

Wob, detecting bullshit is quite easy if you produced that bullshit yourself in the past.
I once ran an engine on the test bench and the Lambda sensor said 'lean', or so I interpreted it at the time. So I jetted up.
Then the Lambda sensor said: 'now it's even leaner!'
What really happened was: at the first test the engine was so rich it was misfiring. And no combustion meant: unused oxygen in the exhaust gas.
Naturally when I jetted up, the misfiring became worse, even more combustion cycles failed and even more unused O2 hit the Lambda sensor.

Lesson learned: a Lambda sensor does not say 'rich' or 'lean'. All it says is: I see ogygen'.

[husaberg]

First let's look at the 'logic' of unvaporized fuel displacing O2. The fuel is carried into the combustion chamber by the air; air and fuel are in there together and there's no way that the air could be forced away by unvaporized fuel droplets.
Unvaporized droplets won't be doing much forcing anyway because the volume of an unvaporized droplet is about a thousandfold smaller than the volume of a vaporized droplet.

Wob, detecting bullshit is quite easy if you produced that bullshit yourself in the past. I once ran an engine on the test bench and the Lambda sensor said 'lean', or so I interpreted it at the time. So I jetted up. Then the Lambda sensor said: 'now it's even leaner!'
What really happened was: at the first test the engine was so rich it was misfiring. This meant no combustion, so unused oxygen in the exhaust gas. Naturally when I jetted up, the misfiring became worse, even more combustion cycles failed and even more unused O2 hit the Lambda sensor.

Lesson learned: a Lambda sensor does not say 'rich' or 'lean'. All it says is: I see ogygen'.
I was going to say something similar but only cause it was in a book i read today.......
Where as you thought of it cause you understood.......
forgive Cameron he was talking about 4 strokes though
http://books.google.co.nz/books?id=J7tQp2LtsYIC&pg=PA70&lpg=PA70&dq=fuel+wash++air+is+not+the+only+thing+flowing+in +the+intake+port&source=bl&ots=qeM0DtkxqB&sig=aZ1f8yCSg6EEY0WRlcYL328xoVI&hl=en&sa=X&ei=YNZ9U8aKFMj98QXh64GQAg&ved=0CCkQ6AEwAA#v=onepage&q=fuel%20wash%20%20air%20is%20not%20the%20only%20t hing%20flowing%20in%20the%20intake%20port&f=false

Can you tell us about the steam in cylinder experiments Frits?

Also if i can be so bold i was lloking at a pic of a RSW or RSA crank the other day and it seemed to have what looked like Brass rings around the Crankpin pressed in the crankcheeks?
Is that what they are? and why are they there?

[Frits Overmars]

.... forgive Cameron he was talking about 4 strokes though http://books.google.co.nz/books?id=J7tQp2LtsYIC&pg=PA70&lpg=PA70&dq=fuel+wash++air+is+not+the+only+thing+flowing+in +the+intake+port&source=bl&ots=qeM0DtkxqB&sig=aZ1f8yCSg6EEY0WRlcYL328xoVI&hl=en&sa=X&ei=YNZ9U8aKFMj98QXh64GQAg&ved=0CCkQ6AEwAA#v=onepage&q=fuel washair is not the only thing flowing in the intake port&f=false Anything Kevin Cameron writes is worth reading.
Can you tell us about the steam in cylinder experiments Frits?Only what I wrote above: that there were no test results, for the above-mentioned reasons.
i was lloking at a pic of a RSW or RSA crank the other day and it seemed to have what looked like Brass rings around the Crankpin pressed in the crankcheeks? Is that what they are? and why are they there?Yes, that is what they are (well, not brass but bronze) and they are there to reduce axial friction between the con rod and the crank webs.

[wobbly]

Amazing Frits how complex logic can get, and more amazing that in reality its all simple when you finally get to understand.
Of course Lambda only reads the O2, what a dumb shit.

Anyway more importantly I have now for the first time seen the inside face of an Aprilia crank.
Apart from the bronze ring ( does that replace a silver plated washer ? ) I now see a huge amount of inserts in the crank face.
These you dont see in the many pics that show a ton of what is obviously Mallory around the circumference increasing the rotational inertia.
I assume the inserts on the inside are filled with lighter material ? in the pic I cant tell if its alloy or even more Mallory heavy metal.

[peewee]

wobby sorry i dont hang around much. you know what the best drag pipes are for a banshee ? probly use some ported stock cylinders. might use some cubs if its in the budget but its not looking like it. was kind of looking for a challenge to see how good i can make the stockers run and it wont cost a ton of money

[2T Institute]

Amazing Frits how complex logic can get, and more amazing that in reality its all simple when you finally get to understand.
Of course Lambda only reads the O2, what a dumb shit.

Anyway more importantly I have now for the first time seen the inside face of an Aprilia crank.
Apart from the bronze ring ( does that replace a silver plated washer ? ) I now see a huge amount of inserts in the crank face.
These you dont see in the many pics that show a ton of what is obviously Mallory around the circumference increasing the rotational inertia.
I assume the inserts on the inside are filled with lighter material ? in the pic I cant tell if its alloy or even more Mallory heavy metal.

This was discussed on the Aprilia FB page Wob, not sure if it was Jan or Thijs that said it was tungsten with a magnesium cap. Thrusts are still there.

[husaberg]

This was discussed on the Aprilia FB page Wob, not sure if it was Jan or Thijs that said it was tungsten with a magnesium cap. Thrusts are still there.

Its something that has been revolving in my mind as they are cracked... they seem to be actually pressed in the full distance of the pin rather than a thrust washer insert replacement? there def seems to be an full insert (steel looking inner one at that on the left side picture)

[WilDun]

Its something that has been revolving in my mind as they are cracked... they seem to be actually pressed in the full distance of the pin rather than a thrust washer insert replacement? there def seems to be an full insert (steel looking inner one at that on the left side picture)

I would doubt very much if that's the case as bronze might be good bearing material but probably not as good as steel to carry the load and help hold the pin against rotation (differential expansion rate and all that).

What interests me most is the placing of the balance plugs, - this picture gives me the notion that all the light plugs appear to be the smaller ones and the heavy plugs are the larger ones.
If you look carefully at the left picture (lets say the crank is at 3 o'clock, the two smaller lighter plugs are grouped together at around 5 or 6 o'clock and the three larger plugs (heavy ones?) grouped together are at about 10 o'clock. - clear as mud? - maybe that's how it normally is these days, I dunno.
No doubt someone can correct me if I'm a bit behind here.:rolleyes:

[Ocean1]

Its something that has been revolving in my mind as they are cracked... they seem to be actually pressed in the full distance of the pin rather than a thrust washer insert replacement? there def seems to be an full insert (steel looking inner one at that on the left side picture)

Think what you're looking at there is the result of the needles trying to escape the rod.

In fact there's plenty of evidence that the rod's been trying to escape the crank...

[Frits Overmars]

The bronze rings are only about 2 mm thick. Their advantage over the usual thrust washers is that they can get rid of friction heat easier and won't vibrate themselves to pieces.
The combination of Mallory slugs and hollow light-alloy caps serves to combine a low total mass of the cranks with a high inertia that made the 250 cc twins more rideable. The same setup was used for the 125 singles, but as Jan Thiel said: 'In seven years of experimenting we have not been able to establish what is best: high or low inertia'.
My approach: when in doubt, choose low; it will be a blessing for the transmission and the rear tire.

[husaberg]

Think what you're looking at there is the result of the needles trying to escape the rod.

In fact there's plenty of evidence that the rod's been trying to escape the crank...

SO the ring shape about 4mm larger than the crankpin is only witness marks.... from the rollers....

[Frits Overmars]

SO the ring shape about 4mm larger than the crankpin is only witness marks.... from the rollers....The internal diameter of the bronze rings is 6 mm (if memory serves) larger than the crankpin diameter; the press fit is at both the internal and external circumferences of the rings.

[husaberg]

The internal diameter of the bronze rings is 6 mm (if memory serves) larger than the crankpin diameter; the press fit is at both the internal and external circumferences of the rings.

OK was it an Aprilia only trick (the pressed in thrust washers) never seen it before but never seen a lot of Euro GP bike cranks either...

