ESE's works engine tuner

[adegnes]

Well,, you have the answer ;)

This summer i dynoed a small 50cc to 19.22hp, and we never started from standstill.
We rolled up into about 200rpm on the roller, then gave it hell ;)

After a run there wasn´t almost any heat buildup at all.
In the future, try remember that, start from rolling. :)

This is much more less aggressive to the belt and gives more precise numbers from pull to pull.

Rgds.

Thanks for the advice!

[Nath88]

With my system there would not be any CDI-curves anymore. Instead of looking up the prescribed amount of ignition advance for a certain rpm and thottle position,
the CDI would constantly monitor the exhaust pulses and adjust the ignition timing accordingly. It would also automatically adjust to a different exhaust pipe.


This is interesting and not so difficult to implement. Could the pulse timing feedback work between a maximum and minimum timing curve? So it could adjust for changes in pipe wall temp, fuel mixture and pipe design?

I still have a few electrical parts to get for my sensor, but the housing is finished, will test later today. It could do ignition timing feedback for sure, just measure time between pressure peaks and compare against RPM, output a signal for the CDI that corresponds with exhaust wave too fast or too slow. Why hasn't anyone done this yet?

[Nath88]

Just tested the pulse sensor. I think this will work well. Would be able to measure time between pulses if you wanted to.
332944

https://youtu.be/DbpsNZnSmnE

[ken seeber]

Nathan,
That's pretty cool, well done. Can I presume the positive pressure pulses are shown as -ve in the Y axis? They do seem to correspond with a fire. I suppose the closer to the pipe the better in terms of response delays etc. Do you think the piezo could stand being faced directly to the pipe wall or embedded in the exh port duct?

[Nath88]

Can I presume the positive pressure pulses are shown as -ve in the Y axis?
Yep pressure rise is shown as -ve. I'll rig up an external trigger so I can speed the scope up and look at the pressure waves over a cycle.


Do you think the piezo could stand being faced directly to the pipe wall or embedded in the exh port duct?
Probably not possible without some isolation like a duct or hose. It's basically a brass disc with some crystals stuck on the back, the crystals are the limiting factor, they lose their formation/polarity like a magnet at temperature. If it was in a heatsinked housing you could get it closer. The hose length on mine will be 150mm, so about half a millisecond delay. The volume in the sensor housing is minimised so the amount of mass moving back and forth in the hose and conduction of heat should be minimal also. If you filled the hose with something other than air the response would be faster but obviously damped as well, could be a possibility if the concept proves to be good.

[Frits Overmars]

With my system there would not be any CDI-curves anymore. Instead of looking up the prescribed amount of ignition advance for a certain rpm and thottle position,
the CDI would constantly monitor the exhaust pulses and adjust the ignition timing accordingly. It would also automatically adjust to a different exhaust pipe.
This is interesting and not so difficult to implement. Could the pulse timing feedback work between a maximum and minimum timing curve? So it could adjust for changes in pipe wall temp, fuel mixture and pipe design?Working between upper and lower timing safety limits would be no problem. And changes in pipe wall temp, fuel mixture and pipe design would not even come into play.
All the system would do is check wether the exhaust return pulse arrives just before exhaust port closure. If the pulse arrives too late, retard the ignition which will raise the EGT and the speed of sound. If the pulse arrives too early, advance the ignition timing. And yes, it would be good to have a limit set for safe maximum advance.


I still have a few electrical parts to get for my sensor, but the housing is finished, will test later today. It could do ignition timing feedback for sure, just measure time between pressure peaks and compare against RPM, output a signal for the CDI that corresponds with exhaust wave too fast or too slow.
Why hasn't anyone done this yet?My original idea was to use a crank angle decoder, but your idea of measuring the time between pressure peaks and comparing it against rpm is much simpler.

Why hasn't anyone done this yet? I could not do it on my own because my electronic skills are insufficient, and the works reaction was: "We are winning anyway. Why complicate things?" My claim that substituting EGT measuring with a more direct, effective approach was not a complication at all, could not persuade the bean counters.

[adegnes]

Working between upper and lower timing safety limits would be no problem. And changes in pipe wall temp, fuel mixture and pipe design would not even come into play.
All the system would do is check wether the exhaust return pulse arrives just before exhaust port closure. If it arrives too late, retard the ignition which will raise the EGT and the speed of sound . If the pulse arrives too early, advance the ignition timing. And yes, it would be good to have a limit set for safe maximum advance.

My original idea was to use a crank angle decoder, but your idea of measuring the time between pressure peaks and comparing it against rpm is much simpler.

Why hasn't anyone done this yet? I could not do it on my own because my electronic skills are insufficient, and the reaction at Aprilia was: "We are winning anyway. Why complicate things?" My claim that substituting EGT measuring with a more direct, effective approach was not a complication at all, could not persuade the bean counters.

Clever!
..........

[dutchpower]

Working between upper and lower timing safety limits would be no problem. And changes in pipe wall temp, fuel mixture and pipe design would not even come into play.
All the system would do is check wether the exhaust return pulse arrives just before exhaust port closure. If it arrives too late, retard the ignition which will raise the EGT and the speed of sound . If the pulse arrives too early, advance the ignition timing. And yes, it would be good to have a limit set for safe maximum advance.



But then you most have a hell of a good engine Frits

[Frits Overmars]

But then you most have a hell of a good engine FritsThat's what I'm aiming for anyway Dutch. But the scheme should work on any two-stroke engine.


Just tested the pulse sensor. I think this will work well. Would be able to measure time between pulses if you wanted to.Nathan, the time between the primary pulses, generated at exhaust port opening, will equal one crankshaft revolution. But what we need for ignition timing control, is the time between a primary pulse and its return pulse.
If I take the Aprilia RSA engine as an example, the primary pulse is generated by an exhaust port releasing a cylinder pressure of up to 12 bar. The return pulse generates a cylinder pressure of about 2 bar. Do you think it is feasible to distinguish the return pulses between those violent primary pulses?
Maybe like this: a pulse that is registered more than half a revolution-time after the ignition spark (and before the next spark), occurs after BDC, so it must be a return pulse.

[shnaggs]

Working between upper and lower timing safety limits would be no problem. And changes in pipe wall temp, fuel mixture and pipe design would not even come into play.
All the system would do is check wether the exhaust return pulse arrives just before exhaust port closure. If the pulse arrives too late, retard the ignition which will raise the EGT and the speed of sound. If the pulse arrives too early, advance the ignition timing. And yes, it would be good to have a limit set for safe maximum advance.

My original idea was to use a crank angle decoder, but your idea of measuring the time between pressure peaks and comparing it against rpm is much simpler.

Why hasn't anyone done this yet? I could not do it on my own because my electronic skills are insufficient, and the works reaction was: "We are winning anyway. Why complicate things?" My claim that substituting EGT measuring with a more direct, effective approach was not a complication at all, could not persuade the bean counters.

Frits, If 2 strokes were in F1 I think they would have done this. That statement "We are winning anyway......" is a passive answer, which is not how to better the 2 stroke. But I guess If I was a team manager with the big money people looking down on me, I might do the same....Why screw with something that is currently working???

Frits, If I win the Lotto, we (ie, you, Wob, Jan, and I'll just be there for fun) are going to build the most badass 2 stroke ever!!!!!

[Frits Overmars]

Frits, If I win the Lotto, we (ie, you, Wob, Jan, and I'll just be there for fun) are going to build the most badass 2 stroke ever!!!!!Don't forget to hand in your Lotto form then :D.

[oktrg500]

Had a minor blowup...

Hi,

Sorry to hear about the blowup. Since I'm also from Norway, I'm curious to know what the goal of this project is. It might have been mentioned before. If so, I totally missed it. Are you racing it, or is it just for the sheer joy of working with a two stroke engine? Me, I am in the second category. I did try a few attempts at track racing many centuries ago. Now, I'm happy being in my shed tinkering with two strokes. My favorite for quite a few years has been the Aprilia RS125 street bike. Much less expensive to mess with than the RG500 street bike I put quite a lot of money into before. I check this thread every day for updates. The more I learn, the more I understand how little I actually know. I guess that's a good thing. :not:

Thanks to all for this thread.

[Nath88]

That's what I'm aiming for anyway Dutch. But the scheme should work on any two-stroke engine.

Nathan, the time between the primary pulses, generated at exhaust port opening, will equal one crankshaft revolution. But what we need for ignition timing control, is the time between a primary pulse and its return pulse.
If I take the Aprilia RSA engine as an example, the primary pulse is generated by an exhaust port releasing a cylinder pressure of up to 12 bar. The return pulse generates a cylinder pressure of about 2 bar. Do you think it is feasible to distinguish the return pulses between those violent primary pulses?
Maybe like this: a pulse that is registered more than half a revolution-time after the ignition spark (and before the next spark), occurs after BDC, so it must be a return pulse.

Once I speed up the scope, we'll be able to see each pressure peak no problem. I just had it scanning slowly so I could see those primary pulses relative to throttle input. The frequency response of the piezo is up to ultrasonic so it will be fast enough to catch everything. The pressure peaks correspond with zero volt output, so we can have a circuit switch when the output crosses zero volts, indicating the positive and negative peaks. Conditioning of magnetic (VR) crank angle sensors in ECUs use the same principle. I modified this megasquirt drawing to illustrate, the pressure trace would be much more sinusoidal.
332950
Have a timer reset and waiting around 90 crank degrees > trigger timer on the primary positive pulse, then stop the timer at the next positive pulse which will be the return. Compare wave travel time to the predetermined ideal time, then adjust the output for more or less timing advance. Could use the TPS input on a 3D ignition to adjust the timing.

At the lower end of the resonant rpm range the system will hit the ignition advance limit, and we won't be able to reduce the wave speed (EGT) any further.
At the upper end of the resonant rpm range, what do you think would be the limit on ignition retard?

Would you just have the system active within the possible rpm range, and use predefined values outside that?
Would you also have the system active for the 2nd harmonic of the exhaust that occurs at low rpm? You could have the timer ignore the 1st positive return pulse in this mode.

[adegnes]

Hi,

Sorry to hear about the blowup. Since I'm also from Norway, I'm curious to know what the goal of this project is. It might have been mentioned before. If so, I totally missed it. Are you racing it, or is it just for the sheer joy of working with a two stroke engine? Me, I am in the second category. I did try a few attempts at track racing many centuries ago. Now, I'm happy being in my shed tinkering with two strokes. My favorite for quite a few years has been the Aprilia RS125 street bike. Much less expensive to mess with than the RG500 street bike I put quite a lot of money into before. I check this thread every day for updates. The more I learn, the more I understand how little I actually know. I guess that's a good thing. :not:

Thanks to all for this thread.

Thanks!
In the same category as you - just for fun/education. If bucket racing was a thing in Norway I would have had a go, but I'm not much of a racer. The RS125 is nice!

[adegnes]

Once I speed up the scope, we'll be able to see each pressure peak no problem. I just had it scanning slowly so I could see those primary pulses relative to throttle input. The frequency response of the piezo is up to ultrasonic so it will be fast enough to catch everything. The pressure peaks correspond with zero volt output, so we can have a circuit switch when the output crosses zero volts, indicating the positive and negative peaks. Conditioning of magnetic (VR) crank angle sensors in ECUs use the same principle. I modified this megasquirt drawing to illustrate, the pressure trace would be much more sinusoidal.
332950
Have a timer reset and waiting around 90 crank degrees > trigger timer on the primary positive pulse, then stop the timer at the next positive pulse which will be the return. Compare wave travel time to the predetermined ideal time, then adjust the output for more or less timing advance. Could use the TPS input on a 3D ignition to adjust the timing.

At the lower end of the resonant rpm range the system will hit the ignition advance limit, and we won't be able to reduce the wave speed (EGT) any further.
At the upper end of the resonant rpm range, what do you think would be the limit on ignition retard?

Would you just have the system active within the possible rpm range, and use predefined values outside that?
Would you also have the system active for the 2nd harmonic of the exhaust that occurs at low rpm? You could have the timer ignore the 1st positive return pulse in this mode.

This is very interesting!

[Frits Overmars]

At the lower end of the resonant rpm range the system will hit the ignition advance limit, and we won't be able to reduce the wave speed (EGT) any further.
At the upper end of the resonant rpm range, what do you think would be the limit on ignition retard?That would be time-dependent. There are quickshift systems that do not just cut the ignition, but retard it by as much as 50° in order to keep temperature in the exhaust gases. But that amount of after-TDC ignition could melt away the piston edge in seconds.
If we look at 'normal' WOT-ignition curves, an Aprilia RSA retards to 6° advance at 15000 rpm. Honda racing engines tend to retard a bit more; I've seen 5° after TDC at 14000 rpm. I think we could set the limit right there.


