ESE's works engine tuner

[TZ350]

TZ, is your Ariel Arrow still languishing under the bench?

........ yes same place as the turbocharged 100cc 4T CVT project, and the turbo 70cc 2T :facepalm:

[husaberg]

Nah; you can't cast decent disc recesses like that anyway; they'll always need some final processing.
I suppose the simplest approach would be to cast those cases 'full' and then dip in a cutter blade.
329483 329482

That port layout looks a lot like side ports on a Mazda Wankel.

Lots of photos of the Alpha (and the disc valved Centuri twin) here: http://www.villiers.info/Alpha/

Here is the race test on the Alpha twin
https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1130237063#post1130237063

[peewee]

I'm looking through the book now!

Nitro just made my hobby alot more exciting!


you may find something useful here http://www.modelairplanenews.com/what-fuel-is-best-for-your-engine/


is this the stuff your using ? https://www.vpracingfuels.com/product-category/rc-fuel/car/

[adegnes]

you may find something useful here http://www.modelairplanenews.com/what-fuel-is-best-for-your-engine/


is this the stuff your using ? https://www.vpracingfuels.com/product-category/rc-fuel/car/

Thanks!
I'm using this stuff:
https://www.hpiracing.co.uk/piw.php?partNo=OP1006
for no other reason than that's the only fuel available locally.
Ideally I would just buy the nitro/methanol/oil separately and blend to my liking, but as nitromethane in higher concentration than 30% by weight(also has to contain at least 10% oil) is illegal to own here in Norway(they think you'll be making bombs) it's difficult to get ahold of.

[husaberg]

Thanks!
I'm using this stuff:
https://www.hpiracing.co.uk/piw.php?partNo=OP1006
for no other reason than that's the only fuel available locally.
Ideally I would just buy the nitro/methanol/oil separately and blend to my liking, but as nitromethane in higher concentration than 30% by weight(also has to contain at least 10% oil) is illegal to own here in Norway(they think you'll be making bombs) it's difficult to get ahold of.

Have you tried a chemist or a Dry cleaners.
http://www.chemical-supermarket.com/Nitromethane-250ml-p58.html
when can get it here.
https://www.rchobbies.co.nz/rchobbies/shop/FUEL+%26+ACCESSORIES/Glow+Fuel+Ingredients/Nitromethane/Nitromethane+1+Litre.html
Vets can be a source of Nitros Oxide refills as well when you decide to have a play with that.

I thought it was the Swedes that were over run with Terrorists now.http://pbs.twimg.com/profile_images/827964929420492802/0R2nPc-i_normal.jpg

[adegnes]

Have you tried a chemist or a Dry cleaners.
http://www.chemical-supermarket.com/Nitromethane-250ml-p58.html
when can get it here.
https://www.rchobbies.co.nz/rchobbies/shop/FUEL+%26+ACCESSORIES/Glow+Fuel+Ingredients/Nitromethane/Nitromethane+1+Litre.html
Vets can be a source of Nitros Oxide refills as well when you decide to have a play with that.

I thought it was the Swedes that were over run with Terrorists now.http://pbs.twimg.com/profile_images/827964929420492802/0R2nPc-i_normal.jpg
Haha! Sorry, guess I shouldn't laugh.
It's not that easy.
Asking for it at the dry cleaner is considered suspicious activity and will be reported, ordering online too.
I'm probably already "on the list" for showing so much interest in the stuff and other chemicals deemed too dangerous for regular people.
1984.
I think it's just as restricted in Sweden now too, otherwise I would just buy it there as I live on the border.
It's not that I care about the legality of it, but others do and that makes it difficult.

[husaberg]

Haha! Sorry, guess I shouldn't laugh.
It's not that easy.
Asking for it at the dry cleaner is considered suspicious activity and will be reported, ordering online too.
I'm probably already "on the list" for showing so much interest in the stuff and other chemicals deemed too dangerous for regular people.
1984.
I think it's just as restricted in Sweden now too, otherwise I would just buy it there as I live on the border.
It's not that I care about the legality of it, but others do and that makes it difficult.
You could always approach the relevant authorities and explain what you want to do as thats something terrorist i guess don't normally do.
Failing that take your complete bike over the border and fill it up there.
Pretty sure I watched some euro-doco on a drag racing (rail)Norwegian team they seemed to be able to get the nitro
The only time i have heard of something similar in NZ was when the guy was making very large rockets and was getting too much interest from Middle easten Businessmen)

https://www.buzzfeed.com/keelyflaherty/magical-facts-that-will-make-you-want-to-move-to-norway?utm_term=.nwzM8vr3j#.vrQxE75bp

[SwePatrick]

I think it's just as restricted in Sweden now too, otherwise I would just buy it there as I live on the border.


Actually no.
It´s not illegal, you just need a couple of hours of study and make a test to get certified to buy it here in Sweden.
It´s not illegal to own in Sweden, just need that certificate to buy it.

If you want to test a lower percentage nitro first, blend in more methanol.

But, buy 2nd hand from a local dragracer if you know anyone that is ;)

[TZ350]

329505

Fuel..... I love all sorts of liquid and gaseous internal combustion go fast joy.

I would just love it, if fuel for Buckets was totally open. Sure, the white coats can still have their boring reliable 96 octane store brought pump fuel, but let's let the real chemists shine.

[adegnes]

Actually no.
It´s not illegal, you just need a couple of hours of study and make a test to get certified to buy it here in Sweden.
It´s not illegal to own in Sweden, just need that certificate to buy it.

If you want to test a lower percentage nitro first, blend in more methanol.

But, buy 2nd hand from a local dragracer if you know anyone that is ;)

Good to know. In Norway it's practically impossible to get certified for "hobby use".

[husaberg]

Fuel..... I love all sorts of liquid go fast joy. I would just love it if fuel for Buckets was totaly open
Let the chemists shine I recon.

tour de france rules then? Only Without the lycra.

[teriks]

Good to know. In Norway it's practically impossible to get certified for "hobby use".
FYI: That ban is EU-wide.


REGULATION (EU) No 98/2013 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL

of 15 January 2013

on the marketing and use of explosives precursors
<snip>

Hydrogen peroxide, nitromethane and nitric acid are widely used for legitimate purposes by members of the general public. It should therefore be possible for Member States to provide for access to those substances within a given range of concentrations by applying a registration system under this Regulation rather than a licensing system.

[adegnes]

329505

Fuel..... I love all sorts of liquid and gaseous internal combustion go fast joy.

I would just love it, if fuel for Buckets was totally open. Sure, the white coats can still have their boring reliable 96 octane store brought pump fuel, but let's let the real chemists shine.

And "chemical supercharging" just sounds cool!

[lohring]

Model boat racers in Europe seem to be able to get nitro, but it's expensive compared to the US. Here, top fuel drag racers run close to 100% nitro. Below is a summary of a series of tests we did on a 26 cc spark ignition industrial engine setup to run gasoline. The open transfer, piston port engine was modified in standard ways for racing. Everything was the same as for gasoline except we changed the needle settings to give best power with the various fuels.

The red text was left out of the published version where we were only talking about different gasolines. The additional tests with methanol and nitromethane were to address whether we needed to use Digitron or similar tests to prevent fuel cheating. These tests prove that fuel alone isn't the answer for more power. You would need to change the combustion chamber volume for higher compression, and the tuned pipe for lower exhaust temperature. In addition, variable ignition timing would help.

Lohring Miller

329506

[adegnes]

Model boat racers in Europe seem to be able to get nitro, but it's expensive compared to the US. Here, top fuel drag racers run close to 100% nitro. Below is a summary of a series of tests we did on a 26 cc spark ignition industrial engine setup to run gasoline. The open transfer, piston port engine was modified in standard ways for racing. Everything was the same as for gasoline except we changed the needle settings to give best power with the various fuels.

The red text was left out of the published version where we were only talking about different gasolines. The additional tests with methanol and nitromethane were to address whether we needed to use Digitron or similar tests to prevent fuel cheating. These tests prove that fuel alone isn't the answer for more power. You would need to change the combustion chamber volume for higher compression, and the tuned pipe for lower exhaust temperature. In addition, variable ignition timing would help.

Lohring Miller

329506

Very interesting, thanks!
Looking forward to seeing if my results will be any different.

[TZ350]

The red text was left out of the published version where we were only talking about different gasolines. The additional tests with methanol and nitromethane were to address whether we needed to use Digitron or similar tests to prevent fuel cheating. These tests prove that fuel alone isn't the answer for more power. You would need to change the combustion chamber volume for higher compression, and the tuned pipe for lower exhaust temperature. In addition, variable ignition timing would help.

Lohring Miller

329506

Very interesting.

[TZ350]

And "chemical supercharging" just sounds cool!

I once tried a pumper carb and hydrogen peroxide for oxygen and cooling from the evaporating water. All I got was lots of gas bubbles choking the pumper and alloy corrosion.
Maybe squirting it in with a windscreen washer pump may have worked better ..... :scratch:

http://www.americanenergyindependence.com/peroxide.aspx

[katinas]

Hi

So, after very busy preparation day ( all that road legal stuff is so boring: head lamps, turns, mirrors, insurance ), but in the end ride it (around 25 km.).

And what a funny things: different engine, but the same carb, pipe, ignition tuning routine stories started again.

1. 0-3100 rpm. - easy ride 1st-2nd gear normal sound from reed cage - aaaaaaaaaaaa

2. 3100-5800 rpm. - no power at all noisy sound from reed cage - b-a-a-a-a-a-a-a or r-a-a-a-a--a-a

3. 5800-8500 rpm. - engine starts to come to life, normal sound again

4. And from 9000 blow begins, but suddenly at the most interesting moment, when real power come in , after 10100 rpm. like switch off ( likely too small main jet- Keihin NSR 250 tb 32mm. main jet 150, never tried this carb before, so for me its new and it takes time for friendship. Test with airbox, with intake tube dia.-31mm. length- 55mm. without foam filter.)

5. Then remove airbox, put on foam filter and try to ride again, but this time engine switch off around 7000 rpm.

6. Then it became dark and rolled back in time for MotoGP FP3.

So, next week I'll try to find something and maybe Your tips and insight will help.

[katinas]

Nah; you can't cast decent disc recesses like that anyway; they'll always need some final processing.
I suppose the simplest approach would be to cast those cases 'full' and then dip in a cutter blade.
329483 329482

Russian outboard engine Vihr 30 (Whirlpool 30), modified copy of Germany 1957 Konig (http://quincylooperracing.us/gpage8.html). Two cylinders, 488 cc, bore x stroke 72mm x 60mm.
Std. engine max power 30hp - 5000rpm. They made it until 2000 or so. Crankcase midsection sand cast. Highly tuned versions used in boat racing on methanol -75-80 hp.

Found my motorcycle old photos with this tuned engine .

[TZ350]

So, after very busy preparation day ( all that road legal stuff is so boring: head lamps, turns, mirrors, insurance ), but in the end ride it (around 25 km.).

Hi Katinas ...... :clap: ..... congratulations on having been able to ride your Ryger for some distance on its first outing.

My hats of to you for a very good engineering effort. ..... :not:

[SwePatrick]

Hi

So, after very busy preparation day ( all that road legal stuff is so boring: head lamps, turns, mirrors, insurance ), but in the end ride it (around 25 km.).

And what a funny things: different engine, but the same carb, pipe, ignition tuning routine stories started again.

1. 0-3100 rpm. - easy ride 1st-2nd gear normal sound from reed cage - aaaaaaaaaaaa

2. 3100-5800 rpm. - no power at all noisy sound from reed cage - b-a-a-a-a-a-a-a or r-a-a-a-a--a-a

3. 5800-8500 rpm. - engine starts to come to life, normal sound again

4. And from 9000 blow begins, but suddenly at the most interesting moment, when real power come in , after 10100 rpm. like switch off ( likely too small main jet- Keihin NSR 250 tb 32mm. main jet 150, never tried this carb before, so for me its new and it takes time for friendship. Test with airbox, with intake tube dia.-31mm. length- 55mm. without foam filter.)

5. Then remove airbox, put on foam filter and try to ride again, but this time engine switch off around 7000 rpm.

6. Then it became dark and rolled back in time for MotoGP FP3.

So, next week I'll try to find something and maybe Your tips and insight will help.

Try stiffer reedpetals.
You got higher pressureratios in 'crankhouse' now, and you might need to tune those.

Rgds.

[TZ350]

This is my exhaust pressure takeoff for the MAP sensor. It is a one way valve with a small ceramic ball with only 0.010" movement, hopefully it wont break up being hammer'd around at 200Hz. The blue hose will have positive pressure in it and a small bleed hole melted into it with a hot pin for a pressure bleed down. Hopefully this will give the 2 bar MAP sensor something worthwhile to work with, that is hopefully a smooth positive pressure that reliably reflects changes in the mass air flow through the motor.

Nath88, thanks for the ideas, hopefully I can make them work for me.

329535

Preliminary try at using the pressure and MAP sensor at the exhaust port to detect a drop in pressure when the pipe wave action collapses during over run.

329534

TPS bottom line.
MAP pressure orange middle line.
RPM top green line.

Interesting, MAP pressure drops below ambient when accelerating ( 30% TPS ) and increases to greater than ambient on overrun. Not what was expected at all, I was expecting it to show high pressure during acceleration and a drop on overrun not increase????

Not sure what is happening, know more when I have adjusted the Alpha-N map and found the right size secondary injector so I can pull full load.

[ken seeber]

329482[/QUOTE]

Frits, I have a question on the above pic. Is the crankcase lower half also machined for the disc valve as well? Otherwise the valve could flop about cos it'd be unsupported.

Katinas, really good effort. Watch you don't get booked for speeding. ;)

[katinas]

Try stiffer reedpetals.
You got higher pressureratios in 'crankhouse' now, and you might need to tune those.

Rgds.

Thank you, add this to trying list.
Now i want to check cylinder head for invisible cracking, because this head skimmed very often from 2000 and aprox. 5mm thinner than original. This engine "switch off" very familiar to cylinder - head leakage from previous practice with air and water cooling engines. And spark plug is very strange, like washed with no signs of work. Have a lot of thicker cylinder heads, so not a problem, just need to modified for plain piston.

Add photo of two modified reed cage. First ride with side windows cage.

[JanBros]

Hi

So, after very busy preparation day ( all that road legal stuff is so boring: head lamps, turns, mirrors, insurance ), but in the end ride it (around 25 km.).

And what a funny things: different engine, but the same carb, pipe, ignition tuning routine stories started again.

1. 0-3100 rpm. - easy ride 1st-2nd gear normal sound from reed cage - aaaaaaaaaaaa

2. 3100-5800 rpm. - no power at all noisy sound from reed cage - b-a-a-a-a-a-a-a or r-a-a-a-a--a-a

3. 5800-8500 rpm. - engine starts to come to life, normal sound again

4. And from 9000 blow begins, but suddenly at the most interesting moment, when real power come in , after 10100 rpm. like switch off ( likely too small main jet- Keihin NSR 250 tb 32mm. main jet 150, never tried this carb before, so for me its new and it takes time for friendship. Test with airbox, with intake tube dia.-31mm. length- 55mm. without foam filter.)

5. Then remove airbox, put on foam filter and try to ride again, but this time engine switch off around 7000 rpm.

6. Then it became dark and rolled back in time for MotoGP FP3.

So, next week I'll try to find something and maybe Your tips and insight will help.

now all we need is a video showing your bike riding with others, and a claim of huge power and we can conclude you are already level with the real Ryger :psst:

[Frits Overmars]

.... Husabergs Cyclemaster picture, showing the engine's most interesting part: the governor. It was a spring-loaded vane that gradually closed the inlet opening in the disc as the revs went up. Removing the vane gave the little engine a second wind.
Might there be some merit in something similar, that adjusts the inlet timing depending on rpm?Yes, there might be. And it has been done, half a century ago.
329539 329540

But instead of varying the disc angle on the fly it is simpler and more effective to vary the width of the inlet opening in the disc cover, as Flettner did.
329541 329542 329543 329544



Preliminary try at using the pressure and MAP sensor at the exhaust port to detect a drop in pressure when the pipe wave action collapses during over run. MAP pressure drops below ambient when accelerating ( 30% TPS ) and increases to greater than ambient on overrun. Not what was expected at all, I was expecting it to show high pressure during acceleration and a drop on overrun not increase??.I suspect your answer may be here: https://en.wikipedia.org/wiki/Pitot_tube



Frits, I have a question on the above pic. Is the crankcase lower half also machined for the disc valve as well? Otherwise the valve could flop about cos it'd be unsupported.Are you pulling my leg Ken? 329483 shows the both the upper and lower crankcase half.