[Frits Overmars]

OK was it an Aprilia only trick (the pressed in thrust washers) never seen it before but never seen a lot of Euro GP bike cranks either...I don't know Husa; I haven't seen it anywhere else. But I did see a solution that I like even better: the Garelli engines had a thin layer of bronze sprayed onto the insides of the crank webs. That way you could make the crankshaft narrower without losing press fit length around the crankpin.

[husaberg]

I don't know Husa; I haven't seen it anywhere else. But I did see a solution that I like even better: the Garelli engines had a thin layer of bronze sprayed onto the insides of the crank webs. That way you could make the crankshaft narrower without losing press fit length around the crankpin.

Great stuff as always and great to see you back on the thread.
Me and rob were jamming up another thread the other day and were wondering what the relationship was with the belly diameter of the pipe for a 2 stroke exhaust.
i was musing it is an expression of the cylinder size with a factor for max suckabilty for want of a better term.
is the diameter just about achieving the required volume....( i have likely got a lot ass about face)
what we were looking for was a way for restrict power output of a two stroke that could be easily measured?

[Frits Overmars]

...wondering what the relationship was with the belly diameter of the pipe for a 2 stroke exhaust. i was musing it is an expression of the cylinder size with a factor for max suckabilty for want of a better term.Yes, it is about the ratio between suction energy and reflection energy. BTW, I like your word suckability (reminds me of Wobbly's long-standing offer :msn-wink:)
what we were looking for was a way for restrict power output of a two stroke that could be easily measured?I haven't got a clue what you're on about; maybe one must be a Kiwi to understand this sentence?

[husaberg]

Yes, it is about the ratio between suction energy and reflection energy. BTW, I like your word suckability (reminds me of Wobbly's long-standing offer :msn-wink:)I haven't got a clue what you're on about; maybe one must be a Kiwi to understand this sentence?

Maybe, the buckets have a 24mm carb restriction for air cooled 125's what had came up (from Dave), was maybe a restriction on pipe belly diameter in order to restrict another engine designs output.

[Drew]

Maybe, the buckets have a 24mm carb restriction for air cooled 125's what had came up (from Dave), was maybe a restriction on pipe belly diameter in order to restrict another engine designs output.Still a poorly formed sentence.

The question is. Would restricting the chamber diameter on an 85cc two stroke, be a good and easily detectable method for capping the power without making it impossible to get a decent power spread?

[wobbly]

Doubt that the marks on the bronze would be the rollers, as for sure they would be encapsulated by the cage - unless that crank has had a cage failure.
Full complement cage less roller big ends were canned back when we used chainsaws on karts.
I think low mass /high inertia is very much a relative term in the case of the Aprilia crank - what you Frits would describe as "low inertia " in relation to most say MX or kart type cranks
would be way higher than most.
I go back to the historical issues that HRC had when they tried total loss on the RS125, take off the high inertia rotor and replace it with a simple timing disk
and all the overev simply disappeared.
The A kits then came out with cranks full of Tungsten, and suddenly we saw aftermarket so called " heavy " cranks come onto the scene for those liking total loss.
So I think what Jan would be referring to in the testing of low Vs high inertia at Aprilia ,is in reality comparing high with Super high in a normal context.
Maxter have for a while, and now TM are finally getting on the band wagon and have lots of alloy and Tungsten inserts in there so called ' factory special ' crank webs.

Restricting pipe belly diameter is a way of limiting ultimate power of any engine - but a restricted carb is so much simpler.
And even simpler is what we use in the new restricted junior kart engines, a full size pipe but with a specified round restricted
diameter in the pipe flange.
In my dyno testing this gave a virtually linear variation in power.
20mm stock was 10Hp, 17mm was around 7Hp, 15mm was around 5,5Hp etc.
Putting a number on the belly just means someone serious would have to test a dozen different geometry's to find the best compromise - old story of the more rules, the more expense to go fast.

[Drew]

Restricting pipe belly diameter is a way of limiting ultimate power of any engine - but a restricted carb is so much simpler.
And even simpler is what we use in the new restricted junior kart engines, a full size pipe but with a specified round restricted
diameter in the pipe flange.
In my dyno testing this gave a virtually linear variation in power.
20mm stock was 10Hp, 17mm was around 7Hp, 15mm was around 5,5Hp etc.
Putting a number on the belly just means someone serious would have to test a dozen different geometry's to find the best compromise - old story of the more rules, the more expense to go fast.
Are those numbers all done with the same pipe fitted, and were the curves still similar? Essentially, it's just like running the same motor at part throttle, don't two strokes really hate that and go bang?

[pete376403]

The bronze rings are only about 2 mm thick. Their advantage over the usual thrust washers is that they can get rid of friction heat easier and won't vibrate themselves to pieces.
.

I read something (probably by Cameron) that some engine builders use thrust washers/spacers in the piston pin to get the rod centralised on the crankpin, and no thrust washers on the crank pin at all. The logic is that the friction between the rod and piston is much less, ie a small oscillating motion rather than the full rotational motion as would normally be at the crankpin, so less heat generated, and more importantly less heat going into the big end bearing. True?

[wobbly]

The tests with the junior engine were with the identical unrestricted pipe, just a header with a step of varying sizes.
No issue with tuning or reliability at all, just less power each size change.
The curve shape was much the same, but as you went smaller the top end power rolled off faster from a lower peak.
In the end we opted for the step header and a rev limiter, over using a smaller carb as this meant an easy upgrade route to just change the header.
The restricted 65cc engine rev limits to 10,000 the unrestricted goes to 14,000.

Thrusts up in the piston are very rare these days, I think RGV was the last,as sure the friction is less with the small oscillating movement
but lack of sufficient lubrication is a reliability issue.
KT100 Yamaha has the option for both, and the lower thrusts are pretty much universal now due to the alloy washers up the top failing
even when made of 7075 or hard anodised.

[husaberg]

Still a poorly formed sentence.

The question is. Would restricting the chamber diameter on an 85cc two stroke, be a good and easily detectable method for capping the power without making it impossible to get a decent power spread?

Drew the day i decide to have you writing my memoirs, I will of course knowledge your help.
But considering you generally start your own sentences with "look Cunt" it may not pan out that way.


For the record Drew i never mentioned the 85's because it was not pertinent to the actual question.

As for the poor formed, your ugly mug springs to mind........:innocent:

Ps thanks Wob........

[Drew]

Drew the day i decide to have you writing my memoirs, I will of course knowledge your help.
But considering you generally start your own sentences with "look Cunt" it may not pan out that way.


For the record Drew i never mentioned the 85's because it was not pertinent to the actual question.

As for the poor formed, your ugly mug springs to mind........:innocent:

Ps thanks Wob........

Look cunt. Hehehehe. Na, been a while since I stopped doing that. Although it was easier to piss people off that way, I now enjoy trolling (or trying to) by presenting the unpopular opinion in a way that nearly makes sense.

Lemme know when we're gonna get started on those memoirs.

Yes, the engine size was not relevant to the question.

Back to two strokes...

I have an RG150 that for the time being will be my road bike till it blows up or I get bored. Is it gonna be more reliable running premix gas, or oiled by the pump?

[TZ350]

I have an RG150 ... Is it gonna be more reliable running premix gas, or oiled by the pump?

2T, be more reliable if you leave it in the shed, last longer that way too. .... :laugh:

[Drew]

2T, be more reliable if you leave it in the shed, last longer that way too. .... :laugh:
Awww, you do get me.:love:

Alas that isn't an option for now. It is a free bike, goes good (I think, it's pissing down right now so I don't want to test ride it) and until I can afford another GSXR1000 it'll have to do.

[TZ350]

297324

The head is off with Flettner to have the combustion chamber machined.

297327

In the meantime I have been using EngMod to explore what needs doing to get the required STA's.

297325

The blowdown STA is the critical one as that pretty much defines what is possible followed by the transfers. Wobs advice is to go a little higher on the transfer STA to make up for any short comings in their real life flow characteristics.

297326 Methanol+15%Nitro297328

I think that next year I will try for a rule change allowing model aeroplane fuel. Fuel for kids toys, cant be any harm in that, and we need to get more kids into Buckets, MX85's and all that, right. ;)

Seriously I hear there is another TF100 project happening, Flettner is building it and if it comes off we will get to test it on the dyno and take it out to the track...:woohoo:

[Ocean1]

SO the ring shape about 4mm larger than the crankpin is only witness marks.... from the rollers....