Would you also have the system active for the 2nd harmonic of the exhaust that occurs at low rpm? You could have the timer ignore the 1st positive return pulse in this mode.Nathan, these kind of questions make me very happy.
I would certainly optimize the 2nd harmonic at low rpm. Instead of just giving heaps of advance there in order to lower the exhaust gas energy, I'd rather have the second return pulse do some useful work. Below is a 2nd harmonic-ignition curve I worked out for the Aprilia RSA.
332952

[RomeuPT]

That would be time-dependent. There are quickshift systems that do not just cut the ignition, but retard it by as much as 50° in order to keep temperature in the exhaust gases. But that amount of after-TDC ignition could melt away the piston edge in seconds.
If we look at 'normal' WOT-ignition curves, an Aprilia RSA retards to 6° advance at 15000 rpm. Honda racing engines tend to retard a bit more; I've seen 5° after TDC at 14000 rpm. I think we could set the limit right there.

Nathan, these kind of questions make me very happy.
I would certainly optimize the 2nd harmonic at low rpm. Instead of just giving heaps of advance there in order to lower the exhaust gas energy, I'd rather have the second return pulse do some useful work. Below is a 2nd harmonic-ignition curve I worked out for the Aprilia RSA.
332952

Did this workout on the Aprilia RSA?

One more thing to try :weird:

At which rpm should the 2nd harmonic came in lower rpm for Honda engines?

With lower gas temps and much cooler exhaust temp I am guessing around 1/4 to 2/5 of the peak power rpm, say 3000 to 5000rpm with help of retard/advance...?

Even if ryger cannot make more then 35/40cv in 125cc, could it be usefull for other types of use besides kart/racing?

[Frits Overmars]

Did this workout on the Aprilia RSA?It was never put into practice. Someone killed the GP125 cc-class, remember?


At which rpm should the 2nd harmonic came in lower rpm for Honda engines?Exhaust gases don't give a damn about the name on the fuel tank, so for Hondas it's the same as for all other two-strokes.


With lower gas temps and much cooler exhaust temp I am guessing around 1/4 to 2/5 of the peak power rpm, say 3000 to 5000rpm with help of retard/advance...?Forget the temperature differences for a moment and think of sine waves. The 1st harmonic should fit just one complete sinus between Exhaust Opening and Exhaust Closure. The 2nd harmonic should fit two complete sinusses between EO and EC, i.e. at half the rpm, and so on for 3rd and 4th harmonics.
But an exhaust pulse loses some of its energy each time it is reflected, so instead of optimizing those higher harmonics via the ignition timing, it will be more effective to concentrate on the combustion/expansion process itself at low revs.


Even if ryger cannot make more then 35/40cv in 125cc, could it be usefull for other types of use besides kart/racing?I fail to see the connection between Ryger and second harmonics. Utilizing 2nd harmonics can be useful to all resonance-dependent engines, but you can forget about using them for karts, as these are compelled to use a fixed ignition timing.

[RomeuPT]

It was never put into practice. Someone killed the GP125 cc-class, remember?

Exhaust gases don't give a damn about the name on the fuel tank, so for Hondas it's the same as for all other two-strokes.

Forget the temperature differences for a moment and think of sinoidal waves. The 1st harmonic should fit just one complete sinus between Exhaust Opening and Exhaust Closure. The 2nd harmonic should fit two complete sinusses between EO and EC, i.e. at half the rpm, and so on for 3rd and 4th harmonics.
But an exhaust pulse loses some of its energy each time it is reflected in the pipe, so instead of optimizing those higher harmonics via the ignition timing, it will be more effective to concentrate on the combustion/expansion process itself at low revs.

I fail to see the connection between Ryger and second harmonics. Utilizing 2nd harmonics can be useful to all resonance-dependent engines, but you can forget about using them for karts, as these are compelled to use a fixed ignition timing.

I mean the RS125 ..

Not talking about harmonics in the ryger, wasnt the engine free from burning oil and had lower emissions? Good to road daily use

[Frits Overmars]

Not talking about harmonics in the ryger, wasnt the engine free from burning oil and had lower emissions? Good to road daily useDon't ask me, I'm not commenting on that subject. Ask LucF. He'll tell you that the Ryger was the best invention since sliced bread.

[JanBros]

Don't ask me, I'm not commenting on that subject. Ask LucF. He'll tell you that the Ryger was the best invention since sliced bread.

wasn't it the best invention since the invention of the invention ?

[F5 Dave]

I'm pretty sure I invented that.

[RomeuPT]

Don't undervalue the engine so much, sometimes new techonology promises but needs time to grow before it makes a worthy difference. example: graphene ;)

[TZ350]

332984

Well another upside down picture, whats with my phone!!!! but I guess its appropriate because its not a 2T or even a GoKart but it is of a period of racing that I think was very exciting. A time when a few clever mates could get together and build something with a bit of skill and with luck take on the world.

332986

Fuel injector positions on my NSR110. Two in the B ports, one each side, one in the boost port that fires through a slot to the under side of the piston and one into the crankcase.

332987

Injector sizing is important, for tune-ability you wan't as small an injector as possible. This one is to big. The straight line indicates it has bottomed out and can't be turned down anymore as it has dropped to its minimum on time. This makes it impossible for me to tune for less than 5% throttle with this injector.

Flettner pointed out to me that timing the injection pulse is very important.

I have found that an under piston injector in the C port likes to finish its injection cycle at BDC and the injectors in the B ports like to finish at transfer port closing, just like Flettner suggested.

I have found that C loves BDC but changing the B port injection ending from BDC to Transfer port closing significantly reduces the fuel load required.

The C port injector on the left likes a different end point to B port injectors on the right of the graph.

332985

With the same timing the slow speed C port injector on the left is having a hard time and the engine cleans up as the injection swaps over to the B port injectors on the right side of the graph.

Things might be much better if I could follow Flettners suggestion of having the two stage injection setup with the low speed injectors in the B ports and the High speed ones in the A ports. That way they would all like the same timing.

There is no such thing as a smooth swap over from BDC C port injector to TPC B port injectors as any smoothing means one or the other is in an un happy place.

Under piston C and injectors firing down the B port require very different end of injection timing, BDC or TPC so just another 2T EFI complication.

[peewee]

wob I got this richer needle about 10days ago and tried it with 10% nitro. once I got it screwed pretty far into the slide there was no idle runaway when the slide is closed after a full throttle run. so now I have some 15 and 20% to try next, hopefully tomorow. im trying to figure out how these needle work, incase I need even a richer one. im guessing the amount of taper from top to bottom controls the fuel from idle to full throttle, like the photo shows ? what I did was measure the thickness from front to back at many points, indicated by the red marks. compared to the old one, the new one appears to be about .05mm thinner at the top and bottom and about .1mm thinner through the center portion. so I think that translates to being alittle richer at 0-1/4 and 3/4-full. with it even more richer 1/4-3/4. since the 1/4-3/4 is mostly not important for this engine, ill just make sure to only have the 0-1/4 richer, if I need another needle.

anyways something else that happened , I made a rookie mistake and left a void when I welded on the tower for the comp release valve and it must have filled with fuel and caused a small explosion which resulted in one of the welds cracking. so I pulled the head off and tried to eliminate the void as much as I could, then rewelded it. the good news is , it appears so far the devcon is holding very well against the methanol and nitro and theres no sign of blackening in the transfer passages

[jbiplane]

Here are a few more pictures showing the velocities in the exhaust. It should give a picture but i keep in mind that I have been told that the calculation grid (mesh) still could do with some refinements and more refinements still. I have also been told (yes I tried to push a little) that doing a fully dynamic cycle, possibly with combustion and everything is quite complicated and I think we would have needed more 2-stroke knowledge. Unfortunately, we have to work with others things during working hours for a while now..:(.

Hi Norman

Could you recommend any available in internet consistent sources to perform CDF analysis of 2-stroke engines in Fluent.
I saw only one tutorial consistent for scavenging efeciency in Fluent.
https://www.mr-cfd.com/two-stroke-engine-scavenging/
and PhD Thesis
https://www.google.ru/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwji_pbpiYHXAhUOLlAKHZDrCM4QFggoMAA&url=https%3A%2F%2Fdiglib.tugraz.at%2Fdownload.php% 3Fid%3D58132aa8b3c2c%26location%3Dbrowse&usg=AOvVaw3osQOcYR1lbH6ebGMaFFa-

Valery

[Frits Overmars]

That is a lot of good reading. Thanks Valery.

[Norman]

Hi Norman

Could you recommend any available in internet consistent sources to perform CDF analysis of 2-stroke engines in Fluent.
I saw only one tutorial consistent for scavenging efeciency in Fluent.
https://www.mr-cfd.com/two-stroke-engine-scavenging/
and PhD Thesis
https://www.google.ru/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwji_pbpiYHXAhUOLlAKHZDrCM4QFggoMAA&url=https%3A%2F%2Fdiglib.tugraz.at%2Fdownload.php% 3Fid%3D58132aa8b3c2c%26location%3Dbrowse&usg=AOvVaw3osQOcYR1lbH6ebGMaFFa-

Valery

Thank you for the interesting information. I earlier got some assistance to make a series of simulations to better understand the airflow paths through a "RSW type" engine (cause I find in general somewhat difficult to fully understand the (dynamical) flow through a two stroke). I would have liked to make them dynamical with a full piston movement, but the circumstances at the time did not allow this. I have a quite new contact with a Ph.D. in CFD calculations. I will discuss this topic with him to see if I there is a possibility to continue somehow. It also depends on the time he is willing to give me on this, because to buy in these kind of simulations is very expensive, you will hardly get a calculation start up under 5000EUR. I cannot give any time schedule on this. However, if and when, I find out something that could be to some use for anyone here, I will share. At the moment I do not know any better source than you presented Valery, I'm afraid.

[Magnus676]

Hi there guys,
I have a question regarding port timings.Most say thats a matter of rpm,but I think its a matter of piston speed.Let me explain my thinking:
Lets say we have 2 engines that both give max power at 10000rpm.The one is a 50cc engine and the other say a KTM 300.Theoritically they both should have the same exhaust timing,lets say its about 192 degrees.But,the way I'm thinking this is wrong because it doen't take into account how fast the piston moving,it takes just how fast the crank is spinning.I know we cannot accurately say at what speed the piston opens and closes the ports,but here are some numbers if we take into account mean piston speed:Lets say the 50cc engine is square just like the KTM,so it'll have a 40mm stroke wich gives us a mps of 13.3 m/s.Thr KTM on the other hand will have a mps of 24 m/s,so the piston will open and close the ports in a greater speed.
So my damn head thinks that if the piston opens and closes the ports faster then we have to give the ports more duration,although the rpm is the same with the 50cc.
This theory of mine may be trash,so I want to hear some opinions from you guys and learn something today :niceone:
Edit:If forgot to mention.With this theory an oversquare engine will need less timing for the same revs than a square at the same displacement.But I think that doesn't apply her because you need more port area than a square engine to make the same power as mentioned before.

[RomeuPT]

Hi there guys,
I have a question regarding port timings.Most say thats a matter of rpm,but I think its a matter of piston speed.Let me explain my thinking:
Lets say we have 2 engines that both give max power at 10000rpm.The one is a 50cc engine and the other say a KTM 300.Theoritically they both should have the same exhaust timing,lets say its about 192 degrees.But,the way I'm thinking this is wrong because it doen't take into account how fast the piston moving,it takes just how fast the crank is spinning.I know we cannot accurately say at what speed the piston opens and closes the ports,but here are some numbers if we take into account mean piston speed:Lets say the 50cc engine is square just like the KTM,so it'll have a 40mm stroke wich gives us a mps of 13.3 m/s.Thr KTM on the other hand will have a mps of 24 m/s,so the piston will open and close the ports in a greater speed.
So my damn head thinks that if the piston opens and closes the ports faster then we have to give the ports more duration,although the rpm is the same with the 50cc.
This theory of mine may be trash,so I want to hear some opinions from you guys and learn something today :niceone:
Edit:If forgot to mention.With this theory an oversquare engine will need less timing for the same revs than a square at the same displacement.But I think that doesn't apply her because you need more port area than a square engine to make the same power as mentioned before.

I think the scale of things is important, example: big engines tend to have high pre comp but have to use lower head comp to work.
Difference in pressure make the gases move from place A to B, but the speed of moving does not have a linear correlation with pressure differences, bigger displacement has longer ducts etc, it takes more time to do the same gas dynamics at the "phisical scale" of a two stroke. In short... gases moving at around the same speed will have much more trouble to scavenging a 72mm bore then a 40mm if they have the same time.

[peewee]

well today didn't go so good. I think the 15% nitro by volume was really more like 25% by weight :laugh:, based off some conversion charts. the difference between volume and weight at the 40F fuel temp made for a hotter mix than I expected. ive included these charts in case anyone wants them for their own reference, they can be handy if no hydrometer is available. anyways I richened the needle as much as I dared, alittle to far in fact. it popped out of the emulsion tube and the slide stuck open which caused a brief moment of panic until I was able to press the rear brake and kill the engine. ill have lectron send another needle and ill try again another day. heres a short crappy video but you can hear its pretty lean when I rev it and the slide closes, it has that zingy sound. sure goes like hell at full throttle though



https://www.youtube.com/watch?v=uak2zYZm1jg

[TZ350]

Hi there guys, I have a question regarding port timings. Most say that is a matter of rpm,but I think its a matter of piston speed. I want to hear some opinions from you guys and learn something today :niceone:

STA (specific time area). It takes into account the things you mention.

A Google search of this thread will bring up plenty of discussion about STA for you to check out and compare ideas.