[JanBros]

But instead of varying the disc angle on the fly it is simpler and more effective to vary the width of the inlet opening in the disc cover, as Flettner did.
329541 329542 329543 329544


on second look, isn't that sliding piece a serious flow disturber ? so in the end for performance it might be more complicated but better for performance to use varying disc angle ?

[Frits Overmars]

on second look, isn't that sliding piece a serious flow disturber ? so in the end for performance it might be more complicated but better for performance to use varying disc angle ?You may well be right, Jan. But Flettner is planning to use that sliding piece also as a throttle, in which case it should disturb the flow.

[husaberg]

I suspect your answer may be here: https://en.wikipedia.org/wiki/Pitot_tube

Some further reading for TZ he might need to reverse engineer it a bit for his application.
http://www.spartgsxrspecials.com/turbo%20do%20and%20dont.htm

[Flettner]

on second look, isn't that sliding piece a serious flow disturber ? so in the end for performance it might be more complicated but better for performance to use varying disc angle ?



http://i1056.photobucket.com/albums/t380/uniflow/attachment_zpsb669a7bf.jpeg

Jan, I don't think the sliding Gib is too much of a problem, after all as Frits said the throttle 40mm further upstream is a restriction anyway. This power curve is a lot better than without the variable housing.
As Frits also noted in my next version this gib will be the throttle as well, with a leading and trailing gib. With a bit of luck these slides will be ECU operated.
I would like to revisit Robs dyno again some time because I've widened the exhaust port and adjusted both fuel and timing since this curve was done, It's a lot more frightening to ride now.
This is rear wheel HP
1973 350cc

[ken seeber]

Are you pulling my leg Ken? shows the both the upper and lower crankcase half.

Totally correct Frits. Better get those new glasses. :facepalm: It would have taken some good fixturing and tolerancing to ensure both faces were co-planar.

[adegnes]

I once tried a pumper carb and hydrogen peroxide for oxygen and cooling from the evaporating water. All I got was lots of gas bubbles choking the pumper and alloy corrosion.
Maybe squirting it in with a windscreen washer pump may have worked better ..... :scratch:

http://www.americanenergyindependence.com/peroxide.aspx

Sounds fun, thanks for the link!
There's very little experimentation with fuel on youtube(as I can find anyway), maybe it can be my niche.

[Grumph]

Sounds fun, thanks for the link!
There's very little experimentation with fuel on youtube(as I can find anyway), maybe it can be my niche.

The most successful nitro user in NZ roadracing when it was legal here had a wife who was a qualified pharmacist - and BSc.
It helped.

[adegnes]

The most successful nitro user in NZ roadracing when it was legal here had a wife who was a qualified pharmacist - and BSc.
It helped.

I'll find and marry a pharmacist's daughter!
Chemistry, yet another road to go down that I know next to nothing about, yet. Love it!


https://youtu.be/kanq44mOJJQ

[adegnes]

Hydrogen peroxide >12% is under the same restrictions as nitromethane in norway. Can't find propylene oxide on the list tho.

[husaberg]

Hydrogen peroxide >12% is under the same restrictions as nitromethane in norway. Can't find propylene oxide on the list tho.

Concentrated H2O2 was used in the V2
Jet packs were also H2O2.
The kiwi version is powered by four CR500's

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

[adegnes]

Interesting read here:

http://www.foxvalleykart.com/fuel1.html

[TZ350]

Know more when I have adjusted the Alpha-N map and found the right size secondary injector so I can pull full load.

329559

Ok, things turned to custard again, will it ever stop. This time it was the servo motor. I was not making much progress and then found the servo was turning backwards, blue line. Changed the cables and got the red line. Then it went in the wrong direction again, I guess its buggered. But at least I got to see that the PV can be closed down further and for longer than I thought.

[Frits Overmars]

... at least I got to see that the PV can be closed down further and for longer than I thought.That may be true power-wise, but watch the temperatures. Water temp may rise too slowly to give a timely warning. Under-plug temp will be more useful. And a deto sensor wouldn't hurt either.

[Nath88]

329535

Preliminary try at using the pressure and MAP sensor at the exhaust port to detect a drop in pressure when the pipe wave action collapses during over run.

329534

TPS bottom line.
MAP pressure orange middle line.
RPM top green line.

Interesting, MAP pressure drops below ambient when accelerating ( 30% TPS ) and increases to greater than ambient on overrun. Not what was expected at all, I was expecting it to show high pressure during acceleration and a drop on overrun not increase????

Not sure what is happening, know more when I have adjusted the Alpha-N map and found the right size secondary injector so I can pull full load.

Good stuff.
The ECU is likely just reading the value at TDC (or some other consistent point) rather than taking the average of the whole cycle. When firing, the pressure peak should be at 90°, followed by peak vacuum at 180°, then a lower pressure peak at 270°. At 0° there should be a weak vacuum from the residual wave in the pipe after the cylinder has captured the bulk of the return pulse, that's probably what you're measuring.

Either way it looks like you have an indicator of airflow, so it should do the job if you can incorporate it into the fuelling. Best response will come from the first exhaust peak, the later peaks will increase the fuelling delay.

I should have my thing running again this week. I'm relocating the fuel pump and filter in front of the radiators to prevent the fuel boiling, adding a pressure accumulator to the system, and repairing the fuel pressure regulator circuit. Turns out putting power electronics in a well insulated box was a bad idea, it now has a heatsink. Steady fuel pressure should help get my tune nailed down.

[tjbw]

http://i1056.photobucket.com/albums/t380/uniflow/attachment_zpsb669a7bf.jpeg

Jan, I don't think the sliding Gib is too much of a problem, after all as Frits said the throttle 40mm further upstream is a restriction anyway. This power curve is a lot better than without the variable housing.
As Frits also noted in my next version this gib will be the throttle as well, with a leading and trailing gib. With a bit of luck these slides will be ECU operated.
I would like to revisit Robs dyno again some time because I've widened the exhaust port and adjusted both fuel and timing since this curve was done, It's a lot more frightening to ride now.
This is rear wheel HP
1973 350cc

Brilliant work!

Have you ever tried an exhaust with variable length, to control the return pulse timing?

[tjbw]

Hi

So, after very busy preparation day ( all that road legal stuff is so boring: head lamps, turns, mirrors, insurance ), but in the end ride it (around 25 km.).

And what a funny things: different engine, but the same carb, pipe, ignition tuning routine stories started again.

...

So, next week I'll try to find something and maybe Your tips and insight will help.

Katinas, congratulations on your build, and progress.

I'm puzzled about some things.

How do you stop the piston from rotating on the thread?

What do you use the vertical cylinder for?

[Flettner]

Have you ever tried an exhaust with variable length, to control the return pulse timing?

Yes I have that in hand, but not move the pipe.

[tjbw]

Yes I have that in hand, but not move the pipe.

By changing exhaust timing?

[Peter1962]

Yes I have that in hand, but not move the pipe.

Are you experimenting with the variable tailpipe area that was designed by Frits Overmars ?
http://www.pit-lane.biz/t3173p60-gp125-all-that-you-wanted-to-know-on-aprilia-rsa-125-and-more-by-mr-jan-thiel-and-mr-frits-overmars-part-2-locked look at page 3

[TZ350]

Are you experimenting with the variable tailpipe area that was designed by Frits Overmars ?
http://www.pit-lane.biz/t3173p60-gp125-all-that-you-wanted-to-know-on-aprilia-rsa-125-and-more-by-mr-jan-thiel-and-mr-frits-overmars-part-2-locked look at page 3

Not variable tailpipe area but I did try varying the pipes internal working pressure with good results.


279980

Tried it open and closed, Red open, Blue closed. The big surprise was how quiet it was when open, hardly any more noise at all, certainly wouldn't need any sort of muffler.

[katinas]

Katinas, congratulations on your build, and progress.

I'm puzzled about some things.

How do you stop the piston from rotating on the thread?

What do you use the vertical cylinder for?

Hi,

Main piston and steel tube screwed with hi-temp locttite with aluminium powder ( for cylinder block liners) so its solid.
Bottom aluminium part screwed and fixed with special screw.
Vertical breathing cylinder, is tube with reed valve (like on four strokes), returning oil tube and foam filter.
Add pic.

[tjbw]

Hi,

Main piston and steel tube screwed with hi-temp locttite with aluminium powder ( for cylinder block liners) so its solid.
Bottom aluminium part screwed and fixed with special screw.
Vertical breathing cylinder, is tube with reed valve (like on four strokes), returning oil tube and foam filter.
Add pic.

Thanks katinas, all is clear with your excellent sketch.

[lodgernz]

I need some advice please folks. I currently race a Honda 50 which runs very happily with a 24mm Mikuni Flat Slide with 28º downdraught.
I'm replacing that carb with a 26mm genuine OKO, but due to some other mods, this carb will need to be mounted with 35º downdraught.
Am I going to have problems?
Would a genuine Keihin be any better?

[diesel pig]

I need some advice please folks. I currently race a Honda 50 which runs very happily with a 24mm Mikuni Flat Slide with 28º downdraught.
I'm replacing that carb with a 26mm genuine OKO, but due to some other mods, this carb will need to be mounted with 35º downdraught.
Am I going to have problems?
Would a genuine Keihin be any better?

I know at 38 degrees from vertical raw fuel run straight out the idle circuit on my PWK keihin flooding the motor brought it back to 13 degrees and it run fine. Since OKO are based on Keihin's you may have the same problem.
I think Wobbly or Grumph mention Keihin's can only go to 15 or 16 degrees from vertical before you have major problems with fuel pick ups in the bowl.

[wobbly]

No way will any Keihin or OKO run at those angles - the fuel level in the bowl is then higher than the idle jet exit hole, so fuel simply pisses out - even before you stomp on the front brake.
The only carb you can use to straighten out the inlet and run at that sort of angle is the Keihin downdraft as used on NS250 - 400 or even better a small Lectron.
Frits countrymen use 30mm HV ( 26mm venturi ) Lectrons in all manner of 50cc rockets for that very reason.

[husaberg]

I need some advice please folks. I currently race a Honda 50 which runs very happily with a 24mm Mikuni Flat Slide with 28º downdraught.
I'm replacing that carb with a 26mm genuine OKO, but due to some other mods, this carb will need to be mounted with 35º downdraught.
Am I going to have problems?
Would a genuine Keihin be any better?

Mikuni TM28SS from a tzr250 IKT or a KR250 (the tandem disc valve one) I think a Dt200 may have also had this carb.
329612


or Yoshimuras YDMJN looks rather neat it actually looks like a mix of Mikuni and keihin bits
It actually wasn't as expensive as you would have thought for a brand new limited production carb.
329611


Your other option is a Keihin downdraft off a MVX250 (Hens teeth)as they were about that size, Some say 24 some say 25mm but same basic body as the nsr250 carb.
329614329613

[lodgernz]

Thanks for your help everyone, re my carb downdraught issue.

[katinas]

No way will any Keihin or OKO run at those angles - the fuel level in the bowl is then higher than the idle jet exit hole, so fuel simply pisses out - even before you stomp on the front brake.
The only carb you can use to straighten out the inlet and run at that sort of angle is the Keihin downdraft as used on NS250 - 400 or even better a small Lectron.
Frits countrymen use 30mm HV ( 26mm venturi ) Lectrons in all manner of 50cc rockets for that very reason.

Honda NS 250 -28mm.

Honda NS 400- 26mm.

But these carbs works best with original airbox with foam filter. Anyway so much modification is needed and not just like change main jet, but with emulsion tube, needle, power jet, etc., because no acceleration.

[shnaggs]

Yes I have that in hand, but not move the pipe.

Curious if you have similar idea as I have. Does it involve an "American style" football shaped butterfly with a hole in the corner that sits in the convergent cone?

[F5 Dave]

Give us a yell Roger. We'll hook you up with nsr or mvx carb.

[Flettner]

Curious if you have similar idea as I have. Does it involve an "American style" football shaped butterfly with a hole in the corner that sits in the convergent cone?
It might, how did it go .

[husaberg]

Curious if you have similar idea as I have. Does it involve an "American style" football shaped butterfly with a hole in the corner that sits in the convergent cone?

Draw a picture because i can't fathom that one.

[Flettner]

I guess the real way is to just build one and test it. With mine I was looking at taking the bleed off from the center section of the chamber anyway, so the 'flap' didn't need a hole in it. Shnaggs, have you tried this idea?

So, say you were to build a cylinder to test a Ryger bottom end, but a standard loop scavenge style, would it be appropriate to put the reeds straight into the transfers? Transfers would now be real short as the piston at this point is also real short (just enough to house a ring or two). So the reed exit could be the transfer in itself almost? Four reed blocks? One for each transfer (A and B) and I guess four carburetors?
Or are we better off putting the reeds further down under the piston aiming up with the transfer flow direction.

I have two bottom ends to test, both seen here earlier but now with 7075 rods, hard chrome plated, against an aluminium bronze bush, under oil pressure. I've got several FOS type cylinders to test BUT I would like to start off with something a little more known, loop scavenge. Both systems will probably need balance shafts but who cares for test.

Where would YOU put the reeds Luc?

Frits, would Ryger have been bleeding small amounts of hydrogen into the inlet to assist with HCCI (spark induced HCCI)? Did you see any funny little unaccounted for pipes near the carburetor? In the short video we did get to see (doctored sound) the kart seemed real/very gutless until it came on song, I thought indicating very retarded ignition timing ,required for spark induced HCCI I would imagine.

[Frits Overmars]

So, say you were to build a cylinder to test a Ryger bottom end, but a standard loop scavenge style, would it be appropriate to put the reeds straight into the transfers? Transfers would now be real short as the piston at this point is also real short (just enough to house a ring or two). So the reed exit could be the transfer in itself almost? Four reed blocks? One for each transfer (A and B) and I guess four carburetors? Or are we better off putting the reeds further down under the piston aiming up with the transfer flow direction.
Where would YOU put the reeds Luc?
Frits, would Ryger have been bleeding small amounts of hydrogen into the inlet to assist with HCCI (spark induced HCCI)? Did you see any funny little unaccounted for pipes near the carburetor? In the short video we did get to see (doctored sound) the kart seemed real/very gutless until it came on song, I thought indicating very retarded ignition timing ,required for spark induced HCCI I would imagine.I haven't been near a Ryger engine since October 2015 so I cannot comment on anything that has been done since then (and I wouldn't be allowed to if I could).
There were no unaccounted for pipes anywhere then.

[shnaggs]

I guess the real way is to just build one and test it. With mine I was looking at taking the bleed off from the center section of the chamber anyway, so the 'flap' didn't need a hole in it. Shnaggs, have you tried this idea?

Flettner, No I have not tried it yet, just a thought scrambling around in my head (I have too many of them). Although, I should just get another pipe to hack apart and see how she does. I tried some quick sims on engmod and saw a slight benefit, but not enough to get excited about....but then again, I think if its executed properly, I think it could work really well and in conjunction with your RV it should work even better.

[SwePatrick]

A question for someone..

My kx250(212cc) cylinder had the exhaustguillotine hanging down into port and as it is an dragracing highrevving machine i decided to delete it and only let the KIPS control the Aux exhaustports.
The question is: how important can it be to get a totally smooth exhaustrunner?
In picture below you can se there are some 'ridges', but nothing that protrude into the port.