Think so. Also, look at all of the other marks on the inside surfaces, either someone's ground the pin in situ, (unlikely) or the rod's a) had an almost full width beam and b) has floated so far sideways that it's begun to do a similar job...

[Ocean1]

Doubt that the marks on the bronze would be the rollers, as for sure they would be encapsulated by the cage - unless that crank has had a cage failure.

Perhaps the cage made the marks? Or the side of the rod journal. Either way, from the cracks and surface colour it looks like the bronze has worn far more rapidly than normal, there's been violence committed inside that unit.

[TZ350]

297338

I have just managed to get a set of three stage power valves.

297337

It looks like the RGV250 three stage timings are:-

104 atdc
90 atdc
84 atdc

I am not sure how much these can be changed but I would like to have fully open at 80 atdc.

[Bert]

297338

I have just managed to get a set of three stage power valves.

297337

It looks like the RGV250 three stage timings are:-

104 atdc
90 atdc
84 atdc

I am not sure how much these can be changed but I would like to have fully open at 80 atdc.

Looking forward to seeing this unfold Rob.
Having seen Mike's one and Scotty rocket many years ago; I'd always wanted to build one (even had all the parts for it)....

[Muciek]

How far the blades are from piston? Could You take for me a foto looking from outside of ex port?

[TZ350]

How far the blades are from piston? Could You take for me a foto looking from outside of ex port?

I wont be back in the shed for a day or two to take a photo but from what I could determine the gap was very close 0.5mm or so.

[husaberg]

There is a tiny bit of gold buried in here, can you find it Rob...

[chrisc]

Interesting read, thanks for posting Husa. How old is that article out of interest

[husaberg]

Interesting read, thanks for posting Husa. How old is that article out of interest

This one i did not scan, but stole from the 2SMX site but i'd say 76-78 as it was a M model.....
Guessing the physics have not changed though.........

below nice pic of atac.

[wobbly]

Ha Ha, amazing - guess who just got the job to do the solid modelling for CNC machining new replica head chamber shapes made on the Webco dies.

[Grumph]

Ha Ha, amazing - guess who just got the job to do the solid modelling for CNC machining new replica head chamber shapes made on the Webco dies.

Those webco heads were much better than some OE for finning area...Are they wanting OE replica shapes or are you sneaking in improvements ? Ask if they'll list unmachined heads too if you would please...

[husaberg]

Ha Ha, amazing - guess who just got the job to do the solid modelling for CNC machining new replica head chamber shapes made on the Webco dies.

Did you see the "gold" buried in there Wayne?
show us a piccy......

[wobbly]

Honda solid copper head ?

All I have at this stage is the CNC shape to do the first head for a 250 twin.
But will keep you lot informed as the project advances.

[husaberg]

Honda solid copper head ?

All I have at this stage is the CNC shape to do the first head for a 250 twin.
But will keep you lot informed as the project advances.

:niceone:12 pounds of it they must have thought it was worth it
http://rx.iscdn.net/2008/11/marty_smith_rc_125_006.jpg

[Grumph]

[QUOTE=husaberg;:niceone:12 pounds of it they must have thought it was worth it[/QUOTE]

From what i remember reading at the time it brought the bike up to the FIM minimum weight - 2 birds with one 12lb stone....

[koba]

From what i remember reading at the time it brought the bike up to the FIM minimum weight - 2 birds with one 12lb stone....

Smart place to put extra weight!

[chrisc]

https://farm4.staticflickr.com/3711/14284160093_19cd73a193_b.jpg (https://flic.kr/p/nLf49i)
_MG_6029 (https://flic.kr/p/nLf49i) by sonscc (https://www.flickr.com/people/120242274@N04/), on Flickr

Notice anything about this photo of the front of the pack today at Mt Welly?

[TZ350]

....... :D

All two strokes .... and the gaggle of FXR's chasing them is no where to be seen.

Fixers 50 ran well to, the race I saw he finished 1st with a best lap time of 31.44 and that puts him in the A grade F4 time bracket along with the hot FXRs, not bad for a 50.


Hi all. The results of Round 7 of the Auckland Buckets Championship have been published on the Mylaps website. You can see the detailed results here: http://www.mylaps.com/en/events/1022466

The current state of all of the 2013-2014 Auckland championships (F4, B-grade, C-grade, F5 and Sidecars) plus the combined results of the Dominic Howe memorial Trophy are here: http://www.mylaps.com/en/championships/31443

Any issues, feel free to shoot me ... I'm not just the messenger.

Tim

All the results for round 7

[Sketchy_Racer]

https://farm4.staticflickr.com/3711/14284160093_19cd73a193_b.jpg (https://flic.kr/p/nLf49i)
_MG_6029 (https://flic.kr/p/nLf49i) by sonscc (https://www.flickr.com/people/120242274@N04/), on Flickr

Notice anything about this photo of the front of the pack today at Mt Welly?

The top 3 are all RS chassis ;)

[chrisc]

The top 3 are all RS chassis ;)

Haha good call. Gary on the MB100 actually finished second in the second points race. He unfortunately didn't finish the first race.
Interesting note on the MB100 is that it has RS wheels, RS forks and fork clamps and has a NF4 RS style rear shock modification. I think it's brilliant although it clearly is still not an RS125 chassis.

[TZ350]

The top 3 are all RS chassis ;)

Hmmm true and the consistent front runner is 80-85cc it must mean something.... just not sure what....:scratch:

[Sketchy_Racer]

They're a great chassis those RS chassis and surprisingly work very well as a bucket racer on our tight tracks!

I'm envious of that RS80.

[TZ350]

297383

Here we have a water cooled 80-85cc (Derbi?) followed by three air cooled 2Ts, a 125cc Kawasaki farm bike, a 125cc Suzuki farm bike and a 125 Honda commuter bike engine, all consistent front runners.

[diesel pig]

I am pretty shore mb's can not be taken out to 125 without going thou the sleeve.

[TZ350]

I am pretty shore mb's can not be taken out to 125 without going thou the sleeve.

Yes my bad .... its a MB100 so 100cc commuter bike engine.

This one is in its original frame but with up rated suspension, I am not sure about its capacity but your right, its probably not going to be 125.

[wobbly]

TeeZee I think your bmep for the RGV Aircooled is a bit high, your numbers would translate into near on 40 RWHP.
Pulling the proposed numbers back to around 12 Bar is still a tough ask, but more doable I think.
Going too radical is just going to create transfers that will loose excessive velocity/stream control - even with a good powervalve setup it will
drop the mid power too much.

[husaberg]

I am pretty shore mb's can not be taken out to 125 without going thou the sleeve.

There is a cylinder available for them for the full 125.....
Search 57mm MB8.........

[ken seeber]

FUEL DROPLET SIZE REALITY CHECK

Some pages ago, there was some discussion on fuel droplets. Got me thinking as to what size a fuel droplet might be.

So, using the RSA 125, 54 hp @ 12,000 rpm as an example. Rounding numbers as we go, this equates to 40 kW. Referring to an SAE paper 2004-01-3561, the instrumented dynamometer performance of a Honda RS125 engine was measured and compared to various computer predictions. This showed a best BSFC (brake mean specific fuel consumption or basically fuel mass flow rate per unit of power) of 400 gm/kWhr. Using this figure as a general guide, we can calculate a fuel flow rate of 40 * 0.4 = 16 kg/hr = 0.27 kg/min = 270 gm/min.

At 12,000 rpm, this gives us 0.023 gm/cycle. Using a fuel density of 0.74, this gives us a fuel volume per cycle of 0.031 mm^3.

If this was a cube of fuel, it would be of (0.031)^0.333 = 0.31 mm per side or if a spherical droplet, it would be of (0.031 *3/4 * π)^0.333 = Ø0.4 mm.

Pretty small stuff really, not something like the Ø3 -4 mm as one might imagine a droplet might be.

Taking this one stage further, if the A/F ratio was 12:1, this would mean 0.023 * 12 = 0.28 gm air was entering the engine per cycle. Using an air density of 1.2 kg/met^3 (at sea level & 15 deg C), this would give us a volume of air entering the engine of 0.000233 met^3 = 233 cc. From this the Delivery Ratio can be calculated at 233/125 = 1.87 : 1. This is pretty good, and sort of correlates with the DR indicated in the SAE paper of around 1.4 : 1, this engine under their test conditions was around 30 kW, not the 40 of the RSA.