Use Google to search this site, use an ordinary search phrase and after it add:- site:www.kiwibiker.co.nz (http://www.kiwibiker.co.nz/)

for example

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

Mick

[F5 Dave]

Hey Peewee nice day out there for Autumn out your way .

[adegnes]

well today didn't go so good. I think the 15% nitro by volume was really more like 25% by weight :laugh:, based off some conversion charts. the difference between volume and weight at the 40F fuel temp made for a hotter mix than I expected. ive included these charts in case anyone wants them for their own reference, they can be handy if no hydrometer is available. anyways I richened the needle as much as I dared, alittle to far in fact. it popped out of the emulsion tube and the slide stuck open which caused a brief moment of panic until I was able to press the rear brake and kill the engine. ill have lectron send another needle and ill try again another day. heres a short crappy video but you can hear its pretty lean when I rev it and the slide closes, it has that zingy sound. sure goes like hell at full throttle though



https://www.youtube.com/watch?v=uak2zYZm1jg

Great that you're doing the nitro thing! I'm out of business for a while until my engine is back together. Until then I can follow your progress.

[jasonu]

Don't undervalue the engine so much, sometimes new techonology promises but needs time to grow before it makes a worthy difference. example: graphene ;)

Not under valuing the engine, just all the shit that those involved spouted.

[peewee]

Great that you're doing the nitro thing! I'm out of business for a while until my engine is back together. Until then I can follow your progress.

i dont know if you could call it progress. more like throwing mud at the wall and hope something sticks :laugh:. but i think ive got the full throttle sorted out. now its just a matter of keeping it rich enough when the slide is closed. one other odd thing ive noticed recently, when idling if the throttle is opened, sometimes it will bog and kill the engine. im not sure if its from being to lean or the engine isnt warming up enough. anyways i dont think i have any spare bits that would be of any value to you (most of my spares are for dirtbikes) but i could help out if youve got a contribution page or something like that

[adegnes]

i dont know if you could call it progress. more like throwing mud at the wall and hope something sticks :laugh:. but i think ive got the full throttle sorted out. now its just a matter of keeping it rich enough when the slide is closed. one other odd thing ive noticed recently, when idling if the throttle is opened, sometimes it will bog and kill the engine. im not sure if its from being to lean or the engine isnt warming up enough. anyways i dont think i have any spare bits that would be of any value to you (most of my spares are for dirtbikes) but i could help out if youve got a contribution page or something like that

😂
That's interesting, I've experienced the same bogging. It goes away if I apply the choke, but the weird thing is with the choke on it acts leaner and idles high. Maybe the fuel part of the pwk choke circuit needs drilling too.

I'm very thankful for all the help I can get! But I don't want anyone to feel they have to. I'm very thankful for you guys watching my videos and contributing with advice and help too!

I've got a Patreon account:
https://www.patreon.com/2strokestuffing

If you don't want to do the monthly Patreon deal you can donate directly via this PayPal link:
https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=BMXLUFKASKAJC

I've started porting the cylinder, can't wait to see how it behaves!

[peewee]

😂
That's interesting, I've experienced the same bogging. It goes away if I apply the choke, but the weird thing is with the choke on it acts leaner and idles high. Maybe the fuel part of the pwk choke circuit needs drilling too.

I'm very thankful for all the help I can get! But I don't want anyone to feel they have to. I'm very thankful for you guys watching my videos and contributing with advice and help too!

I've got a Patreon account:
https://www.patreon.com/2strokestuffing

If you don't want to do the monthly Patreon deal you can donate directly via this PayPal link:
https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=BMXLUFKASKAJC

I've started porting the cylinder, can't wait to see how it behaves!

hey mate ill send some help your way. if you can get it sorted out,it will likely help me. like i said, i havent a clue what im doing with nitro. ive no idea where the spark lead needs to be, what com ratio i should have, what oil ratio is best, where the cylinder temp should be. thats why i describe it as throwing mud at the wall:laugh:. i suppose if it doesnt seize or blow up then i must be going in some what of the right direction

[marsheng]

OT I'm going from Chch to Manfeild this weekend 26-29 October and have space in the closed trailer for one bike either way. If you need a bike moved, please contact me asap. marshland@marshland.co.nz.

Cheers Wallace.

[adegnes]

hey mate ill send some help your way. if you can get it sorted out,it will likely help me. like i said, i havent a clue what im doing with nitro. ive no idea where the spark lead needs to be, what com ratio i should have, what oil ratio is best, where the cylinder temp should be. thats why i describe it as throwing mud at the wall:laugh:. i suppose if it doesnt seize or blow up then i must be going in some what of the right direction

Thanks, means a lot!
Sounds like we're in the same boat concerning nitro...

[TZ350]

Don't undervalue the engine so much, sometimes new technology promises but needs time to grow before it makes a worthy difference. example: graphene ;)
Not under valuing the engine, just all the shit that those involved spouted.

That is right, not undervaluing the engine and the effort that has gone into it at all.

It is the smoke and mirrors and doubtful truths trying to promote it that has attracted all the derision. The reporting has not been transparent at all but more in the style of a sales promotion that has not stood up to even a cursory evaluation. We can see through bullshit and call it out for what it is, but a bit of truth about success and failures would get us all on side and cheering the Ryger team on.

We would all love the Ryger concept to be a success.

[guyhockley]

Not a bucket, but in the same spirit, I think...
https://www.facebook.com/groups/Suzukiracing2strokes/permalink/1249896881716202/

[TZ350]

Not a bucket, but in the same spirit, I think...

https://www.facebook.com/groups/Suzukiracing2strokes/permalink/1249896881716202/ (https://www.facebook.com/groups/Suzukiracing2strokes/permalink/1249896881716202/)

Absolutely, great build.

[Nath88]

The exhaust pressure sensor I was using died by drowning in exhaust oil, so it motivated me to rig up the new exhaust pulse sensor for a test.

333019

Green line is the exhaust pulse, rate of change of pressure. Red lines are the sample window (ECU takes the lowest value inside this window). White lines are the trigger wheel teeth as the crank rotates. There's 20 teeth on the wheel, first tooth is at 72°BTDC. Primary exhaust pulse hits the sensor at around tooth 11 (126°). On this trace we see 2 firing primary pulses followed by a misfire pulse, caused by a throttle blip at 2400rpm, however engine speed increases an unknown amount over the 3 rotations. Either way the pipe is way out of sync with the engine at these revs. I later tweaked the sample window from 30 to 45 degrees duration to properly catch the pulses.

I also took the bike to the dyno, it was running too rich, perhaps due to the dead sensor, maybe some other factors. Made 45hp on the dynojet, sounded rich all the way through but the curve was pretty consistent with carb 2 strokes, maybe a bit stronger coming onto the pipe. I'll scan the chart at some point and post it.

[peewee]

We run R7376-10 plug in everything and its been working great !

Nitro carrying a healthy dose of oxygen , makes the mix as much if not more rich tolerant . Setting the engine very rich also take care of a lot of temperature and atmospheric pressure fluctuation .

Regarding compression ratio , your application being far from my scope of expertise , I wont advise anything . The idea behind reducing the comp ratio is mostly because of the low octane rating of nitro . As stated earlier in this thread , at high rpm the octane needed lowers trendemously wich is probably another reason why we can get away with such high nitro percentage and comp .

im finding out that having the carb well on the rich side is the way to go. leaning it out like a petrol engine would be a huge mistake i think :laugh:

whats the advantage to r7376 ? from what i understand , it has the electrode and ground strap inside the plug body and not protruding into the head chamber. is this the advantage over a standard plug ?

top fuel cars are around 7:1 com ratio from what ive read. i always thought the low ratio was because the huge volume of liquid in the cylinder but the low octane of 90% nitro makes sense

[wobbly]

The R7376 has a fine wire Iridium center electrode, and a very thin Platinum ground strap.
This combination dramatically reduces the voltage necessary to ionize the gap, and unshrouds this gap as well.
The Platinum electrode is laser welded to the body, and unlike plenty of " normal " race plugs I have never seen one drop off from deto damage.
Same with the ceramic insulator,never seen one crack, again seen plenty of cracked ones in things like ordinary cheap Iridium plugs.
You can learn plenty from the colour change position along the thin ground straps length.
This plug is exactly the same nose configuration as the original shorty plugs designed for the Honda RS125/250, but is less than 1/4 the price.
Plus it has a normal body shape and doesn't need the idiot priced special plug caps that cost more than the plug.
All race engines deserve this plug - nothing else comes close as far as reliability and power capability.
I have posted a dyno run on here previously showing the power advantage over everything else, including the Denso equivalent.

[koenich]

there you go: https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner/page702?highlight=7376 (scroll down a bit for the dyno graph)

After Wobblys post I bought a R7376 for my 50cc racer and they brought quite some improvements on the track. Driveability improved, midrange "bog" was eliminated, overrev behavior improved and they seem to last forever (I have one with 50+ hours on it and it's still working like a charm). Only issue in rain races when not revved hard all the time the R7376 tends to clock up faster than a BR10.

[Frits Overmars]

Sounds like we're in the same boat concerning nitro...Here's hoping it doesn't dissolve duct tape :p.
333034

[Frits Overmars]

333019
Green line is the exhaust pulse, rate of change of pressure. Red lines are the sample window (ECU takes the lowest value inside this window). White lines are the trigger wheel teeth as the crank rotates. There's 20 teeth on the wheel, first tooth is at 72°BTDC. Primary exhaust pulse hits the sensor at around tooth 11 (126°). On this trace we see 2 firing primary pulses followed by a misfire pulse, caused by a throttle blip at 2400rpmThat looks very promising Nathan :niceone:.

[Lbracing]

As promised , a couple pictures of what I do .

Pistons are machined out of 4032 . From 50cc to 140cc .

Cylinder with removable transfer port cover . Intake is controled by piston port . You cant really see it but the exhaust port floor is a nice convex shape . 5TH port is fed by a hole in piston , I am working on a better set up for my next engine .

Carburetor is based on walbro wb diaphragm for spacing reasons . Maximum venturi I can put in them with this design is 34mm . I use them on everything under 100cc .

Just a random toroidal shaped head in the works.


333042333037333038333039333040333041

[nitro2tfx]

😂
That's interesting, I've experienced the same bogging. It goes away if I apply the choke, but the weird thing is with the choke on it acts leaner and idles high. Maybe the fuel part of the pwk choke circuit needs drilling too.



The bogging is because the crankcase is loading up with fuel. When you open the throttle after a period of idling the engine goes super rich as it picks up a bunch of fuel from the crankcase as well as from the carb. Rev it up and blip the throttle to clear it out, first. Could take a few seconds or more.

Applying the choke makes the engine go lean because the choke circuit is only rich enough for gas. It is a leaning circuit on a methanol/nitro mix and an excellent way to get a runaway engine, especially at startup when you are in neutral.

[nitro2tfx]

top fuel cars are around 7:1 com ratio from what ive read. i always thought the low ratio was because the huge volume of liquid in the cylinder but the low octane of 90% nitro makes sense

Top fuel cars are highly supercharged and actually run lower compression ratios than that.

Naturally aspirated nitro engines, running straight nitro from the can (no methanol), run compression ratios of 11 to 12:1 and do not experience any detonation, despite the very large displacement and low revs, compared to the engines being discussed in this thread.

[SwePatrick]

The bogging is because the crankcase is loading up with fuel. When you open the throttle after a period of idling the engine goes super rich as it picks up a bunch of fuel from the crankcase as well as from the carb. Rev it up and blip the throttle to clear it out, first. Could take a few seconds or more.

Applying the choke makes the engine go lean because the choke circuit is only rich enough for gas. It is a leaning circuit on a methanol/nitro mix and an excellent way to get a runaway engine, especially at startup when you are in neutral.


Correct!

Already with methanol only you get same effect with having choke pulled to long.
But one can use it for faster warmup, let it 'sniff' on the runaway for a while.
Then engine is more responsive quicker due to heat has started to build faster inside cylinder.
I noticed if starting engine with no choke it spits unburnt fuel through the tailpipe for a long time.
Using choke shorten this a lot.

I also noticed that the mixture it gave as much power as possible on, is way to rich on a cold engine.
Somewhat 'other way around' then a petrol engine =)

Start without choke, pull up the choke, let it touch the runaway, press down choke again.
I gained a lot of time doing this, also saved fuel ;)

A Methanol and/or Nitro could do really well with a termoregulated radiator also.
As it need heat to burn everything properly.
If not having heat, the mixture it produces max power with is actually keeping it from getting warm fast.
Can be really frustrating with dragracing, the engine must produce power quickly.

I did actually a experiment on my dyno.
I pulled through the gears, started on 1st with cold engine.
On 1st it gave only ~46hp
And for every gear the power raised.
On 5th gear i had 68Hp, that´s actually 22hp loss at the most important place in dragracing,, the start.

Pipetemp does also play a part in this, but it is much much more noticable with methanol.

Another experiment i did was to reduce powerjet to get it to warm up faster.
I did nine 5th gear pulls in a row.
And when i saw the exhausttemp raise i turned out the powerjet again.
And yes,. it gained power.