So i welded a plug into the 'hole' for the guillotine and grinded it as smooth as it allows without going nuts in the port/runner.
I did this before i put the new liner in to ensure everything stays round etc etc.

https://scontent.xx.fbcdn.net/v/t31.0-8/17621928_10154793535989475_957213596810163194_o.jp g?oh=c487b310bf00f3a1366a5ed476a86bcf&oe=59596E1F

[Larry Wiechman]

Is Viton the preferred material for O-rings used to seal liquid cooled heads?

[Haufen]

Is Viton the preferred material for O-rings used to seal liquid cooled heads?
Viton would be a bit over engineered to just seal the coolant to the atmosphere, as almost any material will cope with lower temperature coolant. But if you're talking about domes / combustion chambers or exhaust flanges, then it might be beneficial indeed.

[wobbly]

Viton is the material of choice for the inner ring where it seals the chamber to the cylinder top.
But around the outside where it seals only water ,normal O rings are fine.

[Flettner]

I've have a viton O ring in my air cooled 350 head for over 70 hours. Never leaked.I might be wrong I think its a silicon Oring
Both good for high temps

[FastFred]

Thomas is really keen to CC the engine. The best way would be to take the engine out of the bike so it can be levelled up and CC’d through the sparkplug hole.

Looking at the picture it looks like TeeZee was using an "O" ring for a head gasket on his air cooled engine from the very beginning. Maybe Thomas suggested it to him. Pretty sure someplace he said it was a Viton "O" ring.

329674 ... 329675

[lodgernz]

Looking at the picture it looks like TeeZee was using an "O" ring for a head gasket on his air cooled engine from the very beginning. Maybe Thomas suggested it to him. Pretty sure someplace he said it was a Viton "O" ring.

329674 ... 329675

Looks more like a copper ring to me. Often used in racing foul-strokes.

[F5 Dave]

Well Fred would know being Robs right hand
Man

Viton is dark green almost black. Used it for decades as head gasket. Even a smear of red silicon rtv will suffice as outer gasket. Use easily machined round groove on inner and rtv on outer. Never had a failure in 20 + years.

[TZ350]

Yes, Viton, there are different grades (different colours) but I just used a bog standard (black looking) Viton O ring as a head seal on the air cooled motors. No failures, only unfortunate moment was when I tried a proper head gasket and still had the O ring in place. 30 hp on the dyno and the head gasket failed never had a problem with an O ring.



329686

Well that did not go so well, spat the head gasket.

[1948rod]

I have been made aware of dangers of Viton when heated or burned as in fan belts on burnt cars being dangerous. Since then I don't handle the used o rings in my exhausts. Possibly over cautious. If one was given a clean sheet to build an engine possibly wobbly on a new Kz would it be possible to extend the exhaust side of the cylinder especially the ex. Nozzle to a length that could house the required shape and be cooled the full length for cool charge to re enter the cylinder.

[MENTAL490]

Concentrated H2O2 was used in the V2
Jet packs were also H2O2.
The kiwi version is powered by four CR500's

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

Damn thats a bit more ambitious than my join 2 cr500s and throw it into a gsxr250 frame i had.

[MENTAL490]

Viton is the material of choice for the inner ring where it seals the chamber to the cylinder top.
But around the outside where it seals only water ,normal O rings are fine.

Viton has no oil products in it, i used it a lot in designs for BOC oxygen parts its pretty good up 200c but no good under -60c but some how i dont think it would get that cold here.

[jamathi]

I have been made aware of dangers of Viton when heated or burned as in fan belts on burnt cars being dangerous. Since then I don't handle the used o rings in my exhausts. Possibly over cautious. If one was given a clean sheet to build an engine possibly wobbly on a new Kz would it be possible to extend the exhaust side of the cylinder especially the ex. Nozzle to a length that could house the required shape and be cooled the full length for cool charge to re enter the cylinder.

Lengthening the exhaust duct and cool it very well is one of the things I regret not having tried!
I had the idea in 2007, but did not try it because I was planning to retire...
Almost certainly it will give e good power improvement!

[jasonu]

Well Fred would know being Robs right hand
Man

Viton is dark green almost black. Used it for decades as head gasket. Even a smear of red silicon rtv will suffice as outer gasket. Use easily machined round groove on inner and rtv on outer. Never had a failure in 20 + years.

I used viton o rings for inner and outer head seals in the water cooled KERG. They were a red/tan color. I replaced them around twice a season just because. Never had a failure.

[guyhockley]

Damn thats a bit more ambitious than my join 2 cr500s and throw it into a gsxr250 frame i had.

Engine pics:

http://iffitech.com/project/martin-aircraft/

They've gone for Rotron engines now so the V4s should be up for sale at a bargain price! (Yeah, right...)

[Grumph]

Husa put these up way back I think.When i was unable to. There was quite a lot of Christchurch involvement in those motors - at least early on anyway. Has anyone in the NZ bike scene ever come across this iffitech lot ?

[husaberg]

Husa put these up way back I think.When i was unable to. There was quite a lot of Christchurch involvement in those motors - at least early on anyway. Has anyone in the NZ bike scene ever come across this iffitech lot ?

No but on the link above the cylinders in the background of the link above look to be CP industries liger
329705
http://www.cpindinc.com/pub/view_product/63?lm=5&name=3101-9779-144
ie same crowd that does the big bore banshees as well as CR500's

Also the cases apear to have a awesome finish esp the one in the background
looks to me like diecast.
329715
I also note the piston ring crase seal
329706

Here is the staff for ifitech
http://iffitech.com/#staff-module
They even have one of charlies angels.:facepalm:
hes the guy that did this, it looks as if its been rebranded.
http://www.stuff.co.nz/motoring/5614635
http://iffitech.com/wp-content/uploads/2016/04/086-089_Denver-Lawson-Web.pdf

Maybe rob should call in and visit them for a look.

[Grumph]

The prototype cases werre CNC, but I see at least one part line on those cases so someone spent the money on dies...

[Flettner]

Why would they move away from the V4?
Because they had vibration issues (breaking sensors) and crank twisting issues. The flying Webb is not a good idea. The cranks had a short life. I was invited down to Martin Aviation to look at fitting a bolt on balance shaft, but nothing happened as Glen left not long after this.

[husaberg]

Why would they move away from the V4?
Because they had vibration issues (breaking sensors) and crank twisting issues. The flying Webb is not a good idea. The cranks had a short life. I was invited down to Martin Aviation to look at fitting a bolt on balance shaft, but nothing happened as Glen left not long after this.
Short life and not rebuildable either, plus it has split bearings not normally a good idea for anything other than cheap rebuildability
But as I see the pins have been welded in. Which seems to negate the need for the split bearings.....
To me it looks as if there is not enough support arround the crankpin. which is likely why they needed to weld it in.
I am not sure why they needed to try and save so much space with the flying web set up,(other than rocking couple) all they needed to do was configure it like a NSR500.
http://www.geocities.jp/noda_keni/h/00nsr500/00nsr-17.jpghttp://i257.photobucket.com/albums/hh231/thofton/nsr500ENGINE01.jpghttp://i.imgur.com/3hv8Ao3.jpg
Actually even fire 90 would work or two up. plus not be that much wider.
A 2 liter plus v4 2 stroke is going always to tingle a bit.

[wobbly]

The idea floated about lengthening the Ex duct and increasing the cooling in this area is exactly what i will be advocating for the new kart engine design.
Along with a shape change to include the Aux duct ears right down to the header joint and water having access into the back of the bolt on spigot.
I leave in a week.

Funny how well constructed bullshit goes a long way with advertising - " Denver is well known in the two stroke industry " no he's not, as he has never actually achieved anything
apart from the dubious skill of being extremely capable of consuming huge amounts of other peoples money.
And I have strong suspicions that its way more than just coincidental the Martin inventor left the premises, a very short time after he arrived.
Better shutup before I am accused of being angry again.
But talking of consuming other peoples money,where is Luc.

Edit - here is the optimum duct geometry as I have found in EngMod.

[Grumph]

Funny how well constructed bullshit goes a long way with advertising - " Denver is well known in the two stroke industry " no he's not, as he has never actually achieved anything
apart from the dubious skill of being extremely capable of consuming huge amounts of other peoples money.
And I have strong suspicions that its way more than just coincidental the Martin inventor left the premises, a very short time after he arrived.
Better shutup before I am accused of being angry again.

Never that surely...

There have been a very few like that in NZ thankfully. I'd heard much the same from a couple of people who had been involved.

So more "iffy" than "tech" then....

[oldjohnno]

A bit off topic perhaps but I'm a bit puzzled by a MachIII Kaw triple I'm working on at the moment. It always starts fine and will idle fine, runs OK for maybe 30 secs to a minute but then sounds, feels and smells very rich. Stock VM28s. I've checked the obvious things - float level is OK and there's no drooling from the standpipes, jetting is sane, enrichment plungers are seating. Ignition checks out fine, air cleaner has no effect whether fitted or not. Needles and needle jets have been replaced and are stock sizes. Checked for fuel leaking through fuel tap vacuum diaphragm. It'll rev OK when cold (I guess because it'll tolerate the richness cold) but once it's warm I can hold the throttle open with no load and it'll only go to maybe 4 or 5k and does the "baa ba baaaa ba" loaded up routine, as soon as I close it it idles fine. Turning the fuel off makes the engine come to life just before the bowls run dry. Carbs are clean and both main and pilot air bleeds are clear. I put 10psi into each cylinder in turn, suspecting crank seals but no sign or sound of leakage from either the neighbouring cylinders or the gearcase. Engine is stock as is the jetting. It always idles fine even if it's hot but goes rich as soon as the throttle is opened. The centre and right hand cylinder run richer and cooler than the left one when the throttle is opened.

Can crank seals check OK with a pressure test but still leak with the engine running? I can't work out where all the fuel is coming from - have I overlooked something with the carbs? It's acting like the main jets have fallen out...

[Grumph]

Does that model have brass floats ? Punctured ?

Rig the carbs up, off the bike, with a test tank and see if they dribble in running attitude.

[peewee]

No but on the link above the cylinders in the background of the link above look to be CP industries liger
329705
http://www.cpindinc.com/pub/view_product/63?lm=5&name=3101-9779-144
ie same crowd that does the big bore banshees as well as CR500's
.

husa those four barrels on the back table are just standard cr500. years ago I called calvin on the phone about the liger (before it was even available to the public yet ), he was a nice guy and bless his heart but I don't understand his way of thinking. I believe the smallest bore was 95mm or something like that. why not keep a smaller bore and have better transfer passage geometry, not to mention I wonder if the exh passage was miles to short, and those sqaure aux exh ports :facepalm:

[husaberg]

husa those four barrels on the back table are just standard cr500. years ago I called calvin on the phone about the liger (before it was even available to the public yet ), he was a nice guy and bless his heart but I don't understand his way of thinking. I believe the smallest bore was 95mm or something like that. why not keep a smaller bore and have better transfer passage geometry, not to mention I wonder if the exh passage was miles to short, and those sqaure aux exh ports :facepalm:

They look flatter around the exhaust port then i remember a std Cr500 being, they also appear to be coated? which is why i assumed calvin
I guess the reason Calvin concentrates on big bores is because thats what people want. USA market =bigger just has to be better.
I would rather have a balance shaft, a 6 speed gearbox and power valve a way to reliably start it when hot and a decompressor.

[peewee]

unfortunately ive had way more cr500 than I care to admit ( back table theyre just run of the mill cr500 with no exh flange installed). just sold my last cr500 two days ago (thank the good lord). poor kid has probly already ran it into a tree and hurt himself. the yellow coating is cosmoline I think they call it, applied at the factory. prevents the iron bore from rusting until it gets in the hands of the customer

ya the liger is a classic case of "when in doubt, bore it out". but I guess you have to supply what the people want :confused:

[peewee]

while im here what do you guys think of this type of chamber ? ive got to take alittle more material out of the ktm head because com ratio is still very high ( its a spherical chamber now). cutting a bathtub style would add a bit more volume.

[wobbly]

As far as chamber shape is concerned yes, a bathtub works real well with a domed piston, but the first thing to do is get rid of the radius into the chamber from the squish.

And the CP Liger casting had a boss above the Ex duct that could have been a power valve mounting face.
Calvin ,bless him ,was a genius at casting technology, but relied heavily on a closed cabal of trusted "tuners" for his advice on 2T technical detail, and none of them had any idea about actually calculating the blowdown
capability of a design.
The huge Ex port ducts and really dumbarse tiny square Aux ports were testament ( in the god botherer context ) to that advice.
But the biggest issue in terms of " rightness " was that usually all of the CP designs were well conceived in their original bore size, but were routinely bored to buggery as is the Merican way.
There I go being an angry little man again - sorry.

[F5 Dave]

Don't worry Scott's not usually moonshined of a Sunday.

[peewee]

but relied heavily on a closed cabal of trusted "tuners" for his advice on 2T technical detail, and none of them had any idea about actually calculating the blowdown
capability of a design.
.

slowly but surely a few are catching on. still every now and then youll see a main exh ten miles wide below the transfers. and plenty are still convinced the exh floor must be flush with piston top at bdc.

[seymour14]

Don't worry Scott's not usually moonshined of a Sunday.

He's away racing, opposite of talking...:niceone:

[jasonu]

He's away racing, opposite of talking...:niceone:

Bazinga!!!!!

[FastFred]

Scott was riding a borrowed bike at Mt Wellington. Jason Hearn riding a GPR bike made a touch down in the 28's and with bursts of brilliance was keeping Nathaniel very very honest, great racing. In the end it was smooth consistency that won the day for Nathaniel. Nathaniel later took the GPR for a ride and he was very impressed with it.

[seymour14]

Scott was riding a borrowed bike at Mt Wellington. Jason Hearn riding a GPR bike made a touch down in the 28's and with bursts of brilliance was keeping Nathaniel very very honest, great racing. In the end it was smooth consistency that won the day for Nathaniel. Nathaniel later took the GPR for a ride and he was very impressed with it.

The racing looks fantastic on the Auckland facebook, lots going on midpack as well.

[oldjohnno]

Does that model have brass floats ? Punctured ?

Rig the carbs up, off the bike, with a test tank and see if they dribble in running attitude.

Floats were OK. Turns out I'd failed to notice that in 2 of the carbs the little pin that registers in the keyway of the needle jet was missing. Fuel was travelling through the hole, up the annulus around the needle jet and out via the emulsion hole. Like an extra main jet.

Time for new glasses, obviously.

[Nath88]

Update to the redesign of my build, made some radiator guards that include mounting points for the fuel system, which is held in place with 3D printed rubber parts and zip ties. Fuel system now has a pressure damper, 20cc of air in a CO2 canister. Turns out CO2 canister threads are the same as some brake lines. Just need to bend the hard line around the front of the frame between pump and filter. Will be making noise again this week, hopefully more reliably.

Also added a pressure take off in the pipe near the exhaust port, should give a better signal for tuning than from the PV vent hose.

329783
329785329784

[husaberg]

Update to the redesign of my build, made some radiator guards that include mounting points for the fuel system, which is held in place with 3D printed rubber parts and zip ties. Fuel system now has a pressure damper, 20cc of air in a CO2 canister. Turns out CO2 canister threads are the same as some brake lines. Just need to bend the hard line around the front of the frame between pump and filter. Will be making noise again this week, hopefully more reliably.

Also added a pressure take off in the pipe near the exhaust port, should give a better signal for tuning than from the PV vent hose.

329783
329785329784

Likely BSP ,is what a lot of Industry thread are.
British Standard Pipe.

https://www.youtube.com/watch?v=tN9EC3Gy6Nk

[mr bucketracer]

Scott was riding a borrowed bike at Mt Wellington. Jason Hearn riding a GPR bike made a touch down in the 28's and with bursts of brilliance was keeping Nathaniel very very honest, great racing. In the end it was smooth consistency that won the day for Nathaniel. Nathaniel later took the GPR for a ride and he was very impressed with it.it was won on the start but race 2 jase realy was all over nat , great race from both

[TZ350]

329817

My engine runs a 20mm alloy spacer in the header. Encouraged by 1948rod and Jamathi's comments about a water cooling an extended exhaust duct this spacer looks like a good prospect for a water cooling jacket.