Comparing the 233 cc to the volume in the cylinder at the time of exhaust port closure. This (trapping) cylinder volume at the time of exhaust port closure (based on a 120 mm rod, 54 stroke and 192 exh open duration, gives a stroke of 27.45 mm from port closure to TDC) would be 63 cc.

So, ignoring all temperature rises and pressure variations, this means we are stuffing 233 cc of air into a 63 cc volume, a ratio of 3.7 : 1. Some time ago on pitlane.biz, Frits (I think) stated that Jan Thiel took the entire exhaust off the RSA engine and tested it. Would have been a tad noisy I’d imagine. It obviously would have had no benefit of any harmonic supercharging (as with the expansion chamber) and resulted in a power output of 18 hp, compared to the 54 hp which is 3 times the power. Sort of matches the 3.7 : 1. Tells you just how useful the expansion chamber exhausts system.

There you go, a bit of rough trivia.

Ken

[peewee]

i wonder how many pebbles the front tire flipped into the cylinder :killingme


https://www.youtube.com/watch?v=P-O9nDNzPKM

[Flettner]

If you were constructing say a 25cc cylinder, I would imagine you would use model engine cylinder technology?
ABC, aluminium, brass, chrome, do they still make small engines like this with a cast in brass sleeve that takes the hard chrome easily. Is the brass sleeve coated with anything before the alloy is cast on? I think with the model engine I had, the brass sleeve was only pushed in?
Cylinder is water cooled, or it would be if I was making some.

[jasonu]

https://farm4.staticflickr.com/3711/14284160093_19cd73a193_b.jpg (https://flic.kr/p/nLf49i)
_MG_6029 (https://flic.kr/p/nLf49i) by sonscc (https://www.flickr.com/people/120242274@N04/), on Flickr

Notice anything about this photo of the front of the pack today at Mt Welly?

The flagger is asleep.
(and not an RM85 in sight thank goodness)

[TZ350]

TeeZee I think your bmep for the RGV Aircooled is a bit high, your numbers would translate into near on 40 RWHP. Pulling the proposed numbers back to around 12 Bar is still a tough ask, but more doable I think. Going too radical is just going to create transfers that will loose excessive velocity/stream control - even with a good powervalve setup it will drop the mid power too much.

Thanks for the heads up, I will have another look at it ....

[TZ350]

FUEL DROPLET SIZE REALITY CHECK

Some pages ago, there was some discussion on fuel droplets. Got me thinking as to what size a fuel droplet might be.

Great post, very interesting, thanks Ken.

[Frits Overmars]

If you were constructing say a 25cc cylinder, I would imagine you would use model engine cylinder technology? ABC, aluminium, brass, chrome, do they still make small engines like this with a cast in brass sleeve that takes the hard chrome easily. Is the brass sleeve coated with anything before the alloy is cast on? I think with the model engine I had, the brass sleeve was only pushed in? Cylinder is water cooled, or it would be if I was making some.Model engines with Aluminium cooling fins, Brass sleeve and Chrome coating are still being made, Neil, but they are not winning any races anymore. There are also AAC engines (you can figure that out, can't you?) but those are not winning either. Sleeveless alu cylinders with a chrome bore are.
By the way, I never encountered ABC or AAC cylinders with cast-in sleeves. They were all a push fit, with the accompanying bad heat transfer. And I can't see why you would consider using these obsolete technologies for any size of cylinder (well, maybe I can see, considering the kind of engine you're working at. But I fear cooling is going to be a problem).

[WilDun]

If you were constructing say a 25cc cylinder, I would imagine you would use model engine cylinder technology?
ABC, aluminium, brass, chrome, do they still make small engines like this with a cast in brass sleeve that takes the hard chrome easily. Is the brass sleeve coated with anything before the alloy is cast on? I think with the model engine I had, the brass sleeve was only pushed in?
Cylinder is water cooled, or it would be if I was making some.

The ABC pistons/cylinders are still used in model glowplug engines, although they are normally ringless with a very minutely tapered bore and tapered piston to match. The brass/chrome liners are a 'push in' fit.
When you buy a new one and you turn it over by hand there should be a 'click' as it slips over TDC, this is the piston just about locking on the bore, however, when it starts up and the cylinder warms up then it seems to expand away from the piston. Quite hard to manufacture a one off "just right" I'd say!
I believe that companies like OS now use something like Nikasil instead of hard chrome, but I would say that the chrome is cheaper than Nikasil (ABN). There are ringed versions available also but I'm pretty sure they use parallel CI bores.(don't quote me!).
I do get the feeling that with the ABC motors (plated brass liners) the compression is dependent to a large extent on lots of oil, these things use plain bearings and therefore need heaps of oil! and I mean heaps !! - like about 6:1 - yes that's right, 6:1 not 60:1.
Then of course they don't need to worry about fancy ignition , they use glowplugs, which are disconnected when they warm up, they use methanol /nitro fuel.

As a matter of interest, MZ also tried ringless pistons way back, - without success.

There are petrol engines for the bigger model aircraft which normally range from around 15cc to up around 75cc and which are normal petrol engines as we know them but nothing near bucket specs. they are built so light with overhung cranks (like the old Scott motorcycles) which I think would probably disintegrate at bucket outputs! They are normally chrome plated bores which seem to be done directly on the aluminium (like chainsaws).
I've got a Chinese 30cc which weighs FA. and puts out a healthy 3HP. :eek: -
It cost about $320 I think. - nice little engine if it was properly sorted.

Sorry for the ramble but at least I can say something on this - can't keep up with all those tuning guys, they have left me trailing!:rolleyes:

Will.

[WilDun]

FLETTNER,
The model boat guys are well up with the play on small water cooled two stroke racing engines I'm told, - I would think you could get some good info from those forums and sites.

[2T Institute]

297338

I have just managed to get a set of three stage power valves.

297337

It looks like the RGV250 three stage timings are:-

104 atdc
90 atdc
84 atdc

I am not sure how much these can be changed but I would like to have fully open at 80 atdc.

They are 2 stage PV's the highest or eyebrow blade never moves. With the 2 stage valve be very very careful with the centre blade, it can wear enough to fallout. Check the grooves in the other 2 blades and the pin on the centre blade is tight. Also check the collars and the ends of the PV's where the hardened shaft connecting the 2 run through if that is egged out find another set. What I have always made is replacement bronze collars that the shaft rides on and PV problems disappear.

[TZ350]

Thanks for the tips, I will look at these two sliding element ones carefully. I also have some single element ones so not completely stuck for something to use. The initial part of this project is to see if I can successfully air cool what was a water cooled cylinder.

[F5 Dave]

Rob what might be interesting is to set up your air cooled bike. With best jetting for relatively cool and dyno measuring head temp and make a chart of how much it falls off power. Then can do asme with new barrel to see how effective it is

[Flettner]

Model engines with Aluminium cooling fins, Brass sleeve and Chrome coating are still being made, Neil, but they are not winning any races anymore. There are also AAC engines (you can figure that out, can't you?) but those are not winning either. Sleeveless alu cylinders with a chrome bore are.
By the way, I never encountered ABC or AAC cylinders with cast-in sleeves. They were all a push fit, with the accompanying bad heat transfer. And I can't see why you would consider using these obsolete technologies for any size of cylinder (well, maybe I can see, considering the kind of engine you're working at. But I fear cooling is going to be a problem).

Frits, thank you, yes I can see the sleeve would at least have to be cast in. The problem is NZ cylinders can not nickasil these small bores plus the cost will kill the project. No one in NZ can hard chrome straight onto aluminium, but brass no problem.
I do want my own cylinder, not someone elses compromise. Had to ask.

[Flettner]

The ABC pistons/cylinders are still used in model glowplug engines, although they are normally ringless with a very minutely tapered bore and tapered piston to match. The brass/chrome liners are a 'push in' fit.
When you buy a new one and you turn it over by hand there should be a 'click' as it slips over TDC, this is the piston just about locking on the bore, however, when it starts up and the cylinder warms up then it seems to expand away from the piston. Quite hard to manufacture a one off "just right" I'd say!
I believe that companies like OS now use something like Nikasil instead of hard chrome, but I would say that the chrome is cheaper than Nikasil (ABN). There are ringed versions available also but I'm pretty sure they use parallel CI bores.(don't quote me!).
I do get the feeling that with the ABC motors (plated brass liners) the compression is dependent to a large extent on lots of oil, these things use plain bearings and therefore need heaps of oil! and I mean heaps !! - like about 6:1 - yes that's right, 6:1 not 60:1.
Then of course they don't need to worry about fancy ignition , they use glowplugs, which are disconnected when they warm up, they use methanol /nitro fuel.

