ESE's works engine tuner

[wobbly]

You missed the point I made that well outside the nominal tuned length rpm,the flat plate has virtually NO effect.
The long slow angle rear cone has a BAD effect, over a very wide band above and below the area where it does have the positive addition to the powerband width.
Thus the flat plate makes alot MORE power at the extremes of the useable range - it makes this power by doing nothing,and or killing resonant tuning as mentioned above.
The plate in the kart pipe was a square - the pressure bleed rate was done thru the gaps.
And yes the Vevey sytem helps to smooth out big variations in the fuel curve - my first kart pipe had a "proper " long rear cone with no mid section, and it was impossible
to tune out the very rich/lean spots even with all the variables available in the pumper carb.

The Vevey design is a generic name I believe, like Biro pens.
The drawing is not a good indicator of relativity - here is a pic of the fastest kart pipe on the planet, the floor squares are 12", and the holes in the rear cone are 1/8" - on varying
centres to widen the torque curve.
And no there are no generalities in the design process.It took me months of full time dyno, weld,cut,dyno weld,cut to develop the very best for the KT100, and that was
made somewhat easyer in that I had 10 existing designs as a baseline.
Now we have EngMod, that can model the whole system - it will take a year to learn how to use it, and a week to design an RD pipe.
2:1 header designs are a real compromise affair in that to work even 1/2 correctly they need an EPO near 80* - completely counter-intuitive and then super difficult to get
resonance to work positively for your end use.
One way to help is to cut the front of the pistons of the twin such that the Ex port is open with the piston at TDC.
This creates another Helmholtz system that works havoc on the carburation - but when that is sorted it makes a heap of very wide band power.

Yes I have done alot of work on Hydro outboard pipes - but I would have to stab you in the eye with a fork immediately after revealing the names.
But the only "mild" design work I have done is for that twin cylinder aircraft engine ( derived from a fan cooled snowmobile ) and that worked best with the Vevey system.

Killing overev is easy, wind in some advance past peak,crank up the com, use a very steep rear cone, use a tight stinger,use a combination of port timing and pipe length
that has NO superposition resonance past peak.
All will make the powerband drop heavily after peak power, either by lowering the pipe temp or reducing pipe/port efficiency.

[lodgernz]

Here is a pic of a "Vevey" type pipe as modelled in EngMod, and this system works supremely well in exactly the scenario you are looking at.
I made several for Yamaha fan cooled engines used in small aircraft, with a 2:1 header - tuned to just 6000 rpm.
They need a very wide torque curve to enable them to spool the prop up, and then overev when needed.
A very similar end use to pushing a prop thru water, and having trouble reaching planing speed.
Also a pic of the drone pipe as I called it - with a nice stainless racebike pipe for comparison.

Wobbly, is the "box volume" part of the Vevey pipe empty, or stuffed with muffler packing?
Enjoyed meeting you at Hampton Downs. Nice to put a face to the name.

[wobbly]

No, the rear tube is empty,the high frequency harmonics of the snap port opening are attenuated to hell by the holes
and the rear box volume.
The small stinger as such can have some packing, but in a back to back with the Kart Federation noise meter it made no difference to
the DbA reading at all so I never added any in the pipes I built.

Yes good to meet someone I would never have apart from participating here.
I had a major success in finally getting the 71Yr old teenager to agree to use tyre warmers - only because he was spitting the dummy about getting second.
Too far back in a 4 lap race to catch up once the tyres came in.

[lodgernz]

I had a major success in finally getting the 71Yr old teenager to agree to use tyre warmers - only because he was spitting the dummy about getting second.
Too far back in a 4 lap race to catch up once the tyres came in.

Feisty old bugger was riding like a kid. Great to watch.

[lodgernz]

OK Wobbly, I have to ask this, even if the answer makes me cringe:
Why wouldn't I use a Vevey system in my 50 and 91cc buckets that need lots of midrange rather than peak HP?

[wobbly]

Because the system reduces the peak power dramatically,and the only applications where the huge increase in low rpm power and bandwidth is of
any use whatsoever is direct drive - no gears.
The KT100 needs to be able to haul off a hairpin at 8000 rpm and then spin to 16,000 to be able to only use 1 gear.
In this case the torque multiplication of the very short gearing enabled by the peak rev capability makes the system workable.
With a bucket ( basket ) case you have a pile of gears to play with and only need to find the best compromise between powerband width and peak, to enable the least amount of gearchanges per lap.

[lodgernz]

Thanks Wobbly. Clear now. Had to ask.

[morini155]

Great thread, very useful information about exhaust design. My question is : the vevey exhaust type its aplicable to a fixed gear engine with centrifugal clutch or a conventional design is best?
Thanks.

[wobbly]

Clutch pipes only have to be used between the lockup rpm at peak torque, usually 10200 in a KT100 and max rpm of, at most, 15,000
on a sprint track, and 12500 on road racing.
Thus a normal rear cone works just fine as no large amounts of power are needed well outside the tuned rpm range ie at 8000 and or 16000.
I did build several test clutch pipes using the Vevey system, but just as I was starting to make serious dyno power, and beginning to be faster than the conventional
pipes from RLV and Nunnley etc in the USA, clutches were banned in NZ due the idiotic cost of maintenance and even costlier upgrades at regular intervals.

[Gigglebutton]

Thomas thanks, this has 2 B the best 2T tuning thread in the world .... :love:........

[Haufen]

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

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

You don't need grease or anything like it to be able to remove it afterwards. Just pour it in. (I am talking about the red vinamold, I don't know about the other colors)

[TZ350]

http://youtu.be/Oxj_OAb5bqk



50+ hp Turbocharged 125, engine is still in Std trim.

[teriks]

50+ hp Turbocharged 125, engine is still in Std trim. While on the subject...
500+hp two-stroke turbo ;-)
http://www.youtube.com/watch?v=X1Jfd7gGIYQ
Dyno:
http://www.youtube.com/watch?v=T44ZVTQtLUk&feature=youtu.be

[Frits Overmars]

While still on the subject...
500+hp two-stroke turbo

[TZ350]

305129

:doh:

Was it revved to hard, to lean, over advanced or really out of a 150 4T? .....

[teriks]

While still on the subject:
two-stroke turbo Got me there :)
I think the 1100cc triple wins in regard to power to weight though :)


305129

:doh:

Was it revved to hard, to lean, over advanced or really out of a 150 4T? .....
:crazy:

[Yow Ling]

305129

:doh:

Was it revved to hard, to lean, over advanced or really out of a 150 4T? .....

the wartsilla is flat out at 102 rpm maybe the 120 rpm big overrev killed it

[F5 Dave]

Is that Rich's FXR'150' again?

[husaberg]

Is that Rich's FXR'150' again?

KB longest running gag all set up but where is Mike?

[TZ350]

No choice... Run out of RS125 forks (even the TZ125) forks seem hard to find... Fastace now make something very similar to the old polini pre-GP forks. http://www.fastace.es/product_info.php?products_id=130&language=en (Husa found them). But they don't seem that interested in shipping to NZ....

Good forks, worth a look.


try these guys
http://www.nzmotorfactory.co.nz/index.php?option=com_virtuemart&page=shop.browse&category_id=51&Itemid=1
I tried to find the catalogue but can't place it at the moment......

Not forks but worth keeping handy.


I just got a copy of this non-ferrous foundry practices manual and put it on my website here:

http://www.eurospares.com/graphics/metalwork/Foseco-Non-Ferrous-Foundry-Man.pdf

It is about a 2.8mb download and it looks to have a wealth of information.

cheers,
Michael

[trevor amos]

I expect that Wob knows the answer to this question already!

Whilst we now accept that the forward hook on the rearmost flank of "B" transfer ports is ideal where there is a fifth "C" port, but is the same applicable where there is no rear "C" port, as is the case in a lot of older piston port engines? I can perhaps see a situation for un-scavenged gas to lurk in this potentially stagnant area if the hook is in place?

Grateful thanks for any help here.

Trevor

[peewee]

Whilst we now accept that the forward hook on the rearmost flank of "B" transfer ports is ideal where there is a fifth "C" port


let me add something if you dont mind. jan and frits have both said those sharp hooks are no good. theres also other eveidence that suggests a hook is no good. if you look at the newer generation of ktm mx cylinders, they have eliminated all hooks. the rear wall of the B port still has a forward facing trajectory but its definatly not a sharp hook like what you would normally see years ago. i think your better off if you can make the duct wall change direction with out a 'kink' or sharp 'hook'. problem is, many cylinders have the studs in a bad location and simply dont have sufficient material thickness of the transfer ducts to properly shape the ducts walls, atleast not without welding and a bunch of other work

[wobbly]

The so called "sharp " hooks where the angle is formed with a distinct corner were replaced quite a long time ago with a smooth radius.
This I saw for the first time in Harolds early KTM cylinder and then the SA cylinders on the Pulse engine.
Much later on when I finally managed to get a look into an RSA this was the first thing I saw.
The aiming point of 1/3 toward bore centre has been common for a long time.
I have described what the direction change actually does before - but here it is again.
The effect I saw on screen when I first saw the flow regime of a Roberts KR3 analysis on a Czech CNC anemometric flow tester.
The actual stream exiting the port is rotated axially and this clears out a dead area in front of the boost port that would normally be
unscavenged of residual Ex gas.
The rotating flow then attaches to the boost port stream and combined with the direct on collision effect this forms part of the tilted tower of Pisa
rising column Frits has so eloquently described.
You can easily see this axial rotation effect by simply having running water from a tap go down the duct - very easy to see, hard to describe.

As far as doing this without a boost port - no free lunch,as the only way you can get a decent scavenging flow regime with this sort of setup is to
have the B ports collide - head on, and use the backward pointing radial angle on the A ports to get the flow attached to the rear wall and form a loop.

[trevor amos]

Many thanks Wob, more techno information than I could have hoped for, you were able to confirm what I had suspected but was unable to confirm.

Trevor

[peewee]

yes, most, if not all of the more advanced engines have used a smooth radius on the back wall of B port for quit a number of years. however some people still fool around with older design engines that have sharp hooks. banshee for example , which has sharp hooks up until atleast 2012, maybe even to this very day , if theyre still being sold in some countries.

some people arent aware the sharp hook is no good. not knowing which engine trevor was dealing with, or his skill level, i was just offering some advice, in case he wasnt aware the advantage to a smooth radius on the B port back wall, and A port front wall. there was a time when i hardly knew anything, but thanx to jan and frits ive learned quit a bit :2thumbsup

[peewee]

hey guys do you know of any good links where i can learn more about velocity through a duct ?

for example if you have X (high) amount of pressure at the duct opening and Y (low) amount of pressure at the exit, and lets assume the duct cross area is the same from entrance to exit, you will have Z amount of velocity.

now if we keep the pressure differentials the same as the above scenario (high pressure at entrance and low pressure at exit), but change the duct so the cross area converges (gets smaller) as it goes toward the exit. how does that affect the velocity , mass and energy of the air delivered to the low pressure space ?

reason im asking is because some people say you need a huge transfer opening in relation to the small exit at the window. but i thought it was better to have a opening about eqaul or only slightly larger than the exit. but then again the window is partially covered most of the time so maybe its ok to even have the entrance smaller than the exit ?

[TZ350]

... reason im asking is because some people say you need a huge transfer opening in relation to the small exit at the window. but i thought it was better to have a opening about equal or only slightly larger than the exit. but then again the window is partially covered most of the time so maybe its ok to even have the entrance smaller than the exit ?

That is a very interesting question, I would be interested in the answer too.

[adegnes]

Quick question for you TZ; have you modified the rotary "valve seat" with grooves or similar for less drag between it and the valve itself? If so, any measurable gain from doing so?

[peewee]

wob what you think of this. im just gathering the required info for engmod. in the process i put some playdoh in the B port for the hell of it. im sure your familiar with the front wall of the B port and how it twists ( at the entrance its the red line, then as it gets closer to the window it twists back to a trajectory straight across the piston like the green line)

do you see any reason i shouldnt use some epoxy and eliminate that twist so the wall runs straight up from entrance to exit like the orange line ? blue line is bore center

[TZ350]

TZ; have you modified the rotary "valve seat" with grooves or similar for less drag between it and the valve itself?

No sorry, mine are standard Suzuki, alloy plate engine side and fiber?? carb side.

305194305193

[adegnes]

No sorry, mine are standard Suzuki, alloy plate engine side and fiber?? carb side.
Ok, thanks!
Same fiber stuff on the ts100 cover, looks like cork. I have a Tomos a35 moped engine with what looks like the same stuff, lining the wet clutches!

[cotswold]

I spotted this on a classic 50 racing forum, a pretty radical disc valve.

[husaberg]

I spotted this on a classic 50 racing forum, a pretty radical disc valve.

If I only used my powers for good

The Kreidler engine shown by TZ350 was cutting edge technology in 1962, but I do not think any of you want to copy transfer passages that, together with twin rotary disks and a twelve-speed gearbox, produced all of 10 HP out of 50 cc.
In case you wonder: the transfer timing was 142°; the single exhaust was way over 200°. Don't try this at home....
Below are some more pictures of the same engine, showing the twin carbs and the screwed-in caps that gave access to the transfer ports for easy modification.
You can also see the hand-operated three-speed gearbox behind the foot-shifted four-speed box.

[F5 Dave]

I agree it certainly won't be easy but I found this on BDKs webpage, they recon just under 20hp at 10K, and 98 mph, here: http://www.bdkraceeng.co.uk/Bike5.html

A program I have that predicts top speed 1/4 mile etc also seems to think 21hp may just do it (with no wind on a nice day with no slope :confused:) It also uses a predicted Cd.

Dave

Dave
Just. Thread dredge from July last year re Practical Sportbike mag 100mph moped. They didn't make much past 90mph and then went quiet on the subject. Not sure if any more info on Farcebook I don't dabble there.

[TZ350]

305214

For something different, tonight its from the dark side.

305213

Blue is where we started, Red 23.47hp is the best and Green is where we finished up after fitting a longer bell-mouth.

305212

But for real hp, 2T's are where its at.

[Frits Overmars]

I spotted this on a classic 50 racing forum, a pretty radical disc valve.It is, but then you need to know what kind of engine it came from.
Your picture, repeated a little larger below, shows the Kreidler 12V 6x2-engine, which means twelve speeds, 6 foot-operated x 2 hand-operated.
It was the successor of the engine shown above in Husabergs pictures, the 12V 4x3, 4 foot x 3 hand, which drove the riders crazy when they had to brake, shift down and keep count. Suppose you are in 10th or 11th gear and you brake for a hairpin. Was it three times down with the foot and twice up with the left hand that also has to operate the clutch, or was it twice down with the foot and once down with the hand, or... f*ck, wrong again! And reading the notes written on the gastank wasn't good for health either because it could easily make you miss the corner. And we're talking 1960-circuits here, like the Nürburgring with 184 corners over 24 km.
The 6x2 was a lot easier to ride than the 4x3, although still not as easy as the Suzuki 12-speed and 14-speed machines, with just foot-operation.
Suzuki lost out however in downshifting: changing down 13 times for a hairpin simply took too much time.
OK, back to the disc timing. The Kreidler 12V 6x2-picture below left shows one normal disc, from the roadracing engine, and one crazy disc that hardly closed at all because it came from the compressor-blown land speed record engine.

[goose8]

305214

For something different, tonight its from the dark side.

305213

Blue is where we started, Red 23.47hp is the best and Green is where we finished up after fitting a longer bell-mouth.

305212

But for real hp, 2T's are where its at.Is Avalon doing the two hour ?

[Gigglebutton]

305214

For something different, tonight its from the dark side.

305213

Blue is where we started, Red 23.47hp is the best and Green is where we finished up after fitting a longer bell-mouth.

305212

But for real hp, 2T's are where its at.

Thanks for all your help Rob & Cully :)

[trevor amos]

Frits,
I recall reading a magazine article about the fun and games Hugh Anderson had with the 50cc Suzuki in the Island. In the end he gave up trying to compute the actual gear he was in and changed down in groups of three at a time. After that the numbers were a little easier even if racing the bike wasn`t!

Trevor

[Frits Overmars]

Frits,
I recall reading a magazine article about the fun and games Hugh Anderson had with the 50cc Suzuki in the Island. In the end he gave up trying to compute the actual gear he was in and changed down in groups of three at a time. After that the numbers were a little easier even if racing the bike wasn`t!It still doesn't pay to know which gear you're in, as long as the engine is in the powerband. But knowing how many gears you need to change down for any particular corner, does pay.

[seattle smitty]

Who made the carburetor?

[Grumph]

Love the blown Kreidler. Have to wonder though about using a slide carb on a positive displacement compressor - throttle sticking would be a major problem. Looking at what I can see of the second carb body on the manifold I'm assuming it is a blowoff/explosion valve ?

TZee - you need to study the ducting on that thing. A leaf blower attatched to the top inlet would be cool.....

[trevor amos]

The carb looks very like the old Amal TT, the slot in the side housing of the body enclosed a brass slide connected to a handle bar lever. Moving the side up and down enabled the main jet to be adjusted by 3-4 sizes over the full travel. Damn useful in the day, primitive but effective!

Trevor

[mr bucketracer]

Thanks for all your help Rob & Cully :)your bike is going good! what changes have you made

[husaberg]

The carb looks very like the old Amal TT, the slot in the side housing of the body enclosed a brass slide connected to a handle bar lever. Moving the side up and down enabled the main jet to be adjusted by 3-4 sizes over the full travel. Damn useful in the day, primitive but effective!

Trevor

Dellotto ss carbs look very similar
305221305222
but in this case I am picking amal
305223305224

Not so sure now second thoughts as it looks like it has a spigot rather than a flange?

[Grumph]

Dellotto ss carbs look very similar
but in this case I am picking amal
Not so sure now second thoughts as it looks like it has a spigot rather than a flange?

Pretty sure both Amal and Dellorto SS could be obtained with spigot fitting.
I've always assumed Kreidler used Dellorto's as they would possibly have been easier to obtain on the continent...
Academic anyway as the first Dellorto SS carbs were as i understand it, Amal TT's built under licence..

Interestingly, people like MZ always preferred the TT style carb with central needle as they were easier to tune on 2 strokes...The GP and RN types can be a real pain.

[Gigglebutton]

your bike is going good! what changes have you made

Hi Scott
New exhaust with a tapered section from 32 to 38mm, straightened the inlet so the card sits at 35*, taper bored that carb you sold me to 32mm.

[Frits Overmars]

Pretty sure both Amal and Dellorto SS could be obtained with spigot fitting.Yes they could.

I've always assumed Kreidler used Dellorto's as they would possibly have been easier to obtain on the continent. Academic anyway as the first Dellorto SS carbs were as i understand it, Amal TT's built under licence.The carb on the compressor engine was an Amal. The carbs on the roadracing engines were german Bing's, even easier to obtain in Germany than Dellorto's :msn-wink:.

[wobbly]

In regard to the flow in a 2T transfer duct there are several points you must realise about what is actually happening.
Firstly no matter what the porting arrangement ( within the bounds of what we call normal ) there is always more pressure in the cylinder than in the case at TPO.
Thus there is backflow from the excess blowdown pressure at initial opening.
This is what makes port stagger work - the port open first flows last.
As the piston continues to drop, the pressure ratio finally goes negative as the diffuser starts to do its work as the piston approaches BDC.
Next point is that I have thought for a long time that the actual flow into the cylinder is confined in volume to that amount of mixture sitting in the duct.
There is NO actual flow from the case into the duct and then into the cylinder.
This has been confirmed with some nuclear particles - thanks to info from Frits.

So the conclusion I made ( an assumption just waiting to be revealed as an error ) was that the smaller you made the duct volume, the less its inertia
and the quicker it would accelerate into the opening port area.
Sounds good in theory but maybe not based in reality.
I did a simulation run on the RG50 I am working on now with duct entry/port exit ratios of 1:1 and 1.5 :1 - no difference at all.
The sim is using the duct area /volume/length in its calculations, so is a reflection of reality.
The total case volume remained the same - to isolate just the entry change.

So - now it looks like the duct area ratios make little or no difference if the scavenging regime is optimised to use a particular style.
Look at the B port duct entry of an Aprilia - below the gasket line from the end of the radius at the bore ,it is smaller than the port area.
Look at the A port entry area, way bigger than the port in the bore.
Of course the B port has reverse stagger and this may have an effect overcoming the small entry area, but I prefer now to believe that the duct entry
ratio has little effect, the ducts inner and outer wall shape and the exit flow angles are far more important.

Re the perpendicular B port wall with epoxy added.
That is exactly what Jan did at Aprilia to see what happened - it made more power.
Again, possibly dependant upon the scavenging regime,but in general I would expect that NOT twisting the axial flow down the duct would help in any scenario.

[senso]

I think Frits once said that when there is the need to "bend" the flow inside a transfer to only do it on one dimension/axis at a time, probably its related to your findings, there are cylinder form Yamaha(dtr 125, dtx 125, dt 200, and all the variatons of that base engine and all its cylinder models, 3MB, 2RH, 4FU) they all have a very kinky divider curved in lots of directions, the only picture that I have is from one that already had meet the burrs, but none the less its still visible that its not linear, so it might be a better bet to remove a bit more of the divider, and then fill it it epoxy and then leave a chunky divider, like the RSA so there is less turns in the duct.