I dunno actually if it was vaporization or fuel actually releases it´s oxygen when engine is in desired working temp.
But it needs more fuel when it´s hot =)

[adegnes]

As promised , a couple pictures of what I do .

Pistons are machined out of 4032 . From 50cc to 140cc .

Cylinder with removable transfer port cover . Intake is controled by piston port . You cant really see it but the exhaust port floor is a nice convex shape . 5TH port is fed by a hole in piston , I am working on a better set up for my next engine .

Carburetor is based on walbro wb diaphragm for spacing reasons . Maximum venturi I can put in them with this design is 34mm . I use them on everything under 100cc .

Just a random toroidal shaped head in the works.


333042333037333038333039333040333041

Nice work!


The bogging is because the crankcase is loading up with fuel. When you open the throttle after a period of idling the engine goes super rich as it picks up a bunch of fuel from the crankcase as well as from the carb. Rev it up and blip the throttle to clear it out, first. Could take a few seconds or more.

Applying the choke makes the engine go lean because the choke circuit is only rich enough for gas. It is a leaning circuit on a methanol/nitro mix and an excellent way to get a runaway engine, especially at startup when you are in neutral.



Correct!

Already with methanol only you get same effect with having choke pulled to long.
But one can use it for faster warmup, let it 'sniff' on the runaway for a while.
Then engine is more responsive quicker due to heat has started to build faster inside cylinder.
I noticed if starting engine with no choke it spits unburnt fuel through the tailpipe for a long time.
Using choke shorten this a lot.

I also noticed that the mixture it gave as much power as possible on, is way to rich on a cold engine.
Somewhat 'other way around' then a petrol engine =)

Start without choke, pull up the choke, let it touch the runaway, press down choke again.
I gained a lot of time doing this, also saved fuel ;)


Thanks! Makes sense.

[jbiplane]

Thank you for the interesting information. I earlier got some assistance to make a series of simulations to better understand the airflow paths through a "RSW type" engine (cause I find in general somewhat difficult to fully understand the (dynamical) flow through a two stroke). I would have liked to make them dynamical with a full piston movement, but the circumstances at the time did not allow this. I have a quite new contact with a Ph.D. in CFD calculations. I will discuss this topic with him to see if I there is a possibility to continue somehow. It also depends on the time he is willing to give me on this, because to buy in these kind of simulations is very expensive, you will hardly get a calculation start up under 5000EUR. I cannot give any time schedule on this. However, if and when, I find out something that could be to some use for anyone here, I will share. At the moment I do not know any better source than you presented Valery, I'm afraid.

Thank Norman, Frits and others. I found here many interesting ideas. We are small company which works like "engine atelier" for small aircrafts, UAV and other applicarion where weight and fuel economy are vital. To the moment numerous codes like ~bimotion ~mota ~Ricardo Wave ~Lotus concept
gives irreal results on boxer 2-strokes engines I produce. So one of my present objectives is to make parametric CAD model linked with CFD simulation of 2-stroke engine complete from intake to exhaust. I believe will sucseed in ~4+ month by myself and understand what have to be changed.

http://www.reaa.ru/cgi-bin/yabb/YaBB.pl?action=downloadfile;file=2b350.jpg

[Frits Overmars]

Thank Norman, Frits and others. I found here many interesting ideas. We are small company which works like "engine atelier" for small aircrafts, UAV and other applicarion where weight and fuel economy are vital. To the moment numerous codes like ~bimotion ~mota ~Ricardo Wave ~Lotus concept
gives irreal results on boxer 2-strokes engines I produce. So one of my present objectives is to make parametric CAD model linked with CFD simulation of 2-stroke engine complete from intake to exhaust. I believe will sucseed in ~4+ month by myself and understand what have to be changed.
http://www.reaa.ru/cgi-bin/yabb/YaBB.pl?action=downloadfile;file=2b350.jpgThat is a nice-looking engine, Jbiplane.
It takes me back about 20 years when I designed a similar ultralight-powerplant. You may recognize some of the weight-saving ideas :D.
333068

[nitro2tfx]

Correct!

Already with methanol only you get same effect with having choke pulled to long.
But one can use it for faster warmup, let it 'sniff' on the runaway for a while.
Then engine is more responsive quicker due to heat has started to build faster inside cylinder.
I noticed if starting engine with no choke it spits unburnt fuel through the tailpipe for a long time.
Using choke shorten this a lot.

I also noticed that the mixture it gave as much power as possible on, is way to rich on a cold engine.
Somewhat 'other way around' then a petrol engine =)

Start without choke, pull up the choke, let it touch the runaway, press down choke again.
I gained a lot of time doing this, also saved fuel ;)

A Methanol and/or Nitro could do really well with a termoregulated radiator also.
As it need heat to burn everything properly.
If not having heat, the mixture it produces max power with is actually keeping it from getting warm fast.
Can be really frustrating with dragracing, the engine must produce power quickly.

I did actually a experiment on my dyno.
I pulled through the gears, started on 1st with cold engine.
On 1st it gave only ~46hp
And for every gear the power raised.
On 5th gear i had 68Hp, that´s actually 22hp loss at the most important place in dragracing,, the start.

Pipetemp does also play a part in this, but it is much much more noticable with methanol.

Another experiment i did was to reduce powerjet to get it to warm up faster.
I did nine 5th gear pulls in a row.
And when i saw the exhausttemp raise i turned out the powerjet again.
And yes,. it gained power.

I dunno actually if it was vaporization or fuel actually releases it´s oxygen when engine is in desired working temp.
But it needs more fuel when it´s hot =)

The choke technique does work well for methanol and not too too much nitro.

[FastFred]

We are small company which works like "engine atelier" for small aircrafts, UAV and other applicarion where weight and fuel economy are vital.

333047

There you are TZ, maybe a successful 2T EFI system, looks like an injector port in that throttle body.

[peewee]

As promised , a couple pictures of what I do .

Pistons are machined out of 4032 . From 50cc to 140cc .

Cylinder with removable transfer port cover . Intake is controled by piston port . You cant really see it but the exhaust port floor is a nice convex shape . 5TH port is fed by a hole in piston , I am working on a better set up for my next engine .

Carburetor is based on walbro wb diaphragm for spacing reasons . Maximum venturi I can put in them with this design is 34mm . I use them on everything under 100cc .

Just a random toroidal shaped head in the works.


333042333037333038333039333040333041

indeed that's some nice work :niceone:. is this happen to be one of your saws ?

[peewee]

Top fuel cars are highly supercharged and actually run lower compression ratios than that.

Naturally aspirated nitro engines, running straight nitro from the can (no methanol), run compression ratios of 11 to 12:1 and do not experience any detonation, despite the very large displacement and low revs, compared to the engines being discussed in this thread.

do you know of any rules of thumb regarding com ratio and nitro percentage in a 2t or is it just trial and error to see what works ? theres almost no info about 2t and nitro that ive been able to find so far

[husaberg]

do you know of any rules of thumb regarding com ratio and nitro percentage in a 2t or is it just trial and error to see what works ? theres almost no info about 2t and nitro that ive been able to find so far
Bell............................
http://iheartstella.com/resources/manuals/tuning/Graham-Bell-Two-Stroke-Performance-Tuning.pdf

Alcohol fuel is permitted in most categories of speedway and dirt flat-track racing. 117
Two Stroke Performance Tuning
Both methanol (methyl alcohol) and ethanol (ethyl alcohol) have an octane rating by the Research method of 140-160, depending on mixture richness. Therefore these fuels can be used with very high compression ratios. Methanol and ethanol have a very high latent heat of vaporisation, i.e., it takes a lot of heat to convert them from liquid form into vapour. Petrol has a latent heat of evaporation of 135 Btu/lb., methanol 472 Btu/lb. and ethanol 410 Btu/lb. This heat, required for proper atomisation, is removed from the piston crown, combustion chamber and the cylinder, resulting in an internally cooler engine. An engine burning methanol will usually show a 6-8% power increase over one running on Avgas 100/130 (i.e., Racing Fuel 100), without any change in compression ratio. With the compression ratio increased to its maximum, power can rise as much as 15-17%. Where does the power increase come from? The two cycle engine is a type of heat engine, i.e., one that burns fuel to cause the expansion of gas, and the subsequent movement of the piston. The more heat produced by the combustion fire, the more pressure there will be exerted on the piston, which gives us a power increase. Using petrol, the fuel/air ratio for best power (i.e., the strongest force on the piston) is 1:12.5. With methanol, for example, we can increase the fuel/air ratio to 1:4.5, although I usually prefer a ratio of 1:5.5; less than 1:7 is too lean. One pound of petrol has the energy potential of about 19,000 Btu (one British Thermal Unit is the amount of energy required to raise the temperature of one pound of water one degree Fahrenheit.). In comparison, methanol delivers around 9,800 Btu/lb., which means that it produces less than 52% of the heat energy of lib of petrol. However, because we are mixing more methanol with each pound of air (1:5.5) than petrol (1:12.5), we are actually producing more heat energy by burning methanol. To work out how much more heat energy is produced, we have to divide 12.5 by 5.5, which equals 2.27. Next we multiply 9800 by 2.27, which gives us 22,246. This indicates that methanol, in the correct fuel/air proportions, will produce 17% more heat energy than petrol at the correct fuel/air ratio.
By comparison, the maximum increase we can obtain using ethanol is about 10%, although it does have anti-knock and cooling properties very nearly the same as methanol. In coming years, I expect we will see a marked increase in the useage of ethanol in both racing and road engines. As the world's oil supply dries up, more racing organisations and governments will encourage the production and use of ethanol derived from grain and sugar producing plants. Strong public opinion against all forms of motor sport using valuable reserves of crude based fuels will, I expect, soon force many sanctioning bodies to ban the use of petrol in motor racing, with the obvious alternatives being ethanol or ethanol/toluol, ethanol/acetone blends. From the above calculation, you can see that an engine running on straight methanol will burn more than twice as much fuel (1.8 times as much for ethanol) as one burning petrol. Therefore you must be careful to ensure that the fuel tap, fuel lines and needle valve will flow the required amount of fuel. This can present some problems, as many carburettors will not flow the required
amount of fuel through the standard needle and seat. Often a larger replacement is not available, so you will have to enlarge the discharge holes to increase flow by the amount necessary. At times you will find it impossible to get main jets large enough, so again you will have to resort to some drilling. Most Mikuni carburettor jets (the hex head type) are classified with regard to their fuel flow rate, the number stamped on the jet standing for the ccs of fuel the jet is capable of flowing in a certain time. If you are changing from petrol to methanol, then you should start testing with jets at least 2.3 times as large, eg: change 210 jet to a 480. The round head Mikuni jets are rated according to their nominal bore diameter in millimetres, eg: a round head 250 jet has a nominal aperture of 2.5mm. Again, when changing from petrol to methanol you will have to begin with jets with an aperture area 2.3 times as large. (Aperture area = nr2). Keep in mind also when you convert to an alcohol fuel, either neat or blended, that the fuel/oil ratio may have need of adjustment. Straight methanol would require only 80% as much oil, or a 25:1 ratio in many applications, although some engines will require a 16:1 mix. It is always best to start testing at 20:1 and work from there. There are other problems involved in the change to alcohol, some of which will affect you and some your engine. Since your life is the most important, we will deal with you first. Methanol is extremely poisonous and, as it is an accumulative poison, it can build up over a period of time and oxidise to form formaldehyde, eventually causing blindness or even insanity. It is absorbed through the skin and lungs, either by direct contact or from the vapours. Inhalation of the exhaust gas can also be dangerous as vaporised methanol is usually present, especially when rich mixtures are being used. Alcohols are a very effective paint stripper, and they may attack some fibreglass resins. They have a scouring effect on fuel tanks and lines so these should be soaked in alcohol and then drained so that the residue does not find its way into the carburettor when you switch from petrol to alcohol. Methanol and ethanol will absorb huge amounts of water out of the air, so they must always be kept in an air-tight container. The fuel will also have to be completely drained from the tank and the carburettor to prevent the formation of water-induced corrosion and oxidization. This can be particularly damaging to a carburettor and usually results in blocked metering passages. After burning alcohol in a two-stroke engine it is most important to run a petrol/oil mix rich in oil through the engine each time you put your machine away after a day's running. If this is not done, you v,'ill soon find corrosion and etching of the cylinder wall, crank and piston pin, needle and ball bearings that will lead to premature failure. To prevent this occurrence, I would suggest that you run a half pint of 16:1 petrol/oil mixture through the engine. In colder climates, starting difficulties may be encountered when pure alcohol is being burned. Some use other more volatile fuels blended in, to help overcome this problem. Usually 5% acetone or a maximum of 3% ether is used. I do not recommend starting aerosols containing ether, due to the possibility of engine damage being caused by detonation. Personally I feel the best method is to remove the spark plug and pour about a half teaspoon of either petrol or neat acetone into the cylinder before you attempt to start the engine. Alcohol burners demand a good ignition system. Not only does the ignition have to cope with much higher compression pressures, it may also be called on to fire plugs
Two Stroke Performance Tuning
wetted by the very rich mixture being inducted. Alcohol fuels burn much more slowly than petrol, so it will be necessary to experiment with more ignition advance. It is not possible to predict just how much additional advance will be required as there are so many variables involved, but you should begin testing with about an extra 3-5° advance. Before you advance the spark lead, do make sure that the carburation is fully sorted out. If the engine runs just slightly lean, with added spark lead you could very easily hole a piston. As well as a much larger main jet, it is probable that a different needle profile and a larger needle jet will be required. To correct off idle leanness, a bigger pilot jet and a small 1.0 to 1.5mm slide cutaway may be needed.