As a matter of interest, MZ also tried ringless pistons way back, - without success.

There are petrol engines for the bigger model aircraft which normally range from around 15cc to up around 75cc and which are normal petrol engines as we know them but nothing near bucket specs. they are built so light with overhung cranks (like the old Scott motorcycles) which I think would probably disintegrate at bucket outputs! They are normally chrome plated bores which seem to be done directly on the aluminium (like chainsaws).
I've got a Chinese 30cc which weighs FA. and puts out a healthy 3HP. :eek: -
It cost about $320 I think. - nice little engine if it was properly sorted.

Sorry for the ramble but at least I can say something on this - can't keep up with all those tuning guys, they have left me trailing!:rolleyes:

Will.

Will, yes I could just buy something, but I did want to make my own version.
I just can't buy a chinese engine. I don't like to encourage them.

[senso]

Don't take this the wrong way, and I think I'm not forgetting anything, but there will be a lot of thermal interfaces from the inside of your cylinder to the outside fins, why don't you cut out the original water sleeve and directly weld some giant fins directly to the outside of the sleeve, a couple(more like 6-7) years ago in some pirate MX competitions there was a guy that took a water-cooled 100cc cylinder made for the yamaha lc 50 engine, cut out the water sleve and welded 10 or 12 30x20x4mm aluminium plates, got the cylinder re-plated and it could run for half an hour in front of everybody with a cylinder that was always "cold" to the touch.

[WilDun]

I just can't buy a chinese engine. I don't like to encourage them.

Too late to close the door, the horse has bolted!

[fixer]

Just a wee note about the performance of my Aprilia RS50 on Sunday. It's first official outing with the Team ESE inspired 13.6hp. I can confirm that 13.6 well-shaped horses are a lot nicer than 9.9 ugly ones (with Doppler kit but without raised barrel and machined head). It called for some minor mods to how I ride the bike (feathering the clutch rather than changing down made more sense than before at the hairpin), but even in the absence of any real pressure (the championship leader circulating with a broken collar bone - not bad for a 50-something-year-old!) I managed a 31.44. This is 0.3s better than anything I've done in a race before and at least half a second better than what I was generally managing with 11hp (from the ported original barrel). The bike was a pleasure to ride. Now if I can just hit a few more apexes (still learning F5 after years on an FXR), then I might be able to get somewhere near the 30s.

PS. Love Chris C's photo of the front of the F4 class!

[TZ350]

297426


I think ... there will be a lot of thermal interfaces from the inside of your cylinder to the outside fins, why don't you cut out the original water sleeve and directly weld some giant fins directly to the outside of the sleeve ...

Yes I think your right about the thermal interfaces but I plan on trying it first because the cylinder head studs are on the water jacket and I think it would be hard to work around them. And initially I wanted to keep it simple and easiy to replicate.


Rob what might be interesting is to set up your air cooled bike. With best jetting for relatively cool and dyno measuring head temp and make a chart of how much it falls off power. Then can do asme with new barrel to see how effective it is

297425

Hi F5 I have a four channel temperature data logger and intend to pretty much do what you suggest if I can figure out how to work the logger software. If you have a source for light but high temp (250-350 C) K type thermocouple wire I would love to know.

297424

Slow progress but I have the cylinder plate mounted on the cases now, and I will bore the hole for the cylinder spigot tomorrow night (hopefully).

[cotswold]

Fixers 50 ran well to, the race I saw he finished 1st with a best lap time of 31.44 and that puts him in the A grade F4 time bracket along with the hot FXRs, not bad for a 50

shit how well would that go if you guys knew what you were doing. ;)

[speedpro]

shit how well would that go if you guys knew what you were doing. ;)

We'll never know.

[teriks]

FLETTNER,
The model boat guys are well up with the play on small water cooled two stroke racing engines I'm told, - I would think you could get some good info from those forums and sites.
So is Frits :)

[bucketracer]

Fixers 50 ran well ... shit how well would that go if you guys knew what you were doing. ;)
We'll never know.

.......... :laugh:

[WilDun]

So is Frits :)

Couldn't agree more!

[Muciek]

Hi guys, I have a lil problem with measuring and understanding a exh duct angle in cylinder. Should I use 0* angle in my calculations (window in bore is "looking" straight then some weird bumps appear and duct is turning in right side ) or should I use in calculations the angle of end of a flange which is around 20* or something in the middle? This is vintage engine . I hope You can understand me :o Here are few additional pictures http://imgur.com/zyCVS7H,PwF0YGQ,7ZG1woO,7EwAfCo,mdB5Lpz,7gH5pOl,PH PK1G2,1Mohjpw,IDfxFdR,oCUk5J9#0

297430297431297432

[wobbly]

In the port STA calculations the programs use the chordal width and the piston movement over the port height.
If the floor and roof of the duct are parallel exiting the bore then the area is simply Width X Height but if they are angled
then the height in reality is X the cosine of the angle.
If your drawing is correct then its 0*.
PS,this is one big fault in the old TSR software - the duct angle was never taken into account at all.

[Muciek]

In the port STA calculations the programs use the chordal width and the piston movement over the port height.
If the floor and roof of the duct are parallel exiting the bore then the area is simply Width X Height but if they are angled
then the height in reality is X the cosine of the angle.
If your drawing is correct then its 0*.
PS,this is one big fault in the old TSR software - the duct angle was never taken into account at all.

Floor and duct are parallel for something like 10mm and after that duct is turning right side I think it's visible on pictures. Thank You for help. I use bimotion software and actually it take ducts angle into final diameter, not as good as Engmod but still better than calculating all those things by hand on paper...

[wobbly]

Just remember that the actual Ex port effective are is the least critical number in an engine analysis.
If all the testing done is pointing us the any direction it is to have the full port effective and thus the duct way smaller than the raw
numbers would indicate.
Matching the blowdown and the transfer STA correctly is the holy grail to power in a 2T.

One extra thing to add about this for TeeZee and his new RGV based aircooled is that increasing the transfer numbers, above that as required by the STA
predicted, is all about helping to give some reality to the actual flow capability of the ducts - horrible parallel walls with a right angle at the end exiting into
the transfer port will never flow anything like nice teecup handle shape with a proper inner radi etc.
The shape of an RGV duct ( though too big if anything ) is getting about as good as it gets for a production part, so there is no need to overstate the STA for the ports connected to them.

[wobbly]

And one last point to remember is that the duct exit area for a single port works best with around 90% of the Effective area at the bore.

[peewee]

wobbly whats your definition of effective area ? i was under the assumption the blowdown area at the bore should be about 90% to 100% of the total area at the end of the duct. is that basically what you were saying ?

[TZ350]

One extra thing to add about this for TeeZee The shape of an RGV duct ( though too big if anything ) is getting about as good as it gets for a production part, so there is no need to overstate the STA for the ports connected to them.

Thanks Wob, I will re do my simulation.

297440

Ok we now have a hole bored for the RGV cylinder and the cylinder sitting down on the copper plate.

297439

The water jacket is going to be filled with copper dust and high conductivity resin in the hope of making a reasonable thermal path connecting the exhaust duct to the copper plate.

297438

Hopefully the heat from the exhaust duct will find an easy path out to the copper plate.

297437

The next move is to cut a hole in the bottom heat sink so it can go around the cylinder and sit on the copper. The outer edges of the copper will be retained as small fins.

297441

[Flettner]

In the olden days, with cast in iron liners, I'm sure there was some sort of " flux " used to pre coat the iron liner so the alloy would stick ( fuse ) to it. Am I right in thinking the iron liner was nickel plated first? This was better than just pressing the liner in.

I think a Hydrofluric acid bath is needed for the hard chrome straight to alloy process. Not the sort of bath you would want to have.

[Grumph]

In the olden days, with cast in iron liners, I'm sure there was some sort of " flux " used to pre coat the iron liner so the alloy would stick ( fuse ) to it. Am I right in thinking the iron liner was nickel plated first? This was better than just pressing the liner in.