305230
305231

[peewee]

thnx wob. for sure i think devcon is the go to straighten out the front wall of B. i had a hunch it was the right thing to do and you seemed to confirm it also. plus looking at the rsa it seems to make even more sense at keeping that wall straight up

[peewee]

I think Frits once said that when there is the need to "bend" the flow inside a transfer to only do it on one dimension/axis at a time, probably its related to your findings, there are cylinder form Yamaha(dtr 125, dtx 125, dt 200, and all the variatons of that base engine and all its cylinder models, 3MB, 2RH, 4FU) they all have a very kinky divider curved in lots of directions, the only picture that I have is from one that already had meet the burrs, but none the less its still visible that its not linear, so it might be a better bet to remove a bit more of the divider, and then fill it it epoxy and then leave a chunky divider, like the RSA so there is less turns in the duct.

305230
305231


seems like i read in a book one time that the duct initial entry shouldnt be made like a funell , but if so, no more than a couple degrees convergence at most. if i have questions about what or what not to do, i try to look at other cylinders with superior design. the rsa surely doesnt have any funnel shape at the very entrance to the duct. so i would assume its not the best idea to do so. you may want to try some epoxy and make a chunky divider. im doing the same as well on a banshee cylinder :niceone:

[senso]

Sort of my motto, if its really good, it is used in the top competitions/racing, if not, might be old ideas or crazy ramblings.

What epoxy are you going to use if you can say?
For now I have been using Nural 21 from Pattex, its common in Portugal so I can get it in any super-market.

[peewee]

ill probly use devcon F putty. never tried it before but i have a jar of it sitting around so i might as well use it up. the green putty that jan spoke of works well in gas engines, ive used it before. dont try it for methanol though, i found it turns to rubber. if you want something that works good but doesnt cost much i would probly go with the green stuff like jan used. theres probly a handful of other epoxies that work well also

[wobbly]

Well strictly speaking the RSA does have a funnel effect, its the really big ball nose radius on the inner wall intersection with the bore.
Trust me - this is vital and makes up to 1.5 Hp in a near 50Hp 125 that previously had the usual sharp edge.
Let me remind you, the only place we see sharp edges on the leading edge of anything subject to airflow is in supersonic aircraft.
And yes, the flow into a transfer duct is seriously below supersonic.

[peewee]

yes it appears the rsa does have a funel affect between the inner radius wall and outside wall. what i was refering to is sensos pic, if he keeps a knife edge on the transfer divider, it will create a fairly large funell between the front and back side walls, of both A and B ports. the rsa doesnt seem to have the funel affect on the front/back side walls, at the initial duct entrance

[husaberg]

Yes they could.The carb on the compressor engine was an Amal. The carbs on the roadracing engines were german Bing's, even easier to obtain in Germany than Dellorto's :msn-wink:.

few more pics of the Kreider
one from you and one Rob previously posted
305243305244

[TZ350]

... google "anzani walin hallum" and Images.

305245

The first photo on the top left is Hallum's record-breaker Anzani, with its four carbs and megaphones.

Twin cylinders with the big carb on the central through the crank type rotary valve, then reed valve and piston port carbs.


... google "anzani walin hallum" and Images. The first photo on the top left is Hallum's record-breaker Anzani, with its four carbs and megaphones.

When I was racing outboards, a Seattle-area engineer and friend, Jim Hallum, built the fastest 322cc (class B, 20 cu. in.) outfit in the country, using an Anzani outboard which he modified greatly. This Anzani was essentially similar to the bike engine, but had a cast-iron, water-cooled block and water-cooled aluminum head. Jim eventually coaxed 65hp at 9000 rpm out of this poor old crude engine, and his driver, Gerry Walin, set a kilo straightaway record of 100mph with a Karelsen hydro. This was quite a sensation at the time, because not even the 500 or 700cc hydros had gone 100mph at that point. Of course, today the better 250 hydros can hit 100mph on a good-sized oval racecourse, with good acceleration.

Anyway, take a minute and google "anzani walin hallum" and Images. The first photo on the top left is Hallum's record-breaker Anzani, with its four carbs and megaphones (and 45% nitro). A couple of other racers were building these engines, and I have a pair of them, gathering dust. If you look down the page, there are some photos of the outboard crankcases and iron blocks. Farther down there is one photo of a hydro and Anzani that has curving "ram's horns" expansion chambers (the engine exhausted from top and bottom of the cylinders). This was Hallum's follow-on to the open megaphones, and it made about the same power as the old version but on methanol without any nitro.

I might be able to come up with one (there were 250cc and 322cc blocks) when you have the rest of it. One thing to consider is that an outfit called Harrison built what were pretty much Anzani copies during the late Sixties, and their blocks were sleeved aluminum, thus a whole lot lighter (though they might not be accepted as quite as cool as REAL Anzani parts). One of my Anzanis has a Harrison crankcase and magneto.

Some considerations: My pal Jim Hallum spent over ten years working on these engines before he got them to a good level of reliability. The Lucas mag was easily dealt with when electronic ignitions came along (this is all Pleistocene Era stuff, TZ), but factory rod bearings or cages were an issue, IIRC. Heat build-up in rod bearings is less of a problem with methanol than with gasoline. If and when you get to that point, I can ask Jim what he remembers about it.

The Anzani, in factory trim, took in its A/F charge through both a rotary valve in the center of the crankshaft (big square hole)(and the center section was supported by a bushing, not rollers), AND also passed some of it through piston-ports. Hallum separated these intake tracts, and used a big Vacturi carb to feed the rotary valve, and a little pumper Tillotson to feed the piston-ports. This 2nd carb added considerable power. He later added two more pumper carbs feeding small reedblocks into the crankcase. All three of the popular modes of intake in one engine!! The last two carbs added some more power, though not nearly as much more as the second one. But I expect you to find ways to put all four carbs on your bike!! . . . .

Also, you might want to consider building your bike as a 250. The 322cc version has a B/S of 60X57 and the 250 used the same stroke. It seems that modern B/S thinking of our gurus is favoring somewhat under-square arrangements. Now consider that either Anzani verson feeds its absurdly-small transfers largely (or completely, I forget; I ran Konigs) through windows in opposite sides of the piston skirt. It might be that you can create a better (less-bad as compared to anything modern) transfer passage combination with a 250 than a 322. The 322 would make more power and torque, of course, but you might be able to get the 250 a little closer to what modern engines of the same size do.

[TZ350]

305247

Simulation of Team ESE's next RG50 project .... Absolutely no idea if this can be made or not but we are planing it out as best we can in EngMod2T first.

We are risking our arm and taking the single port exhaust out to 85% (we have found 80 is Ok in a 50 with deep thin steel rings) and keeping the transfers low by making them as wide as possible.

305248

Using EngMod2T to check the STA's

And the pipe design was started by using the EngMod design a "Blair pipe" function then running many simulations in EngMod and changing diameters a millimeter at a time and lengths by 5mm or less at a time.

With many references to Wobblys pipe design comments and Frits %%% we came up with this pipe.

305246

It will be interesting to see how it turns out in reality.

[AndreasL]

TeeZee, is that RG50 a aircoold, piston port one? (From pic 2 above it seems to me its piston port at least?) Maybe a stupis question but I'm not very familiar with the different engines for this bikes.

Some 500 pages ago, dinamik2t posted the picture below.
Have any of you EngMod users managed to visualize the red/blue/green transfer port lines or is this just dinamik2t improving things in paint?
I think its a great feature if it was a way to add this lines within EngMod.

[chrisc]

This vertex piston came out of my '98 Honda RS125 tonight whilst I put a fresh one back in as routine maintenance. The bike still felt strong and smooth the last time I rode it and recently made 40 rwhp on the ESE dyno. To my untrained eye there doesn't seem to be anything particularly terrible here but I'm open to be told otherwise.

Click the photo for larger versions

Note the photo of the side of the piston is the exhaust side and there is a ceramic-ey yellow-ey marking on it which I'm unsure about. Thanks!

https://farm4.staticflickr.com/3953/15740353106_5570ccec0e.jpg (https://flic.kr/p/pYVqAo)https://farm8.staticflickr.com/7467/15578888457_17283dd782.jpg (https://flic.kr/p/pJDSM8)
https://farm4.staticflickr.com/3945/15578817027_167feca824.jpg (https://flic.kr/p/pJDvxz)https://farm6.staticflickr.com/5603/15578566868_7a3f654bd4.jpg (https://flic.kr/p/pJCebu)

I also posted some reference photos of the RS cylinder below. Click the blue arrow in the top of the quote box to see the original post with photos. Nothing new here obviously but worth a look for people like myself who are not well experienced 2 stroke tuners.


I put a new Vertex top end into the NX4 tonight and took some photos along the way for my own reference and interests.
Here they are if anyone else is interested.

NX4 cylinder next to a Suzuki GP125 cylinder with the RS base gasket laid over it. The B port shrouds have been cut out of this cylinder but otherwise it is stock at this time.

[seattle smitty]

To anyone who takes a look at the Anzani racing outboard, above, the big carburetor, which feeds the rotary valve, is a Vacturi taken from some early (1930s-'40s) Evinude production motor. Vacturis were used (in place of a single small Amal) by a few people on these 1960s racemotors because their intenal passages could be enlarged sufficiently to flow large quantities of methanol (with castor oil) and nitro. Note how big the supply hose is. The other three small carbs are Tillotson kart carburetors; the one feeds through piston-ports, the pair through reeds into the crankcase. The long aluminum device atop the Vacturi is a home-fabricated rack-and-pinion that opens/closes the main mixture needle, adjustable from he cockpit. When the engine was started, the mixture was set lean so that plugs didn't foul while the boat was planning-off, with the engine bogged down. Once the boat was on plane and engine revs were coming up, the driver moved a lever to reset the mixture rich for racing.

That the plugs (Autolite AE 403 or 203 recessed-gap, very cold) fouled so easily was due to the gear-driven device that you can see forward of the rope-plate/flywheel . . . a Lucas magneto.

[FastFred]

The long aluminum device atop the Vacturi is a home-fabricated rack-and-pinion that opens/closes the main mixture needle, adjustable from he cockpit. When the engine was started, the mixture was set lean so that plugs didn't foul while the boat was planning-off, with the engine bogged down. Once the boat was on plane and engine revs were coming up, the driver moved a lever to reset the mixture rich for racing.

I just love these racing classes where you can make and modify stuff and find simple handmade answers that make a real difference.

[F5 Dave]

TeeZee, is that RG50 a aircoold, piston port one? (From pic 2 above it seems to me its piston port at least?) Maybe a stupis question but I'm not very familiar with the different engines for this bikes.

Some 500 pages ago, dinamik2t posted the picture below.
Have any of you EngMod users managed to visualize the red/blue/green transfer port lines or is this just dinamik2t improving things in paint?
I think its a great feature if it was a way to add this lines within EngMod.
To answer for Rob: Watercooled, 1/2 piston port, 1/2 crankcase reed common to Suzukis of the 80s.

[FastFred]

Getting ready for Mt Welly tomorrow.

303234303237

Chambers RG50.

303235303236

NedKellys RS/Aprilia 50 with pumper carb.

The RG50's :- https://www.flickr.com/photos/sonscc/sets/72157647372063815/page2/

Team ESE RG50's, race numbers 43 and 6 https://www.flickr.com/photos/sonscc/sets/72157647372063815/page2/



TeeZee, is that RG50 a aircoold, piston port one? (From pic 2 above it seems to me its piston port at least?)To answer for Rob: Watercooled, 1/2 piston port, 1/2 crankcase reed common to Suzukis of the 80s.

[wobbly]

TeeZee, my comment would be that you really are dreaming when assigning a bmep of 14Bar at 13500 using the Suzuki 50/50 inlet system.
This as EngMod shows, it gives 23/24 crank Hp, but the sim only makes 19 and is falling off the cliff big time by 14,000.
Thus the transfer/Ex port system is well overspecd in relation to what the rest of the engine can achieve.
Plus something is seriously wrong if a pipe 660 long wont rev to 15,000 +, what pipe wall temp are you using.

Re the EngMod transfer radial coloured lines shown from a previous post of an Aprilia - its not even close to a real Aprilia scavenge system at all, and yes EngMod does
give you the diagram as shown but not with coloured lines.

[TZ350]

TeeZee, my comment would be that you really are dreaming ....

Absolutely, its one of the few things I am truly good at, like ....

305259


... something is seriously wrong if a pipe 660 long wont rev to 15,000 +, what pipe wall temp are you using.

305289

This is the temperature file I used for the original RG50 simulation, Red line.

305287

I grabbed this pre packaged TZ250 temperature file and re ran the simulation, Blue line.

305292

And Wob just like you said it would, it ran to 15,000 no problems.

The problem was, I had 50 as the pipe wall temperature in the RG simulation, maybe it should have been 500.

Ran it again with the pre packaged RS125 temperature file, Brown line, and 500, Green line, the temperature profile sure makes a difference.

I guess, just like in real life, like when the ignition is retarded to heat the pipe..... :blank:

305291

Wob thanks for pointing my mistake out, sure saved me big time. Is there a handy rule of thumb to use for pipe wall temperatures when developing a simulation of a new motor?

[teriks]

Is there a handy rule of thumb to use for pipe wall temperatures when developing a simulation of a new motor?Neels recently updated the pipe temperature model. You'll need to add ~300C compared older simulations if you installed the V5.2.1 update.

[AndreasL]

Yes Wob, I'm using the transfer lay out plot. A possibility to extend the transfer walls like in dinamik2t's example would be a "nice to have" but not super critical.

When touching the subject, is there generally a benefit in letting the rear wall collision point intersect outside the bore diameter insted of meeting at the bore rear wall? I will see what I get from EngMod but if anyone have any theories about this please let us know.

[seattle smitty]

I've observed that people here aren't bothered when two or three tech topics are being discussed concurrently, but I'm a little worried about interjecting this little bit of cross-talk because it comes from my vast ignorance (not entire, but still vast) of bike racing, so I hope that this is not old hat and a yawning bore to y'all.

I do know that traction for big-bore and even 250cc 2-stroke racers was a problem due to the 2Ts turbine-like power delivery, and at the other end of the roadracing world, Harley-Davidson, about three generations behind in engine design, were nevertheless quite effective on either dirt or pavement with their shaking 45degree V-twins, with their ba-bang . . . ba-bang powerstrokes hooking the tire to the track by acting sort of like a backwards version of anti-lock braking. I've stated elsewhere here that traction is no problem in outboard racing, that a modern racing propeller hooks the power to the water very effectively, and that the "droner-motors" and other weird traction remedies by 2-stroke bike tuners were not needed in boats. But I'm curious about engine layouts as relates to motorcycle traction and engine power delivery and balance.

Balance is far from a simple subject, but am I right in my notion that a two-stroke TWIN tends not to shake too much when the cylinders are either:

Opposed (with a crank that's well supported at either end, no center bearing, and a crank center section that's not hugely wide),

Parallel (with the cylinders as close to each other as possible)(which good sweeping ports makes very difficult),

or, a 90degree Vee (with similar crankshaft considerations to the Opposed-twin).

And I think this all applies to a 2-stroke four . . . .

If I have it right so far(??), tell me about 2-stroke V-twins, pros and cons. Were these used in GP bike racing, and did this help traction? (And were opposed-twins tried?). I've never seen a 2-stroke V-twin (except a photo of a street bike sold only in Japan, in the mid-Eighties), much less an opposed-twin (which in a bike calls for an oddball transmission). It would seem that the best modern porting schemes result in cylinders so wide that they are coming near to precluding their use in parallel-twins (without employing the kind of counter-balance shaft used in some singles). In outboards, opposed twins have become the deal-schenielle; light, low C/G, lots of grunt out of the corners, good balance and smooth running. Currently they are displacing opposed-fours of the same displacement that make more top-end power because with the light weight and low C/G the boats work better and they are quicker around the course despite not being as fast as an equally modern four.

The problem with making all your power with an opposed-twin with two cylinders that go bang at the same time is that it really puts the fear in your lower unit gears. To reduce drag, a racing lower unit needs to be as sleek and streamlined and SMALL as possible, with a pair of tiny bevel-gears transmitting those big bangs to the propshaft. That the prop is set up to be about halfways out of the water, with the blades slamming into and ripping out of the water with every revolution, makes life harder yet for those bevel gears. One development that has surely helped is the trend to three-, four-, and even five-blade racing propellors in place of the 2-blade props I raced with; having more blades in the water during each powerstroke of the engine somewhat reduces the loading/unloading of the gears from the propshaft side.

Still, the modern opposed twins tend to be lower-unit-eaters. So I'm wondering about 2-stroke V-twins (and V-fours). They would seem to have the light weight and low C/G of the opposed twins while not shaking too badly and while separating the power strokes so as not to put such big hits to the lower unit gears . . . .

What are the considerations I need to take into account?

(EDIT) Well, a big part of what I thought I "knew" about motorcycle traction turns out to be myth. Check Frits' post #15577, and visit his link.

[F5 Dave]

The street bike sold only in Japan was sold everywhere in the world except US. Along with several variants of models from different manufacturers.

at a min
4 from Honda
3 from Suzuki
1 from Yamaha but also basis of the TZ (in road guise but cases sameish)

[husaberg]

v formation was all mainly about packaging, it allows slimmer designs and less rocking couples with space for decent swooping transfers. In the case of the twin crank designs it allows better weight distribution whilst maintain a suitable short wheel base plus space for reeds in the v4s.
It allows significant packaging advantages with regards to pipes on a solo compared to a inline 4 such as the TZ500

[Drew]

I shouldn't think there's a great deal can be done in the way of mechanical traction advances with a two stroke. V-twin and crossplane inline four cylinder four strokes are better for tyre grip at peak torque, since the tyre gets a good rest between pulses, but there's no way to fake that on a two stroke.

[Drew]

Though, having said that there's a noticeably smoother power from a V-twin two stroke over a parallel twin. More again with a V-3 Honda, which is odd since the two front slugs fire together yet all three slugs are of equal displacement.

To it's natural conclusion, the one slug firing by itself would be half the output of the two firing together on said Honda. In effect, giving the tyre a rest.

Always just figured it was about getting the right square of bore/stroke for the desired capacity, those cheeky wee Honda fellas!

[wobbly]

Opposed 180* twins have perfect primary balance but are a nightmare to fit on a bike, easy on a boat.
The V twin is easy to package on a bike and has no issues with transfer width over the outside of the cylinders.
They have perfect balance when set at 90* with 90* firing, but need a balance shaft when using odd angles as Honda did in late model 250GP bikes.
The cylinders can be set very close together longitudinally so reducing the rocking couple across the crank.

A parallel twin is always a compromise, between wide bore centres causing an increasing rocking couple Vs room for the transfers.
They have perfect primary balance when at 180*, and if the static balance factor is done correctly for the inclined cylinders they can be very smooth
if mounted correctly - despite the rocking couple frequency causing some buzzing at the bars.
The same engineer ( Furusawa ) at Yamaha who did the detail design of the RZ 250/350 balance and mounting did the odd fire M1/R1 race engine design.

Then finally we have a wide cylinder spaced parallel twin, firing at 90* with a balance shaft to correct the primary imbalance.
This is the scenario chosen by Bartol for the KTM250 GP engine as it gave perfectly symmetrical intakes and pipes.
If the balance shaft is used as a drive to the clutch it involves an extra pair of gears in the drivetrain, with inherent ( 3 to 5% ) power loss but KTM decided
this was a small price to pay for a reverse crank rotation,big bang ,good package size and symmetric cylinder operation - the last never achieved in a V twin on a bike.

There have been years of discussion over what effect the big bang engine has and its implementation on a bike to increase corner exit traction.
Furusawa simply said that the odd fire M1 crank reduced the regular shaped,varying inertia torque, as seen in the symmetrical fire engine, and as this crank inertia "noise "
increases as the square of rpm, at 14000+ the crank inertia effect becomes greater than the individual full power cylinder combustion pulses.
Thus the rider cannot "feel" as well,the power pulses effect on rear grip thru the contact patch.
The irregular firing in an inline 4 helps to simulate what the V5 Honda had naturally, and what the Ducati finally had when they also found that the even fire screamer V4 was impossible to ride fast.
This effect should really be described as " long smooth bang " as this reduces the vibration effect of regular power pulses at the contact patch.
Big V twins have always had big bang with only 2 power pulses hitting the tyre per 4 stroke cycle,and helps to explain Ducatis dominance of Superbike for many years.

[Frits Overmars]

The problem with making all your power with an opposed-twin with two cylinders that go bang at the same time is that it really puts the fear in your lower unit gears. To reduce drag, a racing lower unit needs to be as sleek and streamlined and SMALL as possible, with a pair of tiny bevel-gears transmitting those big bangs to the propshaft. I love opposed twins. And for a boat, where you don't need a gearbox, I wouldn't choose anything else.
Smitty, what does the connecting shaft between crankshaft and bevel drive look like? If it has any length to speak of, it could serve as a torque shaft. The smaller its diameter, the more the firing pulses will be smoothed by the time they arrive at the bevel gears. But the boat people will have thought of this, won't they?