PG 120 on

Nitromethane, as such, isn't really a good fuel but it can give two-stroke engines a power boost if used sensibly. Nitro's only virtue is that it contains approximately 53% by weight oxygen, so in effect it is a chemical super-charger. In drag car engines it is blended 80-90% nitro to 10-20% methanol, but there is no way a two-stroke engine can hold together with more than a 20% nitro-80% methanol blend. Even then, I would only use nitro in small and rugged single cylinder dirt track engines. To deter detonation, or other engine damage, it is always necessary to lower the compression ratio. If your engine runs reliably at a 17:1 compression ratio on methanol, then you should be able to use a 14:1 ratio with a 20% nitro-80% methanol fuel mix. As with methanol, nitromethane demands a rich fuel/air mixture. Using a 20% nitro blend, the mixture would be approximately one part fuel to three or four parts air, i.e., 1:3-4. This means that you will have to increase the main jet size by about 22-25% above that required for pure methanol with a 20% nitro-80% methanol mixture. A 12-15% jet increase will be close for a 10% nitro blend. The safest way to avoid error when mixing nitro with other fuels is to mix according to volume, eg: for a 20% nitro blend you will use one gallon of nitro to four gallons of methanol. Care is in order when handling nitromethane, as it may become explosive. Normally nitro is quite safe, but it may be made shock sensitive by any of the following practices:a) the addition of hydrazine in fuel blending b) the use of caustic soda or any other alkaline for cleaning the mixing drum c) the use of 'unpickled' anodised aluminium fuel tanks. After anodising, the tank must be allowed to stand for a few days filled with a solution 10% vinegar—90% water.

[jbiplane]

There you are TZ, maybe a successful 2T EFI system, looks like an injector port in that throttle body.

This throttle body we got from Ecotron. We often have problem with components quality and have to do inhouse.
Now we 5-axis mill bodies and make our proprietary 2T EFI system, very lightweight and poverfull :cool:
We place some of sensors in one ECU box and got by wires cylinder head themperature and throttle angle.
May be one day we will make 2T ECU as a "box product"
http://www.reaa.ru/yabbfiles/Attachments/____093_001.jpg

[ken seeber]

That is a nice-looking engine, Jbiplane.
It takes me back about 20 years when I designed a similar ultralight-powerplant.
333046

Both look like Velocette Viceroy engines. Question for Jbiplane: You have no cooling on the outside of the transfer port passages. Is this because you aren't operating at a high BMEP level or is it because you have so much cooling available with the air speed? Excellent job though. Crankcase machining looks mint. :yes:

[jbiplane]

That is a nice-looking engine, Jbiplane.
It takes me back about 20 years when I designed a similar ultralight-powerplant. You may recognize some of the weight-saving ideas :D.
333046

Nice picture Frits. Your project (1000cc boxer) was either implemented in metals? Do you have more pictures?
We produce at the moment range of engines from 90cc to 350cc. I want to make my own 172 cc completelly milled of blanks cylinders compatible with Malossi or whatelse.
At moment my milled 172cc 66x50mm cylinder weight only 1060 grammes. According our experience milled of 6082 cylinders much more strong than any casting and
much better coated by Nikasil. We experienced now with electroless nikel+ceramic coating and seems when apply thin film of the nikel at the top of galvanic piston rings
survive much longer.

We want try out all very similar to http://www.kanigen.co.jp/english/products.php
If anyone want I could be reached by jbiplane@gmail.com to dont post information which weakly correlate with general moto forum.

My interests are
new scavenging ideas with experimental and CFD validation
topology and parametric structural FEA optimization
all technologies of low volume cost effective cylinder, pistons and crankshaft production
compact lightweight exhaust systems
completelly new engine materials and coatings including ceramics.

[Flettner]

All this talk of alcohol fuel, when I started to experiment with E85 through a carburetor I had no end of trouble. Air cooled engine, the fueling requirement between a cold engine and a hot engine were outside any adjustment I could make within the carburetor. It seems that when the engine is working and the fuel vaperises well is different from the fuel requirement when say same throttle position but a cooler engine. The only successful fix was EFI and a separate graph, master fuel over temperature. Seems to be at 70 degrees is the changeover point, where ethanol vaperises. Anyway that is my experience.
It's interesting to note that with my TPI system on ethanol I can nearly bring the twostroke fuel burn back to that of petrol with a carburetor. All my engines from now will run E85 through TPI (mark two), it is the future.

[Frits Overmars]

Nice picture Frits. Your project (1000cc boxer) was either implemented in metals? Do you have more pictures?Thanks. When the drawings were about done, the customer went bankrupt, so no implementation in metal. As it's a long time ago, I could only find one more picture.
You will notice that the crankshaft main bearings are farther apart than usual, as a consequence of combining head, cylinder and crankcase-half in one single casting. The main bearing seats needed to be far enough apart for the piston to pass through. But in a 2-stroke boxer the radial loads on the main bearings are lower than in any other engine type anyway. And an advantage of this approach was that I needed just one casting, 2 off, for the whole engine. You can't build 'm any lighter than that.
333067

[jbiplane]

Both look like Velocette Viceroy engines. Question for Jbiplane: You have no cooling on the outside of the transfer port passages. Is this because you aren't operating at a high BMEP level or is it because you have so much cooling available with the air speed? Excellent job though. Crankcase machining looks mint. :yes:

We have propeller located very close to the cylinders and no overheating problems. As we encountered thin milled 1,8mm cooling fins in this conditions dissipate much more energy than casted 4mm.
External layer of casting makes real thermal barier.

[SwePatrick]

All this talk of alcohol fuel, when I started to experiment with E85 through a carburetor I had no end of trouble. Air cooled engine, the fueling requirement between a cold engine and a hot engine were outside any adjustment I could make within the carburetor. It seems that when the engine is working and the fuel vaperises well is different from the fuel requirement when say same throttle position but a cooler engine. The only successful fix was EFI and a separate graph, master fuel over temperature. Seems to be at 70 degrees is the changeover point, where ethanol vaperises. Anyway that is my experience.
It's interesting to note that with my TPI system on ethanol I can nearly bring the twostroke fuel burn back to that of petrol with a carburetor. All my engines from now will run E85 through TPI (mark two), it is the future.

78.4 celsius is a good number to remember when burning ethanol one has run through the distiller ;)

I ran an Opel Engine for a couple of years ago on E85.(turbo 700hp yada yada)
And i became really confused when the table to compensate for fuel actually needed to turn around at these 78degree´s.
First, enrichment when cold that slowly ramped away and 'peaked' at 78degree, then it needed to get enriched again to keep the same lambdavalue in exhausts.

[Niels Abildgaard]

Thanks. When the drawings were about done, the customer went bankrupt, so no implementation in metal. Since it's a long time ago, I could only find one more picture.
You will notice that the crankshaft main bearings are farther apart than usual, as a consequence of combining head, cylinder and crankcase-half in one single casting. The main bearing seats needed to be far enough apart for the piston to fit through. But on a two-stroke boxer the radial loads on the main bearings are lower than in any other engine type anyway. And an advantage of the combined casting was that the whole engine needed just one cast part, twice. And you can't build them any lighter.
333067

The torque variations in two stroke boxer is just as big and nasty as in a single 1000 ccm engine.
A V2 will be smother than smooth and crank not very much heavier,if at all.
In Your very informative writing on big bang fallacy there are some curves showing it but I cannot find them.

https://imgur.com/9RprD0t
https://imgur.com/9RprD0t

[Frits Overmars]

The torque variations in two stroke boxer is just as big and nasty as in a single 1000 ccm engine.
A V2 will be smother than smooth and crank not very much heavier,if at all.You're right about the torque variations Niels, but I was talking about the radial bearing loads, which are almost non-existent in a boxer.
The majority of light aircraft are using boxer engines for a reason. A propeller makes quite a good flywheel (low mass, high inertia), flattening the torque fluctuations.
Your V2-crankshaft (below) may not be heavier than a boxer-crank, but in principle it's a four-stroke crank. Unless you use an external blower, adding volume, weight and complication, a two-stroke V-twin needs two separate crankcase volumes, and your crankshaft does not provide for that.
333069

[nitro2tfx]

do you know of any rules of thumb regarding com ratio and nitro percentage in a 2t or is it just trial and error to see what works ? theres almost no info about 2t and nitro that ive been able to find so far

Nitro makes more cylinder pressure. A turbo makes more cylinder pressure. Any engine will only take so much pressure no matter how it is built.

So for a fixed amount of maximum desired cylinder pressure, less compression ratio and more nitro % makes more power than more compression ratio and less nitro %. Much the same as less compression ratio and more boost makes more power than more compression ratio and less boost on a turbo engine.

Changing compression ratios changes peak cylinder pressure a lot but only changes power a little. The same change in peak pressure with a change in nitro %, changes power a lot.

[guyhockley]

You're right about the torque variations Niels, but I was talking about the radial bearing loads, which are almost non-existent in a boxer and far from small in a V-twin.
Vibrationwise it's the same: a V-twin can't compete with a boxer unless it has a balance shaft, adding volume, weight and complication.
The majority of light aircraft are using boxer engines for a reason. A propeller makes quite a good flywheel (low mass, high inertia), flattening the torque fluctuations.
Your V2-crankshaft (below) may not be heavier than a boxer-crank, but in principle it's a four-stroke crank. Unless you use an external blower, again adding volume, weight and complication, a two-stroke V-twin needs two separate crankcase volumes, and your crankshaft does not provide for that.
333069
Couple of thoughts... Some boxer twins seem to end up with an extra main bearing one end, to control crank whip, maybe?
Niels crank wouldn't need too much extra if it was used in a JBB/outboard engine type configuration. Husa has posted relevant pictures, before.
Talking of outboards and referring back to the big bang idea, I've wondered whether racing outboards would be better off from the point of view of "traction" of using other configurations than the universally adopted boxer layouts.

[guyhockley]

There you are TZ, maybe a successful 2T EFI system, looks like an injector port in that throttle body.
Lot easier to do FI on an aero-engine...

[peewee]

Nitro makes more cylinder pressure. A turbo makes more cylinder pressure. Any engine will only take so much pressure no matter how it is built.

So for a fixed amount of maximum desired cylinder pressure, less compression ratio and more nitro % makes more power than more compression ratio and less nitro %. Much the same as less compression ratio and more boost makes more power than more compression ratio and less boost on a turbo engine.

Changing compression ratios changes peak cylinder pressure a lot but only changes power a little. The same change in peak pressure with a change in nitro %, changes power a lot.


makes sense and i think im going to lower the com ratio just a bit. the smaller engines might do fine with high ratios but this one has 90mm piston. mechanically i think it will be better off if its a bit lower. i keep waiting for it to pop the head studs out but luckily is still holding together. not to mention its acting strange when i try to kickstart it on a nitro mix. acts like theres alot of
static cylinder pressure, which it never did on methanol. . and plenty of times its sort of made a backfire noise and tried to make the kick lever go backwards.. couple weeks ago it broke the weld on com release tower but ive since fixed that

maybe you or adegnes has some knowledge about what water temp the nitro mix starts to run good at ? i was thinking atleast 50*C but i havent been able to get mine to that temp yet but ambient temps have gotten colder so maybe thats why. ive got a 70*C thermostat that i might have to install

[Grumph]

maybe you or adegnes has some knowledge about what water temp the nitro mix starts to run good at ? i was thinking atleast 50*C but i havent been able to get mine to that temp yet but ambient temps have gotten colder so maybe thats why. ive got a 70*C thermostat that i might have to install

I remember seeing Don Garlits quoted as saying he found nitro liked to run at around 140deg F. If I converted it right, that's about 55 deg C. But he's looking at the start sequence specifically where he didn't want to be held too long - or rushed through by his opponent. He had an on board tank which gave him enough reserve cooling to ensure he didn't overheat in staging.

I have some experience with a roadrace 4T engine on 20% nitro which ran very well indeed with a 70deg C thermostat installed.

[Flettner]

More than 10% and you can smell it.

[Grumph]

More than 10% and you can smell it.

20% and you get complaints if the field is held on the dummy grid.....makes the eyes water.

[adegnes]

makes sense and i think im going to lower the com ratio just a bit. the smaller engines might do fine with high ratios but this one has 90mm piston. mechanically i think it will be better off if its a bit lower. i keep waiting for it to pop the head studs out but luckily is still holding together. not to mention its acting strange when i try to kickstart it on a nitro mix. acts like theres alot of
static cylinder pressure, which it never did on methanol. . and plenty of times its sort of made a backfire noise and tried to make the kick lever go backwards.. couple weeks ago it broke the weld on com release tower but ive since fixed that

maybe you or adegnes has some knowledge about what water temp the nitro mix starts to run good at ? i was thinking atleast 50*C but i havent been able to get mine to that temp yet but ambient temps have gotten colder so maybe thats why. ive got a 70*C thermostat that i might have to install

I have the same experience with high static cylinder pressure and kickback. It's worst after a stall from loading up. Maybe lots of liquid fuel in the combustion chamber.