[adegnes]

329817

My engine runs a 20mm alloy spacer in the header. Encouraged by 1948rod and Jamathi's comments about a water cooling an extended exhaust duct this spacer looks like a good prospect for a water cooling jacket.

Gas engine rc boat.

http://www.modelgasboats.com/media/kunena/attachments/68/DSCF0922.JPG

[wobbly]

Getting water up to the back of the spigot works very well, I have since made the slots full depth to cool the whole duct to the end.
Having the water inlet/outlet arranged on a spigot with a pressure differential would promote flow and make the setup work even better, if you can
do this in your project.

[SwePatrick]

Just have to show you what a friend of mine is building for me.
My 212cc project needs a new crankshaft as mine is leaving things to wish for.
There will be inserts to fill up the voids.
The lower 'small' hole is for fineadjusting the balancefactor easier later on.


329823

[mr bucketracer]

Just have to show you what a friend of mine is building for me.
My 212cc project needs a new crankshaft as mine is leaving things to wish for.
There will be inserts to fill up the voids.
The lower 'small' hole is for fineadjusting the balancefactor easier later on.


329823nice work! looks like you have a good mate:2thumbsup

[SwePatrick]

Yes. i can do the same things myself as i have the same profession.
But ABB who i work for have strict securityrules about carrying things through the gate.
If they catch you it can lead to one getting fired.
So i better let people that takes no risks, do it.
He is on facebook if you want to look at more things he has done, search for the name in the picture =)

Rgds.

[teriks]

Yes. i can do the same things myself as i have the same profession.
But ABB who i work for have strict securityrules about carrying things through the gate.
If they catch you it can lead to one getting fired.
So i better let people that takes no risks, do it.
He is on facebook if you want to look at more things he has done, search for the name in the picture =)

Rgds.
Local guy?
Looks like someone Id like to get in touch with ;)

[SwePatrick]

He lives in 'Järfälla' Sweden Stockholm.
And he does quite a lot of work for foreign guys.

Don´t hesitate to get in touch with him, he´s a nice guy.
Very professional.

Edit: saw now you are located in Sweden. ;)

[TZ350]

329859

Interesting what you find in the shed when you have a clean up.

An Aprilia cylinder TF100 conversion idea for anyone who might be thinking about a F4 110 2T

329858

The two rear cylinder studs could be through studs located in the crank case.
The two front cylinder studs to be located in the spacer plate
The front of the spacer plate would be held down to the case by cap screws
The rear of the spacer plate is held down by cap screws into the existing case stud holes.

329857

The GP case with the original stud holes plugged with alloy rod glued and screwed into the old stud holes.
Three cylinder studs are in the case. One cylinder stud in the spacer plate and the plate itself held down with a cap screw.

[teriks]

He lives in 'Järfälla' Sweden Stockholm.
And he does quite a lot of work for foreign guys.

Don´t hesitate to get in touch with him, he´s a nice guy.
Very professional.

Edit: saw now you are located in Sweden. ;)
Closer than you think, in Ludvika even ;)
Already contacted him/them, good impression so far.

[TZ350]

The gear box is fixed and the new oil pump seems to be reliable. The radiator and water pump holds the temperature to 42 degrees. So a few issues seem sorted.

329948

I have been using a short throttle body in the belief shorter the better, but it may be a mistake.

329951

Because there is a period between 6 to 7,000 rpm of violent oscillation just before coming onto the pipe. Even cranking the power valve down to ridiculous amounts did not help.

Red line TPS
Blue line O2 sensor
Brown line Small injector
Yellow big injector
Top Green line is RPM

329949329950329952

The violent oscillation in the inlet reminds me of the same issues I had with the plenum. And it was cured by making the inlet tract longer.

I did not expect it to be a problem with EFI, where you can squirt the fuel into the transfers at just the right time, but apparently it can be.

329947
Not sure about where to go from here, maybe back to under piston injection. It still had problems but not so severe.

[teriks]

I have been using a short throttle body in the belief shorter the better, but it may be a mistake.

I have found the same, but then I can make the inlet ridiculously short on my small stuff without throttle.


Not sure about where to go from here, maybe back to under piston injection. It still had problems but not so severe.
Could you do a quick and dirty test lengthening the intake with a pipe fitting on the OD of the ball valve housing and see if and how it effects that region?
Cant judge if there is a simple way of fitting a pipe there from the pictures...

[Flettner]

[QUOTE=TZ350;1131040234]The gear box is fixed and the new oil pump seems to be reliable. The radiator and water pump holds the temperature to 42 degrees. So a few issues seem sorte

I have been using a short throttle body in the belief shorter the better, but it may be a mistake.
Because there is a period between 6 to 7,000 rpm of violent oscillation just before coming onto the pipe. Even cranking the power valve down to ridiculous amounts did not help.

The violent oscillation in the inlet reminds me of the same issues I had with the plenum. And it was cured by making the inlet tract longer.

I did not expect it to be a problem with EFI, where you can squirt the fuel into the transfers at just the right time, but apparently it can be.



I think you might find this is where the sliding valve housing might be useful.

[FastFred]

Could you do a quick and dirty test lengthening the intake with a pipe fitting on the OD of the ball valve housing and see if and how it effects that region?...

Something like this Norton Rotary variable inlet ...... :drool:

<div style="position:relative;height:0;padding-bottom:56.25%"><iframe src="https://www.youtube.com/embed/48foOHK2tyA?ecver=2" width="640" height="360" frameborder="0" style="position:absolute;width:100%;height:100%;left:0" allowfullscreen></iframe></div>

Truly astounding.

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[WilDun]

Something like this Norton Rotary variable inlet ...... :drool:

As far as noise is concerned, those things would have rivalled the pre war DKW two strokes! - I had the good fortune (misfortune) to hear them up close - wasn't funny!
I didn't realise they had extendable inlet tracts.

[Frits Overmars]

Something like this Norton Rotary variable inlet ...... :drool:
As far as noise is concerned, those things would have rivalled the pre war DKW two strokes! - I had the good fortune (misfortune) to hear them up close - wasn't funny!
I didn't realise they had extendable inlet tracts.And those rotary Nortons were silenced!
329953
While we're on the rotary subject, how is this for a lovely sound?
http://www.youtube.com/watch?v=Go3Fgd1wgic
http://www.youtube.com/watch?v=9jAngoCbOMg#t=0m8s
This Mazda 787B also had trombone inlets (at 4:48 in the first video) and an exhaust silencer, deemed necessary even by the most seasoned enthousiasts.

[Nath88]

329951

Because there is a period between 6 to 7,000 rpm of violent oscillation just before coming onto the pipe. Even cranking the power valve down to ridiculous amounts did not help.

Red line TPS
Blue line O2 sensor
Brown line Small injector
Yellow big injector
Top Green line is RPM

Looks like you have a fair bit of lash in the drivetrain with the engine speed jumping around like that. At 15% throttle it looks like the switching between the small and big injector is causing the misfire, possibly injector settings are a bit squif and when it switches over it jumps richer or leaner. Is it just a straight RPM switchpoint with no hysteresis?
At 50% throttle it looks like it's going too rich as the revs climb and pulsewidth goes up, then stops firing, revs fall, pulsewidth drops, then it kicks on again. I think the problem is in fuel delivery not gas dynamics. Guessing it doesn't do it with the carb? Food for thought.

Also there is a big lambda delay on these things off the pipe and it always swings lean when misfiring. Is the motor on the rich limit/four stroking? Your lambda values look ok, but they can appear lean when air is short circuiting the motor. My motor has a 'rich' point between 4500-5500rpm, 50% throttle and up. I think it's the anti-resonance point of the pipe. Shows the same 12.6:1 AFR as other points but its on the verge of four stroking, heaps of blue smoke, similar to how 10.8:1 behaves (which is about the rich 4-stroking limit on mine when on the pipe). So i've tuned that area to be about 1.5 points leaner. I am yet to do a plug chop at that point to check, I'm yet to do any plug chops actually, luckily the YZ isn't too picky on mixtures.

I put some hours on my thing on the weekend, did about 150km around the city and mountains with the new fuel system. It was running a fair bit richer for the same fuel pressure, so the pressure at the injector must be more constant. Also the VE table is starting to look how I would expect, a lot more natural and smooth, apart from the weird anti-resonance peak. Maximum injector duty cycle of 80% at 9200rpm, full throttle, 145km/h uphill. It used to do 150km/h with the carb on the flat, but I haven't leaned the EFI out past peak yet. Next on the list is to get the target AFR table right to maximise power, will probably do a bunch of plug chops to see what the motor likes, maybe hit up the dyno.

[TZ350]

There is a lot to think about here, I think you are definitely on the money about what may be wrong. Very encouraging to hear about you success's with the YZ.

[husaberg]

And those rotary Nortons were silenced!
329953
While we're on the rotary subject, how is this for a lovely sound?
http://www.youtube.com/watch?v=Go3Fgd1wgic
http://www.youtube.com/watch?v=9jAngoCbOMg#t=0m8s
This Mazda 787B also had trombone inlets (at 4:48 in the first video) and an exhaust silencer, deemed necessary even by the most seasoned enthousiasts.

Pretty sure the RC45 had a two postion intake length in later variant as well.
I was going to use the Mazda one though.n But you beat me
Toyota also used to have two stage intake length in early 4age engines (mr2 etc)
The cagiva F4 was designed to have one, not sure if it flowed through to production

f1 had them
http://scarbsf1.com/gallery/inlet_pict0019.jpg

Edit so did the R1 Never knew that
http://www.motorcycle-usa.com/photo-gallery/2007-yamaha/

[Flettner]

So did my Toyota Camry

[WilDun]

So did my Toyota Camry

Didn't Yamaha design the heads for Toyota?

[TZ350]

Didn't Yamaha design the heads for Toyota?

Yep, I had a twin cam turbo Toyota whose head had Yamaha on it so I guess Yamaha designed and actually made them too.

[husaberg]

Didn't Yamaha design the heads for Toyota?


Yep, I had a twin cam turbo Toyota whose head had Yamaha on it so I guess Yamaha designed and actually made them too.

They have a long history of designing not just heads but even complete engines for Toyota starting with the Toyota 2000 GT in the late 60's
Which was borrowed back by Yamaha to create the XS650.

[TZ350]

Looks like you have a fair bit of lash in the drivetrain with the engine speed jumping around like that.

Yes, true.


At 15% throttle it looks like the switching between the small and big injector is causing the misfire, possibly injector settings are a bit squif and when it switches over it jumps richer or leaner. Is it just a straight RPM switchpoint with no hysteresis?

Switching is determined by setting a minimum injector closed time that way you can more or less chose where the switch will occur depending on load/rpm and then there is an adjustable upper and lower ms value for hysteresis. I have been trying to have the small injector doing all the off pipe stuff.


At 50% throttle it looks like it's going too rich as the revs climb and pulsewidth goes up, then stops firing, revs fall, pulsewidth drops, then it kicks on again.

Very good point, I will look carefully at this when I get back to the dyno again.


I think the problem is in fuel delivery not gas dynamics. Guessing it doesn't do it with the carb? Food for thought.


It was definitely gas dynamics in the plenum with its short inlet. Wet fuel was blown out past the front wheel. But I guess that does not mean this is the same issue with the EFI system. But they both had the same blubbering symptoms before coming on the pipe.


Also there is a big lambda delay on these things off the pipe and it always swings lean when misfiring. Is the motor on the rich limit/four stroking? Your lambda values look ok, but they can appear lean when air is short circuiting the motor.

Yes it can be so rich that the lambda shows lean. I can see short circuiting, misfiring and four stroking will all show lean. The less effective the trapping efficiency the leaner the lambda will show even though the air/fuel ratio is correct.

I agree, clearly lambda needs to be interpreted a bit, depending on where in the power curve you are looking.


My motor has a 'rich' point between 4500-5500rpm, 50% throttle and up. I think it's the anti-resonance point of the pipe. Shows the same 12.6:1 AFR as other points but its on the verge of four stroking, heaps of blue smoke, similar to how 10.8:1 behaves (which is about the rich 4-stroking limit on mine when on the pipe).

So i've tuned that area to be about 1.5 points leaner. I am yet to do a plug chop at that point to check, I'm yet to do any plug chops actually, luckily the YZ isn't too picky on mixtures.

Also the VE table is starting to look how I would expect, a lot more natural and smooth, apart from the weird anti-resonance peak. Maximum injector duty cycle of 80% at 9200rpm, full throttle.

The anti-resonance rich point has always been there with my EFI efforts to a greater or lesser degree. I would have thought the power valve would have countered it but that does not seem the case so that is why my thoughts turned to the inlet resonance.

Interestingly things improved when the small injector on time was as wide or wider than the transfer open time. And injection end time was important, I guess so the injection squirt time covered the transfer window.

In the anti resonance area the closer to lambda 1 I got the richer the exhaust sounds.

Lots for me to think about, thanks for your input.

[Martin1981]

This Mazda 787B had an exhaust silencer, deemed necessary even by the most seasoned enthousiasts.

Oh this R26B...Hell of an Engine! Somebody once said it sounds like an f1 engine on steroids :lol: Imagine the sound if it could rev to 15000rpm or so....Frits, why does it only rev to about 9000? Is it because of the complicated Way the "pistons" have to go in the wankel engine in comparison to the simple up and down moving in a normal engine?

[Frits Overmars]

Oh this R26B...Hell of an Engine! Somebody once said it sounds like an f1 engine on steroids :lol: Imagine the sound if it could rev to 15000rpm or so....Frits, why does it only rev to about 9000? Is it because of the complicated Way the "pistons" have to go in the wankel engine in comparison to the simple up and down moving in a normal engine?I 'd say the rotors in a Wankel move in a more straightforward way than the reciprocating pistons that we have all become used to.
A Wankel's revs are limited by flame speed; the combustion chamber has a terrible shape with end pockets everywhere and a flow constriction between the two spark plugs. Moreover, the chamber's bad surface/volume ratio is responsible for a lot of heat losses and an unhealthy fuel appetite.

Apart from that, I love Wankels. They may be four-strokes but they sure know how to open their exhaust ports with a bang; not like those poppet valves that open with an initial velocity of zero, but like a two-stroke that opens its exhaust port with maximum piston velocity. Hence the strong useful pulses and the glorious noise.
I've even got a works racing engine. Not the four-rotor B787B (I wish!) but a twin-rotor 13B turbo for touring car racing. The turbo doubles as a fairly effective silencer. Just as well...
329970 329971

The small intercooler in the pictures is the standard hood-mounted RX7 cooler; just substituting it with a larger front-mounted intercooler brought 60 hp more.

[oldjohnno]

...I've even got a works racing engine. Not the four-rotor B787B (I wish!) but a twin-rotor 13B turbo for touring car racing. The turbo doubles as a fairly effective silencer. Just as well...


I always thought the turbo's primary role was to catch the bits of apex seal...

[WilDun]

Yes they were certainly interesting and had some good qualities like no reciprocating forces (ie no piston reversals, also smoothness) but the disadvantages mentioned outweigh all this and I think Mazda have finally acknowledged it.
I can remember (all I do these days is remember!:laugh:) driving home from work and knowing that there was a Mazda Rotary up ahead even though I couldn't see it! probably much more pleasant driving behind a Trabant!
It's a pity really but as I said earlier lets get back to our little old two strokes and develop them more (in the bucket scene), the "simple" two stroke probably has a brighter future, but that's still a bit difficult to predict through the "haze"! :rolleyes:

[Nath88]

Took the bike for another ride last night. Leaned it out a fair bit in the high load areas, a little in the cruise range, and a bit past peak rpm. Made the bike very happy! Was going to be a short one but ended up cruising around the streets for about half an hour because it was running so well, bike never missed a beat. 'Lean' cruise is a funny feeling, it's very smooth, like a scooter, then when you open the throttle it just rolls into normal YZ250 in every way.
329972

The VE table ended up looking like this, load areas tuned by wideband lambda feedback.
329979

This is the exhaust pressure system in action. Just before the cursor position, I blipped the throttle to 20% and the motor didn't respond (no exhaust pulse = no fire), that's the area I need to work on the most, probably a bit rich at closed throttle at that RPM, lambda offers no useful feedback so it has to be tuned by feel. After the cursor, when opening the throttle to 20% for a little longer, the motor has time to clear, then the injector pulsewidth more or less follows the exhaust pressure. You can see it four-strokes a bit then runs clean. Then opening the throttle to 15% goes into constant light throttle four-stroking, again, fuel following the exhaust pulses.
329973

[F5 Dave]

I 'd say the rotors in a Wankel move in a more straightforward way than the reciprocating pistons that we have all become used to.
A Wankel's revs are limited by flame speed; the combustion chamber has a terrible shape with end pockets everywhere and a flow constriction between the two spark plugs. Moreover, the chamber's bad surface/volume ratio is responsible for a lot of heat losses and an unhealthy fuel appetite.