[Frits Overmars]

V-twin and crossplane inline four cylinder four strokes are better for tyre grip at peak torque, since the tyre gets a good rest between pulses.The tyre is there to work, not to rest. Smoothing the pulses will lower their amplitude, which will permit the use of a softer, grippier tire compound. The 'rest between pulses' originates from an erroneous big-bang explanation. You may want to take a look here: http://www.pit-lane.biz/t1461p32-technique-moteurs-motogp

[wobbly]

Re the pipe temp issue Rob, the original pipe wall temp at 50* is correct - you need to get the latest version and always input
the values of 325*C at the bottom of the usable powerband and 425*C at peak Hp, say 9500 and 13500 in the RG project.
The red line graph with 50*C has another issue that is stopping the VERY short 660 pipe from working with the engine specs - what is the advance curve.
Every time you change the pipe length you have to optimise the advance to work with that length, not the other way around.
But I suspect the very wierd arse pipe design with the steepest diffuser ever known to man isnt helping.
In reality a 660 pipe is way,way too short - in the RG50 sim I am doing there is still good power past 14000 with a 735 pipe length.
And this setup is to try to get as wide a powerband as possible for kart track use with no PV or electronic PJ available ( yet ).
Baselines to remember here are that an Aprilia with 200* and 800 pipe revs to 14500, but needed an electronic powerjet to do this.
A 125 ICC kart engine with 84* and a 760 pipe will rev to 14500 + even with a flat line ignition, 30mm carb and no electronic powerjet.
But both of those scenarios are very well worked optimisations of the parts available.

[FastFred]

<iframe width="560" height="315" src="//www.youtube.com/embed/GmcEDeouN4g" frameborder="0" allowfullscreen></iframe>

If you want to win races it pays to think outside the square ....... :laugh:

[husaberg]

Then finally we have a wide cylinder spaced parallel twin, firing at 90* with a balance shaft to correct the primary imbalance.
This is the scenario chosen by Bartol for the KTM250 GP engine as it gave perfectly symmetrical intakes and pipes.
If the balance shaft is used as a drive to the clutch it involves an extra pair of gears in the drivetrain, with inherent ( 3 to 5% ) power loss but KTM decided
this was a small price to pay for a reverse crank rotation,big bang ,good package size and symmetric cylinder operation - the last never achieved in a V twin on a bike.

.

Anyone got any pics of the inlets of the twin crank NSR250? i wondered if that was what Honda were trying to achieve
Could never figure out another ,unless it was to make it more slippery by being thinner but i can't see how that would work esp when they then made it wider by sticking on side mounted radiators....

[Frits Overmars]

Anyone got any pics of the inlets of the twin crank NSR250? i wondered if that was what Honda were trying to achieve. Could never figure out another ,unless it was to make it more slippery by being thinner but i can't see how that would work esp when they then made it wider by sticking on side mounted radiators....This is the only picture I got from the twin-crank NSR inlet side. HRC didn't exactly invite photographers to their (then very troublesome) worksbikes.

[peewee]

Neels recently updated the pipe temperature model. You'll need to add ~300C compared older simulations if you installed the V5.2.1 update.

when was this update ? i dont recall getting the email about it

[TZ350]

Gigglebutton let me play in his workshop tonight so I could use his benders etc to form the copper head fins. The motor is a little offset to one side in the frame so the room for the fins is a little longer one side and a bit cramped on the other. So I bent the fins differently, same Fin area both sides though.

305315305316

Square fins for the purists.

305312305314

Sun Burst for the adventurous.

305313

This is going to be my interpretation of Seattle Smittys suggestion for header pipe finning.

[TZ350]

Re the pipe temp issue Rob, the original pipe wall temp at 50* is correct - you need to get the latest version and always input the values of 325*C at the bottom of the usable powerband and 425*C at peak Hp, say 9500 and 13500 in the RG project.

Thanks Wob....

305317

Making progress.

305318

But I am still not sure about the 50deg, as I upgraded and the field I am looking at says "Exhaust wall temperature at Max Power". Anyway I will get to have a better look at it over the weekend.

[teriks]

when was this update ? i dont recall getting the email about it
Subject line:
"EngMod2T Updates 26 September 2014"

[seattle smitty]

To Frits, who asked about it, outboarders do try to get the driveshaft between the engine and the lower unit to absorb some of the hit (without itself breaking). Some guys are trying plastics. A problem here is that to keep the C/G as low as possible you want to carry the powerhead as low as possible. The device holding the powerhead and the lower unit, and affixing both to the back of the boat, is called the towerhousing, and it has gotten ever-shorter over the years . . . with the result that the driveshaft (running inside the towerhousing) has gotten quite short . . . good for transmitting power but not good for absorbing shock-loads. This is why I'm wondering about 90degree twins and fours, and hoping to hear more about their pros and cons (relative to my application). I know that if you "had your druthers" you'd rather have exhaust systems that are entirely in a straight line out of the port; you get this with opposed-twins but you'd have to have your header pipe take a 45degree turn with a V-twin. But other than that, what do you see? I see a lot less abuse to the lower unit (and prop, and the "shear-pin" for the prop).

Thanks to all who are advising me here!!!

[seattle smitty]

Frits, I just took a first look at your link. Dang, it seems that the more I learn, the less I feel that I really know!! How interesting that at around thirteen-grand, the con-rod/piston/bearings suddenly are loaded in tension ATDC. And here I always had imagined that in a 2-stroke this tensile loading only happens when you suddenly let off the throttle. Have to go back to the link and see if I can pound this new idea into my old brain. Thank you very much, I think:laugh:

(In thinking about your description of the actual power stroke, where the piston really is putting power to the crank, my first reaction is that here (this part of the stroke in a very-high-rpm 2-stroke) is where a long rod would really pay off . . . )

[TZ350]

Page 1040 is about the basics of pipe design and how to influence where the point of maximum depression occurs.

There are other collections of pipe talk on pages 620 630 640 650 660 670 680 690 700 730 740 which have un edited collections of raw material. If your interested in expansion chambers they are worth a look.



The pipe wall temp makes a huge difference , and much more accurately represents the real world wall temp average over the pipes length.

305355

When you have temp varying with rpm, this overrides the temp at max power entry, and I found in Beta testing that 325 and 425 worked very accurately.

In a situation like the Aprilia model where a powerjet is switched off past peak, 450 is needed at peak rpm to get correlation but is too hot for our "normal" sims.

Well made pipes that go around a corner don’t loose any power to a dead straight one - but dead straight pipes do actually cause deto, and need a deto button of some sort in the header to suppress this artefact. I posted a pic of one of these on here ages ago.


When unleaded became mandatory in 98 most teams had a hell of a time keeping deto under control, having to run very rich and retarded.

The cylinders with the straighter pipes always gave a lot more grief, until a lowly dyno operator at Yamaha discovered that when he stuck a large pressure probe into the header, the deto went away.

They managed to keep this secret for a couple of years but when teams like WCM got hold of the bikes, and left pipes lying about as you see in the pics,word soon got around.

305353305354

The "things " intruding into the header take varying forms,but all do the same thing - the usually bottom "bent "pipes dont have the same issue, so dont need the so called deto buttons.
I have a couple of deto buttons here but cant be bothered looking hard.

All they are in the form used by Yamaha and Roberts etc is a sort of mushroom. Or a penny on a stick. The penny being around 20mm dia by 3mm thick sitting on a stalk big enough for an M6 down the middle and a couple of flats to hang onto. The length being so the penny sits around 1/2 way into the pipe dia.

This thing situated about 50mm from the slip joint fixes the deto issue with a straight pipe.
Any bend that isolates the main body of the diffuser from the port seems to work.

The only plausible explanation I have is they shield the duct from infra red heat radiating from the pipe body interior - that overheats the plugging vol sitting in the duct. Goes along with not using heat wrapping on a header as it instantly causes deto. And as we well know Mr Thiel is a big exponent of keeping the duct charge volume small and cool - works for me.
I did proper back to back testing of the bent Vs dead straight pipes when building the BSL500.

The top pipes could be dead straight with just a small angle where the slip joint fitted onto the header,and these 2 pipes would deto as soon as you got close to spot on tuning.

Fit a deto button and the effect simply disappeared - we always had egt probes fitted and they made no difference.
On the bottom pipe of the tripple, this had a serious S bend to get the belly forward enough for it to fit nicely into the banana arm.

I found that as long as we had about 100mm of dead straight header fitting onto the slip joint I could get identical Hp within 1/2 in 55 as long as compensation was made for weld shrink on every joint, as well as every joint being hammered smooth. And the S bent pipe did not need a deto button at all.

I discussed the straight header effect with the Yamaha R&D chief at the time called "Suzan" and he opined that if you had a bend too close to the slip joint especially if it was bent in any way than on the vertical plane, this gave rise to an asymmetric plugging pulse flow, and this adversely affected the loop scavenge regime. Sounds pretty plausible to me.


- you need to get the latest version and always input the values of 325*C at the bottom of the usable powerband and 425*C at peak Hp, say 9500 and 13500 in the RG project.

The RG50 sim I am doing there is still good power past 14000 with a 735 pipe length. And this setup is to try to get as wide a power band as possible for kart track use with no PV or electronic PJ available ( yet ).

Baselines to remember here are that an Aprilia with 200* and 800 pipe revs to 14500, but needed an electronic powerjet to do this.

A 125 ICC kart engine with 84* and a 760 pipe will rev to 14500 + even with a flat line ignition, 30mm carb and no electronic powerjet. But both of those scenarios are very well worked optimisations of the parts available.



To get a deeper depression later in the cycle this is why we have a 3 section diffuser with a relatively shallow front end, then a long steep main diffuser leading up to the mid.

A short section of shallower angle leading into the belly helps to get a steeper angle on the main diffuser - closer to the mid at around 66%.

So - as a general rule the closer we have the steep section to the mid - the later ,and lower ,in the cycle toward TPC the depression will act.

But if we have the diffuser lengths correct the deep part of the depression will always move from closer to TPO under the peak, then ideally is centred on BDC at peak power rpm, then moves toward TPC
in the over rev area.

Thus - if you feel you need to move the max point closer to TPO you need to move the steep section closer to the header.


In regard to the flow in a 2T transfer duct there are several points you must realise about what is actually happening.

Firstly no matter what the porting arrangement (within the bounds of what we call normal ) there is always more pressure in the cylinder than in the case at TPO.

Thus there is backflow from the excess blowdown pressure at initial opening. This is what makes port stagger work - the port open first flows last.

As the piston continues to drop, the pressure ratio finally goes negative as the diffuser starts to do its work as the piston approaches BDC.



OK Wobbly, I have to ask this, even if the answer makes me cringe:
Why wouldn't I use a Vevey system in my 50 and 91cc buckets that need lots of midrange rather than peak HP?
Because the system reduces the peak power dramatically, and the only applications where the huge increase in low rpm power and bandwidth is of any use whatsoever is direct drive - no gears.

The KT100 needs to be able to haul off a hairpin at 8000 rpm and then spin to 16,000 to be able to only use 1 gear. In this case the torque multiplication of the very short gearing enabled by the peak rev capability makes the system workable.

With a bucket ( basket ) case you have a pile of gears to play with and only need to find the best compromise between powerband width and peak, to enable the least amount of gearchanges per lap.


Killing overev is easy, wind in some advance past peak,crank up the com, use a very steep rear cone, use a tight stinger,use a combination of port timing and pipe length
that has NO superposition resonance past peak.

All will make the powerband drop heavily after peak power, either by lowering the pipe temp or reducing pipe/port efficiency.


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

Thus in effect it "affects " the engine even more when well outside the tuning range of the mean reflection point than a shorter steeper design.

Taking this concept to the extreme, a flat plate "works" over a super narrow range ( and even then its not that effective due to the super short duration period ) and does virtually nothing outside the TL rpm.



A shallow diffuser does not create much negative pressure ratio around BDC, thus does not over scavenge the poorly configured transfers.


Once you have a well functioning sim of your engine and have run the Turbulent Entrainment model for your combustion Wiebe parameters the data feedback from TubMax is super accurate.

Getting the advance and stinger dimensions on the money to have this figure sitting on mid 900*C without WARNING - DETO - WILL ROBINSON screaming at you from the screen.

There are some very old guidelines that still work remarkably well today. Take as an example the RG50 T port cylinder I am working on at present. It has a 75% duct exit area at the flange = 24mm oval area. Take 0.58 of this diameter and we have 14mm, what is in the sim right now - 13.7mm with 18Hp at the crank. Thankyou Kevin Cameron.


A pair of transfers is a nightmare. I did an old 390 aircooled Husky and the only way to get any power at all was to re-liner and divide the HUGE transfer pair in two.

And for sure you cannot even think about using Frits or my design styles for what is essentially a lawnmower due to the pipe over scavenging the transfer system.

This means that at BDC a good diffuser (read fat) will create so much negative pressure ratio, most of the uncontrolled transfer streams will do a U turn and exit the cylinder.

When it comes to the piston port, the only approach I can see is to create a port as wide as you want, then use as little timing as is needed to match the STA to the blowdown and transfer numbers.

These small size (50cc) pistons can easily go 80% of bore with the Exhaust, so the limiting issue is going to be how much transfer you can create.

My first guess would be 60* back and 30* up, that at least will create some sort of loop effect for you.
Is it possible to get a reed into the inlet, then a boost port can be added and this works well, going all the way back to Kaden et al.


Page 950 .....
Its all about Exhaust blowdown...........
Pipes need to suck deep at BDC.....
297806

297808

Pay to follow Frits links to read the whole story.

297809

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

[wobbly]

TeeZee,the older version used a completely different pipe modelling code.
In this setup we found that 50* gave the best correlation to dyno tested powerbands, and was a source of real frustration for Neels
who hates " fudging " numbers with a passion.
He came across a new thesis that modelled an RSW and this included a new pipe simulation technique, and this has been written into the new code.
Now the pipe wall temp makes a huge difference ,and much more accurately represents the real world wall temp average over the pipes length.
When you have temp varying with rpm, this overides the temp at max power entry,and I found in Beta testing that 325 and 425 worked very accurately.
In a situation like the Aprilia model where a powerjet is switched off past peak, 450 is needed at peak rpm to get correlation
but is too hot for our "normal" sims.

Re using the driveshaft to flex and absorb some of the rotational shock load - in a World Champs winning 1080cc twin SeaDoo making over 230Hp
I designed a shaft made from a special steel grade ( no I cant remember ) that was only 12mm dia.
This replaced a 35mm tube that ran thru behind the water intake grate and made a huge difference to the performance, and no it didnt break even with many
jumps out of the water where it hit the limiter then snapped the rpm down again on contact after a wave.

Well made pipes that go around a corner dont loose any power to a dead straight one - but dead straight pipes do actually cause deto, and need a deto button of some
sort in the header to suppress this artefact.
I posted a pic of one of these on here ages ago.

[dinamik2t]

Some 500 pages ago, dinamik2t posted the picture below.
Have any of you EngMod users managed to visualize the red/blue/green transfer port lines or is this just dinamik2t improving things in paint?
I think its a great feature if it was a way to add this lines within EngMod.


It's been a long time; I think I was trying to derive the angles from the blueprints of the APC cylinder Frits has provided back then.
This could be a more accurate representation of an APF (?) cylinder, having a straight horizontal front wall angle for the B tfr and it's rear wall flow direction towards the 1/6th of the bore on the vertical axis.
Total eff area is ~1302mm2, like stated by Frits on a pic of TFR/Blowdown angle-I think-areas.

305320305321

Coloring is through paint.net and I agree that it would be a visually usefull add-on, if Neels ever has the time to implement it! I borrowed the idea from Frits.

-----------

I have a question: what sampling rate should be used when monitoring a knock sensor and an EGT sensor in a control unit making ignition timing corrections?

Furthermore, Wob could you give some directions on how to extend the depression of a pipe towards the rear side (towards TPO point)?

[husaberg]

Re using the driveshaft to flex and absorb some of the rotational shock load - in a World Champs winning 1080cc twin SeaDoo making over 230Hp
I designed a shaft made from a special steel grade ( no I cant remember ) that was only 12mm dia.
This replaced a 35mm tube that ran thru behind the water intake grate and made a huge difference to the performance, and no it didnt break even with many
jumps out of the water where it hit the limiter then snapped the rpm down again on contact after a wave.

.

As an aside Velocette used to design their bevel drives waisted for a similar reason.......from memory it worked like a torsion bar.
pretty sure I posted the Roarer story on the oldies thread. later maybe not.......

[AndreasL]

Like Wobs says, a thin shaft that flex.
I would have a look at "Orvar Supreme" from Uddeholm. Have heard about several successful applications when used in performance drive shafts.
http://www.uddeholm.com/files/PB_orvar_supreme_english.pdf

Regarding the colored lines in EngMod, rumors say that they are in the making. ;)

[Flettner]

torsional vibration, you want to be sure you are not designing a thin shaft ( spring ) that will hit a natural frequency and bust everything.

[AndreasL]

torsional vibration, you want to be sure you are not designing a thin shaft ( spring ) that will hit a natural frequency and bust everything.

Thats true, but that it takes some calculations to get it right was so obvious to me I did not mentioned it. Sorry if misleading anyone to belive it was a simple task.

[wobbly]

Re sampling frequency for a det feedback system - 12,000 rpm is 200Hz so to get instant response to a det event from a single cycle
this would need to be the sampling rate.
But this would probably be to responsive to random noise or det events, so 100 would be ample.

To get a deeper depression later in the cycle this is why we have a 3 section diffuser with a relatively shallow front end, then
a long steep main diffuser leading up to the mid.
A short section of shallower angle leading into the belly helps to get a steeper angle on the main diffuser - closer to the mid at around 66%.
So - as a general rule the closer we have the steep section to the mid - the later ,and lower ,in the cycle toward TPC the depression will act.
But if we have the diffuser lengths correct the deep part of the depression will always move from closer to TPO under the peak, then ideally is centred on BDC at peak power rpm, then moves toward TPC
in the overev area.
Thus to answer the question - if you feel you need to move the max point closer to TPO you need to move the steep section closer to the header.

[dinamik2t]

I was trying to generalize some power improvement-over-dimension changes on the 'default' HighPerf pipes and noticed that I was unable to create a deep trapezoid depression at peak, like you have described in the past as beneficial. Default dimensions (of either HiPerf or 3stage -and of the simple FOS) seem to always create a depression biased towards TPC. I will try these the next time, thank you for the explanation Wob!


ps. I 've been reading this http://books.google.gr/books?id=wC2dThrY2BMC&pg=PA83#v=onepage&q&f=false . The chapter (8) on Ignition is very illustrative if anyone is interested, describing among others the ignition process itself. I found interesting a comment on p.88, column2 : -talking about after-ignition events- "... The more mixture is consumed, the more heat is released, and this happens at the cube of the distance the flame front has traveled from the ignition source. In other words, the temperature rises more quickly as the flame front moves farther and farther from the point of origin. If this were to continue for very long, the remaining mixture would ignite simultaneously, causing severe detonation."

[TZ350]

305313

This is going to be my interpretation of Seattle Smittys suggestion for header pipe finning.

More ideas for a exhaust header cooler.

305343

A piece of finned pipe.

305344

Or maybe one of these Bates motorcycle exhaust pipe clamps would be the way to go for header pipe cooling.

If anyone has an old Bates clamp to sell I would love to cut a deal.

[husaberg]

More ideas for a exhaust header cooler.



A piece of finned pipe.

Or maybe one of these Bates motorcycle exhaust pipe clamps would be the way to go for header pipe cooling.

If anyone has an old Bates clamp to sell I would love to cut a deal.

Those sort of things were very common factory on triumphs bsa's etc...
http://allenmuseum.com/images/a10_rhs_450.jpghttp://upload.wikimedia.org/wikipedia/commons/8/84/Triumph_Speed_Twin_500_cc_1937.jpg
But I think DIY on a grandscale might be better and more potentially effective.
305350305351305352

[TZ350]

I've observed that people here aren't bothered when two or three tech topics are being discussed concurrently, but I'm a little worried about interjecting.

Wouldn't worry, its a bit like a party, with different conversations all going on in the same room.... :laugh: ... :drinkup:... :scratch::killingme... :chase:

[seattle smitty]

[QUOTE=wobbly;1130792247
Well made pipes that go around a corner dont lose any power to a dead straight one QUOTE]

Sigh . . . Well, that's what I had always understood for the last 45 years, but reading the Aprilia masters on the French site, I ran into one of them saying that a straight shot is best, or so I thought. If I can ever find it again, maybe I'll find he was only referring to the port itself. But then why would it matter for the port to be straight if it's okay for the header pipe and the rest to curve?

Talking about pipes, I guess everybody here is aware of Frits' new engine design, with ports as far as the eye can see. Has anyone asked how he's going to package it, given the two exhaust ports per cylinder? No problem on a single, but where do you put all the pipes as you add cylinders? Or do you run the headers from the two ports around into a single pipe? An American outboard tuner, Harry "Zak" Pasturzak, used to do this with Konig opposed-fours, connecting the top pair of cylinders (which amounted to a simultaneous-firing opposed-twin) to one pipe and the bottom pair of cylinders to another pipe (everybody else was connecting upper and lower pairs of cylinders (firing 180degrees apart) to a single pipe). (I haven't found a photo of Zak's pipes).