I think a Hydrofluric acid bath is needed for the hard chrome straight to alloy process. Not the sort of bath you would want to have.

According to Irving, it was sandblast the liner, preheat and slip it into the mould sharpish....pour making sure there was a good flow up past the liner and it was shaped so as to eliminate undercuts or areas which would trap air....Very unsophisticated.

You may be thinking of the "Al - fin" process which had several steps before casting in - and once in even though it was a parallel wall could never be removed. generally 4 stroke only, that one.

[Flettner]

According to Irving, it was sandblast the liner, preheat and slip it into the mould sharpish....pour making sure there was a good flow up past the liner and it was shaped so as to eliminate undercuts or areas which would trap air....Very unsophisticated.

You may be thinking of the "Al - fin" process which had several steps before casting in - and once in even though it was a parallel wall could never be removed. generally 4 stroke only, that one.

What is this " Al - fin " process? I will never need to remove the sleeve.

[Frits Overmars]

What is this " Al - fin " process? I will never need to remove the sleeve.If I remember correctly (it is about a century ago) Al-Fin meant dipping the sleeve in molten aluminium and then inserting it in the mold after which the fins were cast.

[Flettner]

If I remember correctly (it is about a century ago) Al-Fin meant dipping the sleeve in molten aluminium and then inserting it in the mold after which the fins were cast.

We won't go there.

Frits, do you have any idea on pre treating ( brass in this case ) liners to make the aluminium " stick ".
I would rather not use a liner but if I want these small cylinders I will need to use brass so I can hard chrome onto the bore.

[Ocean1]

I think a Hydrofluric acid bath is needed for the hard chrome straight to alloy process. Not the sort of bath you would want to have.

No personally, no.

Is solid cast high silicon aluminium not an option?

[husaberg]

No personally, no.

Is solid cast high silicon aluminium not an option?
Yam are doing something similar now Chevy Vega flashbacks

[Ocean1]

Yam are doing something similar now Chevy Vega flashbacks

Corvair. If high silicon alloy casts as well as it welds it'd be a starter I reckon.

[husaberg]

Corvair. If high silicon alloy casts as well as it welds it'd be a starter I reckon.

Vega had em too high silicon copper bit iron bit mag etched after casting to expose silicon
Add link if I can be arsed
http://bbs.homeshopmachinist.net/archive/index.php/t-60286.html
Hard case they had to iron coat the pistons (actually oh that makes sense)

We won't go there.

Frits, do you have any idea on pre treating ( brass in this case ) liners to make the aluminium " stick ".
I would rather not use a liner but if I want these small cylinders I will need to use brass so I can hard chrome onto the bore.

Worth a read half way down page can add text on silly tablet ......
. GM Research Labs had been working on a sleeveless aluminum block since the late '50s. The incentive was cost. Engineering out the four-cylinder's block liners would save $8 — a substantial amount of money at the time. Reynolds Metal Co. developed an alloy called A-390, composed of 77 percent aluminum, 17 percent silicon, 4 percent copper, 1 percent iron, and traces of phosphorus, zinc, manganese, and titanium. The A-390 alloy was suitable for faster production diecasting which made the Vega block less expensive to manufacture than other aluminum engines. Sealed Power Corp. developed special chrome-plated piston rings for the engine that were blunted to prevent scuffing. Basic work had been done under Eudell Jackobson of GM engineering, not at Chevrolet. Subsequently, Chevrolet was given job of putting the ohc sleeveless, aluminum block into production.

The Vega engine block was cast in Massena, New York - at the same factory that had produced the Corvair engine. Molten aluminum was transported from Reynolds and Alcoa reduction plants to the foundry, inside thermos tank trucks. The block was cast using the Accurad process. The casting process provided a uniform distribution of fine primary silicon particles approximately 0.001 inches in size. Pure silicon provides a hard scuff and wear resistant surface, having a rating of 7 on the mohs scale of hardness, the same as quartz, as compared to diamond which is 10. The blocks were aged 8 hours at 450 °F to achieve dimensional stability. Before being shipped to Tonawanda, the blocks were inpregnated with sodium silicate, where they were machined through the outer skin. From Massena, the cast engine blocks were shipped as raw castings to Chevy's engine plant in Tonawanda, New York. Here they underwent the messy etch and machining operations. The cylinder bores were rough and finish-honed conventionally to a 7-microinch finish then etched by a new (then) electro-chemical process. The etching removed approximately 0.00015-inch of aluminum leaving the pure silicon particles prominent to form the bore surface.

The technical breakthroughs of the block lay in the die-casting method used to produce it, and in the silicon alloying which provided a compatible bore surface without liners. With a machined weight of 36 pounds, the block weighed 51 pounds less than the cast-iron block in the Chevy II 153 CID inline-4. Plating the piston skirts was necessary to put a hard iron skirt surface opposite the silicon of the block to prevent scuffing. The plating was a four layer electo-plating process. The first plate was a flash of zinc followed by a very thin flash of copper. The third and primary coating was hard iron, 0.0007-inch thick. The final layer was a flash of tin. The zinc and copper were necessary to adhere the iron while the tin prevented corrosion before assembly of the piston into the engine. Piston plating was done on a 46 operation automatic line. From Tonawanda, the engineswent to the Chevrolet assembly plant in Lordstown, Ohio.

Eudell Jackobson of GM engineering pointed out one of the early problems with unexplained scuffing and discovered excessive pressure on the bore hones was causing the silicon to crack. He said:"...We were trying to put a product into production and learning the technology simultaneously. And the pressure becomes very, very great when that happens. The hone-pressure problem was solved before engines actually went out the door, affecting only pre-production engines.
Makes you think only one side needs to be hard ?Neil isn't that how it works ???????

[Frits Overmars]

Frits, do you have any idea on pre treating ( brass in this case ) liners to make the aluminium " stick ".Nope.
I would rather not use a liner but if I want these small cylinders I will need to use brass so I can hard chrome onto the bore.If you must use a liner, think about Jan Thiel's idea of a conical fit. He used a morse cone angle for both sleeve and cylinder; then you can stick them together and take them apart as often as you wish; only the last mm of depth required a light axial press fit.
Why use brass at all? Hard chroming an aluminium bore should be a piece of cake. You could even consider doing it at home. We used to do it for the prototype cylinders of our 6.5 cc aero engines (the production engines are made by Profi in Charkov, Ukrain)
('we' being chemist professor Bert Metkemeijer who passed away recently, so I can no longer ask him for details).

[Yow Ling]

I watched a youtube on car engine manyfacturing where just before thy poured the block they inserted induction heating coils to preheat the sleeves, they were only in there for maybe 5 seconds , so maybe just getting it real hot is all thats necessary

in this video at 3.16

https://www.youtube.com/watch?v=yXVLbzI3xTE

[wobbly]

The term port "effective area " is defined as the port chordal width * height * cosine of down angle,and I have found that getting the duct exit down to 90% of this actual area
gives the best power for a single port in the bore.

The other scenario of say a tripple port, the duct exit area that is the best, is around 75% of the total effective - and this works out in most cases to be exactly the effective area of the main port only
( ie deduct the area of the Aux ports ).

[Flettner]

Nope.If you must use a liner, think about Jan Thiel's idea of a conical fit. He used a morse cone angle for both sleeve and cylinder; then you can stick them together and take them apart as often as you wish; only the last mm of depth required a light axial press fit.
Why use brass at all? Hard chroming an aluminium bore should be a piece of cake. You could even consider doing it at home. We used to do it for the prototype cylinders of our 6.5 cc aero engines (the production engines are made by Profi in Charkov, Ukrain)
('we' being chemist professor Bert Metkemeijer who passed away recently, so I can no longer ask him for details).

Talking to the hard chrome platers here at Hamilton airport ( they chrome steel aviation cylinders ) and they say the only way to plate to aluminium direct is to pre etch with Hydrofluric, which they are not interested in using. It's not a very nice acid to have kicking around the workshop. Perhaps they are wrong, perhaps there is another way? Did you used a 4 volt DC power supply?
You are right, often the best way is to just do it yourself, the only way to get what you want.

[TZ350]

297448

Some of the sophisticated tooling to be found in the ESE workshop.

A grunty skill saw with a fine blade does a good job of cutting alloy plate and heat sinks.