Apart from that, I love Wankels. They may be four-strokes but they sure know how to open their exhaust ports with a bang; not like those poppet valves that open with an initial velocity of zero, but like a two-stroke that opens its exhaust port with maximum piston velocity. Hence the strong useful pulses and the glorious noise.
I've even got a works racing engine. Not the four-rotor B787B (I wish!) but a twin-rotor 13B turbo for touring car racing. The turbo doubles as a fairly effective silencer. Just as well...
329970 329971

The small intercooler in the pictures is the standard hood-mounted RX7 cooler; just substituting it with a larger front-mounted intercooler brought 60 hp more.
Sorry Frits you seem to have posted the wrong photos. That appears to be a helicopter crash.

[Frits Overmars]

I see what you mean Dave. A bit clumbered, isn't it? But if you remove everything that you don't need for racing, what remains is a very compact engine.

[F5 Dave]

I helped move a 12A (I think thats what they are called) across the garage floor. It was like the rest of the car was still attached.

[Peter1962]

I helped move a 12A (I think thats what they are called) across the garage floor. It was like the rest of the car was still attached.

That can be fixed. Racing Beat is producing aluminium housings and flywheel. http://www.racingbeat.com/RX7-1975-1985/Rotor-Intermediate-Housings.html Saves 50 to 60% of the weight of the original cast iron housings.

[breezy]

Frits, can you tell me what type and name of race fuel was actually used in your world champion winning aprilia 125 race bikes. thanks, nigel.

[Peter1962]

Frits, can you tell me what type and name of race fuel was actually used in your world champion winning aprilia 125 race bikes. thanks, nigel.

breezy, I don't think that Jan Thiel will feel OK with the assumption that he is not the father of the winning aprilia 125.

[Frits Overmars]

Frits, can you tell me what type and name of race fuel was actually used in your world champion winning aprilia 125 race bikes. thanks, nigel.

breezy, I don't think that Jan Thiel will feel OK with the assumption that he is not the father of the winning aprilia 125.You are quite right Peter.
Breezy, this is one of those seemingly simple questions to which there is not just one simple answer.
For starters, there was a leaded era followed by an unleaded era. The leaded fuel was 130 octane, the unleaded was a mandatory 102 octane if memory serves.
Then there is the fact that the various world champion winning machines were leased by various teams, with various fuel and oil manufacturer's contracts.
The Italian Agip fuel probably was most frequently used.

[TZ350]

Page 1710 ..... :jerry:


Here's a product called Composimold being used by a Thomas H who appears to cruise this forum, if not only the ESE thread. It's far more expensive though at $66NZD + $30 shipping for 20oz of the stuff -_-

http://bucketracing.blogspot.co.nz/2017/01/port-molds-with-composimold.html

https://4.bp.blogspot.com/-xXoJKt0qIGw/WI5B3c9h3zI/AAAAAAAAAfs/IW5qOcnbqg0ULUYPwarY6ArSSr65ZPM5wCLcB/s400/Port_Molds3.jpg


Google.co.uk came up with:

Vinamold - Best Value - - Direct from the manufacturer‎ (http://www.extruflexonline.co.uk/vinamold.html)

Ad<cite class="_WGk">www.extruflexonline.co.uk/vinamold</cite>‎
Large UK Vinamold Stocks, 24 Hr Delivery

4 hardness types?

I thought Vinamold was american.


ATAC in general works much lower down the powerband than a powervalve does, and cannot be gradually reduced in its effect.
It works very well to reduce the effect of the pipes return pulse being way too early at lower rpm, but this effect kills the power badly as soon
as the pipe efficiency starts to rise - thus the valve connecting the Helmholtz chamber to the pipe must be switched instantly at a specific rpm.
In a 125 race engine the ATAC would be off at around 8000 rpm, where as the PV may not be closed fully to within 1000 rpm of peak power.


Detonation.

This started te be a problem when 50cc engines started giving more than 17HP, around 1975.
At the time I thought this was a limit on engine power.
Nikasil plated cylinders were very prone to detonation.
Because of the rounded off edge at the top.
At Minarelli/Garelli I solved this problem by sticking the cylinder head insert 3mm into the cylinder.
A good solution, used for many years.
But at Aprilia we found an even better solution: plate the first 5 mm around the bore at
the top of the cylinder.
Later this was machined to a very sharp corner, and this eliminated completely the unnecessary
'dead room' at the top of the cylinder, it also gave 0,3HP more.....
A little bit of still remaining detonation was eliminated by modifying the inner wall of the
transfer ducts, cooling the piston.
But part-throttle detonation remained a problem.....
Which we never had on the dyno!
On the photo you see a piston after a 54HP run...
As long as you keep the throttle wide open a 2 stroke doesn't brake down!


The Aprilia RSW was a ROTAX design.
Later Aprilia made their own engines, but closely followed the original ROTAX design.
Except some small details.
Now they could say everything was 'made in Italy'
Which had financial 'advantages' for certain people!
Who could now take a bribe from the suppliers......as is usual in Italy.
So I am certainly not the 'father' of the Aprilia engines!

I was responsible for cylinder development, starting with 46,5HP and ending with 54HP.
Later, when working at DERBI, I had the idea of making the RSA engine, and made the first sketches.
The actual design was, of course, done on a computer by a professional designer.
Although it won several world championships I don't consider it a big success...

Aprilia always used AGIP fuels and oils for dyno testing
102 octane.
We were given face masks and special gloves, which we never needed for the 130 octane fuel.....


When modifying a cylinder measuring duct sizes is not easy, especially in the curves!
You can see our solution to this problem on the photo....
Round 'sensors' fitted to a piece of welding rod!
We had them from 7-7,25- 7,5 and so on until 28mm.
Behind the cylinder, in the wooden block.



330096

I did not design this engine, nor did Frits.
It was Aprilia who wanted their 'own' engine.
The designs and the engines were made by ROTAX.
I still consider a V engine with a single crankshaft as the best solution!!


A Dutch friend of mine, Thijs Hessels, had improved the original cylinders by epoxying the outside curve, and giving the mixture a more upward direction. His private Aprilia proved faster than the 'works' bikes. The Aprilia racing boss, Jan Witteveen, demanded that Thijs should give those cylinders to him. Otherwise Thijs would not be able to get any more spare parts for his bike!!


I started working with an existing engine, a ROTAX, with an existing cylinder and exhaust pipe.
During the year dozens of different exhaust pipes were tested.....

330100

The original Rotax A duct was something like this....

With this modification a ROTAX cylinder gave 46,5HP instead of the normal 44.
This happened in 1994, a year later I started working for Aprilia.
They were still epoxying ROTAX cylinders, but had decided to make their own cylinder.
The development of this cylinder was to be my work.
This cylinder was called the APC, and was destined for all 125 and 250 private riders.
It gave the same 46,5HP, but of course without epoxy.
I got the oldest dyno there was, and had to learn to use the computerized system.
As I had never touched a computer before it was not so easy.
But I quickly learned, the system was very precise and repeatable.
I was given the casting models and had to go to the foundry to have some cylinders cast,
While waiting for the castings to be machined I worked with ROTAX cylinders.
I won some power by making the auxiliary ports bigger, but they were already too high I thought.
So I made sure the APC cylinders had lower auxiliary ports, and I also filed their sand cores to make the exhaust duct a lot smaller, as I had already, successfully, tried on some ROTAX cylinders.
There were some small mistakes in the casting models, they were quickly corrected.
And then real development could begin!
I started by making the B-ports and ducts as wide as I could, and this improved bottom power, without losing at the top.
And I had one casting with a narrower C-port, made by filing the sand core.
Here the B-ports could still be made wider, and it proved to be the best cylinder of the lot.
So we got to 48HP
We also bought a lot of dentist tools and burrs, and a filing machine.
And a flow bench.
Power improved by making the auxiliary ducts longer, and wider.
But at a certain point we made a hole, ending up in the cooling water space!!!!
To cure this the casting model had to be modified.
I also had a wooden model made for use on the flow bench.

330098

To determine the best size of the auxiliary ports and ducts.

330099

They seemed to 'like' having a downward angle.
The casting model was modified in this way, and so we reached 49HP.

330097

I decided to try to make the exit of the exhaust duct, and the flange, a bit wider, and won another 0,6HP


I discovered that making the underside of the transfer ports even with the piston in BDC
was very important: considerably more power, less detonation and far better piston cooling.
We started to have the exhaust ducts CNC machined in 1999 I think.
But first we had to overcome the new fuel regulations in 1998
102 octane had to be used instead of 130 octane.
We expected BIG problems.....
But within a couple of month's we had more power than before!
The compression ratio was lowered from 19,5:1 to 16:1
And the tailpipe restrictor was made 0,25mm bigger.
Then a very serious combustion chamber development was started.
The result was that parallel squish was the best, with a squish height of 0,75mm
Less squish height would give more torque but less revs.
At 0,45 the piston touched the head....
Then a head insert with a much wider squish band (50% of cylinder surface) was tried.
And that proved to be the final touch.
We now had more power than with the 130 octane fuels, and less problems.

330092

The sharp edge between combustion chamber and squish band proved to be very important.
Even a small radius would give 0,5HP less..



Vannik or anyone that knows stuff, I don't have your software so don't know this, if combustion does not happen, what happens to the air velocity in the combustion chamber at / after TDC? Does the rapid turbulence in the combustion chamber stop and reverse at some stage, as the squish starts to open up again? Or does it keep going but just slow down a bit?

The turbulence is caused by the breakdown of the main flow. Because of the viscosity (in effect the internal friction of the fluid) the main flow progressively break down into ever smaller eddies and if left long enough all the main flow and all the eddies will stop. The main flow is from the transfer port loop and a stronger better directed flow with more kinetic energy can generate a lot of turbulence before it stops. If you have weak flow by the time combustion happens you need the extra flow from the squish to generate extra turbulence to get good combustion.

On the other side if you have strong flow and thus good turbulence the extra turbulence can speed up the combustion too much and you loose power but mostly overrev. This explains why engines do not always behave the same to squish changes. Good engines use squish to minimize end gas to stop detonation while poor engines use squish to add turbulence.

So to answer the question: Turbulence cannot reverse, it is a one way street after creation. The bulk flow with the squish opening will loop slower and slower, both because of the increase in volume and because it keeps generating turbulence until it completely stops.


Pistons:


We had cast and forged pistons.
Cast pistons gave slightly more HP, but sometimes cracked.
0,8mm piston rings gave more HP than 1mm rings.
As the auxiliaries and transfers overlapped each other a certain power los was caused by this.
So closing the pin hole in the piston was tried.
There were many solutions that were tested, but they all caused some trouble.
In the end the best, and most reliable, solution was welding then closed.
This was very well done by PANKL in Austria, and never caused any trouble!




Do you mind me asking why do you think cast pistons made more hp than forged? Because forged pistons had a tendency to 'bend' their top inwards.


Transfer ducts.

Many transfer ducts with small differences were tried.
We found more power by enlarging the A-port in the direction of the exhaust.
Only the lower half, but it was important to give the A-duct an inclination away from the exhaust!
The ducts were very conical, the smallest point being the port.
In and outside walls of the ducts had a constant radius from top to bottom.
The flow remained attached to the inside radius and so cooled the piston and eliminated detonation.
Flow bench testing and the Jante type testing proved useless for power improvement.
Giving the rear side of the B-duct an inclination versus the middle of the cylinder gave a big improvemet

[jamathi]

breezy, I don't think that Jan Thiel will feel OK with the assumption that he is not the father of the winning aprilia 125.

The Aprilia RSW was a ROTAX design.
Later Aprilia made their own engines, but closely followed the original ROTAX design.
Except some small details.
Now they could say everything was 'made in Italy'
Which had financial 'advantages' for certain people!
Who could now take a bribe from the suppliers......as is usual in Italy.
So I am certainly not the 'father' of the Aprilia engines!

I was responsible for cylinder development, starting with 46,5HP and ending with 54HP.
Later, when working at DERBI, I had the idea of making the RSA engine, and made the first sketches.
The actual design was, of course, done on a computer by a professional designer.
Although it won several world championships I don't consider it a big success...

Aprilia always used AGIP fuels and oils for dyno testing
102 octane.
We were given face masks and special gloves, which we never needed for the 130 octane fuel.....

[Niels Abildgaard]

I was responsible for cylinder development, starting with 46,5HP and ending with 54HP.
Later, when working at DERBI, I had the idea of making the RSA engine, and made the first sketches.
The actual design was, of course, done on a computer by a professional designer.
Although it won several world championships I don't consider it a big success...


We are many that will love to read a short step describtion of going from 46 to 54 and I will like very much to hear how a Jan Thiel 125ccm engine would have looked with freedom and money no problem.Pure phantasy.
Please?

[jamathi]

We are many that will love to read a short step describtion of going from 46 to 54 and I will like very much to hear how a Jan Thiel 125ccm engine would have looked with freedom and money no problem.Pure phantasy.
Please?

My wife is going a couple of days to her sister, then I will do it.....
At least if more than 1 person is interested!

[diesel pig]

My wife is going a couple of days to her sister, then I will do it.....
At least if more than 1 person is interested!

Believe me much more than one person is interested.

[tjbw]

My wife is going a couple of days to her sister, then I will do it.....
At least if more than 1 person is interested!

Jan, we are all interested.

[Tim Ey]

Jan, we are all interested.

Nothing else to add to that statement :2thumbsup

[ken seeber]

jan, we are all interested.

yes, yes & yes

[teriks]

My wife is going a couple of days to her sister, then I will do it.....
At least if more than 1 person is interested!
The above might become the most quoted message the thread. ;)

Count me in as interested, very much so!

[shnaggs]

Count me in Jan... I am all ears!!!

[guyhockley]

Plus one (more)...

[breezy]

breezy, I don't think that Jan Thiel will feel OK with the assumption that he is not the father of the winning aprilia 125.

ouch....:hug::hug: please dont shout at me peter.... my apologies ... my english is very poor.. sorry Jan and sorry Frits if my wording made you feel uncomfortable, thanks for reply and information,which i have passed on to the interested party...:niceone:

i am, as others, interested in Jans work

[TZ350]

My wife is going a couple of days to her sister, then I will do it.....

We would love to hear more.......:yes:

[Carel H]

Jan, I just mist the 1968 TT by a year, but you're lot inspired me to build motorcycles. Just at home. And maybe winning. Winning is a combination of many things.

[husaberg]

My wife is going a couple of days to her sister, then I will do it.....
At least if more than 1 person is interested!

Keener than kernel mustard's potato peeler

[ief]

Interested as well (offcourse) but what I'm even more interested in is... how much of it was thinking/ calculating/ theorising and how much just try and see what came out of it.

My feeling is a lot of the latter with gut feeling as a precursor? (witch comes back to thinking/ calculating and theorising I guess ;))

[F5 Dave]

Alternatively if you've picked up any tips for making the perfect PadThai:drool:

. . , sorry, its coming up to lunchtime and I'm hungry.

[ief]

Dave, you are a funny one :)

[jamathi]

We are many that will love to read a short step describtion of going from 46 to 54 and I will like very much to hear how a Jan Thiel 125ccm engine would have looked with freedom and money no problem.Pure phantasy.
Please?

How can I upload drawings and pictures?
That would make it a lot more interesting.

Why is it so complicated?
I downloaded this with pure luck, don't know how I did it
Now I finally understood|

[jamathi]

Interested as well (offcourse) but what I'm even more interested in is... how much of it was thinking/ calculating/ theorising and how much just try and see what came out of it.