[Haufen]

Well made pipes that go around a corner dont loose any power to a dead straight one - but dead straight pipes do actually cause deto, and need a deto button of some sort in the header to suppress this artefact. I posted a pic of one of these on here ages ago.

Can an EGT probe serve as a deto button on a straight pipe?

[wobbly]

I did proper back to back testing of the bent Vs dead straight pipes when building the BSL500.
The top pipes could be dead straight with just a small angle where the slip joint fitted onto the header,and these 2 pipes would deto as soon as you got close to spot on tuning.
Fit a deto button and the effect simply disappeared - we always had egt probes fitted and they made no difference.
On the bottom pipe of the tripple, this had a serious S bend to get the belly forward enough for it to fit nicely into the banana arm.
I found that as long as we had about 100mm of dead straight header fitting onto the slip joint I could get identical Hp within 1/2 in 55 as long as compensation was
made for weld shrink on every joint, as well as every joint being hammered smooth.
And the S bent pipe did not need a deto button at all.
I discussed the straight header effect with the Yamaha R&D chief at the time called "Suzan" and he opined that if you had a bend too close to the slip joint
especially if it was bent in any way than on the vertical plane, this gave rise to an asymmetric plugging pulse flow, and this adversely affected the loop scavenge regime.
Sounds pretty plausible to me.

[TZ350]

Links to pictures of pipes with det buttons.


Here's some pics of rgv500 cylinders and pipes...hhmmm...


Hi all, Attached is some pictures of a late model TZ yamaha titanium GP 125/250 pipe. Can anyone explain what the part inside the pipe is.

Why is it there?
What is it called?
How does it work?


Ten carrot actors.

follow the posts for the RGV500 version and pictures

http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=258136&stc=1&thumb=1&d=1329761342http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=258135&stc=1&thumb=1&d=1329761341http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=258134&stc=1&thumb=1&d=1329761339


When unleaded became mandatory in 98 most teams had a hell of a time keeping deto under control, having to run very rich and retarded.
The cylinders with the straighter pipes always gave alot more grief, untill a lowly dyno operator at Yamaha discovered that
when he stuck a large pressure probe into the header, the deto went away.
They managed to keep this secret for a couple of years but when teams like WCM got hold of the bikes, and left pipes lying about as you see in the pics,word soon got around.
The "things " intruding into the header take varying forms,but all do the same thing - the usually bottom "bent "pipes dont have the same issue, so dont need the so called deto buttons.
I have a couple somewhere from a Red Bull bike - I will pic them and post here .

Here is a shot of a cylinder I have been working on - its just come back from plating - the duct entry shape looks a bit familiar doesnt it.
The plating must have more Nickel in it, that would be why some of the previous shots on here look as though the cylinders have a liner, its the colour of the plating process.

[adegnes]

I did proper back to back testing of the bent Vs dead straight pipes when building the BSL500.
The top pipes could be dead straight with just a small angle where the slip joint fitted onto the header,and these 2 pipes would deto as soon as you got close to spot on tuning.
Fit a deto button and the effect simply disappeared - we always had egt probes fitted and they made no difference.
On the bottom pipe of the tripple, this had a serious S bend to get the belly forward enough for it to fit nicely into the banana arm.
I found that as long as we had about 100mm of dead straight header fitting onto the slip joint I could get identical Hp within 1/2 in 55 as long as compensation was
made for weld shrink on every joint, as well as every joint being hammered smooth.
And the S bent pipe did not need a deto button at all.
I discussed the straight header effect with the Yamaha R&D chief at the time called "Suzan" and he opined that if you had a bend too close to the slip joint
especially if it was bent in any way than on the vertical plane, this gave rise to an asymmetric plugging pulse flow, and this adversely affected the loop scavenge regime.
Sounds pretty plausible to me.

Do you have any rule of thumb numbers on what is bendy enough to not need the button? I was planning a straight exhaust for my build, but this is giving me second thoughts.

[seattle smitty]

Everybody else here seems to know this term, not me. I went to Advanced Search, tried both "deto button" and "detonation button" with wobbly as author, hoping to find out more but got zero hits.

[adegnes]

Everybody else here seems to know this term, not me. I went to Advanced Search, tried both "deto button" and "detonation button" with wobbly as author, hoping to find out more but got zero hits.

You are not alone.

[husaberg]

Everybody else here seems to know this term, not me. I went to Advanced Search, tried both "deto button" and "detonation button" with wobbly as author, hoping to find out more but got zero hits.


You are not alone.

Don't use advanced search, it searches all of KB
use the search thread which is below it.then search
Using your same key words pulled up everything;)
305356305357

[wobbly]

I have a couple of deto buttons here but cant be bothered looking hard.
All they are in the form used by Yamaha and Roberts etc is a sort of mushroom.
Or a penny on a stick.
The penny being around 20mm dia by 3mm thick sitting on a stalk big enough for an M6 down the middle and a couple of flats to hang onto.
The length being so the penny sits around 1/2 way into the pipe dia.
This thing situated about 50mm from the slip joint fixes the deto issue with a straight pipe.
Any bend that isolates the main body of the diffuser from the port seems to work.
The only plausible explanation I have is they shield the duct from infra red heat radiating from the pipe body interior - that overheats the plugging vol
sitting in the duct.
Goes along with not using heat wrapping on a header as it instantly causes deto.
And as we well know Mr Thiel is a big exponent of keeping the duct charge volume small and cool - works for me.

[adegnes]

Any bend that isolates the main body of the diffuser from the port seems to work.

Thanks! Could you elaborate on the isolate part? If I where the diffuser I should not be able to see the port?

[TZ350]

Wob explained to me that with the "Wall Temp a Function of RPM" box ticked the 50 deg entered in the "Exhaust Wall Temp at Max Power" has no effect(the 50 was more applicable to an older version of EngMod). He also suggested to me to use 325 at the start of useful power and 425 for max power and 450 for extra heat in the pipe in over rev if you have an elec power jet and or retarding the ignition.

305358

Thanks Wob for the Heads-Up on the Temperatures to use with the EngMod2T simulation file.

305359

Making progress with the RG50 pipe design.

Cheated a bit by making the inlet a large piston port in the simulation as I don't really know how to represent a 50/50 piston/case reed setup. But I forgive myself as I am only learning about pipes and how to use this simulation software for designing our own expansion chamber.

Page 1040 is about the basics as explained by Wob of how to influence where the point of maximum depression occurs.

There are other collections of pipe talk on pages 620 630 640 650 660 670 680 690 700 730 740 which have un edited collections of raw material. If your interested in expansion chambers they are worth a look.

[TZ350]

Everybody else here seems to know this term, not me. I went to Advanced Search, tried both "deto button" and "detonation button" with wobbly as author, hoping to find out more but got zero hits.

Some good search methods....


Some may find this useful. Rather than use the site search which usually fails, use Google so to search this site use an ordinary search phrase and after it add
site:www.kiwibiker.co.nz (http://www.kiwibiker.co.nz)
for example
Frits priceless site:www.kiwibiker.co.nz (http://www.kiwibiker.co.nz)
or
Frits pisa site:www.kiwibiker.co.nz (http://www.kiwibiker.co.nz)
the same will work for other sites with the appropriate site address
Mick


Don't use advanced search, it searches all of KB
use the search thread which is below it.then search
Using your same key words pulled up everything;)
305356305357

[Larry Wiechman]

The only plausible explanation I have is they shield the duct from infra red heat radiating from the pipe body interior - that overheats the plugging vol sitting in the duct.
Goes along with not using heat wrapping on a header as it instantly causes deto.
And as we well know Mr Thiel is a big exponent of keeping the duct charge volume small and cool - works for me.

Very interesting, Wob.
Wouldn't the button itself be glowing red hot?
Do these buttons function as a fluid diode for the return pulse?
I notice quite a difference in the downward angle of exhaust ducts. Does the escaping exhaust mass have a natural downward vector, or is this to direct the returning charge?

[wobbly]

Dunno about the mushroom theory, maybe I didnt take enough when I looked like Hendrix to get some insight.
Flux capacitor - fluid diode , take your pick before taking lysergide and peering into the running engine.

The down angle of the Ex duct has been thoroughly tested, again by Mr Thiel - 25* is the magic " mushroom " number.
This is to do with the initial flow adhering to the roof at low piston openings - the flow bench and the dyno dont lie to each other or us
in this case, again.

[seattle smitty]

Tried Husaberg's search, got hits, mostly from what's right here but a couple from some time back.

Weird, Wobbly. Weird! If a good curved exhaust system can make the same power as a equivalent straight system, why would the detonation effects be different? . . . well, I guess we know by sad experience that we don't have answers for everything in this lifetime, especially regarding 2-strokes as Frits has commented (but maybe he didn't consider the mushroom mode of inquiry).

[wobbly]

Being a Dutchy you can be sure several modes of serious inquiry were heavily investigated.
Nowdays I have the odd weed with my sons at Yes concerts, but being a Chemical Brother is relegated to serious testing of single malts.
My preference now is for a 16 yr old - no not schoolgirls, a Lagavulin lightly peated joy to the taste buds.

[2T Institute]

https://www.youtube.com/watch?v=fiUr7s6LC3U

Here you go then Wob bit of reminising,your favourite rider too :crazy: :mad: :brick:

[Frits Overmars]

Talking about pipes, I guess everybody here is aware of Frits' new engine design, with ports as far as the eye can see. Has anyone asked how he's going to package it, given the two exhaust ports per cylinder? No problem on a single, but where do you put all the pipes as you add cylinders? Or do you run the headers from the two ports around into a single pipe?If you exploit the rpm potential of the FOS scavenging system, the pipes will become very short so you won't be able connect the headers into a single pipe.
Packaging the short pipes won't be a problem with a V-twin or a boxer twin, but will be difficult for other multi-cylinder configurations.

[Frits Overmars]

Being a Dutchy you can be sure several modes of serious inquiry were heavily investigated.
Nowdays I have the odd weed with my sons at Yes concerts, but being a Chemical Brother is relegated to serious testing of single malts.
My preference now is for a 16 yr old - no not schoolgirls, a Lagavulin lightly peated joy to the taste buds.The picture below of Holland's finest products may give you some more ideas to help you through the dark winter months.
Oh no, that's over here; you will be sunbathing while we shovel snow and scrape car windows.

[seattle smitty]

That's one of their 16 year old schoolgirls, Wobbly, don't even think about it.

The thumbnail won't open for me, Frits. The problem might be here, nothing but problems for me with Windows 8.1. (Why couldn't they have stopped with XP Professional; I could mostly manage with that. Ah, but I know a kid, one of those genius computer-nerds, who's going to get me switched to some version of "puppy Linux").

Frits, I'm hoping for you to comment on my notions, above, about V-twins and V-fours as an alternative configuration for racing outboards . . .

[peewee]

hey wobbly i finished putting all the banshee info into engmod. i hear guys say they get 100hp from these things with methanol. not sure if i believe it but ill give it my best effort to see if its true. anyways i noticed something that ive seen before with other engines in engmod. the banshee cylinder as well as one of my old ktm cylinders ( and likely many other cylinders out there ) , show a undersized cylinder inlet and more so a reed cage thats far too small. have you noticed this also, where the reed cage and intake seem to be way too small ? something else, i plan to use vforce 4 reed block, although i havent input the block dimensions yet, but i suspect it will likely still be undersized. is there any modification that can be done to the vforce4 to help it be closer to the rest of the engines performance numbers or is there simply nothing that can be done, short of cutting the intake off the cylinder and welding a larger intake system back on ?

[wobbly]

Yes the Banshee reeds are way small - the VF3 that fits is alot better in port area,but to make serious power it needs a bigger reed box and the 60mm
size VF3 off a CR125 etc.
This is quite common on drag RD400s etc.
Then also it needs big Boyesen ports and the piston cutting like a Blaster to get the cylinder intake area need.
But you can make some really good power with the smaller VF3, as when really pushing the intake - the reeds just stay open longer.
Here is dyno sheet of a 400cc Banshee based road racer with CPI cylinder, on AvGas its 96RWHp.
This is 8 port transfers and 3 port Ex and powervalved, but setup to make a wide spread of power ,so I seriously doubt 100 from Banshee castings even running Methanol.

[peewee]

ill be cutting in large boyesen ports. and aux exh windows also. :Punk:. replacing the entire intake with a larger one is more work than i want to get involved with.

[peewee]

wobbly if i can bother you with another question. most cylinders ive seen have a removable exh manifold. this one doesnt however. still i would think the flange piece protruding from the cylinder would be considered the manifold. for the exh passage length in engmod, i assume it would be the green arrow length ? i would get the passage end diameter from this point also ? or would it be the yellow arrow length ?

[Frits Overmars]

Frits, I'm hoping for you to comment on my notions, above, about V-twins and V-fours as an alternative configuration for racing outboards . . .I went back 6 pages, but I can't find any unanswered questions Smitty. I assume you took a look at the Pit-Lane link?
If I missed something, let's have some specific questions. But don't hold your breath because workload is such that I really need a watercooled brain at the moment.

[seattle smitty]

I've visited that link three times and will do so again; invaluable information, fascinating!! And between what Wobbly and you have already said, I have certainly got more and better responses than I deserve to get from busy men. Thank you both, and I'm going to "lurk-mode." Like everyone else here, I do hope to hear about the development story of the new engine, when/if you have time.

[wobbly]

The code does not care about what part of the input is used to represent the duct/pipe, except to say that the duct temp is part of
the jigsaw as much as the pipe wall temp is.
Thus in this case we have an alloy spigot extension that has the slip joint around it, and water is a fair distance away.
I would opine that this alloy extension would be closer to the pipe temp than the duct wall temp, so should be considered part of the header.

Re the relative "betterness" of any one physical layout for a boat, in the case of the 4 cylinder the differences between say a twin crank
contra rotating stack ie a square 4 Vs an inline 4 Vs a V4 would all come down to the number of seals/bearings in total used to support
the flywheels.
As it would appear that balance, firing order and rotational precession have little bearing on the final result then FMEP would become important, except
maybe the inline 4 would have a much higher C of G and this may overcome any perceived frictional advantage.
Maybe the best compromise ( but problematic to implement reliably ) is a flying web setup.
Go buy a Swiss Auto, they were cheap enough in comparison to a Japanese factory engine at the time.

[husaberg]

The code does not care about what part of the input is used to represent the duct/pipe, except to say that the duct temp is part of
the jigsaw as much as the pipe wall temp is.
Thus in this case we have an alloy spigot extension that has the slip joint around it, and water is a fair distance away.
I would opine that this alloy extension would be closer to the pipe temp than the duct wall temp, so should be considered part of the header.

Re the relative "betterness" of any one physical layout for a boat, in the case of the 4 cylinder the differences between say a twin crank
contra rotating stack ie a square 4 Vs an inline 4 Vs a V4 would all come down to the number of seals/bearings in total used to support
the flywheels.
As it would appear that balance, firing order and rotational precession have little bearing on the final result then FMEP would become important, except
maybe the inline 4 would have a much higher C of G and this may overcome any perceived frictional advantage.
Maybe the best compromise ( but problematic to implement reliably ) is a flying web setup.
Go buy a Swiss Auto, they were cheap enough in comparison to a Japanese factory engine at the time.

.
LOL they were still pretty pricey.
I seen this the other day whilst I was looking for the Roarer stuff.
This was the coupling and set up on a Guzzi 4 Inline along the frame Supercharged fuel injected bike from the 40 or 50's
it had posted I think the injection or the hidden plugs stuff from it before.
305442
Honda at the time they did the big bang for Doohan had another design they played with but kept in reserve, I am pretty sure it was a ultra close bang with shared crankcases.

[seattle smitty]

Was going to lurk but, . . . An inline four with modern wide-sweeping ports would be hugely tall, and a twin-crank four would be heavy. It seems to me that a V-twin or V-four need not be any taller or heavier than an opposed-twin or four, so that's what I was asking about (and about which I learned a lot).

Some American outboard racing history trivia: Talk about heavy engines, take another look at the four-carb Anzani in the photo above. The builder of that 322cc engine once put two of those engines side-by side on a gearbox to make an engine for the 700cc class; 1968 I think. Two engines, thus two cranks, two cast-iron blocks, and the special gearbox; also four megaphones, lots of carbs, and 20% nitro. One engine had its cylinders pointed forward, one engine pointed aft (like the single engine in the photo). In those days, ignitions were pretty weak, and to keep from fouling plugs two crew members would bodily lift the back of an alky boat to get the prop free of the water on start-up. The driver or a 3rd crewman would rope-start the engine, the driver would give it a little throttle to keep it running for several seconds to warm up slightly and clear the plugs, and then the two guys holding up the back of the boat would sort of throw it forward as the driver gave the engine enough throttle to climb on plane. Well, I had the questionable luck to be one of four crew who held up the back of the boat which carried this twin-Anzani monster. As it happened, the boat was a big and old and HEAVY DeSilva runabout, with a big HEAVY driver! I think all four of us got hernias!! Unfortunately the engine kept fouling plugs, and never got fully on-plane with several tries, so we gave up. The whole deal was a last-minute project for a single race, and there just wasn't enough time to sort it out. The project was abandoned, the powerheads were taken off the gearbox and went back to normal use. Sort of too bad the project was not tried again a couple of years later when good electronic ignitions came into use. It would have been a handful in the turns, but 120-plus horsepower would have been quite a ride for those days. This is the sort of project that far-gone 2-strokers love; not entirely practical, but wild and cool and FUN.

[husaberg]

Was going to lurk but, . . . An inline four with modern wide-sweeping ports would be hugely tall, and a twin-crank four would be heavy. It seems to me that a V-twin or V-four need not be any taller or heavier than an opposed-twin or four, so that's what I was asking about (and about which I learned a lot).

.

there is a few ways around this the Kawa Trapezoid 750/4 shorter than a square 4 narrower than a 3

.....
305460305461



Yamahas OW48R or TZ500J
305459305457
http://classic-motorbikes.net/wp/yamaha-500-gp-history-part-3/

BSL500 note how much room there is for the Transfers on both triples
305463

NS500/RS500
305464

Then again for a boat you could do a stacked crankcase radial.........

[seattle smitty]

Wonderful engines and photos, thanks for those! They all look big and heavy for today's outboard racing, but certainly food for thought. I think any triple has to have four main bearings, whereas an opposed-four can do with three and an opposed twin with two. One of the things I wondered about is if that also could be done with 90degree V-twins and fours; could adjacent crankcase sections (for adjacent cylinders) have a wide, flat, full-circle crank throw between them (no main bearing), with a labyrinth seal around the crank-wheel, . . . would a seal like that work at high rpm and effectively seal the two crankcase sections, and if it did would the oil retained by the seal have a lot of drag?

Rossi built a 350 triple for several years, an opposed triple, with number one and three cylinders pointing left and number two pointing right. Funny-looking thing, but it won races. Now he sells a 350 opposed twin, lower and lighter and lots of snort out of the corners, and hard on lower units.

There was at least one radial outboard, though not for racing. in the 1950s, the Riley 75 was a five-cylinder 4-stroke flathead radial, big, heavy, complex, and expensive, intended to power cabin cruisers. I don't think many were sold, and never saw one. George Riley was a talented mechanical innovator, built aftermarket hop-up heads for Model T and Model A Fords, and other stuff. Google "Riley 75 Outboard" and click on the FiberGlassics link for photos.

[seattle smitty]

(EDIT) I'm trying to delete this . . . ???

[Grumph]

Wonderful engines and photos, thanks for those! They all look big and heavy for today's outboard racing, but certainly food for thought. I think any triple has to have four main bearings, whereas an opposed-four can do with three and an opposed twin with two. One of the things I wondered about is if that also could be done with 90degree V-twins and fours; could adjacent crankcase sections (for adjacent cylinders) have a wide, flat, full-circle crank throw between them (no main bearing), with a labyrinth seal around the crank-wheel, . . . would a seal like that work at high rpm and effectively seal the two crankcase sections, and if it did would the oil retained by the seal have a lot of drag?

Do you have any personal experience with the OMC V4's ? I have in a book here a couple of pics of the OMC cranks which are pretty much as you describe but with large dia piston ring type seals on the webs. Intake was compromised with small reeds feeding at very poor angles and restricted areas. I may yet scan the pics and send them to husa...unless he finds them on the web first....

[seattle smitty]

I know of them, at least the old cross-flow V-4s of my youth, but never had one apart.

[wobbly]

What you describe is exactly what SA Design did with the flying web V4 - 500, but needed no sealing between the crank pairs.
The Swiss Auto had adjacent cylinders crankpins running at 90* opposite each other off a common web that was sitting inside a common crankcase volume.
This eliminated a seal and bearing between those cylinder pairs.
Gave a very small package, but required very expensive materials, extensive FEA and heat treatment to overcome the stress levels generated in
the unsupported "flying web".

http://www.swissauto.com/d/motor/projekt_galerie.jsp?ID_Display=20000D

[jonny quest]

How did the SA seal between the crankcases?

It also said that motor has numerous wins... what teams did they win with?

[Frits Overmars]

One of the things I wondered about is if that also could be done with 90degree V-twins and fours; could adjacent crankcase sections (for adjacent cylinders) have a wide, flat, full-circle crank throw between them (no main bearing), with a labyrinth seal around the crank-wheel...What you are exactly describing, is the French JBB 250 V-twin. The pictures below should speak for themselves but I would add that, given your freedom of shape on a boat, a boxer would be simpler, lighter and more vibration-free.