297449297450

Lower heat sinks in place with copper fins on the side, these will get bent up at 45 deg later and the sharp edges rounded off.

Just got to figure out how to get the fuel injection in there too .... :scratch:

[monkeyfumi]

Hello Guys,
Although I don't really contribute to this thread, I do read all of it, and greatly appreciate the shared knowledge it provides.
Given that Tee Zee is now playing around with RGV cylinders, I thought now might be a good time to show some of the stuff I've been attempting as a result of the thread.

First, some background. Bike is an Aprilia RS250 (road bike), which as we all know, uses the VJ22 RGV engine.

It is currently copping a crank up rebuild due to a wayward big end.
For the moment I'm concentrating on the cylinders. Port heights are standard (though I will be using cougar power valves, which give a slightly different timing), but the transfers have got some work, inspired by this thread.
The A transfers roof has been filled to angle it at 25 degrees, and the B port wall has been filled to make it perpendicular to the bore, as well as some small filling of the B-port rear hook. I've also radiused the bore edge at the start of the transfers.
https://farm3.staticflickr.com/2918/14293238311_e0d37d60dd_n.jpg (https://flic.kr/p/nM3zMi)IMG_3459 (https://flic.kr/p/nM3zMi) by monkeyfumi13 (https://www.flickr.com/people/97968553@N05/), on FlickrI'm now looking to make an exhaust duct nozzle, with an oval to round transition, like Wobbly has advised often.
I have sourced some high temperature putty, and had a fitment model of my flange 3D printed in ABS to help when it comes to grinding the duct to size.
https://farm3.staticflickr.com/2925/14316765253_b7cc782191_n.jpg (https://flic.kr/p/nP8awe)IMG_3456 (https://flic.kr/p/nP8awe) by monkeyfumi13 (https://www.flickr.com/people/97968553@N05/), on Flickrhttps://farm6.staticflickr.com/5553/14109940720_085ed172be_n.jpg (https://flic.kr/p/nuR8N1)IMG_3457 (https://flic.kr/p/nuR8N1) by monkeyfumi13 (https://www.flickr.com/people/97968553@N05/), on Flickr

I just wanted to ask Wobbly if he runs a crush gasket with his nozzle flanges, and what grade of alloy he makes them from?
Hope this triggers some productive discussion for your RGV cylinder conversion Tee Zee

[TZ350]

Your project looks good, keep posting and thanks.

[Neal]

I had some ally oval to round stubs made , we used a viton o ring instead of the crush washer and it worked very well . One of my stubs eventually sheared off , there was a straight edge instead of a radius where the spigot joined the flange causing a weak spot .

[wobbly]

As above a Viton O Ring on the spigot face.I have had the oval to round transition made in alloy 7075 as well as some in simple mild steel.
Biggest issue is trying to get enough weld far enough into the duct,its a real bitch to get even a tiny Tig into the right places.
Im about to try some alloy stick welding rods, to build up the intake floor on a poxy Triumph 750 head,so this technique may save a hell of alot of drama.
The rods are only 3mm thick, so it should be easy to add material where needed, and even if it turns out a bit porous,its the shape that matters.

[jasonu]

As above a Viton O Ring on the spigot face.I have had the oval to round transition made in alloy 7075 as well as some in simple mild steel.
Biggest issue is trying to get enough weld far enough into the duct,its a real bitch to get even a tiny Tig into the right places.
Im about to try some alloy stick welding rods, to build up the intake floor on a poxy Triumph 750 head,so this technique may save a hell of alot of drama.
The rods are only 3mm thick, so it should be easy to add material where needed, and even if it turns out a bit porous,its the shape that matters.

Try an alloy mig welder with a small torch.

[TZ350]

Page 950 .....

Its all about Exhaust blowdown...........


hey wobbly or anyone else. ive seen what happens with insufficient blowdown. is there such a thing as too much blowdown ?


Its not so much the issue of too much blowdown per se in an engine spec.

The real issue is how did the excess blowdown for the planned Hp/rpm actually occur.
Using a CAD program it is easy to see a mismatch between the STA numbers for any combination of port area and timing.

If for example we see really big numbers for the EX and Bl STA but a mismatched small Tr STA then the performance will be transfer limited - and we wont see the power as the BL STA would predict..

Go the other way and we can have big Tr STA and big Bl STA, and this in fact may not be an issue, as in many cases having the TR and Bl correct, but an undersize Ex STA
will just mean that a clever person has filled in the EX floor and the bottom corner rads to reduce short circuiting.

This scenario will perform as per the correct BL and TR STA numbers predict.
What I was going on about the other day was to point out that taking a cylinder with low Tr and low Ex timings and simply jacking it up, will for sure give a useful improvement.

Simply due to the better timing numbers suited to alot more performance, but having huge 130* transfers and a relatively low 192* Ex points to the engine then being BL STA limited.

Drop the cylinder and grind up the Ex to get all 3 STA numbers complementing each other,and more power than the simple jack up scenario is a given.

297807 297810

Here are the STA numbers for an Athena 50 - one with the cylinder jacked up, the other with the same transfers but the Ex ground up to match.


Again this is the old story of trying to put specifics onto a huge generality.
The reed cavity of course is connected to the case, and it depends entirely what the total volume is,as to the advisability of
filling in the so called dead areas.

I have found that unlike a full noise rotary valve engine there seems to be no power increase if the case volume is made bigger than a 1.3 ratio when using reeds
be they direct into the case or cylinder mounted.
And another generality seems to be that the crappyer the transfer ducts, the ratio should tend the other way toward a smaller 1.4 ratio.

If the case was too small to start with and you fill the reed cavity dead areas, this will make it worse, and vise versa, but as all the factories are now tending toward making the reed box
smaller and smaller it would seem that filling the cavities and also filling the volume in front of the reed ( to the point where you would think the flow would for sure be affected badly )
then I would say its a good thing AS LONG AS YOU ARE MEASURING AND CORRECTING THE TOTAL CASE VOLUME.


The term port "effective area " is defined as the port chordal width * height * cosine of down angle,and I have found that getting the exhaust duct exit down to 90% of this actual area gives the best power for a single port in the bore.

The other scenario of say a tripple port, the duct exit area that is the best, is around 75% of the total effective - and this works out in most cases to be exactly the effective area of the main port only
( ie deduct the area of the Aux ports ).

Pipes need to suck deep at BDC.....


This may seem counter intuitive, in that most people think ( wrong ) that when the piston rises it creates a depression and it is this that causes inflow into the case.

The rising piston may make a piston port lawnmower operate, but the vast majority of bulk flow in a race 2T is caused by the pipes diffuser depression, around BDC - when the piston is very much in the way.

This negative pressure ratio at the Ex port is then communicated to the crankcase via the transfer ducts, creating flow when the piston is at BDC.


Cutting or sleeving headers to do a dyno test, is that simply doing that and trying to analyze the results is completely pointless if you have not measured the pipes beforehand to see what the original design intent was.

If the header is short to start with, and you then shorten it more, the tuned length may be perfect, but the negative effect from the now silly short header length will overpower any of the good effects of the overall length.

Conversely if the header was short and you lengthened it, the power increase may be mainly due to now having a " correct " % of header - though the pipe length may be completely wrong for the port timing.

297806

having a header say 28% or 36% of the tuned length will invariably produce huge holes in the torque curve - due to the incorrect positioning of the diffuser.

297808


As we were on the subject of scavenging angles, now would be a good time to write something about the radial angles of the A-transfers.

Surely a duct with a radial angle of over 20° offers a smaller cross-section to the flow than a duct that enters the cylinder perpendicularly?

Yes it does. But there are two good reasons to angle it upward anyway.

First, perpendicular mixture streams coming from the A-ports would collide and slow one another right down. The upward angles provide for less velocity losses and less pressure losses, so despite their smaller cross-section, upward ports may flow as much, if not more, than perpendicular ports.

(Now you may well ask why the B-ports do not get the same treatment; that is because the central scavenging column, resulting from all incoming scavenging streams together, must not have too much radial velocity, or the loop scavenging will result in a loop-loss into the exhaust).

Second, there is a thing called scavenging balance (I invented the word for my personal use, so this may well be the first time you ever saw it).