There seemed to be traces of combustion outside the combustion chamber when I pulled the head, it might be lifting it slightly.
Can't help with the water temp, just CHT ang EGT yet.

[SwePatrick]

A small aircooled twostroke(novarossi) Nitro blend engine(20%) runs best at about 90-105degree celsious.
But, you might need to run it a little bit lower in temp to still have some margins to piston meltdown ;)

And guys!
Remember to setup engine for increases heats.
More gap on the rings, more tapered piston.
As all tempratures get´s higher the margin to when piston melts is getting closer.
And you do not want to have smeared aluminium all over the bore that increases blowby.
And thereby heats the piston even more.,,, aaaaaaand 'good night' as result.

You want more gap on the rings to have more margins to when the ring warps in the ring groove.
If it warps, it´s also 'good night' but often with nicasil pulled off the cylinder.

I recommend steelliner in cylinder with nitro.
Just because it can take some beating and still beeing able to use again.

[lohring]

The torque variations in two stroke boxer is just as big and nasty as in a single 1000 ccm engine.
A V2 will be smother than smooth and crank not very much heavier,if at all.
In Your very informative writing on big bang fallacy there are some curves showing it but I cannot find them.

https://imgur.com/9RprD0t
https://imgur.com/9RprD0t

You can make an opposed piston alternate firing twin that should run smoothly with a 1:1 balance shaft. There is a split ring seal between the two crankcase areas. See below.

Lohring Miller

333072

[136kg136ps]

In a motorcycle,it would seem that a boxer would require an additional gearset to change the plane of rotation to that of the wheel.Or would a 90 bevel gear work?I'm having a hard time wrapping my head around that,it seems like it would offset any weigh loss.Particularly after lugging older BMW motors as a kid.

[Frits Overmars]

Funny that you'd mention BMW. Below is their first boxer, with no additional gearsets, no bevels, no nothing. That included no cooling to speak of for the rear cylinder,
so after this first model, BMW turned the engine from longitudinal to transverse. But now that their boxers are liquid cooled, maybe we should send them an email asking them to turn it back to its original position; parking the bike in my garden shed would become a lot easier.
BMW was by no means the only brand to build fore-aft boxers; Douglas was a well-known example. And let's not forget König; they even did it with four cylinders.
333073 333076 333074 333075

[Niels Abildgaard]

You can make an opposed piston alternate firing twin that should run smoothly with a 1:1 balance shaft. There is a split ring seal between the two crankcase areas. See below.

Lohring Miller

333072

The reaction torque variations will be the same as for an inline twin like Flettners newest gyro engine.
The V2 varies less.
The split ring is common outboard technology.
For a V2 it is not nessecary to sepparate cranks for starting engine and for an aircraft engine it is either idle or 60 to 110% power.
At the high end either tuned exhaust or turbocharger.
The reaction torque is what rattles aircraft.
Inertia of propeller is important for lowest possible rpm but not for smoothness during fligth.
Have flown Cessna 172 with both 6 cylinder and 4 cylinder engines and Yes there is a difference in comfort.

https://i.imgur.com/SOqAT4f.jpg

[Frits Overmars]

For a V2 it is not nessecary to sepparate cranks for starting engine and for an aircraft engine it is either idle or 60 to 110% power. At the high end either tuned exhaust or turbocharger.Niels, I would love to see a measured power curve of your V-twin with a common crankcase and tuned exhausts.

[Niels Abildgaard]

Niels, I would love to see a measured power curve of your V-twin with a common crankcase and tuned exhausts.

Me too but two is to few for crowdfunding

[Flettner]

Power 40 or 110%? When I fly (gyro) it is important to have a smooth a power delivery as possible ( hence my fitment of the power valve) for when running up the rotors you can not go to full power directly. Or else bad stuff happens, get rotor flap, rotors strike the ground, craft tips over. Standard gyro accident, all to do with rotor management and that comes from throttle control. The last thing you want is an engine that comes on strong, like a twostroke that relies heavily on the exhaust only. Just my observation.

[136kg136ps]

Frits, thanks.That last motor looks like a big chunk of metal.Bet it turns beads.

[Grumph]

Power 40 or 110%? When I fly (gyro) it is important to have a smooth a power delivery as possible ( hence my fitment of the power valve) for when running up the rotors you can not go to full power directly. Or else bad stuff happens, get rotor flap, rotors strike the ground, craft tips over. Standard gyro accident, all to do with rotor management and that comes from throttle control. The last thing you want is an engine that comes on strong, like a twostroke that relies heavily on the exhaust only. Just my observation.

Interesting to hear and it makes sense too. I recall reading about the last of the piston engined fighters which had major torque reaction problems on takeoff.
I think the experimental very highly supercharged versions had major problems till they developed contra-rotating props.

[TZ350]

Ok, so it is a 150cc four stroke Bucket. ..... 4T ..... :dodge:

But posted to show what can be achieved by paying attention to small detailed changes.

333079

Down draft inlet tract length optimized to suit cam and exhaust.

333078

Moved steadily from the red line to the blue line by 10mm then 5mm incremental changes in the inlet tract length.

333080

It will be interesting to see if the low speed torque dips can be filled in with an Exup valve.

[Brett S]

Hey TZ is that a tacho pickup on the low voltage side of the coil on that Foulstroke?

[Nath88]

TZ, what ignition coil is that?
Does it have a separate primary winding ground?
Would it have enough gusto for the YZ250?

I did some experimentation with the piezo sensor on the road yesterday, saw much less signal amplitude than the previous test and DC voltage seemed to vary a bit over time, but I think the hose was kinked and I know the wiring was crap. So I've fixed those things and will see if it's better/back to normal today.
Also leaned it out from where it was on the dyno, target AFR is 14:1 before 5300rpm (anti-resonance point) then 13.4:1 AFR to 8500rpm (peak power) then it slowly leans out to 13.8:1 at 9800rpm. It feels pretty happy, probably more to gain here. I think it still blows a little smoke on full throttle before anti-resonance, might be able to go a bit leaner still.

[Niels Abildgaard]

Power 40 or 110%? When I fly (gyro) it is important to have a smooth a power delivery as possible ( hence my fitment of the power valve) for when running up the rotors you can not go to full power directly. Or else bad stuff happens, get rotor flap, rotors strike the ground, craft tips over. Standard gyro accident, all to do with rotor management and that comes from throttle control. The last thing you want is an engine that comes on strong, like a twostroke that relies heavily on the exhaust only. Just my observation.

It was my intention to ask why You had power valves so thank you for answering.Is the propulsion propeller turning when You spin up rotor?

[Flettner]

It was my intention to ask why You had power valves so thank you for answering.Is the propulsion propeller turning when You spin up rotor?

Yes it is, there is a small cone clutch driving off the balance shaft, through an angle drive. Spooling up the rotor, this is the trickiest part of gyro flying.
Apply brakes, engage clutch, bring rotor system up to about 250 rpm, release brakes and build ground speed as the rotors spool up. Above 300 rpm you can just nail it, stick forward and it will lift off, as at these revs you are outside the rotor flap danger zone. Flys at about 400 rotor rpm.
Sorry, getting off track.
I intend to run the next engine on E85, injected ( with an autolube)

[Frits Overmars]

For a V2 it is not nessecary to sepparate cranks for starting engine and for an aircraft engine it is either idle or 60 to 110% power. At the high end either tuned exhaust or turbocharger.
I would love to see a measured power curve of your V-twin with a common crankcase and tuned exhausts.

Me too but two is too few for crowdfundingYeah, I know the feeling.

Anyway, I wonder about a couple of things. I think the trailing cylinder will receive less mixture and do less work than the leading cylinder.
When the leading piston is moving upward from BDC towards transfer closure, the trailing piston is still moving downward, increasing the scavenging pressure in your common crankcase. But by the time the trailing piston is moving upward from BDC towards transfer closure, the leading piston will already have moved up quite a bit, noticeably lowering the crankcase pressure.

And to what extent will your scavenging depend on exhaust suction? A tuned exhaust needs strong primary pulses. Exhaust ports can provide these, because they open with a speed of about 1,5 x mean piston velocity. But exhaust valves, as shown in your drawing below, can't, because they open with an initial speed of zero.
Exhaust valves will also make it difficult to achieve sufficient blowdown time.area, unless you plan to stick to really low rpm numbers. But that would mean a low power-to-weight ratio, which is not desirable, especially not in a light aircraft engine.
333083

[jbiplane]

I think the trailing cylinder will receive less mixture and do less work than the leading cylinder.
...
333083
Simple idea
V-2 with stepped pistons and isolated crancase, like Ryger or similar

60 years ago in Soviet union produced 2-stroke star engines, 23...500 hp range. They had good reputation.
Sorry for picture with russian comments, seems clear enough without translation.
http://img-fotki.yandex.ru/get/3205/kvadrat67.e/0_1bd6c_3a12ce63_XL.jpg

Design with numerous exhaust pipes and transfer ports... A bit remind FOS :)

[Frits Overmars]

60 years ago in Soviet union produced 2-stroke star engines, 23...500 hp range. They had good reputation. Sorry for picture with russian comments, seems clear enough without translation. Design with numerous exhaust pipes and transfer ports... A bit remind FOS :)Russian is not exactly my first language, but I managed to decipher most of the 'skhema raboty dvigatelya' :p.
I don't suppose there is a video or a soundtrack from these engines? I'd love to hear them.

[TZ350]

Hey TZ is that a tacho pickup on the low voltage side of the coil.

Yes


TZ, what ignition coil is that?
Does it have a separate primary winding ground?
Would it have enough gusto for the YZ250?

I think so, but not totally sure as its not my bike and other than recording the dyno runs and trying to keep people from changing to much at once I don't know very much about it. I will see what I can find out.


I did some experimentation with the piezo sensor on the road yesterday, saw much less signal amplitude than the previous test and DC voltage seemed to vary a bit over time, but I think the hose was kinked and I know the wiring was crap. So I've fixed those things and will see if it's better/back to normal today.

Also leaned it out from where it was on the dyno, target AFR is 14:1 before 5300rpm (anti-resonance point) then 13.4:1 AFR to 8500rpm (peak power) then it slowly leans out to 13.8:1 at 9800rpm. It feels pretty happy, probably more to gain here. I think it still blows a little smoke on full throttle before anti-resonance, might be able to go a bit leaner still.

Totally looking forward to hearing how your piezo sensor experiment goes. I have been trying to re map my CPU for all low throttle fully on pipe running in the hope I will be able to get a piezo sensor switch from you sometime to see if I can use it to switch between low throttle on and off pipe maps.

[katinas]

Simple idea
V-2 with stepped pistons and isolated crancase, like Ryger or similar

60 years ago in Soviet union produced 2-stroke star engines, 23...500 hp range. They had good reputation.
Sorry for picture with russian comments, seems clear enough without translation.
http://img-fotki.yandex.ru/get/3205/kvadrat67.e/0_1bd6c_3a12ce63_XL.jpg

Design with numerous exhaust pipes and transfer ports... A bit remind FOS :)

Thanks, very interesting, Valentin Poliakov was great engineer.
Found very interesting russian experimental aviation engines forum


http://www.reaa.ru/cgi-bin/yabb/YaBB.pl?num=1180373404/all

[katinas]

Russian is not exactly my first language, but I managed to decipher most of the 'skhema raboty dvigatelya' :p.
I don't suppose there is a video or a soundtrack from these engines? I'd love to hear them.

Will be glad to help you, this was my second language ( learn in school from the fourth grade, long long time ago)
Read that this engine had some problems with overheating pistons (holes in dome) because no cooling from fresh mixture under dome.

[Frits Overmars]

Thanks, very interesting, Valentin Poliakov was great engineer. Found very interesting russian experimental aviation engines forum
http://www.reaa.ru/cgi-bin/yabb/YaBB.pl?num=1180373404/allThanks Katinas. Very interesting indeed; I found Ryger-type engines with 4 and 5 cylinders, dated 2010 (the recent Ryger patent was filed in 2015...).
333093 333090 333091 333092

[Nath88]

Totally looking forward to hearing how your piezo sensor experiment goes. I have been trying to re map my CPU for all low throttle fully on pipe running in the hope I will be able to get a piezo sensor switch from you sometime to see if I can use it to switch between low throttle on and off pipe maps.

I did another test just free revving, signal output looks better than before, I'll do another road test this afternoon. The sensor follows the rise and fall of the overall pressure in the pipe, throws the cycle to cycle numbers off a bit so I'll add a filter to get rid of that. Hopefully a switch isn't too far off, putting the pressure on!

Current test rig:
333094

A more general question, if the engine is 'clear' but it's blowing some blue smoke at low-rpm full throttle, is it too rich? Is there any harm in going leaner until the smoke clears?