[wobbly]

The SA didnt need to seal adjacent cylinders - they fired together off a common case volume.
ie the crank pins on each side of the flying web were displaced by 90*, as were the cylinder axes - thus both pistons arrived at TDC together.
Put two of these pairs in line and you have a V4 with the minimum seals/bearings.

[jonny quest]

Look at that fancy cylinder head in the pic Frits posted.

Frits' motor pics also show a sealing ring between crankcases. How would the dual carbs work then?

Thanks Wobbly for info

[husaberg]

Look at that fancy cylinder head in the pic Frits posted.

Frits' motor pics also show a sealing ring between crankcases. How would the dual carbs work then?

Thanks Wobbly for info
works like this.....
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=301115&d=1411112018

A few pics of a Rotax homebuild special flying web
http://www.kiwibiker.co.nz/forums/album.php?albumid=4834

JBB
http://www.kiwibiker.co.nz/forums/album.php?albumid=4836

Swisauto
http://www.kiwibiker.co.nz/forums/album.php?albumid=4833

Konig inc crank pics
http://www.kiwibiker.co.nz/forums/album.php?albumid=4851

Boxer 2 strokes
http://www.kiwibiker.co.nz/forums/album.php?albumid=4879

[fatbastd]

Apologies in advance for the thread hijack, but I'll keep it brief..

Question for Frits really-I see you name in connection with a Yamaha 3 cylinder article from some time ago. In Dutch, sadly for me!

I am contemplating buying such a machine-in terms of reliability and usability, assuming properly maintained and prepared, would you suggest avoiding the idea or see it as no worse than anything else similar?

Thanks.

Now, back to the regular programme...

[seattle smitty]

Well . . . as the old traveling, Bible-thumping preachers used to shout at their big-tent revival meetings, "ASK-uh and yew shall RECIEVE-uh!!!!"

What a great website!! My only problem is that my brain gets full, and I have to go away and do other things.

There are several things that jump right out at me from the responses and photos on which I could comment, but they are equally obvious to all, and I've already taken more than my share of space and attention, so I'll resist for a while (have I said that before??).

Many thanks, gentlemen.


(EDIT) AW DANG, okay, here I go again, ONE observation/question: On some of the photographed engines, it appears that the stubs on either end of the crankshaft only have room for a single-row bearing. Given the power, and twisting forces that these engines put out, would it not be better to support the crank with double-row bearings whenever possible, even at the cost of a small increase in overall width??
I once read an account by American auto racing engine-builder Smokey Yunick. Smokey described watching a sort of dyno run in which a dummy engine with some viewing-ports cut into it was spun up to racing rpm with a powerful electric motor. Stroboscopic lighting was used to see the effects of horsepower and rpm on various components (I think this was all done at GM). Smokey said that at 7000 rpm a camshaft twists and wriggles and winds-up and releases like a snake that is desperately trying to tear itself free of the engine. And I had heard a similar description of a dyno run of the first Mercury Mk75 outboard in the mid-1950s, as witnessed by a local racer/tuner, Bill Rankin. Bill said that the Mercury engineers had the base of this 60hp inline six mounted rigidly to a plate of steel . . . and had a measuring device (machinist's scale or dial indicator or ?) set against the top of the tall engine to see how much it might twist along its length. Bill told me when they put full throttle to that motor you didn't have to read the scale . . . the top of that engine visibly twisted waaaayyy out-of-line!!
So I have a hunch that as you add power and rpm, and heat, to any sort of racing engine, it is twisting and ringing and wiggling and oscillating to a degree that would be alarming if you could see it "slowed down" with strobe-lighting or some-such method (AND, different subject, that the lovely round and parallel cylinders that you examined cold with your bore-guage are a good deal less round and parallel when hot). IF this hunch is at least somewhat true, wouldn't it follow that you want REAL GOOD mainbearing support at the ends of a crankshaft?? And maybe the fattest, longest, best-supported crankpins (consistent with their trade-offs)??

Sorry, I can't seem to stop myself.

[Grumph]

Smitty, the answer is yes - and no....from personal experience i've seen big end pins in pressed up cranks get bigger as power has gone up - but there is a limit to this. Pressed up cranks can and do flex to accomodate case movement.

There's a very good - but 4 stroke - example local to me. One of the last survivors of the 1927 Delage straight 8 GP cars was being rebuilt here. The car changed ownership part way through the rebuild. First rebuilder (friend of mine) had copied the original crank - one piece, about 3 feet long, split roller big ends...Second rebuild shop took one look at the crank and said "we can do better" so beefed it up...
When the finished car was run, the stiff crank cracked the block...It's now running with a stitch repaired block and my friend's OE copy crank in it...And flexes quite happily.

[seattle smitty]

Oh sure, it has to be an integrated set of design changes.

[RomeuPT]

I did proper back to back testing of the bent Vs dead straight pipes when building the BSL500.
The top pipes could be dead straight with just a small angle where the slip joint fitted onto the header,and these 2 pipes would deto as soon as you got close to spot on tuning.
Fit a deto button and the effect simply disappeared - we always had egt probes fitted and they made no difference.
On the bottom pipe of the tripple, this had a serious S bend to get the belly forward enough for it to fit nicely into the banana arm.
I found that as long as we had about 100mm of dead straight header fitting onto the slip joint I could get identical Hp within 1/2 in 55 as long as compensation was
made for weld shrink on every joint, as well as every joint being hammered smooth.
And the S bent pipe did not need a deto button at all.
I discussed the straight header effect with the Yamaha R&D chief at the time called "Suzan" and he opined that if you had a bend too close to the slip joint
especially if it was bent in any way than on the vertical plane, this gave rise to an asymmetric plugging pulse flow, and this adversely affected the loop scavenge regime.
Sounds pretty plausible to me.

Good info. Thanks
I usually divide the header into several pieces, starting from cuts of 5 or 6º to 7/8º depending on the needed bend. So the first 100mm of header encouters 2 or 3 hamered cuts of 5º and 6º. Some other pipe builders give the a bit of straight header and then a 90º of sharper bend follow by other straing and other bend to go under the bike

Don't know what's better.

[peewee]

i had a similar thought not long ago for a banshee crankshaft. why not use a cylindrical roller bearing on both ends ( instead of a 6 ball ballbearing) and 8 ball ballbearings in the center ( instead of 6 ball ballbearing). crankworks told me this may cause too much stiffness and create a failure. im not sure i believe it though. didnt some of the yamaha twins have a similar setup with roller bearings on each end and two hefty ballbearings in the center ?

[koba]

Is anyone getting to the point where the crankshaft bearing setup or crank is a problem?

Or are we just being a bit like the guy that built the beefy straight 8 crank?

[speedpro]

MB cranks are good. There are better bearings available but they are more for insurance than anything. I run steel cage C3 or C4 mains. On my old Suzuki I had a main bearing cage go to pieces once but no problems with the Honda so far. Little end and big end bearings are worthwhile improving. I have had issues with them, luckily nothing terminal, just the cages cracking.

[TZ350]

Is anyone getting to the point where the crankshaft bearing setup or crank is a problem?

305558

Probably not a real problem, it just took a while to figure out. Chambers finally cured the smoky bike issue. After lots of work changing seals and re gluing inlet manifolds and rotary valve covers etc all to no avail.

The smoky problem was cured after a re true of the crank and a new drive side main bearing.

We guess the end of the crank wiggling around in the oil seal was acting like a pump and passing gear box oil to the RV chamber. Anyway, truing the crank and fitting a new drive side main bearing cured it.

[Frits Overmars]

Question for Frits really-I see you name in connection with a Yamaha 3 cylinder article from some time ago. In Dutch, sadly for me! I am contemplating buying such a machine-in terms of reliability and usability, assuming properly maintained and prepared, would you suggest avoiding the idea or see it as no worse than anything else similar?"Some time ago" would be about 35 years. My memory is good, but not so good that I could recall the article without diving into about a ton of paper archive. Besides:
A: I'm working 24/7 already.
B: I can't get to my archive because we're in different countries right now.
C: 3-cylinder yamahas have been built by at least five different people that I know of, and quite possibly a few others that I don't know of.
D: even if you're talking about the one engine that I truly knew, I have no way of telling what state it is in right now.

There have been some pretty good 3-cylinder yamahas in their time, but why would you want to go that road now?
Take any twin-cylinder jetski or skidoo engine and you'll have less work, less problems and more power.

[fatbastd]

Thanks Frits, that's about the depth I'd hoped for! All I really needed to hear was that they "could be a good thing", or 'NO!, they are a hand grenade!"

You, of course, correct with respect to the use of the newer engines, but they don't qualify for racing in old bikes!

[peewee]

wob what you think of this. im just gathering the required info for engmod. in the process i put some playdoh in the B port for the hell of it. im sure your familiar with the front wall of the B port and how it twists ( at the entrance its the red line, then as it gets closer to the window it twists back to a trajectory straight across the piston like the green line)

do you see any reason i shouldnt use some epoxy and eliminate that twist so the wall runs straight up from entrance to exit like the orange line ? blue line is bore center






wobbly i got a few question to your response about my question regarding using epoxy to straighten out the twist in the entry on the front wall of B port on that banshee cylinder. i had a feeling its better to have the front wall of B maintain a constant angle straight up from entrance to exit and you seem to agree.

however it slipped my mind that in the process i would be slightly reducing the duct volume. but you say you tested different entry / exit ratios and found little performance difference. in lamens terms , you also changed duct volume, same as what i would be doing with epoxy. so it sounds like keeping the wall going straight up, with entry and exit angles the same, has more importance than ratio of entry / exit ? any half decent cylinder ive seen does not have any twist at the entrance, so im guessing its not a great idea to keep it like

the other question. im not familiar with what other yamaha cylinders were similar to a banshee but have you tried different transfer stagger ? just wondering if its worth it or not, trying the reverse stagger where B open first ?

oh ya and i got a large boyesen port cut in. probly still not large enough but theres not alot of room before you hit the stud

[husaberg]

Thanks Frits, that's about the depth I'd hoped for! All I really needed to hear was that they "could be a good thing", or 'NO!, they are a hand grenade!"

You, of course, correct with respect to the use of the newer engines, but they don't qualify for racing in old bikes!

http://www.yamahaclassictwostrokes.nl/tripples-zelf/zegers-500cc-3-cylinder/
das speacken.......

[AndreasL]

Husa, you never stop to surprise us when it comes to finding pictures and information about stuff most people did not even know exist. :yes:

One other point when try to read the article is how much I really understand of the dutch lingo. If I have hade German added to my Swedish and English I guess old dutch 2t articles would make even more sense. Maybe thats why the dutch was so succesfull in 2 stroke? They all seems to speak at least 5 languages each so no problem working with anybody.

[peewee]

hey guys i have a question for the people who have used engmod with vforce 3 or 4. i just got some vf4 but im sure theyre similar in construction as the vf3. it appears the outside petals have the ability to lift further than the inside petals. i say this because the inside petals can only lift halfway then contact would be made with the other corresponding inside petals. when engmod asks for the maximum tip displacment, to me it doesnt seem correct to use neither the outside or inside petal displacment because they have different amounts of maximum lift. is it better to use the average value of the inside and outside petal lift for the maximum displacment that engmod asks for ?

[husaberg]

There is a wee surprise there for F5Dave
http://mylifeatspeed.com/greatest-bike-hoard-youve-never-seen-full-iwashita-collection/

Gets more traffic here best era ever for GP

ENJOY....

http://vimeo.com/105779434

http://www.youtube.com/watch?v=Yx5rJ-L7-zk
Eddie Vs Kevin
http://www.youtube.com/watch?v=jLuMZMskRCE

[fatbastd]

Thanks Husa -yeah, that was the article. Moot point anyway now - I elected not the buy the bike, though it was well put together from known components. 83-85hp as a 350 wouldn't be a huge advantage in the world I live in, though as a 500 it could make 110, which is where I wanted to be. Cost of making the 350 into a 500, plus the purchase price premium over a good 350 was just too much...would have ended-up on the NZ$30k+ realm.

[husaberg]

Thanks Husa -yeah, that was the article. Moot point anyway now - I elected not the buy the bike, though it was well put together from known components. 83-85hp as a 350 wouldn't be a huge advantage in the world I live in, though as a 500 it could make 110, which is where I wanted to be. Cost of making the 350 into a 500, plus the purchase price premium over a good 350 was just too much...would have ended-up on the NZ$30k+ realm.

http://jfrmc.ganriki.net/ow24/ow24.htm
Yamaha did a works 350/4 cute.

http://www.youtube.com/watch?v=zS4jSCfz4T8



Parallel two-cylinder of YZR350 (0W16) GP350 factory machine that has been developed as a successor model. To pursue a more lightweight, high-output, engine is based on a parallel four-cylinder YZR500 (0W23), bore × stroke: 49 × 46.2mm, the new design in a compact size of cylinder pitch 92mm. Moreover frame also as fuel tank integral monocoque structure of the novel box type, and lightweight, low center of gravity and high rigidity. Maximum output of 84PS at the test, but was recorded a maximum speed 268km / h, but could not come to a battle on.

Image

● Engine type: Liquid-cooled, 2-stroke, in-line 4 cylinder, 348cm 3 ● Piston valve intake ● Transmission: 6-speed ● Maximum power output: 61.8kW (84PS) / 13,000r / min

other triple I could think of was the Sparton that was available in 350 or 500
So Krauser or ADM500 then?
what other ones were there?(Yamaha like in line 4's) I am not sure re the Euro sidecar engines

[F5 Dave]

Well I saw a Wolf. Didn't expect to see an Apollo.

[husaberg]

Well I saw a Wolf. Didn't expect to see an Apollo.

Neither did I..........that is some eclectic collection

[peewee]

guys do you have any advice on this. since the outside petals can open further than the inside, what value should be used for the maximum tip displacment in engmod ? the average between the larger and smaller number ? thnx

[2T Institute]

Thanks Husa -yeah, that was the article. Moot point anyway now - I elected not the buy the bike, though it was well put together from known components. 83-85hp as a 350 wouldn't be a huge advantage in the world I live in, though as a 500 it could make 110, which is where I wanted to be. Cost of making the 350 into a 500, plus the purchase price premium over a good 350 was just too much...would have ended-up on the NZ$30k+ realm.

There is a 3 cylinder TZ/ADM based machine that races regularly here it's both fast and reliable

[husaberg]

Re using the driveshaft to flex and absorb some of the rotational shock load - in a World Champs winning 1080cc twin SeaDoo making over 230Hp
I designed a shaft made from a special steel grade ( no I cant remember ) that was only 12mm dia.
This replaced a 35mm tube that ran thru behind the water intake grate and made a huge difference to the performance, and no it didnt break even with many
jumps out of the water where it hit the limiter then snapped the rpm down again on contact after a wave.

.


As an aside Velocette used to design their bevel drives waisted for a similar reason.......from memory it worked like a torsion bar.
pretty sure I posted the Roarer story on the oldies thread. later maybe not.......

http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=302777&d=1411967633


Velocette Roarer
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=302780&d=1411967639
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=302779&d=1411967637
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=302778&d=1411967635
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=302777&d=1411967633
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=302776&d=1411967631
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=302775&d=1411967628
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=302774&d=1411967626
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=302773&d=1411967624
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=302772&d=1411967622
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=302771&d=1411967619

[husaberg]

Twin cylinders with the big carb on the central through the crank type rotary valve, then reed valve and piston port carbs.


To anyone who takes a look at the Anzani racing outboard, above, the big carburetor, which feeds the rotary valve, is a Vacturi taken from some early (1930s-'40s) Evinude production motor. Vacturis were used (in place of a single small Amal) by a few people on these 1960s racemotors because their intenal passages could be enlarged sufficiently to flow large quantities of methanol (with castor oil) and nitro. Note how big the supply hose is. The other three small carbs are Tillotson kart carburetors; the one feeds through piston-ports, the pair through reeds into the crankcase. The long aluminum device atop the Vacturi is a home-fabricated rack-and-pinion that opens/closes the main mixture needle, adjustable from he cockpit. When the engine was started, the mixture was set lean so that plugs didn't foul while the boat was planning-off, with the engine bogged down. Once the boat was on plane and engine revs were coming up, the driver moved a lever to reset the mixture rich for racing.

That the plugs (Autolite AE 403 or 203 recessed-gap, very cold) fouled so easily was due to the gear-driven device that you can see forward of the rope-plate/flywheel . . . a Lucas magneto.

For you, I knew I had this somewhere.
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=301898&d=1411462358

[seattle smitty]

Wonderful!! I'll print a copy and give it to Jim Hallum, who did so much development work on the outboard version. For anyone who looks at that article, the drawings of the cylinder block are of the motorcycle version, which is different (and of more limited potential) from the outboard blocks.

Can you tell me the source of the article, so I can find and print the whole thing?

[husaberg]

Wonderful!! I'll print a copy and give it to Jim Hallum, who did so much development work on the outboard version. For anyone who looks at that article, the drawings of the cylinder block are of the motorcycle version, which is different (and of more limited potential) from the outboard blocks.

Can you tell me the source of the article, so I can find and print the whole thing?

I am not sure, it looks like I have cut and pasted it together. It could have been from the net?

[Grumph]

I am not sure, it looks like I have cut and pasted it together. It could have been from the net?

Original style is similar to two British motorcycle mags of the 50's and 60's - if I had to guess i'd say "Motorcycling" as they tended to use more illustrations.

I've got a fairly similar article which is in a Classic Bike mag of the 80's and is obviously a rewrite of an original - These oddball technical articles get recycled as filler for the classic bike mags.

[seattle smitty]

For anyone who looks at that article, the drawings of the cylinder block are of the motorcycle version, which is different (and of more limited potential) from the outboard blocks.

Quoting myself, that's pretty bad! But I wanted to add something on the very slim chance that somebody might get an irrational 2-stroke urge to build a bike with an Anzani engine, not a restoration but a Kustom, a contrarian ride that would never be duplicated, would get all the attention at any gathering of motorheads, and might get some ink in a magazine. The world's coolest café racer.

So, for what it's worth for the 2-stroke lunatic who might actually consider this, if you are serious I might be able to find you a water-cooled cast-iron outboard block and water-cooled aluminum head for such a project. While heavier and more complicated, water-cooling would let you get some respectable power out of the engine (either 250 or 322cc). Just from looking at the photos (I've never seen one of the motorcycle blocks) it appears to me that the outboard block can be made to have better flow through the tranfers than the motorcycle version, by some margin. As mounted in a bike, the exhaust ports in the outboard block would aim out to either side, which would add to the novelty of the thing, if you can figure out a way to route the pipes away from your legs.

Uh, don't retain the Lucas magneto . . . .

[seattle smitty]

"NOISE" is the word non-enthusiast neighbors use when referring to the lovely music produced by unmuffled racemotors of many kinds. Because non-enthusiasts greatly outnumber us and have infinitely more political clout, our tracks and race courses get legislated out of existence because of "NOISE," so it's a subject in which we have some reluctant interest.

I'm at about page 440 in my "catching up" on this mega-thread, and found this in a short discussion of silencers:


I spent forever working weekends for the NZ Kart Federation with a Db meter hung above the track trying to find a way to quieten down the 250s.
On the meter the sound level was always less when using a bigger muffler core - to the ear it was alot "louder".

My immediate reaction to this is, are we trying to please the meter? Or human ears? I'm not at all diminishing the effort, but wondering if we are getting the right answers from it.

A few questions come to mind. Have studies been done plotting various kinds of racing noise (measureable, analyzable) against human irritation (subjective, but very important to us)? Has anyone related noise intensity and make-up measured at the track (as Wobbly was doing) to the noise as it is received out in the neighborhoods near the track? In other words, the folk who want to shut us down are not at the track. They're in their backyards or in their houses. So what are the amplitudes/ frequencies/harmonics/etc. that are most irritating where they are?

I have an example of supposedly scientific understanding that is at odds with subjective human experience (mine): We in the States are told that the new blue-tinged headlights for cars are less bothersome to human eyes than the traditional headlights. I think this is a load, and I hate those blue headlights with their beams boring into the back of my skull!!

With this example in mind, might it be that we don't yet have a good idea of exactly what sound qualities are most irritating to the neighbors? Every one of us has remarked that those who don't like OUR noise are not complaining about delivery trucks driving by, or about chainsaws, weed eaters, barking dogs, and other noise pollution. Maybe setting up Db meters at the track isn't telling us as much as we need to know. Mufflers can be designed to be effective against particular frequency ranges (and therefore at particular harmonic combinations), and I'm wondering if efforts in that direction might be more helpful that what's being done now.


Now, before you tell me, "It isn't really the noise, mostly they just hate us and want us shut down completely," I am well aware, personally VERY well aware that that is often true, and that THOSE people will not be mollified by anything we do. Neither will the hordes of land speculators and developers and tax-collecting agencies that covet our tracks, our little airports, etc.. But if we can show a good-faith effort to answer their stated complaints (noise), at least it give our lawyers something to work with.

[Yow Ling]

Smitty , have a look at this post http://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1130229157#post1130229157

It is Frits's FOS cylinder concept it has the exhausts exiting either side or front and rear from a single cylinder,

Frits has this worked out well ?