My feeling is a lot of the latter with gut feeling as a precursor? (witch comes back to thinking/ calculating and theorising I guess ;))

Of course I read a lot of books and articles about 2-strokes.
And saw a lot of what other people were doing.
A flow bench was very helpful too.
And a lot of thinking, not much calculation, except for exhaust pipes.
So first you think, and later have to try to see if what you thought works......
It is really not just try and see!

[husaberg]

How can I upload drawings and pictures?
That would make it a lot more interesting.

Seems I finally found out!

Is it true that you had to design the cylinders arround existing pipe designs as these were initially not allowed to be changed?

[jamathi]

Is it true that you had to design the cylinders arround existing pipe designs as these were initially not allowed to be changed?

I started working with an existing engine, a ROTAX, with an existing cylinder and exhaust pipe.
During the year dozens of different exhaust pipes were tested.....
The original Rotax A duct was something like this....

[jamathi]

I started working with an existing engine, a ROTAX, with an existing cylinder and exhaust pipe.
During the year dozens of different exhaust pipes were tested.....
The original Rotax A duct was something like this....

A Dutch friend of mine, Thijs Hessels, had improved the original cylinders by epoxying the outside curve, and giving the mixture a more upward direction.
His private Aprilia proved faster than the 'works' bikes.
The Aprilia racing boss, Jan Witteveen, demanded that Thijs should give those cylinders to him.
Otherwise Thijs would not be able to get any more spare parts for his bike!!
With this modification a ROTAX cylinder gave 46,5HP instead of the normal 44.
This happened in 1994, a year later I started working for Aprilia.
They were still epoxying ROTAX cylinders, but had decided to make their own cylinder.
The development of this cylinder was to be my work.
This cylinder was called the APC, and was destined for all 125 and 250 private riders.
It gave the same 46,5HP, but of course without epoxy.
I got the oldest dyno there was, and had to learn to use the computerized system.
As I had never touched a computer before it was not so easy.
But I quickly learned, the system was very precise and repeatable.
I was given the casting models and had to go to the foundry to have some cylinders cast,
While waiting for the castings to be machined I worked with ROTAX cylinders.
I won some power by making the auxiliary ports bigger, but they were already too high I thought.
So I made sure the APC cylinders had lower auxiliary ports, and I also filed their sand cores to make the exhaust duct a lot smaller, as I had already, successfully, tried on some ROTAX cylinders.
There were some small mistakes in the casting models, they were quickly corrected.
And then real development could begin!
I started by making the B-ports and ducts as wide as I could, and this improved bottom power, without losing at the top.
And I had one casting with a narrower C-port, made by filing the sand core.
Here the B-ports could still be made wider, and it proved to be the best cylinder of the lot.
So we got to 48HP
We also bought a lot of dentist tools and burrs, and a filing machine.
And a flow bench.
Power improved by making the auxiliary ducts longer, and wider.
But at a certain point we made a hole, ending up in the cooling water space!!!!
To cure this the casting model had to be modified.
I also had a wooden model made for use on the flow bench.
To determine the best size of the auxiliary ports and ducts.
They seemed to 'like' having a downward angle.
The casting model was modified in this way, and so we reached 49HP.
I decided to try to make te exit of the exhaust duct, and the flange, a bit wider, and won another 0,6HP
Take a look at the photo if I succeed to attach it.

[Grumph]

Some time back, I commented in response to pics Frits had posted, that after looking at pics of the early Rotax engine as tested by Cycle magazine with the race kart barrel, the differences were subtle. Visually they are very much the same layout - but obviously the devil - and the time - is in the detail.

I'm curious as to the manufacturing/design process. After establishing what the new parts for next season would look like, were the hand made prototypes turned over to a draftsman for copying ? Or was it a process where you and a designer collaborated with you saying what was wanted and them specifying casting details and flange thicknesses etc ?

Locally we've had the example of John Britten where he laid out in a general way what he wanted in the engine - and basically the guys making it made the decisions from there....

Greg

[jamathi]

Some time back, I commented in response to pics Frits had posted, that after looking at pics of the early Rotax engine as tested by Cycle magazine with the race kart barrel, the differences were subtle. Visually they are very much the same layout - but obviously the devil - and the time - is in the detail.

I'm curious as to the manufacturing/design process. After establishing what the new parts for next season would look like, were the hand made prototypes turned over to a draftsman for copying ? Or was it a process where you and a designer collaborated with you saying what was wanted and them specifying casting details and flange thicknesses etc ?

Locally we've had the example of John Britten where he laid out in a general way what he wanted in the engine - and basically the guys making it made the decisions from there....

Greg

First we went to a model maker, later we made all models ourselves.
I have no pictures of the models, but I have some of the sand cores.
In the end they were printed!

[Niels Abildgaard]

Thank You Jan

I did not know how extreme the ratio ring support/guiding to open area is in modern two stroke port belt.
Wonder what my old MZ301 could have been made to give?
Volume ratio 295/125=2.35 gives linear ratio 1.33 and thus maximum blowdownarea 1.8 times bigger.
power 56*1.8=100 horsepower?

[F5 Dave]

This is gold, thank you. I remember looking at a mates 256 back in the day, and thinking that it was the most advanced thing I had ever seen in my life,

[jamathi]

To be continued tomorrow....

[JanBros]

My wife is going a couple of days to her sister, then I will do it.....
At least if more than 1 person is interested!

please Jan, send your wife more money so she can stay longer and write that book you should have written all along :msn-wink:

[jamathi]

please Jan, send your wife more money so she can stay longer and write that book you should have written all along :msn-wink:

Writing a book is too much work for me, as I hate typing........
It would take me more than a year.
What I am doing here now is my limit!
And my wife returns sunday

[husaberg]

Writing a book is too much work for me, as I hate typing........
What I am doing here now is my limit!
And my wife returns sunday
You don't need to type Jan. It even speaks Dutch.
https://support.google.com/docs/answer/4492226?hl=en
https://zapier.com/blog/best-text-dictation-software/#docs

[JanBros]

Writing a book is too much work for me, as I hate typing........
It would take me more than a year.
What I am doing here now is my limit!
And my wife returns sunday

no problem Jan, it was more of a joke and any info no matter how small is very much apreciated :not:

[Martin1981]

Sorry if this was asked already... Jan and Frits, what was the reason the 250ccm 2 cylinder gp engine had 2 crankshafts? the engine would have been much more simple if it had only 1 crankshaft. but you knew that back then of course and decided to make it a 2 crank engine nevertheless. why?

[Larry Wiechman]

Jan,
Can you explain your methods of testing with the flow bench? What factors were indicative of engine performance? Was any testing done using Jante's anemometric methods?

Please collaborate with a technical editor and write a book. There is a fellow called Frits that has a gift for putting concepts into words, maybe you've heard of him? :msn-wink:

[jfn2]

Jamathi:
In the picture where someone is holding a exhaust flange there is a pipe attached to the flange. Was this an attempt to cool that flange?
Also keep the thoughts and insights flowing. Great information.

[Niels Abildgaard]

Sorry if this was asked already... Jan and Frits, what was the reason the 250ccm 2 cylinder gp engine had 2 crankshafts? the engine would have been much more simple if it had only 1 crankshaft. but you knew that back then of course and decided to make it a 2 crank engine nevertheless. why?

Try to see a picture of a Trabant crank with two rotary inlet discs.The Aprilia solution is very much narrower and has fewer parts.

[Frits Overmars]

Jan and Frits, what was the reason the 250ccm 2 cylinder gp engine had 2 crankshafts? the engine would have been much more simple if it had only 1 crankshaft. but you knew that back then of course and decided to make it a 2 crank engine nevertheless. why?Martin, Jan was not responsible for the 250 cc Aprilia twin (and even less for the 500 twin, which he despised). The 250 cc engine originated when Rotax built a tandem-twin by putting a second crankshaft in front of their 125 cc single. In fact, you could build a 125 cc single using one 125-crankcase half and one 250-crankcase half.
Rotax decided to build a series of these engines for the 1981 GP season and we had the "pleasure" of receiving the first two specimen in the winter of 1980.
I worked on one of those and the other one went to Dolph van der Woude, who later went on to work for Aprilia and gained their first 250 cc GP-win in 1978.
After this, Aprilia decided that they wanted an engine with an 'own' appearance, upon which Dolph designed the 250 cc V-twin that we still know today as the RSW250.

Jan Thiel had already built his own 250 cc single-crank V-twin in 1985, when working for Garelli. The engine was a beauty: light, compact and powerful, but participating in two GP-classes (125 and 250 cc) proved to be too ambitious for the small factory.

[Frits Overmars]

Jan, please collaborate with a technical editor and write a book. There is a fellow called Frits that has a gift for putting concepts into words, maybe you've heard of him? :msn-wink:Jan and I go back more than 40 years, Larry. So yes, he may have heard of me :p. But thanks for the compliment.
We discussed writing a book, but friends with more commercial insight than us figured that it could only be profitable if we where to produce both an English and an Italian edition, plus we would have to take care of all the copyrights to photos and drawings that I hadn't made myself.
Jan had already achieved everything that one man can achieve, and I am lazy by nature, so nothing came of it. Instead we write a little on forums.
By the way, you should know that Albert Einstein distinguished four kinds of people:
dumb + lazy: harmless
dumb + diligent: disastrous
smart + diligent: not much better than dumb + diligent
smart + lazy: the only useful kind; those are the ones who seek efficient solutions.

[Peter1962]

Martin, Jan was not responsible for the 250 cc Aprilia twin (and even less for the 500 twin, which he despised). The 250 cc engine originated when Rotax built a tandem-twin by putting a second crankshaft in front of their 125 cc single. In fact, you could build a 125 cc single using one 125-crankcase half and one 250-crankcase half.
Rotax decided to build a series of these engines for the 1981 GP season and we had the "pleasure" of receiving the first two specimen in the winter of 1980.
I worked on one of those and the other one went to Dolph van der Woude, who later went on to work for Aprilia and gained their first 250 cc GP-win in 1978.
After this, Aprilia decided that they wanted an engine with an 'own' appearance, upon which Dolph designed the 250 cc V-twin that we still know today as the RSW250.

Jan Thiel had already built his own 250 cc single-crank V-twin in 1985, when working for Garelli. The engine was a beauty: light, compact and powerful, but participating in three GP-classes (50, 125 and 250 cc) proved to be too ambitious for the small factory.

I think that the last picture is the most important one : three good friends together , who have written motorcycle history each in their own way. Be it on a drawing board, at the dyno or on a track, for sure they were succesfull together. I have a lot of respect for that.

[Larry Wiechman]

Jan and I go back more than 40 years...


My point, exactly!

Who better to set the scene and tell the story?

[Niels Abildgaard]

Jan Thiel had already built his own 250 cc single-crank V-twin in 1985, when working for Garelli. The engine was a beauty: light, compact and powerful,

Does a picture of that Garelli V crankshaft exist and can we see it?

[Frits Overmars]

Does a picture of that Garelli V crankshaft exist and can we see it?I could have done even better with the original Hoeckle-drawing of that crankshaft but I lent it to a friend who is building a 50 cc V-twin.
330075 330076 330077

[guyhockley]

I could have done even better with the original Hoeckle-drawing of that crankshaft but I lent it to a friend who is building a 50 cc V-twin.

Was that Garelli the one with the washer/shim labyrinth seal that you posted earlier?

[Lightbulb]

Does anyone know how or what the velocities of the gases are inside the crank case and transfer passages at their peak velocities?
What is the approx velocity of air through a venturi is?
Is there an advantage to adding the fuel before it all gets to the venturi point or is the fuel best added after the venturi point ?
This is for engines that are not allowed direct fuel injection.
Thanks for any replies, Neil

[husaberg]

Sorry if this was asked already... Jan and Frits, what was the reason the 250ccm 2 cylinder gp engine had 2 crankshafts? the engine would have been much more simple if it had only 1 crankshaft. but you knew that back then of course and decided to make it a 2 crank engine nevertheless. why?

Frits and Jan forgive me for speaking out of turn

The two single cranks can be contra rotating resulting in better balance without the need for a balance shaft.
Two single crankshafts are also likely easier to service as well as not having a large rocking couple a wide spaced single crankshaft would have.
They can also have a simpler ignition system as they both fire at the same time
Also with a single crankshaft engine both carbs can be on one side. This can make it easier for servicing and well as packaging a decent airbox
Additionally when the tandem Rotax was converted to a V formation the weight distribution improved as it could be mounted further forward with its rear facing front exhaust.
It could also use many already in use, Rotax parts. A big consideration for a small factory.
330079330080

Also here are two further pics that might better illustrate Jans story.
330081330082

[Frits Overmars]

Frits and Jan forgive me for speaking out of turn.I didn't even know there were turns Husa. Besides, I welcome a bit of anarchy. And you're absolutely right on all accounts.
But allow me to stipulate one drawback of both the Rotax tandem-twin and the Aprilia V-twin: the vertically split crankcases make working on them a lot harder than horizontally-split cases would. Especially the first Rotax engines with their shrink-fit/press-fit crankshaft ball bearings were a pain.

[jamathi]

Jamathi:
In the picture where someone is holding a exhaust flange there is a pipe attached to the flange. Was this an attempt to cool that flange?
Also keep the thoughts and insights flowing. Great information.

No, that was the attachment for the exhaust temperature sensor.

[Niels Abildgaard]

Frits and Jan forgive me for speaking out of turn

The two single cranks can be contra rotating resulting in better balance without the need for a balance shaft.
Two single crankshafts are also likely easier to service as well as not having a large rocking couple a wide spaced single crankshaft would have.
They can also have a simpler ignition system as they both fire at the same time
Also with a single crankshaft engine both carbs can be on one side. This can make it easier for servicing and well as packaging a decent airbox
Additionally when the tandem Rotax was converted to a V formation the weight distribution improved as it could be mounted further forward with its rear facing front exhaust.
It could also use many already in use, Rotax parts. A big consideration for a small factory.
330079330080

Also here are two further pics that might better illustrate Jans story.
330081330082

The 258 drawing is only 23 kB and very difficult to read?

[husaberg]

The 258 drawing is only 23 kB and very difficult to read?
You may need new glasses its also in Austrian
It was all there was on the Net sorry.:bleh:
http://www.artmotorsport.com.au/new/Rotax%20Manual%20Pt1.pdf
There are plenty of pics here of the crankcases
including a scaled down wood pattern someone made for 50cc cylinders.
https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=324357&d=1473333807
https://www.kiwibiker.co.nz/forums/album.php?albumid=4839

https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=304255&d=1413591174
https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=304256&d=1413591175
https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=303429&d=1413021975

[Niels Abildgaard]

I could have done even better with the original Hoeckle-drawing of that crankshaft but I lent it to a friend who is building a 50 cc V-twin.
330075 330076 330077

Thank You for very clear pictures.
I wake up every morning hoping that somebody has seen the shining ligth and made a 50 ccm V2 with a one throw crank ,one carb and crankcase.
I will either have to make it myself or get very old.
Maybe making a 100ccm is easier.
Can one find reasonably powerfull(up to date) 50 ccm cylinders,pistons and exhausts without silly money and where?

[husaberg]

Can one find reasonably powerfull(up to date) 50 ccm cylinders,pistons and exhausts without silly money and where?

09 onwards KTM50

[jamathi]

[QUOTE=Martin1981;1131040981]Sorry if this was asked already... Jan and Frits, what was the reason the 250ccm 2 cylinder gp engine had 2 crankshafts? the engine would have been much more simple if it had only 1 crankshaft. but you knew that back then of course and decided to make it a 2 crank engine nevertheless. why?

I did not design this engine, nor did Frits.
It was Aprilia who wanted their 'own' engine.
The designs and the engines were made by ROTAX.
I still consider a V engine with a single crankshaft as the best solution!!

[jamathi]

[QUOTE=jamathi;1131041110][QUOTE=Martin1981;1131040981]Sorry if this was asked already... Jan and Frits, what was the reason the 250ccm 2 cylinder gp engine had 2 crankshafts? the engine would have been much more simple if it had only 1 crankshaft. but you knew that back then of course and decided to make it a 2 crank engine nevertheless. why?