[nitro2tfx]

A small aircooled twostroke(novarossi) Nitro blend engine(20%) runs best at about 90-105degree celsious.
But, you might need to run it a little bit lower in temp to still have some margins to piston meltdown ;)

And guys!
Remember to setup engine for increases heats.
More gap on the rings, more tapered piston.
As all tempratures get´s higher the margin to when piston melts is getting closer.
And you do not want to have smeared aluminium all over the bore that increases blowby.
And thereby heats the piston even more.,,, aaaaaaand 'good night' as result.

You want more gap on the rings to have more margins to when the ring warps in the ring groove.
If it warps, it´s also 'good night' but often with nicasil pulled off the cylinder.

I recommend steelliner in cylinder with nitro.
Just because it can take some beating and still beeing able to use again.



If there is a particular reason to run 20% nitro or some other fixed amount, and you want the most power for that fixed nitro%, then run decent compression ratio, higher water temps, best air/fuel ratio and modify the engine to suit the heat. However, that's only true if you are deadset on getting the most power out of some set in stone nitro %.

If you are not deadset on the nitro %, then the easy way to get the same desired power and not hurt anything, is to drop the compression ratio quite a bit, lower the water temps, run a richer than ideal mixture, and increase the nitro %.

The fuel can be a fantastic coolant/engine saver, and dropping the CR a good bit drops the peak pressures back to where they already were on gas.

[tjbw]

Simple idea
V-2 with stepped pistons and isolated crancase, like Ryger or similar

60 years ago in Soviet union produced 2-stroke star engines, 23...500 hp range. They had good reputation.
Sorry for picture with russian comments, seems clear enough without translation.
http://img-fotki.yandex.ru/get/3205/kvadrat67.e/0_1bd6c_3a12ce63_XL.jpg

Design with numerous exhaust pipes and transfer ports... A bit remind FOS :)

About 77 years ago Ransome Olds patented a stepped piston engine. Transfer ports link to an adjacent cylinder!

More recently Bernard Hooper, of Villiers, also patented a similar stepped piston engine. However neither of these patents resulted in production of stepped piston engines.
IIRC a prototype of Hooper's engine is on display at the National Motorcycle Museum near Birmingham UK

[tjbw]

Thank Norman, Frits and others. I found here many interesting ideas. We are small company which works like "engine atelier" for small aircrafts, UAV and other applicarion where weight and fuel economy are vital. To the moment numerous codes like ~bimotion ~mota ~Ricardo Wave ~Lotus concept
gives irreal results on boxer 2-strokes engines I produce. So one of my present objectives is to make parametric CAD model linked with CFD simulation of 2-stroke engine complete from intake to exhaust. I believe will sucseed in ~4+ month by myself and understand what have to be changed.

http://www.reaa.ru/cgi-bin/yabb/YaBB.pl?action=downloadfile;file=2b350.jpg

Did you try to model your engine with Engmod?
Quite a few here use it, though I'm not sure if it would need to be tweaked for altitude.

[peewee]

If you are not deadset on the nitro %, then the easy way to get the same desired power and not hurt anything, is to drop the compression ratio quite a bit, lower the water temps, run a richer than ideal mixture, and increase the nitro %.

.

that's the approach im going to take, lower com ratio and increase nitro %. since I just ride for fun theres really no reason to try and tune it to the breaking point with risk of hurting parts. got a couple richer needles on the way and a different cyl head for lower compression. 12:1 seems like a good place to start and see what happens. probly give it a go with one of them r7376 also.

[katinas]

Same operating conrod-free engine

https://www.youtube.com/watch?v=dwwvidC8CWo

In second video, he said that bigger engine 1600cc 45kg 200hp.

https://www.youtube.com/watch?v=_fuR3HLz-0A

Its very very precise and too much moving parts

https://www.youtube.com/watch?v=LboS59_0j1w

[Niels Abildgaard]

Yeah, I know the feeling.

Anyway, I wonder about a couple of things. I think the trailing cylinder will receive less mixture and do less work than the leading cylinder.
When the leading piston is about to close its transfer ports, the trailing piston is still moving downward, increasing the scavenging pressure in your common crankcase. But by the time the trailing piston closes its transfer ports, the leading piston will already have moved up quite a bit, noticeably lowering the crankcase pressure.

And to what extent will your scavenging depend on exhaust suction? A tuned exhaust needs strong primary pulses. Exhaust ports can provide these, because they open with a speed of about 1,5 x mean piston velocity. But exhaust valves, as shown in your drawing below, can't, because they open with an initial speed of zero.
Exhaust valves will also make it difficult to achieve sufficient blowdown time.area, unless you plan to stick to really low rpm numbers. But that would mean a low power-to-weight ratio, which is not desirable, especially not in a light aircraft engine.
333083

It is not a nature law that two pistons in a V2 -twin shall be same diameter.Same mass and do same work yes.
The aircraft engine shown is directly coupled to airscrew where limit is ca 200 m/se tipspeed for noise reason.
Two grown up in an arcraft need 80 horsepower to go places and a propeller of ca 1.6m diameter.40 RPS OR 2400 RPM.
Piston speed is ca 12m/sec at take of rpms for aircraft engines be they small or big.We need a a stroke of 150 mm.
About 90mm bore looks nice and make 2 litre.
Two litre two-stroke at 40rps at pme 7.5 bar gives 80 horsepower.
My MZ301 (Kanuni) did 80000km unopened with me as driver at this power level.
BMW WW1 inline six engines was ca 15 kg/litre and worked sligthly harder.
If I can make a 2 litre/30 kg 80hp engine the sky will be ROTAX free

[Grumph]

It is not a nature law that two pistons in a V2 -twin shall be same diameter.Same mass and do same work yes.
The aircraft engine shown is directly coupled to airscrew where limit is ca 200 m/se tipspeed for noise reason.
Two grown up in an arcraft need 80 horsepower to go places and a propeller of ca 1.6m diameter.40 RPS OR 2400 RPM.
Piston speed is ca 12m/sec at take of rpms for aircraft engines be they small or big.We need a a stroke of 150 mm.
About 90mm bore looks nice and make 2 litre.
Two litre two-stroke at 40rps at pme 7.5 bar gives 80 horsepower.
My MZ301 (Kanuni) did 80000km unopened with me as driver at this power level.
BMW WW1 inline six engines was ca 15 kg/litre and worked sligthly harder.
If I can make a 2 litre/30 kg 80hp engine the sky will be ROTAX free

I've posted this elsewhere previously. It's the Martin jetpack engine based on CR500 Honda components.
Rumour has it that it's to be replaced by a small turbojet. I've got my hand up for one of the prototype engines....

But I'm not hopeful.

[jbiplane]

Did you try to model your engine with Engmod?
Quite a few here use it, though I'm not sure if it would need to be tweaked for altitude.

No, I tried expensive
Lotus engine simulation
and Ricardo Wave
Results too far of what we measure.

Probably cause our engines have very different of "moto" geometry and exhaust.
So I afraid Engmod will not give us some useful guidance. We are going to prepare full scale CFD
calculation from intake to exhaust.

May be anyone can share Engmod user manual or complete tutorial?
I hate ask for evaluation and be regularly advertized.


Same operating conrod-free engine

https://www.youtube.com/watch?v=dwwvidC8CWo

In second video, he said that bigger engine 1600cc 45kg 200hp.

https://www.youtube.com/watch?v=_fuR3HLz-0A

Its very very precise and too much moving parts

https://www.youtube.com/watch?v=LboS59_0j1w

Guys. Dont waste your time on "conrod free" like many factories in Soviet union
Step engines in different flavors should be much more sucsessfull.

[Frits Overmars]

drop the compression ratio quite a bit, lower the water temps, run a richer than ideal mixture, and increase the nitro %. The fuel can be a fantastic coolant/engine saver,
and dropping the CR a good bit drops the peak pressures back to where they already were on gas.The nice thing about a low compression ratio is not only that the peak pressure remains decent, but also that this pressure does not drop so much during expansion.
So even with an unaltered peak pressure there will be a much higher average pressure pushing the piston down. You gotta love nitro, don't you?
Well, maybe not always...
333102 333100 333101 333103 333104

[41juergen]

[QUOTE=jbiplane;1131069175]No, I tried expensive
Lotus engine simulation
and Ricardo Wave
Results too far of what we measure.

Probably cause our engines have very different of "moto" geometry and exhaust.
So I afraid Engmod will not give us some useful guidance. We are going to prepare full scale CFD
calculation from intake to exhaust.

May be anyone can share Engmod user manual or complete tutorial?
I hate ask for evaluation and be regularly advertized.

Don't worry, Neels is nice guy engineer... :-) he is more in technology rather than asking people to buy his (very good!) software...:msn-wink:

[WilDun]

. You gotta love nitro, don't you? ............Well, maybe not always...

:eek5: So where is the rider??

[Frits Overmars]

:eek5: So where is the rider??Cooling down, I guess. He probably won't be using nitro as a deodorant again any time soon.
333106

[guyhockley]

Under the picture of the Hooper V4, the caption reads, "BERNARD HOOPER evolution of Poliakov engine". When their stepped piston prototype was announced back in their Norton Villiers days Hooper and Flavill said they were inspired by an earlier motorbike engine, not sure anything would have been known about Russian technology by the general public in those cold war days...
Anyway, I'm away from my computer at the moment, so couldn't just look it up. Went a-googling, didn't find the answer but found this
http://www.ac-aero.com/jet-a/
Thought this bit was interesting;
Maintenance.
Our technology eliminates most of the maintenance operations required with conventional two and four-cycle engines. Operating conditions in the crankcase of a stepped piston engine are very similar to those in a four-cycle engine. The copious supply of oil to the working parts minimises wear. However, blow-by gases, to which the bearings and the oil are usually exposed, are isolated above the piston step. Bearing corrosion problems, well known, especially in two-cycle engines, are therefore completely avoided.
In addition to these more obvious points, analysis of oil, taken from one combined cycle automotive engine, revealed that after 400 hours the lubricant was still within the specification for new oil. Normal degradation of the additives had not occurred.
In a four-cycle engine all of the oil passes at some time into the high temperature region adjacent to the piston compression rings and is then returned to the crankcase. Therefore in a four-cycle engine all of the oil is exposed periodically to temperatures well in excess of the degrading point of the additive pack. This causes the qualities of the oil to decline throughout the period between oil changes.

[Frits Overmars]

this engine had some problems with overheating pistons because no cooling from fresh mixture under dome.
after 400 hours the lubricant was still within the specification for new oil.
in a four-cycle engine all of the oil is exposed periodically to temperatures well in excess of the degrading point of the additive pack.
So those stepped pisons perished but the oil remained as new. I think I'd prefer it the other way round, with oil squirting upward to cool the pistons from the inside.
But what am I talking about; I don't even fancy stepped pistons, let alone use foul-stroke practices to keep them alive.

[lohring]

[QUOTE=jbiplane;1131069175]No, I tried expensive
Lotus engine simulation
and Ricardo Wave
Results too far of what we measure.

Probably cause our engines have very different of "moto" geometry and exhaust.
So I afraid Engmod will not give us some useful guidance. We are going to prepare full scale CFD
calculation from intake to exhaust.

May be anyone can share Engmod user manual or complete tutorial?
I hate ask for evaluation and be regularly advertized.

Don't worry, Neels is nice guy engineer... :-) he is more in technology rather than asking people to buy his (very good!) software...:msn-wink:

I've been an Engmod user for a long time. It's based on Gordon Blair's work on engine simulation that duplicates the resonant nature of a two stroke. It does not replicate scavenging or combustion like CFD but uses empirical models. If you understand the details of the engines you are trying to model, it's great for getting the resonant parts like the intake tract, reed valves, and pipes right. It has great graphs to help with understanding what's going on. It has been continually improved with inputs from some very experienced two stroke builders, several that post here. Neels is always ready to help, the help files are great, and my updates have been free for years. See http://vannik.co.za/EngMod2T.htm for the details.

Lohring Miller

[jbiplane]

I don't even fancy stepped pistons, let alone use foul-stroke practices to keep them alive.

Other idea a bit similar to ancient DKW
https://ac.els-cdn.com/S1876610214000800/1-s2.0-S1876610214000800-main.pdf?_tid=eb192512-bb24-11e7-99f8-00000aacb35f&acdnat=1509115469_e5fa47c386ae1885db66615a1f664ffa

[nitro2tfx]

The nice thing about a low compression ratio is not only that the peak pressure remains decent, but also that this pressure does not drop so much during expansion.
So even with an unaltered peak pressure there will be a much higher average pressure pushing the piston down. You gotta love nitro, don't you?
Well, maybe not always...


Yes, and on a 2 stroke both the lower CR and the nitro also put more energy into the exhaust, so it's win-win or maybe win-win-win, at least up until the point where you lose parts and start to shed tears :laugh:

[RomeuPT]

Yes, and on a 2 stroke both the lower CR and the nitro also put more energy into the exhaust, so it's win-win or maybe win-win-win, at least up until the point where you lose parts and start to shed tears :laugh:

which % can you use nitro on unleaded fuel without kill the engine right away? does it really make a dif?

Is there any product you can buy to mix with gasoline? Small percentages can really change jetting behavior?

[nitro2tfx]

which % can you use nitro on unleaded fuel without kill the engine right away? does it really make a dif?