[Frits Overmars]

My immediate reaction to this is, are we trying to please the meter? Or human ears?The meter, definitely, because you will never please those ears.
I have a simple definition: noise is a sound that people don't like. If you halve the amount, they still won't like it.



Smitty , have a look at this post http://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1130229157#post1130229157 It is Frits's FOS cylinder concept it has the exhausts exiting either side or front and rear from a single cylinder, Frits has this worked out well ?I drew this solution for 50 and 125 cc engines only. More cubic capacity will require longer and fatter pipes.

[seattle smitty]

I saw those photos, Yow.

In fact, I ran into that post about an hour after I had been sitting with a notebook full of blank paper, making drawings of how I might "carve" a cylinder of Frits' FOS concept in my own shop. Frits' photos of his friend's "carved" prototype showed that his friend had come up with a better idea for doing this than I had at that point.

But I was and am much saddened to see those photos, for more than one reason.

In the corner of the photo is a tag that informed me that Frits' friend doing the carving is Giuseppe Rossi, who is one of only three manufacturers currently producing racing outboard motors of the type I have described elsewhere (in my self-introduction): alcohol-burning, race-only engines of motorcycle-sized displacement (125 to 1100cc). Rossi's motors are the most popular; well-made, up-to-date designs that are fast right out of the box.

My disappointment in seeing the photo is two-fold. Personally, I thought that carving a version of Frits' FOS design might give me a chance to get an edge on the competition for a little while. But someone, maybe more than one person since at least one other boatracer is a member here, already had the idea two years ago. Rossi is surely well along with the process of building and troubleshooting the concept, something he can certainly do far faster and far better than I could hope to do. But this isn't a great big deal to me, because I haven't raced in decades and even if it turns out that I'm able to drive a raceboat in competition at my age, I'll never be more than a local club-racer, never nationally-competitive as a driver.

What bothers me is what it does to the sport I used to know and love. Alky outboard racing used to be one of the best cheap sports for the 2-stroke do-it-yourself gearhead, the mechanically-skilled guy with maybe some machining and/or welding capability. In the 1950s and early '60s this was because we raced production-based Mercury outboards that had to be heavily modified to go fast. From the mid-'60s to mid-'80s we got purpose-built race engines from Quincy, Konig, Anzani, Crescent, and Yamato, but they were designs which were already semi-obsolete or otherwise inadequate and left a lot of scope for the gear-heads in the sport to be creative. And if the gear-head wanted an engine of a current design, he could build one using motorcycle engine components. All this was a lot of fun, and none of us particularly envied the bike guys, who could go to their dealerships or the big aftermarket and just write checks for a big variety of speed parts that bolted on, and required no knowledge or shop-skills.

But now Mr. Rossi and another engine-maker, Carlo Verona, are shipping engines that are close enough to state-of-the-art that the gearhead is as likely to slow them down as find more power. State-of-the-art engines are what we used to think we wanted, but today maybe some of us better understand the saying, "Be careful what you wish for." Alky outboard racing today has become little more than a faster and much more expensive version of stock outboard racing . . . you write checks and run what came out of the box. This is fine for those, probably the large majority, who just want to be raceboat drivers. But it is not so good for the hands-on gear-head, the mechanical individualist whose joy is winning races while making chips in his home shop late into the night.

So Rossi is working on an FOS engine. He'll put it on the market sooner or later, and everything else will become obsolete, and everybody will have to buy new motors . . . for a little hobby sport with no prize money and a lot of trailering your outfit all over the USA, burning thousands of dollars on gas for your tow vehicle. More guys who have only blue-collar incomes, on which they may be raising famiies, will be pushed out of the sport. This is in no way meant to diminish the work of Rossi and Verona, to whom we are most grateful for the beautiful engines they build, which they surely do for the love of it and not for the little money they can make. Those two, like Frits and Jan Thiel, could be thought of as the ultimate racing gear-heads, and like us little guys they do it because they love it.

I don't know that there are any answers to the problems. As of now there remains a (very) small amount of scope for a good mechanic-tuner to do little things with the new engines, and possibly this will be so when everybody has to write big checks for Rossi's FOS engines. Meanwhile, outboarders are trying to find sponsors for races and racers, to defray some of the expenses. But with our numbers small and declining, sponsors understandably have little interest.

If you happen to see this, Frits, maybe you'll understand why there's a group of guys here on KB and elsewhere who get their kicks, cheaply, by trying to get the most out of old, crude engines that you haven't even thought about in decades. Even though we know that this is not your bag, at least it is something WE can DO with our own two hands.

[Frits Overmars]

If you happen to see this, Frits, maybe you'll understand why there's a group of guys here on KB and elsewhere who get their kicks, cheaply, by trying to get the most out of old, crude engines that you haven't even thought about in decades. Even though we know that this is not your bag, at least it is something WE can DO with our own two hands.I understand it very well Smitty. I am driven, as is Jan Thiel, by the desire to understand what goes on in a two-stroke engine. I spent 50 years of my life pondering, and testing my ideas, and Jan had a 10 year headstart on me. But I haven't forgotten how I started. I try to promote moped racing in Holland and Germany by drawing up technical regulations that are intended to give youngsters with little means a fighting chance, and both Jan and myself try to spread the understanding of two-strokes that we gathered.
I wasn't going to tell what Giuseppe Rossi is doing, but since you found out for yourself: you've seen the pictures; there isn't anything fancy that you can't do with your own hands. And creating something new can sometimes be simpler than trying to extract power from an old engine that was never meant to deliver that much.

[FastFred]

But I was and am much saddened to see those photos, for more than one reason.

I guess that proves the truism, "Things Change".

We are fortunate here, Bucket rules require the engine to come from a "Non Competition" motorcycle, no race engine parts allowed, this and the fact we are a very small market seems to protect us from the packaged engine supplier and their check book racing customer. And F4/F5 (Buckets) is fairly self governing, a home made cylinder would be applauded but don't try to sell them. Aftermarket purpose built parts are a very grey area that probably wouldn't be allowed to flourish.

Like Democracy and the Freedom to be yourself, things can change, so I guess, be vigilant so as to enjoy it for as long as you can.

[wobbly]

Just got back from the Karting World Final in Vegas where we were fastest in every session, won the heats, won pole by 4/10s, got fastest lap,and got smashed into
the wall by a mad bastard driver intent on taking us out of the final.
Lost the championship, lost 10,000USD,and wreaked a brand new prototype chassis.
Happy,NO.
The impact ripped the front wheel off the kart and ripped a hole in our collective nighty's.
Anyway, no more to say really.

In answer to a couple of questions - re the noise issue.
I agree that we should have been trying to placate the neighbours not the meter, but the meter is the tool by which the legislation was enforced for sound level at the boundary.
We easily complied, so the council enforcement team told the howling complainants to shut up and or go somewhere else - my job done as asked..

Re the B port wall, yes getting rid of the axial duct twist is far more important for flow bench numbers as well as power delivered, as it would seem the duct entry/exit ratio has little effect.
Re stagger in a Banshee style cylinder - yes, I tested the CPI monoblock 8 port with the A port lowest to allow a much bigger Aux Ex port size, and got back alot more total STA
by having the B,C, and Boost higher.
Power went up from 88 to 96, with a much wider power band width.

Re the VF3 tip deflection, I use the average lift.
But in most cases the curtain area of the reeds far exceeds the port effective area, so tip lift isnt the limiting factor at all.

Re Banshee crank bearings.
Using the HiCap balls in the centre isnt really needed as the two bearings side by side have way more load capacity than is needed.
Running the rollers ( with double the radial load capability ) on the outside is a great idea as the highest load seen is from the drive teeth deflection force, and when running a large stock flywheel there is a huge force from precession.
Yamaha TZ250/350 ran this system for decades with absolutely no issues with unreliability from excess stiffness or any other wank idea about crank dynamics at 11,000 to 12,000 rpm in GP racing.

Ok, I will get back to slashing my wrists.

[peewee]

wobbly what you think so far. i got a dummy engine to practice on before i grind into my good engine. i have all the STA numbers lined up well in engmod. the intake is looking appropriate sized and the boyesen ports really helped. vf4 showed a good improvement over the standard reed block also. likely ill use weld instead of epoxy next time on a few areas though. forgot to mention some wanker on another site suggested the trench in the trasfer area of the cases is to collect oil and it drains down to the bearing. my response was: i dont see that happeneing when the oil only stays in the crankcase for .024 of a second :laugh:

[wobbly]

The only thing to add is you can make the Boyesens bigger and lower by cutting back the gasket area that does nothing.
Depending on how far back you go you may need to fill the cavity in the case with epoxy, this also gives better gasket support anyway.

[190mech]

Smitty,Have you seen the Rossi thread on PitLane?
http://www.pit-lane.biz/t1666-technique-rossigrm-2strokes-boat-engine

[peewee]

i checked where the ring gap ends up, i plan to bring the B ports alittle further around back which will leave hardly no sealing surface afterwards, so ill be filling in the cavity at the back of the crankcase. might as well make the boyesens bigger while im at it :Punk:

[dtenney]

Seattle Smitty….I think you may find that the pictures of the FOS cylinder that Yow pointed you to is not the work of Giusseppe. Those pics are the result of the work of a well known outboard race engine builder in Texas…..experimentation, for some, is alive and well in pro outboard racing.

[wobbly]

Of interest to those in watercraft racing involved with trying to add power at the bottom of the powerband is that the complication of sliding pipes is way to hard to implement on a multi motorcycle.
One of the World Champ winning twin cylinder open Jetski motors I built had a powervalve that was originally a Rotax type pneumatic system.
Completely dumb and mostly ineffective except out of the gate - as in the turns as soon as the injection was moved from WOT the pipe pressure would drop, and the valves followed suit.
When getting back on the gas, it took way too long for the pressure to rise again to open the PVs at the correct rate and rpm.
The boat had a small tank on board that held 100 psi, this was used to activate small flaps on the rear of the hull, to drop the nose when entering the turns.
So to get control over the PV electronically I simple connected the tank to the bottom of the PV diaphram via a small regulator and with 5psi drove the valves up and down with PWM
control from the injection computer against a return spring.
No extra power required and a linear opening rate was easy to program against rpm and a TPS to give a 3D map.
Then we took the next step, and used my experience from the BSL500 and added an ATAC volume on top of each header tube, controlled by a flat blade that simple slid back
to connect the header to the ATAC volume via a short tube 1/2 the header diameter.
This was like the flat plate sliding throttles as used in F1 car injection systems.
The ATAC was only required to be opened instantly at a set rpm, so was also activated by the 5psi pressure under another diaphram.
The air driven ATAC added another 32% of extra power at the very bottom of the powerband, needed no extra power, easily lasted all day and was simply controlled by the ECU with an rpm switch in software.
Seems like the perfect system to be used in a 125/175/250/500/700 hydro boat.
A diaphram can easily be made to have sufficient stroke to do both jobs, without having to push a pipe 130mm or so with lots of power needed for a servo controlled system on a multi cylinder.

[seattle smitty]

190mech, I had not yet encountered that thread (having been absorbed with Frits' thread in the same location); will check it out, much appreciated.

Well, well, here's another boat racer, a boat racer NOW, not decades ago, and a good one. And his appearance here is timely.

For any of the rest of you who might have any interest in my outboard racing references here, David Tenney is the son (right, David?) of Bill Tenney, one of the very big names in the history of our sport. Bill Tenney was, I believe, a participant in the intercollegiate outboard racing circuit of the "golden age" of American sport in the Thirties. After the war, Tenney, an inventor, designed and manufactured a small pulse-jet engine for the sport of control-line model airplane racing. He was still racing boats, and won several national class championships and set some competition and straightaway records. A little later he became the North American importer of British Anzani outboard motors (see my posts over several previous pages), and developed alcohol-burning versions of the 250 and 322cc twins which became popular with racers particularly in the Midwest and South. David, you really should be the one telling your dad's story; if you have done a good biography, I'd like to see it.

Anyhow, at some point in the Fifties, Jim Hallum, mechanical engineer, outboard mechanic, tuner of his dad's racemotors, and a model airplane racer using a Tenney Red-Head pulse-jet, went back to the Midwest to run his 150mph little control-line airplane at a nationals meet. There he met Bill Tenney. A couple of years later, Hallum was further developing Tenney's Anzanis for driver Gerry Walin. The most famous (though not ultimate) version was the 65hp, 100mph Class B engine as shown in the photo a few pages back.

David, I met your dad in 1968 during the NOA Nationals, when I drove back there from Seattle with Ron Anderson and Chuck Walters. For the rest, Ron Anderson is a mechanical engineer and racer who became a close friend of Jim Hallum, and a co-developer of Anzani engines (Ron and Jim used to get their stuff together and have friendly "dyno-races"). Ron and Jim co-developed the twin-powerhead-on-a-gearbox 700cc class Anzani, which I described a few pages back and which we took back to that race and attempted unsuccessfully to run. On Friday evening of the race weekend, David, your mom and dad invited us Seattle boys (plus Ron's wife) to dinner at your house. Nice folks, a good time.

Now that David Tenney has appeared here, I should leave any further descriptions of our part of the 2-stroke sporting world to him, since he knows a lot more than I.

(Sending you a PM, David)

[husaberg]

Of interest to those in watercraft racing involved with trying to add power at the bottom of the powerband is that the complication of sliding pipes is way to hard to implement on a multi motorcycle.
One of the World Champ winning twin cylinder open Jetski motors I built had a powervalve that was originally a Rotax type pneumatic system.
Completely dumb and mostly ineffective except out of the gate - as in the turns as soon as the injection was moved from WOT the pipe pressure would drop, and the valves followed suit.
When getting back on the gas, it took way too long for the pressure to rise again to open the PVs at the correct rate and rpm.
The boat had a small tank on board that held 100 psi, this was used to activate small flaps on the rear of the hull, to drop the nose when entering the turns.
So to get control over the PV electronically I simple connected the tank to the bottom of the PV diaphram via a small regulator and with 5psi drove the valves up and down with PWM
control from the injection computer against a return spring.
No extra power required and a linear opening rate was easy to program against rpm and a TPS to give a 3D map.
Then we took the next step, and used my experience from the BSL500 and added an ATAC volume on top of each header tube, controlled by a flat blade that simple slid back
to connect the header to the ATAC volume via a short tube 1/2 the header diameter.
This was like the flat plate sliding throttles as used in F1 car injection systems.
The ATAC was only required to be opened instantly at a set rpm, so was also activated by the 5psi pressure under another diaphram.
The air driven ATAC added another 32% of extra power at the very bottom of the powerband, needed no extra power, easily lasted all day and was simply controlled by the ECU with an rpm switch in software.
Seems like the perfect system to be used in a 125/175/250/500/700 hydro boat.
A diaphram can easily be made to have sufficient stroke to do both jobs, without having to push a pipe 130mm or so with lots of power needed for a servo controlled system on a multi cylinder.

Do you have any pics of the BSL set up Wayne I don't think I have ever seen it.........

[fatbastd]

Pardon the ignorance Wobbly, but what culled is that? Reed valves and meat in the wrong places makes it looks NOT like a 350F/G..

[wobbly]

I may have a pic somewhere - will search it out.
The BSL had a tube volume above the headers on the top cylinder pairs.
We found that this made less power when under one cylinder displacement ( 166cc ) and made no more when above 1.5x.
The short connector tube was 1/2 the header diameter with a rotating valve like a carb throttle plate.
The ECU snapped it shut with a solenoid at around 10200 in an engine that peaked at 12200 and reved to 12800
This added 32% as I said over the extra power made by the normal powervalved setup, and it would take full throttle from well under the pipe at 6000 and above.
Without the powervalve it was virtually unrideable, with both the PV and the Boost bottles in place it was easy to produce wheel spinning controlled power sides
from down at 8000 rpm.

[Haufen]

Can you show us some dyno graphs or tell us power numbers of the BSL?

With todays information and technology available, how much (crank)hp could be achieved with a 500cc triple? What would you say?

[wobbly]

We got 56Hp at the sprocket at 12200 on the single dyno test engine - near on 160 at the sprocket on the bike that weighed 13Kg less than the 180Hp
4 cylinder bikes at the time.
The 500. twin Honda factory bike made 140, so the package was dead on where it should be in relation to cylinder size.
This was a 59.6 square setup and I believe today I could with little effort achieve 60, that is 13.9 Bar BMEP at 12200 giving 63 crank Hp on FIM unleaded..
The single test engine had only a 3:1 primary drive, so I deduct about 5% from crank to sprocket.

[F5 Dave]

Interesting. so 3 x 56 is 168. I would have thought less loss with multi, but you will tell me next the single test had no gearbox.

so you are getting 8hp loss through that gearbox, so 4% which sounds reasonable. yes no otherwise?

[wobbly]

Yea, the single mule engine had a 1:3 primary drive to the dyno shaft.
So 56 sprocket power = 59 Crank = less 5%.
Translate the single dyno power to the tripple = 168 less another 5% for the gearbox and you have around 160 at the bike sprocket.
On a Dynojet it made 155 at the wheel, so that translates close to the very usual 12.5% reduction from crank to Dynojet power for a racebike = 177crank.

As I said I can now say with confidence, I would easily get say 63 crank, that would be 189 less 12.5% =165 RWHp, and at the time that would have been super quick.
Issue was we didnt have Jan and 100 R&D festerers looking for things to do - just me and 3 others with no time to sleep.

[F5 Dave]

Cool, interesting figures to know real world outcome.

[Frits Overmars]

Issue was we didnt have Jan and 100 R&D festerers looking for things to do.... never needed anybody looking for things to do, Wob; there were always more things to do than time, equipment and the Great Leader:argh: permitted.

[seattle smitty]

(Back from a one-day holiday in which Americans traditionally eat themselves into immobility).

Reading Wobbly's account of his team's final rotten luck after blowing the rest into the weeds at the big kart meet, it strikes me that this should be said:

As endlessly pleased and grateful as the rest of us are to Frits and Jan Thiel for their wiilingness to unreservedly share the findings of their long 2-stroke careers, it seems to me that Wobbly goes well beyond the call with his open-handed assistance, because far from being retired from racing he still is fully involved and makes a living from it. Active racers generally want to keep some things to themselves, rightly feeling that whatever little edge they have gained over competitors is privileged, and further, that up-and-comers should understand that at some point you stop asking for more detail and start learning from your own cut-and-try labors. Frits may recall that after I asked the members about what 80cc powerheads were well-designed, he not only told me what engine, but then, to my great surprise, told me very specifically what port-timing to start with. Incredible! And Wobbly volunteers this sort of thing, too, despite being currently involved in racing at the highest level.

We would get nothing remotely like this kind of disclosure from active NASCAR or NHRA crew chiefs. Thank you for all of it, Wobbly. And I hope you can come back and take full revenge.

[seattle smitty]

To FastFred, who described bucket racing:

We do have a category of outboard racing that is conceptually similar to that. Called "Modified," it uses old production outboard powerheads such as Mercury and Evinrude, two, three, and four-cylinder in the traditional range of displacements, burning gasoline and mounted on short towerhousings with direct-drive lower units. The intent was to provide cheap racing and some scope for owner modification and creativity.

But the devil is in the details, and my personal opinion is that the Mod rules, established with the best intent, are really stupid rules with the result that most veteran alky racers aren't interested. I gather from comments here that some of you are not entirely happy with your bucket rules, as currently written.

[husaberg]

(Back from a one-day holiday in which Americans traditionally eat themselves into immobility).

Reading Wobbly's account of his team's final rotten luck after blowing the rest into the weeds at the big kart meet, it strikes me that this should be said:

As endlessly pleased and grateful as the rest of us are to Frits and Jan Thiel for their wiilingness to unreservedly share the findings of their long 2-stroke careers, it seems to me that Wobbly goes well beyond the call with his open-handed assistance, because far from being retired from racing he still is fully involved and makes a living from it. Active racers generally want to keep some things to themselves, rightly feeling that whatever little edge they have gained over competitors is privileged, and further, that up-and-comers should understand that at some point you stop asking for more detail and start learning from your own cut-and-try labors. Frits may recall that after I asked the members about what 80cc powerheads were well-designed, he not only told me what engine, but then, to my great surprise, told me very specifically what port-timing to start with. Incredible! And Wobbly volunteers this sort of thing, too, despite being currently involved in racing at the highest level.

We would get nothing remotely like this kind of disclosure from active NASCAR or NHRA crew chiefs. Thank you for all of it, Wobbly. And I hope you can come back and take full revenge.
No offence

http://www.youtube.com/watch?v=rBZCnG1HwDM

That said, Frits Wob and Jan are extremely generous with their time, as frits mentions a few seconds to ask a question can result in hours to answer it.

[wobbly]

Sorry i missed the question about the cylinder I pic'd with the big Boyesesns - this is a CPI monoblock casting for a 400cc Superlight
bike - RZ based same as a Banshee.
But I have done a 400cc version of the TZ350 ( RD based of course for a Pre 82 Classic ) using the 6 port 3G3 TZ350 cylinder - added reed blocks/cavitys
from CR125 and this had a split intake port same as the CPI so I could add a couple of boost ports up the back.
All period legal, as Yamaha did the same thing externally for the 82 TZ500.
Big issue is the close stud spacing, not allowing Boyesens nor 3 port Ex layout,but it still made around 10Hp more than the best TZ350 and way wider powerband.