If you looked closely at the scavenging picture of the MB-cylinder I posted earlier today, you may have noticed that the 'radial scavenging directional resultant'
had a value of 101,045°. 90° would have meant 'straight up'; more than 90° indicates that the central scavenging column is leaning towards the exhaust side of the cylinder.

But we don't want that; it is bad for the scavenging of the rear part of the cylinder, and it is risky because it may provoke scavenging losses straight into the exhaust.

But how can we prevent a scavenging column from toppling over to the exhaust side like the leaning tower of Pisa? Not by pushing against its basis, but by pushing higher up. Hence the radial angle of the A-ports.

The pictures will tell the story. (If only the Pisa architect had known a bit more about two-stroke tuning....)


The sine of this 'axial scavenging directional resultant' is an indication of the scavenging column's axial velocity. If the column moves too fast in relation to the mean piston velocity, there will be severe scavenging losses; if it doesn't move fast enough, the cylinder will not be completely scavenged.

Pay to follow Frits links to read the whole story.

297809


When you are running big combustion chamber volumes, the plug is way too far from the piston and you need to change to a toroid.


Running 98 pump I would go to 13.8 : 1 and no more - this would give you 9.7cc combustion volume or 11.9cc to the top of the plug with a (14mm 3/4” reach) 10 range plug. The 17mm shown is the thread length for the plug to ensure the tip protrudes into the chamber.

From memory the plug tip also needs to be about 6.5mm from the piston crown.


The squish following the piston shape by using CNC is very important if you are pushing the limits with around 50% SAR and very tight squish clearance (0.65mm for a 125 54/56mm bore). This also works together with the sharp edge into the bowl.

[Grumph]

As above a Viton O Ring on the spigot face.I have had the oval to round transition made in alloy 7075 as well as some in simple mild steel.
Biggest issue is trying to get enough weld far enough into the duct,its a real bitch to get even a tiny Tig into the right places.
Im about to try some alloy stick welding rods, to build up the intake floor on a poxy Triumph 750 head,so this technique may save a hell of alot of drama.
The rods are only 3mm thick, so it should be easy to add material where needed, and even if it turns out a bit porous,its the shape that matters.

Jesus Wob - bolt the bloody thing to the biggest heaviest fixture you've got - then pre and post heat it. They warp like an overripe banana.

[DaisyB]

Chaps, my vintage single exhaust port barrel has a very short port (30 mm from piston to exhaust stub), should I be aiming my 90% of area in the barrel or further along in the exhaust manifold?

Also, reading the fuel posts, I went to mow my grass the other morning and the (plastic) can had collapsed slightly ie a partial vacuum, has the "good stuff" been re-absorbed? If so can't I cool the fuel in storage before use to make it last a bit better?
Cheers
Dave

[Drew]

Chaps, my vintage single exhaust port barrel has a very short port (30 mm from piston to exhaust stub), should I be aiming my 90% of area in the barrel or further along in the exhaust manifold?

Also, reading the fuel posts, I went to mow my grass the other morning and the (plastic) can had collapsed slightly ie a partial vacuum, has the "good stuff" been re-absorbed? If so can't I cool the fuel in storage before use to make it last a bit better?
Cheers
DaveHmmmm, I think you'd need to compress and freeze it, before the process started for that to work.

[wobbly]

I would aim to get the end of the Ex stub at 90%,and I would suspect that the area at the flange face is too big now, so get in there with the tig.
Re the collapsed plastic fuel can, only way this could happen would be that the RVP of the original fuel was way low,and when you opened and then stored it last the ambient temp was alot warmer.
Now the liquid has cooled down, its volume has reduced, and with no vapour flash off its sitting with negative pressure in the open space.

[husaberg]

http://www.classic-motorrad.de/cm2002/schier/2zyl-11.jpghttp://www.classic-motorrad.de/cm2002/schier/2zyl-6.jpg
http://www.classic-motorrad.de/cm2002/schier/2zyl-8.jpghttp://www.classic-motorrad.de/cm2002/schier/2zyl-12.jpg



http://imageshack.us/a/img171/1059/41344441924cddfba089o.jpg

[DaisyB]

I would aim to get the end of the Ex stub at 90%,and I would suspect that the area at the flange face is too big now, so get in there with the tig.
Re the collapsed plastic fuel can, only way this could happen would be that the RVP of the original fuel was way low,and when you opened and then stored it last the ambient temp was alot warmer.
Now the liquid has cooled down, its volume has reduced, and with no vapour flash off its sitting with negative pressure in the open space.

Thanks Wob, so no free (or even cheap) lunch with the fuel then.
How far (in mm) as a rough guide should the reduction to 90% be from the bore? (stroke 57, bore 67) I've not tuned this one yet - grinder to metal this week.

[wobbly]

Its an interesting point about the so called " restriction " point - I havnt tried moving the venturi actually into the duct,though thru a PM one member has failed miserably trying this
due to lack of room past the header face, but reported it did " work " in EngMod.
I think the important issue is to have as smooth an area change as you can thru the duct- helping the now smaller return slug to transition past the rising piston into the cylinder space.
In most older cylinders - TZ350 being the best example, the duct is gradually tapered out to be bigger than necessary,so counterboring and pressing in a sleeve
as far as is possible is easy enough.
But for example with the TZ400 I did, the bigger port area needed then matched perfectly with a dead stock duct and header diameter.
The idea being, I believe,is to reduce the total duct volume, starting at the port by filling the bottom corner radi, thus reducing A port short circuiting,then gradually get a smooth transition
out to the 90% number where the header slips on.

[Muciek]

I have read that Yamaha in their 250 model through years changed the ex outlet diameter AC was 37mm then RD LC was 35 and finally Rz250 32mm but I don't know is it 90% .

[Flettner]

http://www.classic-motorrad.de/cm2002/schier/2zyl-11.jpghttp://www.classic-motorrad.de/cm2002/schier/2zyl-6.jpg
http://www.classic-motorrad.de/cm2002/schier/2zyl-8.jpghttp://www.classic-motorrad.de/cm2002/schier/2zyl-12.jpg



http://imageshack.us/a/img171/1059/41344441924cddfba089o.jpg

Are you having me on Husaberg! I've just odered two GSX gearboxes to mate up to my three cylinder gyro engine ( new cases so the gearbox and engine are one, 1050cc ). Water cooled, water cooled crank case, case reed, power valve, reverse turning crank. I was thinking of dressing it like an H2 sort of. Frame is chrome molly tube, ladder type, wire wheels.
Two engines are taken already.

[husaberg]

Are you having me on Husaberg! I've just odered two GSX gearboxes to mate up to my three cylinder gyro engine ( new cases so the gearbox and engine are one, 1050cc ). Water cooled, water cooled crank case, case reed, power valve, reverse turning crank. I was thinking of dressing it like an H2 sort of. Frame is chrome molly tube, ladder type, wire wheels.
Two engines are taken already.

No....... I posted the pic of the GSXR H1 cause I thought it was cool
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=297548&d=1401098239
the one with the NICE""pipes I posted to give Wob some welding hints lol.
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=297547&d=1401359372
still cool bike though
the Maico CAD cause it was purrty

[koba]

the one with the NICE""pipes I posted to give Wob some welding hints lol.
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=297547&d=1401359372


I feel better about my mess after seeing that.

[TZ350]

297567

I need 5.5Amps to run the electrics on the EFI bike.

Ignitec ignition, Power Valve Servo, EFI fuel pump, EFI Cpu and the four channel temperature data logger.

Not being able to find something small that will do the job I have resorted to using an original Suzuki GP125 unit with two 6Volt lighting coils wired in series. Its a very heavy flywheel compared to the KX80 one that I am using now, so not to sure how it will go.

297568297569297570

When riding a bike you would not normally get to see it, but on the dyno we were able to check the temperatures of some different flywheels. They were all very hot, to hot to touch.

This was very surprising and at first we thought there was something wrong, the poles touching or eddy currents or something. But then we checked one that had no generating coils and that was very hot to.

So the conclusion is that this heat is coming from inside the motors. The next engine is going to have a cooling duct feeding fresh air to the generator cover in the hope of reducing some of the heat in that area. With the idea, that any cooling is good cooling on a air cooled 2T.

297571297566

With the big flywheel it was difficult to find a place for the ignition pickup but this should do the trick.

I am heading off for a week working in the SI so wont be any more progress for a bit but I am keen to get these projects finished and back on the dyno to see how they measure up.