I did not design this engine, nor did Frits, who never worked for Aprilia.
It was Aprilia who wanted their 'own' engine.
The designs and the engines were made by ROTAX.
I still consider a V engine with a single crankshaft as the best solution!!
Much more compact, less friction losses and vibration free!
And lighter....

[Niels Abildgaard]

09 onwards KTM50

Thank You and have found a dealer 150 km away.After easter.

[jamathi]

The original ROTAX tandem gave 62HP 'out of the box' in 1981.
So you can see a 31HP cylinder on the left, and a 53HP cylinder on the right.

[jamathi]

I discovered that making the underside of the transfer ports even with the piston in BDC
was very important: considerably more power, less detonation and far better piston cooling.
We started to have the exhaust ducts CNC machined in 1999 I think.
But first we had to overcome the new fuel regulations in 1998
102 octane had to be used instead of 130 octane.
We expected BIG problems.....
But within a couple of month's we had more power than before!
The compression ratio was lowered from 19,5:1 to 16:1
And the tailpipe restrictor was made 0,25mm bigger.
Then a very serious combustion chamber development was started.
The result was that parallel squish was the best, with a squish height of 0,75mm
Less squish height would give more torque but less revs.
At 0,45 the piston touched the head....
Then a head insert with a much wider squish band (50% of cylinder surface) was tried.
And that proved to be the final touch.
We now had more power than with the 130 octane fuels, and less problems.
The sharp edge between combustion chamber and squish band proved to be very important.
Even a small radius would give 0,5HP less..

[jamathi]

Transfer ducts.

Many transfer ducts with small differences were tried.
We found more power by enlarging the A-port in the direction of the exhaust.
Only the lower half, but it was important to give the A-duct an inclination away from the exhaust!
The ducts were very conical, the smallest point being the port.
In and outside walls of the ducts had a constant radius from top to bottom.
The flow remained attached to the inside radius and so cooled the piston and eliminated detonation.
Flow bench testing and the Jante type testing proved useless for power improvement.
Giving the rear side of the B-duct an inclination versus the middle of the cylinder gave a big improvemet

[jamathi]

Pistons:

We had cast and forged pistons.
Cast pistons gave slightly more HP, but sometimes cracked.
0,8mm piston rings gave more HP than 1mm rings.
As the auxiliaries and transfers overlapped each other a certain power los was caused by this.
So closing the pin hole in the piston was tried.
There were many solutions that were tested, but they all caused some trouble.
In the end the best, and most reliable, solution was welding then closed.
This was very well done by PANKL in Austria, and never caused any trouble!

[Peter1962]

Was that Garelli the one with the washer/shim labyrinth seal that you posted earlier?

I think you are referring to the JBB 250 cc.
http://www.50c.nl/Archief%20Ton%20Kooyman-Album-4/6-Racers/250cc%20racers/JBB/index.html

[mr bucketracer]

Pistons:

We had cast and forged pistons.
Cast pistons gave slightly more HP, but sometimes cracked.
0,8mm piston rings gave more HP than 1mm rings.
As the auxiliaries and transfers overlapped each other a certain power los was caused by this.
So closing the pin hole in the piston was tried.
There were many solutions that were tested, but they all caused some trouble.
In the end the best, and most reliable, solution was welding then closed.
This was very well done by PANKL in Austria, and never caused any trouble!thanks for your imfo:2thumbsup

[diesel62]

Do you mind me asking why do you think cast pistons made more hp than forged?

Sent from my SM-P555 using Tapatalk

[jamathi]

Because forged pistons had a tendency to 'bend' their dome inwards.

[diesel62]

Wow thanks for that.

Sent from my SM-P555 using Tapatalk

[jamathi]

When modifying a cylinder measuring duct sizes is not easy, especially in the curves!
You can see our solution to this problem on the photo....
Round 'sensors' fitted to a piece of welding rod!
We had them from 7-7,25- 7,5 and so on until 28mm.
Behind the cylinder, in the wooden block.

[Flettner]

Vannik or anyone that knows stuff, I don't have your software so don't know this, if combustion does not happen, what happens to the air velocity in the combustion chamber at / after TDC? Does the rapid turbulence in the combustion chamber stop and reverse at some stage, as the squish starts to open up again? Or does it keep going but just slow down a bit?

Jan, thank you, this is gold.

[guyhockley]

I think you are referring to the JBB 250 cc.
http://www.50c.nl/Archief%20Ton%20Kooyman-Album-4/6-Racers/250cc%20racers/JBB/index.html
No, I'm not. I'm familiar with the JBB 250. When it was discussed, earlier, it was me that pointed out it uses the same sealing system as many outboards.
Frits posted a picture of a labyrinth seal made up of various diameter washers.

[husaberg]

No, I'm not. I'm familiar with the JBB 250. When it was discussed, earlier, it was me that pointed out it uses the same sealing system as many outboards.
Frits posted a picture of a labyrinth seal made up of various diameter washers.
He did indeed

You can easily build you own labyrinth with a stack of shims. Jan Thiel used this system in the Garelli 250cc V-twin. The whole shim package was only 5 mm thick.
322755322756

[Niels Abildgaard]

Because forged pistons had a tendency to 'bend' their dome inwards.

I do not understand .If the dome bends inward compression ratio go down and that is less power?

[jamathi]

Detonation.

This started te be a problem when 50cc engines started giving more than 17HP, around 1975.
At the time I thought this was a limit on engine power.
Nikasil plated cylinders were very prone to detonation.
Because of the rounded off edge at the top.
At Minarelli/Garelli I solved this problem by sticking the cylinder head insert 3mm into the cylinder.
A good solution, used for many years.
But at Aprilia we found an even better solution: plate the first 5 mm around the bore at
the top of the cylinder.
Later this was machined to a very sharp corner, and this eliminated completely the unnecessary
'dead room' at the top of the cylinder, it also gave 0,3HP more.....
A little bit of still remaining detonation was eliminated by modifying the inner wall of the
transfer ducts, cooling the piston.
But part-throttle detonation remained a problem.....
Which we never had on the dyno!
On the photo you see a piston after a 54HP run...
As long as you keep the throttle wide open a 2 stroke doesn't brake down!

[jamathi]

I do not understand .If the dome bends inward compression ratio go down and that is less power?

Yes...I think so.

[jamathi]

He did indeed

The shim package of the 250 Garelli was about 1mm.

[Vannik]

Vannik or anyone that knows stuff, I don't have your software so don't know this, if combustion does not happen, what happens to the air velocity in the combustion chamber at / after TDC? Does the rapid turbulence in the combustion chamber stop and reverse at some stage, as the squish starts to open up again? Or does it keep going but just slow down a bit?

The turbulence is caused by the breakdown of the main flow. Because of the viscosity (in effect the internal friction of the fluid) the main flow progressively break down into ever smaller eddies and if left long enough all the main flow and all the eddies will stop. The main flow is from the transfer port loop and a stronger better directed flow with more kinetic energy can generate a lot of turbulence before it stops. If you have weak flow by the time combustion happens you need the extra flow from the squish to generate extra turbulence to get good combustion. On the other side if you have strong flow and thus good turbulence the extra turbulence can speed up the combustion too much and you loose power but mostly overrev. This explains why engines do not always behave the same to squish changes. Good engines use squish to minimize end gas to stop detonation while poor engines use squish to add turbulence.

So to answer the question: Turbulence cannot reverse, it is a one way street after creation. The bulk flow with the squish opening will loop slower and slower, both because of the increase in volume and because it keeps generating turbulence until it completely stops.

[Haufen]

Thanks for the insight, Jan!

do you remember the difference between both of the A-port variations from the picture? Which was better, version A or version B?
330106

And did you ever have the pin come loose on the pistons? I guess not, buit it does look brave to me.
330105

[guyhockley]

The shim package of the 250 Garelli was about 1mm.
Very impressive! Thank you (both of you). You can tell we're all interested, Husaberg hasn't posted any boob pictures for ages...)

[guyhockley]

Some pictures of the 250 engine.
330116330117330118330119330120

Think Rotax built a V twin as a one off for Cotton before the tandems came along.
Presumably the engines had more and more Aprilia built parts as time went on.
I saw an article in an Italian magazine about the development of the 250 and (I think!) it said that power slowly increased over the years but the biggest jump was the introduction of crankcase cooling.
Was that similar to the 125?

[guyhockley]

Found this

[Tim Ey]

The shim package of the 250 Garelli was about 1mm.

Jan, did you ever thought about using bearings with steel cover discs instead of a labyrinth seal?
(6204-z-c3 would be an example)
so you may use two bearings right next to each other without the need of any extra parts.

the question is where to place the covered side.
1. covers at the crank webs with an oil feeding hole between them
pro: crankcase volume does not differ
con: might get full of oil


2. covers facing each other, feeding hole in the middle
con: probably not enough oil supply

3. using only one closed bearing with feeding hole in the middle
pro: more vented bearings than 1.
con: crankcase volume of one gets higher than the other

[Fabio15]

Can one find reasonably powerfull(up to date) 50 ccm cylinders,pistons and exhausts without silly money and where?

Malossi, Polini and Roost make very good cylinders for the 50cc piaggio engines.

[jamathi]

Thanks for the insight, Jan!

do you remember the difference between both of the A-port variations from the picture? Which was better, version A or version B?
330106

And did you ever have the pin come loose on the pistons? I guess not, buit it does look brave to me.
330105

Version A was the best.
The pin never came loose.

[ken seeber]

Jan,
In all your time at Aprilia and others, when you wanted to try a different port or passage shape, did you actually reshape the sand cores yourself (eg by rubbing, filing or even building up with more sand) or was the new design formally designed/drawn up and new coreboxes made?
Otherwise this is a great unfolding of the history, even though you’re not writing a book, I’m sure the likes of Husa will compile something.

[jamathi]

I often modified sand cores by filing
We also used to 'cast' ducts in some resin, and modified these.
After that we made new core boxes, using the modified resin cores.
Our core boxes were really very nice, I shame I never made some pictures of them!
We mostly did those things by ourselves, without involving the technical office.
When we had arrived at the best transfer ducts the whole sand core was put on design.
So a one-piece cylinder core could be printed.
Also a study was made to improve cooling, especially the hot spots, as were the bridges in the exhaust duct.
A cooling channel through the inside wall of the transfer ducts brought an additional 0,5HP
The result of this was the APF cylinder.

[jamathi]

Some pictures of the 250 engine.
330116330117330118330119330120

Think Rotax built a V twin as a one off for Cotton before the tandems came along.
Presumably the engines had more and more Aprilia built parts as time went on.
I saw an article in an Italian magazine about the development of the 250 and (I think!) it said that power slowly increased over the years but the biggest jump was the introduction of crankcase cooling.
Was that similar to the 125?

I don't know when water cooled crankcases were introduced at Aprilia.
When I started working there in 1995 all engines already had water cooled crankcases.
I made my first 50cc with water cooled crankcase in 1972.

[jamathi]

The cooling channels at the inside wall of the transfers.

[lodgernz]

I do not understand .If the dome bends inward compression ratio go down and that is less power?


Yes...I think so.

And maybe because the depressed dome pushed the crown outwards a smidgen causing more friction?

[breezy]

I don't know when water cooled crankcases were introduced at Aprilia.
When I started working there in 1995 all engines already had water cooled crankcases.
I made my first 50cc with water cooled crankcase in 1972.

Jan, which area of the cylinder would you say water cooling has the greatest effect on improving power? does the cooling have to bring the temps down really low to have the best effect? would having that area benefit from having its own dedicated cooling circuit and radiator rather than being part of the a general cooling circuit?

regards, nigel.

[Niels Abildgaard]

Hello Jan

It strange that You could see 0.5 horsepower differences on dyno and be able to decide if it was a good or bad change.
How much running in was nessecary to get reliable data?How often did You compensate for air pressure,humidity and temperature?

[F5 Dave]

Whoa, this Bs look bigger than any other picture I've seen of them before. A lot bigger.

[jamathi]

Jan, which area of the cylinder would you say water cooling has the greatest effect on improving power? does the cooling have to bring the temps down really low to have the best effect? would having that area benefit from having its own dedicated cooling circuit and radiator rather than being part of the a general cooling circuit?

regards, nigel.

The lower the water temperature was the more power there was!
40° was the lowest we tried, each 5° more giving a power loss of about 0,4-0,5HP.
On the dyno we normally used 50°
The exhaust duct had to be cooled really well, especially the bridges in it.
In the beginning we had some trouble with holed pistons, caused by auto-ignition.
But bringing the water closer to the spark plug cured this completely!
We also found out that the quicker the water circulated the better.
An electric water pump was insufficient!!

[jamathi]

Hello Jan

It strange that You could see 0.5 horsepower differences on dyno and be able to decide if it was a good or bad change.
How much running in was nessecary to get reliable data?How often did You compensate for air pressure,humidity and temperature?

Our computerized testing program was fully automatic and very precise.
There was, of course, automatic compensation for temperature, humidity and air pressure.
You could choose the cooling water temperature you wanted, and it was kept constant.
Also the dyno room was air conditioned, with constant temperature and humidity.
You could be sure that if you saw a 0,1HP gain that it was 100% true!!
And I repeated every modification at least 3 times....
A test went as follows: The engine was started and put at 10.000 rpm to warm up, full throttle.
When the desired temperature was reached you had to push a button.
Then the test was executed fully automatically, say from 9000 until 14500rpm
When maximum revs was reached you had to stop the engine.
Tests were 99,9 % repeatable

[Niels Abildgaard]

Our computerized testing program was fully automatic and very precise.
There was, of course, automatic compensation for temperature, humidity and air pressure.
You could choose the cooling water temperature you wanted, and it was kept constant.
Also the dyno room was air conditioned, with constant temperature and humidity.
You could be sure that if you saw a 0,1HP gain that it was 100% true!!
And I repeated every modification at least 3 times....

That set up must have cost a lot.
Did Aprilia get the money back?
What would the optimum 125 ccm look like?
The 250 would have been two of these one a single V2 throw crankcase and one fuel inlet of course

[jamathi]

Sometimes riders complained about not being able to change gear.
With their 'spark interruption' system.
So I had a button fitted to my desk so that I could interrupt the ignition.
At certain revs the engine kept running without a spark!!!
The power did not change, and there was no detonation......

[ken seeber]

The power did not change, and there was no detonation......

HCCI surely. I assume this was mainly observed at full throttle, however did you ever gradually close the throttle under this HCCI condition to see at what point it cut out? . It'd be good to know what rpm range this might have occurred., but again I would probably think that you were only concentrating in the max power range where the engine was being used on the bike.

[Haufen]

HCCI surely. I assume this was mainly observed at full throttle, however did you ever gradually close the throttle under this HCCI condition to see at what point it cut out? . It'd be good to know what rpm range this might have occurred., but again I would probably think that you were only concentrating in the max power range where the engine was being used on the bike.

Please excuse me for being a smart ass here, but without further investigation there is absolutely no evidence that this was a) homogeneous and b) triggered by compression alone. What's wrong with some old fashioned ordinary pre-ignition? I would regard pre-ignition as far more likely in this case, especially as the EGT did not seem to be affected (I guess riders would have complained about engines suddenly hitting a rev wall due to a too cold EGT).

Did you notice a change in EGT when the engines were runing independent of the spark plug, Jan?

[tjbw]

That set up must have cost a lot.
Did Aprilia get the money back?


Won multiple world championships, value: priceless, well almost ;)

[Niels Abildgaard]

Won multiple world championships, value: priceless, well almost ;)

Exactly.
I once talked to a man who made kart engines for a living and it was winning on saturdays or no sales next week.
How much did the journey from 46 to 54 cost and how much did it sell? Just round millions (not Lira please)?

[Flettner]

Vannik, thank you, it all makes sense.