Thanks for the kind words about the finals disaster in Vegas, and yes we will return to get our title back.
My attitude re disseminating 2T knowledge is that I believe its incumbent upon the knowledgeable in this arena to pass on as much as possible ,now, or so much
will simply fade away and be lost forever.
With only a few niche sports still actually working on high performance 2T race engines there is still a chance for some of us to make a living doing clever shit
but for most even the things that were common place 10 years ago, are still a mystery, so anywhere I can help I am glad to.
We have hugely powerful computer code now that Neels has developed into a supremely accurate modelling tool, but you need real inputs to make real Hp as crap
in = crap out so the better the knowledge base is the better our 2T efforts will turn out on the track.

[peewee]

hey wobbly whats the best choice for a 115mm rod ? only thing i see is the hotrods which i dont really care for. or the prox rd400 rod but it appears to use smaller bearings

[wobbly]

Ask me for a good one.

[fatbastd]

ProX Rd400 rods are fine at 75+ HP up to 11500rpm, fitted with decent big ends, in my experience. Have run them for years. Price is good too. Have 4 spare basic kits and could probably find decent big ends as well, if required.

[peewee]

rd400 prox rod crossed my mind. been using prox rods in other engines and theyve never let me down. however i had another idea. what about a samarin GP competition rod ?

[speedpro]

and you need a better more expensive rod than the one that would do the job because . . . . . ?

[peewee]

im just kicking around different ideas :cool:

[AndreasL]

and you need a better more expensive rod than the one that would do the job because . . . . . ?

For me it's because I'm a sucker for buying cool tech stuff. :)
Smart? Naaa…

[wobbly]

The RD400 based rods are narrower,thus would need spacing with another washer if used in a Banshee/RZ based crank.
I use rods that were made to my specs by Wiseco after they were fired by Kurt of Hotrods.
They had an international marketing exclusive deal, that Wiseco typical of them botched completely.
Not long after the deal collapsed, the CEO that had caused all the drama was fired, and I ended up with a box of really good sample rods
with no identifying markings, but they were made by Taiwans best rod/crank maker Shunchi.
At the same time I got some Peek coated flat race cages done to go with them.
Cheap and bulletproof and plug and play - the best combination known to man.

[seattle smitty]

No offense taken, obviously, and thanks Husaberg, I'll take a look.

But if it really is, as I expect, "NASCAR 101," that's not surprising because they aren't giving away anything of the sort we get from OUR instructors, who are teaching a graduate course. When I started racing outboards there was NOTHING, NOTHING on 2-strokes other than repair manuals for fishing motors, an occasional parts blow-up of a race motor in Outboard Speed Sport magazine (long gone!!), and an engineering book on DIESEL 2-strokes by Schweitzer (IIRC) translated from German that I found in the Engineering Dept library at the Univ. of Washington in Seattle. When Gordon Jennings little red book came out in about 1968 or so, we were blown away! Here was our Racing 2-Stroke 101, or even 201. Further enlightenment over the years from Kevin Cameron, John Robinson, and Graham Bell was invaluable. But I never imagined finding anything like the pearls that our esteemed profs are casting before us here. The contrast with fifty years ago is stunning.

[seattle smitty]

Okay, I have an idea. Maybe old-hat, but I haven't seen it discussed:

In the early era (MY era) of loop-scavenged 2-stroke bike motors and outboards, the boost-port (or as it is now called in discussions of more modern engines, the C-port) was not very wide, and was VERY short in length because it had to fit above a piston-ported intake tract. It was fed from a small matching hole in the piston, close to the crown and just below the ring. Nobody expected more than a small contribution to power, but it was thought that any A/F mixture flowing through the piston, under the crown and out the hole and into the boost-port should have a cooling effect on the piston crown. To what extent this was actually true, I don't know. Some people theorized that as the piston slowed as it approached bottom-center, whatever mixture that was trapped inside the piston tended to be accelerated out of the bottom of the skirt, so that there really was not much in the way of A/F remaining in under the piston crown for the boost-port to access, or to cool the crown. (FWIW, my personal experience with these very short, piston-fed boost-ports came from my 1963 FA Konig 250cc racing outboard).

In any case, I have read comments from our profs telling us that those old, short, piston-fed boost ports are nowhere near as effective as a modern full-length C-port fed from the crankcase area.

However, I wonder if a combination of old and new could be better yet. Suppose you take a modern (okay, Aprilia) cylinder with full-length C-port, AND have a hole in the piston, at the old location under the crown and ring, flowing into the side of the C-port, roughly halfway up. Would the very good flow and velocity of the modern C port draw strongly from that hole, and really have a good effect on piston cooling (any power effect of accessing mixture trapped under the crown would be incidental, piston cooling being the chief motivation). If this were done on a clean-sheet engine, you could specifically shape the long C-port to have a venturi section that might pull even harder on the A/F coming out of the hole in the piston, for added cooling.

And if this would work to good effect (piston cooling) on an Aprilia or similar cylinder, could it not be even better if applied to Frits' FOS concept, with its ring of transfer ports? Maybe you could have two or four holes (in a piston structurally designed for them) each one feeding one of two or four transfers, creating a cooling outflow under the piston crown.

Any merit to this idea at all, Frits? Prof. Thiel has taught us the importance of shaping and aiming the inside curve of the A and B ports to cool the outside of the piston crown. Might this idea help that cooling effect?

[husaberg]

That reminds me ages ago I said would post some pics of the TD1C Port slots.
No use these days, but more for giggles.

[Frits Overmars]

...those old, short, piston-fed boost ports are nowhere near as effective as a modern full-length C-port fed from the crankcase area.That is true if you look at transfer flow. But from a cooling perspective, scavenging through the piston does help.


Suppose you take a modern (okay, Aprilia) cylinder with full-length C-port, AND have a hole in the piston, at the old location under the crown and ring, flowing into the side of the C-port, roughly halfway up. Would the very good flow and velocity of the modern C port draw strongly from that hole, and really have a good effect on piston cooling.It might work, and it might help cool the piston. But at the same time it would raise the average temperature of the fresh charge, so it would be useful only if piston temperature is a limiting factor in that engine.


And if this would work to good effect (piston cooling) on an Aprilia or similar cylinder, could it not be even better if applied to Frits' FOS concept, with its ring of transfer ports? Maybe you could have two or four holes (in a piston structurally designed for them) each one feeding one of two or four transfers, creating a cooling outflow under the piston crown.Theoretically, yes. But where should I put those holes? They must not run over the exhaust windows, which leaves only the areas fore and aft (the exhaust ports are on the right and left sides). But mid-fore and mid-aft there are no transfer ports because I reserved those areas for the piston to lean against, and for the ring gap.
The picture of the cut cylinder below shows the available areas for piston cooling windows in red. But I'm not sure whether I want to make four holes in a piston that will be very highly stressed once the rpm potential of the FOS porting system is fully exploited.

[Frits Overmars]

That reminds me ages ago I said would post some pics of the TD1C Port slots. No use these days, but more for giggles.Giggles indeed: 306138 I wonder if they really fitted that cylinder upside-down back in 1967.... :rolleyes:.

[TZ350]

Okay, I have an idea. Maybe old-hat, but I haven't seen it discussed:

In the early era (MY era) of loop-scavenged 2-stroke bike motors and outboards, the boost-port (or as it is now called in discussions of more modern engines, the C-port) was not very wide, and was VERY short in length because it had to fit above a piston-ported intake tract. It was fed from a small matching hole in the piston, close to the crown and just below the ring. Nobody expected more than a small contribution to power, but it was thought that any A/F mixture flowing through the piston, under the crown and out the hole and into the boost-port should have a cooling effect on the piston crown. To what extent this was actually true, I don't know. Some people theorized that as the piston slowed as it approached bottom-center, whatever mixture that was trapped inside the piston tended to be accelerated out of the bottom of the skirt, so that there really was not much in the way of A/F remaining in under the piston crown for the boost-port to access, or to cool the crown. (FWIW, my personal experience with these very short, piston-fed boost-ports came from my 1963 FA Konig 250cc racing outboard).

However, I wonder if a combination of old and new could be better yet. Suppose you take a modern (okay, Aprilia) cylinder with full-length C-port, AND have a hole in the piston, at the old location under the crown and ring, flowing into the side of the C-port, roughly halfway up. Would the very good flow and velocity of the modern C port draw strongly from that hole, and really have a good effect on piston cooling (any power effect of accessing mixture trapped under the crown would be incidental, piston cooling being the chief motivation).

I have been working on that C port piston hole and proper transfer duct combo for direct cooling of the underside of the piston crown and would be interested in other peoples experiences with the idea too.



289789

I am trying to get the injected fuel to squirt up inside the piston crown for cooling of the piston top from the underside and better fuel vaporization.

I am hoping the EFI system will give me more under piston cooling and by being able to control the fueling more accurately some reduction in detonation during over rev (13,000 + rpm). With the carburetor set up, over rev and part throttle deto is a real problem.

289786




286286

The boost port is mostly cut into the crankcase on the magneto side.

286283

The magneto side needs gluing up here, I didn't bother with the carb crankcase side as you hardly cut into it.

286287

The original boost port was just a trench in the rear wall of the cylinder, now its more or less a proper port and duct.

286288

[peewee]

The RD400 based rods are narrower,thus would need spacing with another washer if used in a Banshee/RZ based crank.
I use rods that were made to my specs by Wiseco after they were fired by Kurt of Hotrods.
They had an international marketing exclusive deal, that Wiseco typical of them botched completely.
Not long after the deal collapsed, the CEO that had caused all the drama was fired, and I ended up with a box of really good sample rods
with no identifying markings, but they were made by Taiwans best rod/crank maker Shunchi.
At the same time I got some Peek coated flat race cages done to go with them.
Cheap and bulletproof and plug and play - the best combination known to man.

ill let you know which direction i go. not sure i want to tie up $500 on rods if $250 will get the job done just fine. but still kicking around ideas. appropriate thickness washers are easily available as several other engines used them, if i decide to use a slightly thinner rod.

do you have complete sets of unassembled crankwheels also or just the rods ?

[husaberg]

Giggles indeed: I wonder if they really fitted that cylinder upside-down back in 1967.... :rolleyes:.

Never noticed that lol, back to front....
In addition to your answer above to smithy, the area above the gudgeon on the modern cylinders is rather smaller than the older designs like this below. That has acres of real estate available above the pin and on the cylinder walls (An old Greeves Silverstone. )
I note also all the older style pistons have the gaps either side of the windows rather than the middle of the c port although not sure if it would matter or not.

306140

Smithy compare, this above, to some of the space available these various Aprilias (below)
306141

Ps as I have already pm'd Pewee I think the KTM200 rod would be a good start as it is 118mm long and seems to be Yamaha sized.

[seattle smitty]

[QUOTE=Frits Overmars;1130798068] It might work, and it might help cool the piston. But at the same time it would raise the average temperature of the fresh charge (end quote).


I keep forgetting you guys run gasoline. Why don't you switch to real racing fuel? Gasoline is for cleaning parts.

Frits, I sure have a hard time wrapping my pore 'ol brain around that damned engine of yours!!:rolleyes:


Husaberg, thanks for the enlightening photos, as always (though I wish you had one with the short little boost-port above the piston-port intake, like I was describing), but it's SMITTY, two t's, not "Smithy." Smitty is the traditional American form, while I understand Smithy is the Brit and dominions style, yes?


Back to Frits, how do you think about the trade-off between a cooler A/F charge being more dense versus having a warmer charge that keeps the fuel in suspension better, with less in the way of big ugly drops of liquid being slung off the upper edges of the ports? Car guys think about this a lot, HEAVY liquid fuel being slung out of the less-heavy air against the outside turns of the runners and ports. When I was young and dumb and handsome, and racing with methanol blends, my notion was that ideally I wanted cool, dense air getting mixed with fairly warm fuel.

(I should have stated an additional advantage of my idea, that it should lubricate the small-end bearing better than usual).

[husaberg]

[QUOTE=Frits Overmars;1130798068] It might work, and it might help cool the piston. But at the same time it would raise the average temperature of the fresh charge (end quote).


I keep forgetting you guys run gasoline. Why don't you switch to real racing fuel? Gasoline is for cleaning parts.

Frits, I sure have a hard time wrapping my pore 'ol brain around that damned engine of yours!!:rolleyes:


Husaberg, thanks for the enlightening photos, as always (though I wish you had one with the short little boost-port above the piston-port intake, like I was describing), but it's SMITTY, two t's, not "Smithy." Smitty is the traditional American form, while I understand Smithy is the Brit and dominions style, yes?

the Greeves pic I posted has one.
306174


Ah, when I put my forehead against the screen, I can see it; sorry. :brick:

click on it a few times it gets bigger........

[seattle smitty]

Ah, when I put my forehead against the screen, I can see it; sorry. :brick:

[richban]

Hi Guys

As some of you know I have been developing my 300cc NSR. Next weekend see's its first proper racing at Hampton downs. Its going really well except the pipes are cracking and braking all the time. They are SS no surprise. They really do cool very quickly and obviously heat fast as well. I was wondering if lagging the pipes for the first 300mm is a good idea to keep a bit of heat in there and not let them cool so fast. Will this help with the cracking yah reckon. Also could it help with throttle response. The pipes are the next thing to come but will not be made till after xmas.

Any bright ideas welcome. Cheers Rich.

[mr bucketracer]

Hi Guys

As some of you know I have been developing my 300cc NSR. Next weekend see's its first proper racing at Hampton downs. Its going really well except the pipes are cracking and braking all the time. They are SS no surprise. They really do cool very quickly and obviously heat fast as well. I was wondering if lagging the pipes for the first 300mm is a good idea to keep a bit of heat in there and not let them cool so fast. Will this help with the cracking yah reckon. Also could it help with throttle response. The pipes are the next thing to come but will not be made till after xmas.

Any bright ideas welcome. Cheers Rich.years ago on pre 95 rs hondas guys used to put beads of high temp red silacon around the chambers to take the zing out of them to stop cracking , the promblem was the rubber mounts but it did work not to bad but looked crap

[speedpro]

I'm not sure how the SS works as I've never had a SS pipe. As with nearly everything I've owned, if the pipe was cracking the cure was to mount it so it was free to move around while still supported. You probably already on to that idea.

[Frits Overmars]

Why don't you switch to real racing fuel? Gasoline is for cleaning parts.Yeah, and alcohol is for drinkin'. So what have we got left? Nitromethane? Or should we go straight to nitroglycerine? Or TriNitroToluene? Oh no, that's not a liquid. Hydrazine maybe?


Frits, I sure have a hard time wrapping my pore 'ol brain around that damned engine of yours!And it's so simple. there is one bridged exhaust port, with its twin brother opposite, and there's just one shape of transfer port, not five different shapes as in conventional engines. Everything is symmetrical, which by the way ensures that the bore will always stay round and straight and not go banana-shaped as in present-day engines.


how do you think about the trade-off between a cooler A/F charge being more dense versus having a warmer charge that keeps the fuel in suspension better, with less in the way of big ugly drops of liquid being slung off the upper edges of the ports? Car guys think about this a lot, HEAVY liquid fuel being slung out of the less-heavy air against the outside turns of the runners and ports. When I was young and dumb and handsome, and racing with methanol blends, my notion was that ideally I wanted cool, dense air getting mixed with fairly warm fuel.You only offer two choices for that trade-off; I prefer a third option: that the mixture is cool because all of the fuel is evaporated. That requires a carburettor delivering fine drops to begin with; then it takes some time and some stirring which is taken care of by the crankshaft, cooling the conrod in the proces. And finally it depends on the fuel. Unleaded petrol (gasoline for you 'Mericans) is pretty good. Heavy fuels like the toluene that was used in the first turbo-F1 era, are notorious. Honda even specified 85°C for the fuel before being injected.


I should have stated an additional advantage of my idea, that it should lubricate the small-end bearing better than usual.It would, but I haven't seen small-ends suffering from scanty lubrication in a long time.

[seattle smitty]

(Quote Frits) Yeah, and alcohol is for drinkin'. (end quote)

(singing) "We never stumble, we never fall; we mix our drinks with wood alcohol." The "drinkin'" stuff is for mixing with parts-cleaner, Frits; I'm talking RACING fuel.

Fuels: FWIW, the driver of that Anzani (photo back on pg. 1038) and lots of other outboard racers from the Thirties through the Sixties usually ran anywhere from 20 to 40% nitromethane in the methanol, with a few other fractions, plus castor oil. What I wanted to tell you was that he did try hydrazine. He summed it up for me by saying, "You use half as much (as you would of nitro), but it costs twice as much." This was in the last days of open pipes. When he went to the "bounce-pipes" (what we called expansion chambers), the engine made about the same power without any nitro. And it was hard to successfully run much nitro in a bounce-pipe engine, so everybody got away from it, since it cost a lot and has other issues. About the only outboard racers who still "tip the can" (of nitro) are those who run in the antique classes, or still use old open-pipe engines in a couple of classes in local races.

All racing fuels have their pros and cons, but one handy thing about having no limitation on the fuel you can use is that the people running the race don't have to bother with testing your gasoline to see if you're cheating. Seems like a lot of bother for local club racing.

[seattle smitty]

Wobbly, or anybody who has tried this, tell me about expansion chambers made of aluminum, examples of which I saw on the French site. Since, I assume, they'd have to be made thicker than steel, does the weight savings balance the drawbacks? I assume the big drawback is heat-loss, but maybe that could be largely addressed with a ceramic coating. What alloy and thickness has worked (if any has worked)?

I had a friend in California long ago, John Alden, one of the top outboard engine-builders of the time, who wanted to try making expansion chambers of titanium . . . until the supplier quoted him a price for one 4X8' sheet. That ended that!

[Frits Overmars]

the driver of that Anzani... did try hydrazine.Is he still alive? And what about the guys that breathed his exhaust fumes?


tell me about expansion chambers made of aluminum.... Since, I assume, they'd have to be made thicker than steel, does the weight savings balance the drawbacks? I assume the big drawback is heat-loss, but maybe that could be largely addressed with a ceramic coating.Don't do it. There is no weight saving, aluminium (aluminum to you) pipes won't work without an internal ceramic coating, and they will crack despite the increased tickness. Aluminium does that.


I had a friend... who wanted to try making expansion chambers of titanium . . . until the supplier quoted him a price for one 4X8' sheet. That ended that!Titanium works great for pipes if you use the right grade 306191. But stainless steel is almost as good, cheaper and easier to weld.

[jasonu]

Hi Guys

As some of you know I have been developing my 300cc NSR. Next weekend see's its first proper racing at Hampton downs. Its going really well except the pipes are cracking and braking all the time. They are SS no surprise. They really do cool very quickly and obviously heat fast as well. I was wondering if lagging the pipes for the first 300mm is a good idea to keep a bit of heat in there and not let them cool so fast. Will this help with the cracking yah reckon. Also could it help with throttle response. The pipes are the next thing to come but will not be made till after xmas.

Any bright ideas welcome. Cheers Rich.

I'd look at the way the pipes are mounted. Post a couple of pix would ya. Then again, I have never owned a SS pipe.

[twotempi]

Yeah, and alcohol is for drinkin'. So what have we got left? Nitromethane? Or should we go straight to nitroglycerine? Or TriNitroToluene? Oh no, that's not a liquid. Hydrazine maybe?


The early American board racers used a mixture of picric acid and ether !! In case you didn't know picric acid is the main ingredient of denonators !!! What ever you do ,don't fall off your bike !!:woohoo::woohoo:

[TZ350]

306220306221

4 cylinder, 2 stroke, supercharged and rotary valve. you will have to go to the original page to read more about this interesting engine.

http://www.pacificp.com/forum/viewtopic.php?t=11126&sid=1766b2420160ed8da626651e50f27459

and a whole bunch here on 2T hydroplanes http://www.quincylooperracing.us/index.html

[F5 Dave]

if someone released mild steel on the market for the first time today it would be hailed as a 'wonder product'

[jonny quest]

Frits, you must not have built any pipes. SS is much harder to weld than Ti. SS is simpler, but definitely not harder. Ti flows almost as good as solder.

[seattle smitty]

I'm assuming (titanium) you set up some sort of fixed or trailing back-gas apparatus, rather than weld it in a chamber . . . . (ditto the "wonder product," Dave!!).


Nitro is fun, cuddly stuff!:

"Nitromethane can detonate and cause serious harm to people and property. A single 5-gallon can of nitromethane
has a fatality range of 42 feet and can cause significant injury or damage at a range of 316 feet. A full 55-gallon
drum of nitromethane has a blast radius of 92 feet and can cause significant injury or damage up to 700 feet away
from the center of the blast."