[ken seeber]

Please excuse me for being a smart ass here, but without further investigation there is absolutely no evidence that this was a) homogeneous and b) triggered by compression alone. What's wrong with some old fashioned ordinary pre-ignition? I would regard pre-ignition as far more likely in this case, especially as the EGT did not seem to be affected (I guess riders would have complained about engines suddenly hitting a rev wall due to a too cold EGT).

Did you notice a change in EGT when the engines were runing independent of the spark plug, Jan?

You’re absolutely right, as HCCI is a form of pre-ignition. HCCI, by definition is a compression ignition phenomenon that can occur under a certain set of conditions (mainly lean from my understanding which is not what a high performance 2 stroke would be using), but it is certainly a form of pre-ignition, ie combustion commencing prior to the spark within the plug. Classic pre-ignition, well in my mind, is caused by something within the combustion chamber envelope being hot enough to initiate ignition. Typical causes being a spark plug earth electrode, carbon or an overly hot exh valve. Combustion temps and pressures can rise prematurely, worsening the initial cause, and then can lead to detonation. To me, it’s hard to imagine that a well cooled and internally clean engine such as the Aprilia 125 test engine would provide such conditions for classic pre-ignition.
How would you find out? Probably through using cylinder pressure transducers, quartz windows & high speed cameras, exhaust analysis etc. Maybe a change in EGT as you are suggesting. What would you suggest the change would be? Maybe there was engine damage after such conditions were experienced?

[husaberg]

Sometimes riders complained about not being able to change gear.
With their 'spark interruption' system.
So I had a button fitted to my desk so that I could interrupt the ignition.
At certain revs the engine kept running without a spark!!!
The power did not change, and there was no detonation......

Jan i beleive that is the third form of ignition
1 Spark ignition
2 Compression ignition
3 ARC (Activated Radical Combustion) now called HCCI


Please excuse me for being a smart ass here, but without further investigation there is absolutely no evidence that this was a) homogeneous and b) triggered by compression alone. What's wrong with some old fashioned ordinary pre-ignition? I would regard pre-ignition as far more likely in this case, especially as the EGT did not seem to be affected (I guess riders would have complained about engines suddenly hitting a rev wall due to a too cold EGT).

Did you notice a change in EGT when the engines were runing independent of the spark plug, Jan?


You’re absolutely right, as HCCI is a form of pre-ignition. HCCI, by definition is a compression ignition phenomenon that can occur under a certain set of conditions (mainly lean from my understanding which is not what a high performance 2 stroke would be using), but it is certainly a form of pre-ignition, ie combustion commencing prior to the spark within the plug. Classic pre-ignition, well in my mind, is caused by something within the combustion chamber envelope being hot enough to initiate ignition. Typical causes being a spark plug earth electrode, carbon or an overly hot exh valve. Combustion temps and pressures can rise prematurely, worsening the initial cause, and then can lead to detonation. To me, it’s hard to imagine that a well cooled and internally clean engine such as the Aprilia 125 test engine would provide such conditions for classic pre-ignition.
How would you find out? Probably through using cylinder pressure transducers, quartz windows & high speed cameras, exhaust analysis etc. Maybe a change in EGT as you are suggesting. What would you suggest the change would be? Maybe there was engine damage after such conditions were experienced?



Honda readies Activated Radical Combustion two-… engine for production motorcycle
Honda has been researching and developing the Activated Radical Combustion (ARC) two-… engine for several years. As a showcase of the engine’s viability and durability in the most arduous conditions, Honda’s RD Asaka Center successfully raced the experimental EXP-2, 440-cm 3. single-cylinder, off-road motorcycle in the gruelling Granada-Dakar Rally in 1995, the event that covered 8000 km of mostly desert terrains and in which the two-… had been thought to be at a disadvantage for its inherent gas-guzzling trait. The EXP-2 placed fifth overall in the motorcycle category, proving its worth in this most arduous test of machines and riders.
Honda is now readying a production dual-purpose (on- and off-road) motorcycle employing the ARC technology. With the ARC, Honda is applying a third combustion process to the piston-compression, internal combustion engine. The first and second piston-compression, internal combustion engine types are, of course, the spark-ignited gasoline (and alternative fuels) engine and the compression-ignition diesel.
Honda observes that the burning of gasoline in an engine is not a simple, procedural process; mix fuel with air, add ignition source, bang, and let the process take its effect. It is chemically more complex, with a large number of intermediate chemical reactions. In essence, asserts Honda, combustion begins with an initiating reaction that forms highly reactive intermediate molecules, or activated radicals, from the stable fuel and air of the incoming charge.
Propagating reactions continue with various molecules reacting with these active radicals. These propagating reactions from both additional reactant molecules and more active radicals to continue the combustion process, which goes on as long as it unleashes enough energy to continue the chain.
The ARC phenomenon was observed by many owners of two-…-powered motorcycles, generators, and other products, whose engines would continue running after the electrical ignition was shut off. This auto-ignition was generally attributed to a pre-ignition caused by hot spots in the combustion chamber, and engineers’ attention was focused on eliminating it. Honda pays due homage to the researchers who had earlier discovered the role of active radicals in the auto-ignition phenomenon: Yakov Zoldvitch in the 1930s, and more recently notable efforts by Toyota’s Masaaki Noguchi and his team (The Toyota-Nippon-Soken combustion, SAE 790840), and Shigeru Ohnishi of the Nippon Clean Engine Research Institutes who had actually constructed a stationary engine for generators on the active radical principle in the late 1970s.
In 1992, Honda started a small research project, under the direction chief engineer Minoru Matsuda, to determine if this auto-ignition process could practically solve the irregular combustion problem for two-… engines. The team, led by Yoichi Ishibashi, made surprisingly rapid and fruitful progress. While Ohnishi had earlier broadened the engine’s auto-ignition range by throttling the flow of fresh charge from the crankcase into the cylinder (usual two-… breathing practices), this was not sufficient for a mobile power plant.
Honda engineers determined that, for any given engine load, the most important variables controlling the occurrence of the auto-ignition process were the temperature of the residual gas and the pressure remaining in the cylinder when the exhaust port was closed. That last value, explains Honda, pressure at exhaust closing, or PEC, could be readily regulated by a very simple mechanical design, a movable valve to throttle flow at the exhaust port, and thus retain higher pressures in the cylinder.
For a vehicle engine, the ARC auto-ignition process could not be the sole source of ignition over the engine operating range. So in the Honda ARC application, spark ignition is still employed at very lowest load conditions, such as at idling, for which there was so little incoming charge that sufficient temperatures could not be maintained, and at high loads for which there was too little residual charge and too little heat from the charge. The ARC could operate from roughly 5% of peak load to 60%, but it is most efficient from about 6 to 22% load, almost exactly the range at which irregular combustion causes the most problems in a conventional spark-ignited two-… engine.
The EXP-2 experimental motorcycle’s 402-cm 3 capacity was chosen to compete in the Granada-Dakar rally against a horde of large-displacement four-… competitors. Honda took its own NX4780 Vee-twin four-… offroader, whose performance and fuel consumption characteristics were placed under scrutiny, whereupon the EXP-2’s specifications were determined. The EXP-2 employed an exotic PGM-FI fuel injection system, hitherto reserved to Honda’s Grand Prix racers.
The fuel injection was chosen for the computer’s ability to be readily brought in to control the exhaust valve operation, not because it was essential for fuel feed.
The production-prototype ARC engine is a liquid-cooled, single-cylinder 250-cm 3 unit breathing from a conventional side-draft carburetor. The electronic control unit controls the stainless-steel ARC (exhaust port control) valve which is actuated by an electric servo motor, ignition change-over between spark-ignition and ARC-auto-ignition, and carburetor idling and slow-jet. The ECU is fed with various information including transmission gear position, engine rpm, coolant temperature, and throttle opening angle.
Honda claims the following improvements with the ARC:
Fuel economy improvement: 27% improvement on Honda’s own real-life operating mode; 29% improvement at a steady 60 km/h
Reduction of hydrocarbon emission by 50%
Market improvement in driveability.
click on the attachments three times

Another intersting thing Cameron says is the peak cylinder pressure occurs arround 11-15 degrees after TDC
He also says that combustion is symetrical ie if it starts at 18 Degrees BTDC it finishes arround 18 Degrees ATDC.
during the 15 degrees on either side of TDC the piston is of course pretty much motionless ,depending of course on the stroke and conrod length.

[jamathi]

HCCI surely. I assume this was mainly observed at full throttle, however did you ever gradually close the throttle under this HCCI condition to see at what point it cut out? . It'd be good to know what rpm range this might have occurred., but again I would probably think that you were only concentrating in the max power range where the engine was being used on the bike.

Yes, I think it was HCCI
Auto-ignition by a too hot spark plug had quite a different effect!
That always ended with a seized engine....
HCCI caused no damage at all, the engine ran very well.
It happened with max. power carburation, and around and above max power.
I did very few experiments with it, which now I regret!
The test without spark was only done to find out where the gear change problem came from....

There was also part-throttle auto ignition which caused a lot of damage to piston and head!
Incredibly strong detonation!

[jamathi]

A complete dyno room cost maybe half a million Euro.
They are using them to test 4 stroke engines now!
We had 3 dyno rooms for 2stroke racing development

[jamathi]

That set up must have cost a lot.
Did Aprilia get the money back?
What would the optimum 125 ccm look like?
The 250 would have been two of these one a single V2 throw crankcase and one fuel inlet of course

This was the 250.

[Niels Abildgaard]

330177330178

Hello Jan

Thank You for the Test beds picture.
I had not realised that there was and is an Aprilia before and after Your two strokes.
It is was not important at any rate.
My pictures show the ultimate two stroke configuration.
Ligth,even pull ,simple and nobody can claim that it will not work yet.

[Haufen]

You’re absolutely right, as HCCI is a form of pre-ignition. HCCI, by definition is a compression ignition phenomenon that can occur under a certain set of conditions (mainly lean from my understanding which is not what a high performance 2 stroke would be using), but it is certainly a form of pre-ignition, ie combustion commencing prior to the spark within the plug. Classic pre-ignition, well in my mind, is caused by something within the combustion chamber envelope being hot enough to initiate ignition. Typical causes being a spark plug earth electrode, carbon or an overly hot exh valve. Combustion temps and pressures can rise prematurely, worsening the initial cause, and then can lead to detonation.

I agree if you switch pre-ignition with auto-ignition in your first sentence. :drinknsin (sorry, I am doing it again :confused: but it is also difficult for me to find the right line to differentiate as english is not my first language)

In the wide range of auto-ignition, which also covers pre-ignition and HCCI, the latter is only a very rare and exotic special case, whereas there are many other forms of auto-ignition which can be triggered by different things do not necessarily lead to engine damage.
For me, saying "it was HCCI because the engine ran without a spark plug and without damage" is like saying "it must have been beer, because it was definitely not wine".

Also, I don't know of any reference in literature having achieved HCCI in rich condition and at a corresponding BMEP (15+ bar 2stroke, 30+ bar 4-stroke). Does not mean that this is not possible, but could be that other things are more likely.


To me, it’s hard to imagine that a well cooled and internally clean engine such as the Aprilia 125 test engine would provide such conditions for classic pre-ignition.
How would you find out? Probably through using cylinder pressure transducers, quartz windows & high speed cameras, exhaust analysis etc. Maybe a change in EGT as you are suggesting. What would you suggest the change would be? Maybe there was engine damage after such conditions were experienced?

I am quite sure any 2-stroke can be brought to the point where pre-ignition is likely to take over, just squeeze the exhaust pipe outlet more and more. And of course you push for the limit in racing. What this does, is that it increases EGR ratio which could then trigger auto-ignition. But ignition in such a scenario would probably not become homogeneous, rather initiated from the exhaust port side as this is the hotter side.

I guess you could find out with pressure indication and become quite sure, but to be really really sure that all the mixture is burning homogeneously and commencing the burn at the same time some optical measurement would be necessary.

With pressure indication, the zig-zag knocking signal after tdc should become smaller and smaller until it disappears, also the burn should become much faster and thus the pressure signal would become narrower and higher with no more bump on the left side (assuming there was one in the first place).
I would love to throw some high tech lab equipment at a RSA engine and then stay there for a couple of months or so for sure, who would not. As for now, the destiny of lottery has not answered to my prayers unfortunately :)

With HCCI the EGT would become lower, as the burn would be faster and thus there would be more time for the charge to cool. I would expect to see at least 50deg C lower EGT. So we have less energy for the pipe to work with and after peak we are switching suddenly a longer pipe? You don't want that in a racing two-stroke. Also, power should increase with faster combustion and if not, positive and negative work gained by faster combution would be the same, which would be another rare coincidence.

[jamathi]

At Aprilia we never had any high tech equipment, just an EGT sensor.
Nothing else was needed for finding more power!

[husaberg]

This was the 250.

Quite different looking in cylinder detail from the Biagi 250
330179

whoops wrong pic thats the 500.
https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=314852&d=1439765447

So the pic on the right is the Biagi cylinders made elsewhere?

These is the cylinders i normally associate with an early Aprilia
https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=330165&d=1492314330https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=314851&d=1439765439
I have an DEA almost copy of it

[Martin1981]

330177330178


My pictures show the ultimate two stroke configuration.
Ligth,even pull ,simple and nobody can claim that it will not work yet.

Does it have a common crankcase for both cylinders?

[husaberg]

Seen this today neat
https://grabcad.com/library/aprilia-rsw-125-250-cylinder-incompl-1
seeing one in 3d is pretty neat
Needs a little work on the AUX exhaust

[Niels Abildgaard]

Does it have a common crankcase for both cylinders?

Yes,thats the big plan and only one common inlet for crankcase.
If the underside of the lagging piston controls this inlet we get the phase skewing as a disc valve without the complication.
I have some parts but lack motivation for the time being

http://i.imgur.com/n36caso.jpg

Hi Martin You are from Trabant country.
Find an used engine and let us make the Trabant engine like this
Should hae been done really many years ago.

[Martin1981]

Yes,thats the big plan and only one common inlet for crankcase.
If the underside of the lagging piston controls this inlet we get the phase skewing as a disc valve without the complication.
I have some parts but lack motivation for the time being

http://i.imgur.com/n36caso.jpg

Hi Martin You are from Trabant country.
Find an used engine and let us make the Trabant engine like this
Should hae been done really many years ago.


yes, indeed. i was born in the GDR. :yes: but i am not proud of the trabant and it is engine. it is crap in my opinion. but the reason for that are for sure not stupid engineers but stupid assholish politicans... 26bhp?:angry: i don`t agree!

[jonny quest]

Jan you settled on a dome piston. Which other types were tried and what were the results?

[jamathi]

We tried various flat, and radiused pistons, but the original ROTAX dome always gave the best results.
With flat pistons the flow detaches which gives less piston cooling.

[diesel62]

Hi Guys new here
Trying to learn a bit about EGT .I would have thought the temp would have kept climbing to max rpm .Is the lag just the time it takes for the sensor to heat up ? or is there another reason
Any help would be appreciated
330190

[2T Institute]

https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=314852&d=1439765447

So the pic on the right is the Biagi cylinders made elsewhere?


That looks like the unloved APD cylinder.

My take on the twin crank is the single crank engines the head angle has to be steeper to over come the gyro effect of the crank. Early Kobas frames used at 27* head angle which is mx territory. The Kobas could run that rake but still change directions a fast as the TZ/RS's. Contra rotating cranks seem to have less tyre chatter as well. Less vibrations make them far easier to ride faster. :lol:

[2T Institute]

You may need new glasses its also in Austrian
It was all there was on the Net sorry.:bleh:
http://www.artmotorsport.com.au/new/Rotax%20Manual%20Pt1.pdf
There are plenty of pics here of the crankcases
including a scaled down wood pattern someone made for 50cc cylinders.
https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=324357&d=1473333807
https://www.kiwibiker.co.nz/forums/album.php?albumid=4839

https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=304255&d=1413591174
https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=304256&d=1413591175
https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=303429&d=1413021975

They are 3D printed cases from a 18yr old fellow in Italy (shits me someone so young can have all that talent :niceone:) for 125cc he is getting help fram Garbriel Gnani (his cylinders)

http://www.2t-special.it/forum/viewtopic.php?f=14&t=5065