One of the fun things is it's ability to auto-ignite. An occasional occurance in the nitro years of outboard racing was the runaway engine in the pits. Your boat is sitting on its stands, the motor attached and all the throttle and steering stuff hooked up and adjusted. You have blown up (pressurized) the fuel lines and got some fuel into the carburetor float-bowls (some were altered to be floatless, with an overflow). The fuel (you're using 25% "go-juice" in your methanol today) gets from the tank in the bottom of the boat up to the motor by one of three means: the tank is pressurized via a line from the crankcase (it has a check-valve in-line), or there is a crankcase-actuated fuel-pump, or there's an electric pump. You're ready to go, your heat is coming up, and you want to make sure the engine's going to run, and warm it up a little. Because of the safety rules, you haven't yet put a propeller on the propshaft. Your pal has a hand on the throttle, and you rope-start the engine. YOU should have had YOUR hand on the throttle, because you have already learned where to position it where your engine generally doesn't want to run away, and you should know that others may not pay attention to your instructions, and like to get busy with the throttle, thinking to help the engine clear out and run smooth.

You whip the rope through, the engine fires, your pal blips the throttle a couple of times, . . . and your open-pipe engine commences making an odd sound and slowly increasing rpm. Your pal drops the throttle, which in a raceboat closes the butterflies completely. Doesn't matter; nitro can provide its own oxygen. The pal quickly switches off the ignition. Doesn't matter; this is auto-ignition. If you cut the fuel supply, it will stop, but unless you have the third fuel option, an electric pump that you can turn off, the crankcase of your running engine is making its pressure pulses and helpfully supplying more fuel. Your pal madly grabs the nearest solid object, say a wooden oar, and shoves it against the side of the spinning flywheel while you madly disconnect a hose-clamp somewhere to interrupt the fuel flow. With the butterflies closed the engine has a hard time pumping, so it never makes real power or spins up very fast, but it IS unnerving!! With the float-bowls finally evacuated the engine goes quiet, and you can now hear all the nitro-users around you laughing their heads off. Been there, done that.

Now I ask you, with such delights, why would any real racing man want to burn the same stuff that his wife uses in her four-door sedan to take the kids to soccer practice?

[Grumph]

Smitty, they tell me adrenaline is brown...

You don't need nitro for that scenario. i was racing a Mach 3 kawa, came into the pits, switched off and it kept running - at about 7000rpm. Fuel off, ignition off and myself and two others start attempting to strangle it by squeezing the carb air inlet hoses. Eventually the float bowls emptied and it stopped.
Cause was plating flaking off the surface gap plugs and igniting the mixture.

Frits - one of the squeezers was my racing friend of the time - Mike Sinclair...Bet that never happened at GP level.

[peewee]

i had a methanol engine keep running full tilt one time. kill switch was pulled which should of prevented any juice to the plug but that did no good

[AndreasL]

To carry on about the fuelstories.

I now remember that we (me and a friend) tried nitro in his old Yamaha RD125 twin...just to see what would happend.
Yes, dynamite fule works and the sound of that little 125 was more like a 250 at low rpm and WOT. A "lot" of extra power.

Idle rpm? 7000-ish.
Kill switch? Dont bother.

Informative and fun experiance I almost hade forgotten.

[Frits Overmars]

There's an old saying: "Nitro does not add power. It multiplies it".

[2T Institute]

i had a methanol engine keep running full tilt one time. kill switch was pulled which should of prevented any juice to the plug but that did no good

Not entirely uncommon
https://www.youtube.com/watch?v=4Qtu8BiGIVA

[jonny quest]

Lol at guy in green eating his food like no big thing ^^^

[monkeyfumi]

Now I ask you, with such delights, why would any real racing man want to burn the same stuff that his wife uses in her four-door sedan to take the kids to soccer practice?

Probably because his balls have to sit directly behind the fuel tank...

[TZ350]

Developing a new pipe for the RG50 using the EngMod2T engine simulation software.

Ex port opens 85 atdc and 85% wide, Transfers 121 atdc and Inlet 95 btdc and fully open 15 btdc so the inlet has a period of 30 deg fully open.

306295

The blowdown STA show 22 hp (at the crank) is possible.

306293

So far I have only been able to develop a pipe that will make 20hp so a little bit of development to go.

306294

TubMax end gas temperatures are below the detonation threshold.

306292

The pipe design so far, the % lengths of header (FOS 34%) diffuser (FOS 68%) start of reflector section (FOS 76.4%) are close to the FOS concept.

306296

[seattle smitty]

"Different strokes" Dept. (and, Admin, or TZ, if this doesn't belong here, it's fine with me if you delete it):


A Saturday evening party at a big hotel, during a two-day race weekend. A four-stroke guy is wandering around, sampling the food at the buffet tables and watching the ladies. He has also been watching a couple of 2-stroke guys, and has noticed that they always seem to have four or five women hanging around them, stroking their hair and chatting in a most animated fashion. Four-stroke-guy watches the pair until there is a momentary lull when there aren't any women around them, then walks up to them.

"Say, I've been watching you 2-stroke fellas, and you always seem to have a crowd of gals around you. I've been at this party for two hours, and I can't get any interest from the women; they talk for a minute, but then they wander off. What do you think I ought to do??"

The 2-stroke guys look at each other, then one of them lays his hand on the shoulder of the four-stroker:

"Well, big guy, you could try this: See that door over there? That leads to the kitchen where they make all of the chow for this shindig. You go ask 'em for a couple of good-sized raw potatoes. Take the potatoes, go to the men's room, and stuff them into your pants, your shorts. Then come out here and see how you make out."

"Hey, I'll give that a try!," says four-stroke guy, and heads for the door to the kitchen, while the 2-strokers snort and roll their eyes.

An hour later, there's another lull when the 2-stroke pals are momentarily by themselves, and the four-stroker walks up with a baffled expression on his face (the customary four-stroker facial expression??!!).

"Well, fellas, I tried that trick with the potatoes in my pants, but I still can't get women to talk to me. In fact, it has gotten worse, now they won't even come near me!!"

The two 2-strokers look at him, then one says, with exasperation in his voice, "Look, big guy . . . you were supposed to put the potatoes in FRONT . . . ."

[TZ350]

P1050 ... EngMod2T setup talk about pipes, transfer ports and the TubMax graph



As some of you know I have been developing my 300cc NSR. Its going really well except the pipes are cracking and braking all the time. They are SS no surprise. They really do cool very quickly and obviously heat fast as well. I was wondering if lagging the pipes for the first 300mm is a good idea to keep a bit of heat in there and not let them cool so fast. Will this help with the cracking yah reckon.

Years ago on pre 95 rs hondas guys used to put beads of high temp red silacon around the chambers to take the zing out of them to stop cracking , the promblem was the rubber mounts but it did work not to bad but looked crap


I'm not sure how the SS works as I've never had a SS pipe. As with nearly everything I've owned, if the pipe was cracking the cure was to mount it so it was free to move around while still supported. You probably already on to that idea.



...anybody who has tried this, tell me about expansion chambers made of aluminum, an examples of which I saw on the French site. Since, I assume, they'd have to be made thicker than steel, does the weight savings balance the drawbacks? I assume the big drawback is heat-loss, but maybe that could be largely addressed with a ceramic coating. What alloy and thickness has worked (if any has worked)?

Don't do it. There is no weight saving, aluminium (aluminum to you) pipes won't work without an internal ceramic coating, and they will crack despite the increased thickness. Aluminium does that.

Titanium works great for pipes if you use the right grade 306191. But stainless steel is almost as good, cheaper and easier to weld.


hey wobbly let me ask something. in EngMod 2T, where it asks for the flow width of the window. if the duct exit and window are the same size and there is no kicker or radius turn at the duct exit, its rather easy to figure the flow width.

But like most cylinders, there is either a kicker or a radius turn just as it enters the cylinder. is there a easy way to get a close approximation of the flow width in this situation ?

306419

Green arrow would be the flow width if both duct walls went parallel into the cylinder. but what if there was a radius or kicker. Would it still be as simple as the blue arrow suggests or is it more complicated than that ?


Where you have an angled exit on one wall like that I use a combination of the flow and chordal width. In reality the port flow area will be very close to the chordal width, as when the flow exits the duct its effective area will be less than a straight flow port, but more than the flow area measured vertically as you have drawn it. In between approximation is the chordal width as I have shown.


Imagine that you have a collection of coins. The diameter of the largest coin that you can shove through the window from within the cylinder bore, is the dimension you are looking for.


Well its sort of like I said, with parallel walls the coin will push into the duct and give you the exact "flow width".

With one wall angled a smaller coin will push into the port, but this gives a smaller flow width, and in this case its the chordal port width. Neels (EngMod2T) code asks for the actual "flow width" and even he says you need some judgement to approximate this where weird angles are involved.

ONLY a 1 mm change, that is enough to completely ruin any engine - 0.1mm should be an ONLY to everyone - in a KT100 0.05mm in any port size can ruin an engines power.


As Neels says you have to use some judgement to get the actual flow width correct.

Using the example he gives in the help file, if we call the bottom port an A port with a heavily sloping front wall, the flow width will be very close
to the original flow width as he drew it .

306480

If we call the top port a B port with a hook, its effective flow width will be very close to the chordal as he dew it. The A port may in fact be much wider chordally, but because of the entry geometry the actual flow thru that port will be reduced by the cosine of the entry angles - exactly the same as the software reduces the effective area by the cosine of the axial upward angle of the duct.

Where there are two distinct entry angles, use your judgement to get what would be the real flow width.


wobbly how did you go about calculating the entrance ? the engmod help file doesnt seem to be real specific about this.

did you just use chordal width x height from case to cylinder sleeve, like the green arrow ?

or did you use something more like a flow width as the red arrows show. red arrow A + red arrow B x height of case to cylinder sleeve ?


306490
Actually if you used a chordal width you would probly do something more like this , with the opening width split into 2 parts to give designation for the A port and B port. then simply green arrow A x height. green arrow B x height


Depends upon the cylinder design. In the case of the Yamaha you are working on the septum divider is very tapered, so the effective entry area is pretty much as you say for each port - the two green arrows times the height.

But in an Aprilia where the septum is very wide, the effective duct acts much more like the angled flow widths times the height. Then there is the extra entry coefficient added by the shape of the inner bore wall.

The length is the important factor, the entry area/exit area ratio does not make a big difference at all, except where you do not have the transfer duct volumes as part of a measured input.

I recently ran a test on this out of interest - with everything kept constant ( including the case vol ) having a 1:1 entry/exit ratio and a 1 :1.5 ratio made virtually no difference.

This ties in with my assertion that all of the mixture transferred into the cylinder is sitting in the ducts, there is no actual flow from the case into the cylinder when the transfers are open.


The duct length is very short in the MZ style thru the piston feed entry, but this is probably offset by the fact that the axial angle is so steep the effective area at the bore is tiny - thus the actual flow cc is tiny as well. But even that small duct has to be filled from somewhere, and the hole in piston,into the duct works well compared to non at all.

I worked at EMC building pipes in the early days of the Rotax 256 , and the idea of a hole in the piston, lining up with a hole in the boost port duct made a couple of Hp in the twin. We tried doing the same thing with all the transfers, spending hours grinding holes in the bores, but sadly this made less power.

Later on in the Rotax development it was worked out that the boost duct entry was badly shrouded, and once this was fixed along with a 1/2 moon cutaway in the piston skirt was introduced, power went up another couple of Hp over the hole in piston idea.

Joe's boost ports were a quick fix for crap scavenging in a piston port, and really were just a band aid - but as he was very good at ,Yamaha paid a fortune to him for the idea to be used in the twin 125 Yamaha that really was a very good little engine in its time.

Yamaha paid Joe another fortune for the dumb offset combustion chamber patent, that only got into production for 1 year in a TZ. Then they finally realised that having no squish on one side, and huge squish velocity on the other ,actually caused detonation - someone at Yamaha Corp must have felt really stupid/and or got fired.

But Dr Joe went laughing all the way to the bank - then started taking loads of cash from USA outboard people, again mostly bullshit technology, but hey I dont want to overly deride those that taught a young Kiwi plenty about the workings of a racing 2T.


You will make more power if you have a transition from the 23.7 duct outlet ( this will of course be oval ) up to the 26 pipe diameter ( round ) ie no steps at the joint face.
This is usually around 25 to 30 long and will be the slip joint spigot - this can be inserted into the pipe in front of the header as part of the header length %.


306420

Hi Wob, this is getting into deeper water than I am used to. I worked hard playing with the ignition to get a flat TubMax (squish end gas temperature), but was I doing the right thing, is Ief's red line on this graph more appropriate? I just don't know what a good TubMax graph should look like.


You will know when TubMax is too high ( around 980*C ) as the program will scream DETONATION at you.

On a DynoJet you will need around 12.5% multiplier ( down ) to go from indicated crank Hp in EngMod to RWHp when testing your average racebike.


EngMods TubMax is a reflection of the % of fuel energy retained in the unburned end gases trapped in the squishband. The shape of this curve is affected by a myriad of elements but the biggest factor is the real ignition timing.

In a race engine the results are supremely useful for juggling the ignition timing to fix any major anomalies that can produce low bmep at one point or several in the usable powerband. Where you are running what i would call "normal" numbers for timing - say 28* at the bottom of the range and 15* at peak then some further retard to get heat in the pipe for overev capability ,the curve shape will be close to that of the torque produced, a flattened bell.

ie low 900 rising to high 900*C at peak torque then dropping away again as more of the combustion heat energy is dumped into the pipe. You have to be careful of part throttle deto at the beginning of the powerband, and then of course if the temp starts hovering at 1000* in the high power range you will get DETO lighting up on the screen.

To drop the temp it is easy enough to simply retard the timing - but more power may often be had by adjusting the stinger, or reducing the com/squish velocity. Then re-running the Turbulent model to account for the differing flame propagation speed through the chamber due to squish turbulence changing the combustion delay numbers etc.

These factors are just as important, sometimes more - than the "raw" ignition timing number at any rpm point. Each end of the bell curve can be tipped, by use of a powervalve for example,or a solenoid powerjet that is simulated by a change in A/F ratio past peak power.


A huge part of Neels efforts to recreate reality in EngMod2T’s sim results is all around the code needed to model the wave action within the pipe.

A 2T lives and dies on the correct timing and amplitude of the particle flow down the pipe, much as a 4T lives and dies on the intake tracts influence. The latest code change that now has an accurate model of the actual wall temps effects has got the results even closer, without the demon fudge
factors Neels hates with a passion.

The only caveat i would add is that there is still some leeway for idiocy to creep in, and still get a result that seems fine ie 25* diffuser angles. Go back to the old texts and you will find that very early on in the development of expansion chambers it was found that the angle that gave the best energy recovery ( amplitude Vs period ) of the depression communicated to the Ex port during the scavenging phase was 16* included.

This is now modified somewhat in that we can and do have up to 6 different cones. All interacting and changing the shape of the negative pressure ratio plot as seen at the port face when the piston is around BDC, but as is human nature we always think more must be better - even with single malts.

Just keep in mind that any energy used in the diffuser, must then reduce the energy available to be used in the reflection phase - there is only a finite ( and ever decreasing ) energy level available that starts when the piston cracks open the port.

[peewee]

hey wobbly let me ask something. in engmod where it asks for the flow width of the window. if the duct exit and window are the same size and theres no kicker or radius turn at the duct exit, its rather easy to figure the flow width. but like most cylinders, theres either a kicker or a radius turn just as it enters the cylinder. is there a easy way to get a close aproximation of the flow width in this situation ?

green arrow would be the flow width if both duct walls went paralell into the cylinder. but what if there was a radius or kicker. would it still be as simple as the blue arrow suggests or is it more complicated than that ?

[wobbly]

Where you have an angled exit on one wall like that I use a combination of the flow and chordal width.
In reality the port flow area will be very close to the chordal width, as when the flow exits the duct its effective area
will be less than a straight flow port, but more than the flow area measured vertically as you have drawn it.
In between approximation is the chordal width as i have shown.

[Frits Overmars]

green arrow would be the flow width if both duct walls went paralell into the cylinder. but what if there was a radius or kicker. would it still be as simple as the blue arrow suggests ?Your blue arrow is faulty because your dotted red line does not exist. As the Italians say: izze reelly simple: find the smallest passage.
Imagine that you have a collection of coins. The diameter of the largest coin that you can shove through the window from within the cylinder bore, is the dimension you are looking for.

[ief]

Tnx for the files Rob, gives me something to play :)

Looks to easy though, hehe. (4 runs, 2 pipes, basicly from scratch, I couldn't resist and changed 1 thing on the engine, only a mm, nothing drastic,hope thats ok :Police:)

q's:

1. My baseline reading differs slightly from yours, might that be due to using a different version, I think I have the latest not publicly available.
(not to big of a difference though but still)
2. What would max acceptable tubmax reading be?
3. What hp figure would you say is needed to get 16 RWhp?
4. Is your combustion file 'good'? Seems such a strange curve to me (?)

[TZ350]

Good Work....

[seattle smitty]

As the Italians say: izze reelly simple: find the smallest passage.

Okay . . .


Imagine that you have a collection of coins. The diameter of the largest coin that you can shove through the window from within the cylinder bore, is the dimension you are looking for.

WHAT?? I'm just a dumb welder but this seems to contradict your Italians.
If you have a parallel-sided port (like those shown) that is aimed straight into the cylinder toward its center, no chordal angle, then your Italian coin will fit equally well all the way from the opening in the cylinder and on into the port. But if you start angling that same port at an ever-increasing angle to the cylinder's center-point, with your coin size unchanged, the parallel walls of the port get closer and closer together, and the port can pass less and less A/F. Leaving aside the matters of how the inlet streams effect each other and exhaust-clearing for the moment, what are you trying to measure, the size of the holes in the cylinder (why would you care about that?), or how much A/F you can pass through the ports?

I guess you mean that when you push your coin into the port from within the bore, you hold it at a right angle to the port, not to the bore centerpoint . . . right?

(I have that baffled-four-stroker expression on my face; dang!!)

[seattle smitty]

Deleted while I think more about it, LOL.

[wobbly]

Well its sort of like I said, with parallel walls the coin will push into the duct and give you the exact "flow width".
With one wall angled a smaller coin will push into the port, but this gives a smaller flow width, and in this case its the chordal port width.
Neels code asks for the actual "flow width" and even he says you need some judgement to approximate this where weird angles are involved.

You will know when TubMax is too high ( around 980*C ) as the program will scream DETONATION at you.
On a DynoJet you will need around 12.5% multiplier ( down ) to go from indicated crank Hp in EngMod to RWHp when testing your average racebike.
ONLY a 1 mm change, that is enough to completely ruin any engine - 0.1mm should be an ONLY to everyone - in a KT100 0.05mm in any port size can ruin an engines power.

[ief]

Tnx Wob, in my defence, it made 1+ hp ;) (was an educated guess)

2nd try turned out te be a good one, rest of the day was more like pissing in the wind, just as I like it.

Anyway, last run is now going with another cbd file, attached run with my exhaust, Robs files as is except smaller exh port outlet (23.7 mm, that was the mm, 1.3 to be exact) en 1 cm shorter carb, hope I recall that right.

And the last run, didn't want to mess with Robs files to much but the cbd file looked wierd, on the other hand, what do I know, I still have no clue on all the vibes, delays and what not... anywayzzz, I enjoyed myself, hope Rob can do something with the exhaust as a start or something.

edit: the cbd run could obviously do with some more tweaking but I'm done for now.

[wobbly]

In reality you will make more power if you have a transition from the 23.7 duct outlet ( this will of course be oval )
up to the 26 pipe diameter ( round ) ie no steps at the joint face.
This is usually around 25 to 30 long and will be the slip joint spigot - this can be inserted into the pipe in front of the header as part of the header length %.

[peewee]

Well its sort of like I said, with parallel walls the coin will push into the duct and give you the exact "flow width".
With one wall angled a smaller coin will push into the port, but this gives a smaller flow width, and in this case its the chordal port width.
Neels code asks for the actual "flow width" and even he says you need some judgement to approximate this where weird angles are involved.

You will know when TubMax is too high ( around 980*C ) as the program will scream DETONATION at you.
On a DynoJet you will need around 12.5% multiplier ( down ) to go from indicated crank Hp in EngMod to RWHp when testing your average racebike.
ONLY a 1 mm change, that is enough to completely ruin any engine - 0.1mm should be an ONLY to everyone - in a KT100 0.05mm in any port size can ruin an engines power.

since nearly every cylinder uses some sort of radius turn or kicker, dont you think neels should do a update for such port arrangments ? ive seen 1 cylinder in my life that uses paralell walls and its old outdated ktm scrap

[TZ350]

Post Classic possibility for the Tiddler class.

306371

One cylinder of a RG125T bore stroke 43x43, 44 crank hp as a twin.

[ief]

In reality you will make more power if you have a transition from the 23.7 duct outlet ( this will of course be oval )
up to the 26 pipe diameter ( round ) ie no steps at the joint face.
This is usually around 25 to 30 long and will be the slip joint spigot - this can be inserted into the pipe in front of the header as part of the header length %.

Yeah, I remeber that was mentioned before and I tried to sim it, gave worse result in engmod, same in this instance. Looking at the tubmax some more (never saw that before), what would be an ideal/ logical outcome if any? (more of a straight line or more start low and build up to high)

Re: Peewee and parralel walls, wouldn't the different scavenging configurations account for that?

[TZ350]

306373

Hi Wob, this is getting into deeper water than I am used to. I worked hard playing with the ignition to get a flat TubMax (squish end gas temperature), but was I doing the right thing, is Ief's red line on this graph more appropriate? I just don't know what a good TubMax graph should look like.