Is there any product you can buy to mix with gasoline? Small percentages can really change jetting behavior?

0 % unless you are really good at your chemistry.

Nitro doesn't blend directly with gas, it just sinks to the bottom because it is far more dense than gas. Nitromethane is used with methanol applications.

Nitropropane will blend with gas, but nitropropane is hard on the engine and gives not very much of a power increase compared to nitromethane. You probably would get more power just switching from gas to methanol than you would by adding nitropropane to gas, and the power on methanol would be reliable.

[breezy]

Same operating conrod-free engine

https://www.youtube.com/watch?v=dwwvidC8CWo

In second video, he said that bigger engine 1600cc 45kg 200hp.

https://www.youtube.com/watch?v=_fuR3HLz-0A

Its very very precise and too much moving parts

https://www.youtube.com/watch?v=LboS59_0j1w

some great videos you have found there katinas.... led me onto the joseph newman electric motor videos ... which i found very interesting although off topic.:niceone:

[lodgernz]

...A 14,75 mm end cone restriction should be good for over 22 crankshaft-HP, so no problem there.

Frits: I'm using your formula for end cone restrictor Dtailrestrictor = 3.06*SQRT(HP).

My 50 produces 11.8HP at the wheel, optimistically 13 at the crank, so this tail restrictor diameter calculates as 11.0mm.

When I made my pipe, I just couldn't believe such a small outlet was viable, so I made de Laval nozzles of 14.0, 14.25, 14.5 and 14.75.
On the dyno, we started with three pulls on the 14.0, then 3 pulls on each of the others. In every case, the power went up as the nozzle size went up.
I didn't have any bigger nozzles to try, so the last set of pulls was with no nozzle, just the 19mm ID tailpipe. The power dropped markedly.
The 11.8HP reading (at 13,000RPM) was with the 14.75.

Have I got the formula for end cone restrictor right? If so, is 11mm really safe on a 50?

[Frits Overmars]

You've got a couple of things right, starting with the crankshaft power.
As a rule of thumb I assume a power loss of 2,5% per transmission step (this is not carved in stone; CVT transmissions and bevel gears will properly mess things up).
So 97,5% of the crankshaft power arrives at the gearbox input shaft (if the oil level in the transmission and the oil viscosity are not too high).
97,5% of 97,5% exits at the output shaft (if: see above).
97,5% of 97,5% of 97,5% arrives at the wheel via the chain (if the chain and sprockets are well lubricated and not worn).
97,5% of 97,5% of 97,5% of 97,5% arrives via the tire at the dyno drum (if the tire pressure is not too low).
So the total efficiency from crankshaft to dyno is 0,975^4 = 0,904.

You quote 11,8 HP at the wheel, but I take the liberty of assuming that it was not measured at the wheel, but on a dyno drum driven by the wheel. Then the crankshaft power will have been 11,8 / 0,904 = 13,06 HP , so your estimate is realistic and your 11 mm restrictor should be about right.

The restrictor factor of 3,06 that you quoted, stems from an older version of my FOS exhaust concept; you'll find the latest version below. that factor has now grown to 3,1 but that won't make a world of difference; 13,06 crankshaft-HP would now require a Ø 11,2 mm restrictor.

Is that safe on a 50 cc engine?

That depends. The engine has to be thermally sound. A cylinder with a pressed-in liner is not great in this respect, and neither is aircooling. And watercooling is OK only if you have sufficient circulation of not-too-hot water.
You'll also need sufficient blowdown time.area, otherwise hot combustion gases will enter the transfer ducts and heat up the cylinder. So don't rev it too high.

The above thermal requirements apply to tuned engines. 13 crank-HP out of 50 cc should not give big problems, but you must be aware of a possible interaction.
Your power was measured with a Ø 14,75 mm restrictor. If you were to try the 'correct' 11 mm size, power might go up and 11 mm would not be correct any more...

Finally, a smaller restrictor will increase mean pipe pressure. If the blowdown time.area is insufficient, this increased pressure will enhance the problem of exhaust gases entering the transfer ducts.
A smaller restrictor will also increase the exhaust gas temperature, and hence the resonance frequency of the exhaust pipe. If the pipe was too short already, switching from too big a restrictor to a 'correct' restrictor size will cause a loss of power and power band.

That's two-strokes for you: they seem simple :D.

333115

[RomeuPT]

Frits: I'm using your formula for end cone restrictor Dtailrestrictor = 3.06*SQRT(HP).

My 50 produces 11.8HP at the wheel, optimistically 13 at the crank, so this tail restrictor diameter calculates as 11.0mm.

When I made my pipe, I just couldn't believe such a small outlet was viable, so I made de Laval nozzles of 14.0, 14.25, 14.5 and 14.75.
On the dyno, we started with three pulls on the 14.0, then 3 pulls on each of the others. In every case, the power went up as the nozzle size went up.
I didn't have any bigger nozzles to try, so the last set of pulls was with no nozzle, just the 19mm ID tailpipe. The power dropped markedly.
The 11.8HP reading (at 13,000RPM) was with the 14.75.

Have I got the formula for end cone restrictor right? If so, is 11mm really safe on a 50?

That is a good test. I follow some experience I have and things I have read here for the pipes I do. I do the restrictor depending on the expected horse power and the tail pipe diameter along 0.5 to 2mm bigger depending on what is available, I also have found that having less then 10cm of stinguer hurts power in many cases. But those are not real state of the art tests or anything just some experience. I also give less restriction for aircooled or poeple wanting broad power.

I would say optimal restrictor to expected HP:

12-15hp - 14 to 16
15-20hp - 16 to 18
20-25hp - 18 to 20
25-30hp - 19.5 to 22 (125 road bikes)

and so on

[Juho_]

If running the engine on alcohol fuel (like E85, methanol..), shouldn't the tail pipe diameter be larger? Am I correct?

My new pipe has a 16mm ID tail pipe, but the engine is supposed to rev +16,000rpm.
Peak hp is around 14,000rpm depending on jetting, deck height.. and so on. Was 'designed' for 13,000rpm peak hp (700mm length).
Probably on E98 fuel it'll produce its peak hp at ~13,000rpm, going to test it some day because of cold temperature (less than 0*C)

Previous pipe had a 19mm ID tail pipe and peak hp @ ~13,000rpm and produced higher peak torque and hp numbers.
Currently the engine is having problems with producing power... something is restricting it and power has went every time to the 'wrong direction'.
Sometimes I didn't need to do any changes and the power had already dropped -- probably some of this is caused by loose fit on clutch side ball bearing on crankshaft.. and cylinder itself is restricting it to rev any further or producing more power. Sadly my 90 degree mini grinder (modified ebay dentist grinder) broke, again, and cannot do anything for it..

Of course, the pipe itself might be worse than the previous one.
I had an idea to get the engine rev higher with the new pipe and find more hp by doing modifications on the cylinder (mostly).
20hp at real dyno (the numbers posted are gsf dyno numbers, not comparable) and 16,500-17,000 max. rpm is my goal currently.
Probably it won't be achieved on this engine because of its many problems (gearbox and clutch do not really like the 16,000rpm revs when doing full throttle pulls through all 6 gears...)

[RomeuPT]

If running the engine on alcohol fuel (like E85, methanol..), shouldn't the tail pipe diameter be larger? Am I correct?

My new pipe has a 16mm ID tail pipe, but the engine is supposed to rev +16,000rpm.
Peak hp is around 14,000rpm depending on jetting, deck height.. and so on. Was 'designed' for 13,000rpm peak hp (700mm length).
Probably on E98 fuel it'll produce its peak hp at ~13,000rpm, going to test it some day because of cold temperature (less than 0*C)

Previous pipe had a 19mm ID tail pipe and peak hp @ ~13,000rpm and produced higher peak torque and hp numbers.
Currently the engine is having problems with producing power... something is restricting it and power has went every time to the 'wrong direction'.
Sometimes I didn't need to do any changes and the power had already dropped -- probably some of this is caused by loose fit on clutch side ball bearing on crankshaft.. and cylinder itself is restricting it to rev any further or producing more power. Sadly my 90 degree mini grinder (modified ebay dentist grinder) broke, again, and cannot do anything for it..

Of course, the pipe itself might be worse than the previous one.
I had an idea to get the engine rev higher with the new pipe and find more hp by doing modifications on the cylinder (mostly).
20hp at real dyno (the numbers posted are gsf dyno numbers, not comparable) and 16,500-17,000 max. rpm is my goal currently.
Probably it won't be achieved on this engine because of its many problems (gearbox and clutch do not really like the 16,000rpm revs when doing full throttle pulls through all 6 gears...)

If you have a 1000rpm disparity from your calculations you may have failed the temp prediction from far, your ignition may need more retard at 13000, you may got wrong on the lenght/port height dimensions maybe both or all things combined

[Frits Overmars]

If running the engine on alcohol fuel (like E85, methanol..), shouldn't the tail pipe diameter be larger? ... Previous pipe had a 19mm ID tail pipe and peak hp @ ~13,000rpm and produced higher peak torque and hp numbers.... 16,500-17,000 max. rpm is my goal currently.... Probably it won't be achieved on this engine because of its many problems (gearbox and clutch do not really like the 16,000rpm revs when doing full throttle pulls through all 6 gears...)If the engine does not behave stable, you can never be sure whether a modification is positive or negative, so I think that should be the first point to address.
When you are talking about tailpipe diameter, do you mean the restrictor diameter? These are two distinctly different things! The restrictor diameter depends on the engine power, not on the kind of fuel. The tailpipe diameter should be markedly bigger than the restrictor diameter, as shown in the above exhaust concept.

There are very few cylinders that have sufficient angle.areas for your current goal of 16,500 - 17.000 max. rpm.
Your remark that your previous pipe had a peak hp @ ~13,000rpm and produced higher peak torque and hp numbers, may be an indication that the angle.areas are already too small for max. power at 14.000 rpm. In that case, raising the rpm with a new pipe will lead to less power instead of more.

[Juho_]

If you have a 1000rpm disparity from your calculations you may have failed the temp prediction from far, your ignition may need more retard at 13000, you may got wrong on the lenght/port height dimensions maybe both or all things combined
On E98 fuel the peak hp is at ~13,000rpm (quick test).

When I did testing on the previous pipe, the peak hp was at ~12,000rpm on E98 fuel.
Switched to E85, and the peak hp rpm raised nearly 1,000rpm and engine revved further when re-adjusted the carburetor.

Current problems on the engine haven't existed very long, and I've done quite a lot testing with the new pipe.
With programmable cdi unit I did not get much more peak hp or revs, like I had thought because the old cdi unit's ignition curve was quite stupid for this engine. That's when I accepted the cylinder (39.90mm D50B0 with single ring piston, and 44mm stroke with 94mm conrod - Minarelli AM6 engine) was restricting it to revving more and producing more power , but unfortunately my 90 degree mini grinder broke as said on previous post so couldn't try it out.
This engine is going to be replaced as soon as I can get new tools to modify the new engine's cylinder.. larger cylinder bolt pattern, and reed valve case..and way better gearbox and clutch. But overall it isn't much different engine than the current one.


When you are talking about tailpipe diameter, do you mean the restrictor diameter?
Yes, sorry, I meant the restrictor diameter.

[lodgernz]

You've got a couple of things right, starting with the crankshaft power.
As a rule of thumb I assume a power loss of 2,5% per transmission step (this is not carved in stone; CVT transmissions and bevel gears will properly mess things up).
So 97,5% of the crankshaft power arrives at the gearbox input shaft (if the oil level in the transmission and the oil viscosity are not too high).
97,5% of 97,5% exits at the output shaft (if: see above).
97,5% of 97,5% of 97,5% arrives at the wheel via the chain (if the chain and sprockets are well lubricated and not worn).
97,5% of 97,5% of 97,5% of 97,5% arrives via the tire at the dyno drum (if the tire pressure is not too low).
So the total efficiency from crankshaft to dyno is 0,975^4 = 0,904.

You quote 11,8 HP at the wheel, but I take the liberty of assuming that it was not measured at the wheel, but on a dyno drum driven by the wheel. Then the crankshaft power will have been 11,8 / 0,904 = 13,06 HP , so your estimate is realistic and your 11 mm restrictor should be about right.

The restrictor factor of 3,06 that you quoted, stems from an older version of my FOS exhaust concept; you'll find the latest version below. that factor has now grown to 3,1 but that won't make a world of difference; 13,06 crankshaft-HP would now require a Ø 11,2 mm restrictor.

Is that safe on a 50 cc engine?

That depends. The engine has to be thermally sound. A cylinder with a pressed-in liner is not great in this respect, and neither is aircooling. And watercooling is OK only if you have sufficient circulation of not-too-hot water.
You'll also need sufficient blowdown time.area, otherwise hot combustion gases will enter the transfer ducts and heat up the cylinder. So don't rev it too high.

The above thermal requirements apply to tuned engines. 13 crank-HP out of 50 cc should not give big problems, but you must be aware of a possible interaction.
Your power was measured with a Ø 14,75 mm restrictor. If you were to try the 'correct' 11 mm size, power might go up and 11 mm would not be correct any more...

Finally, a smaller restrictor will increase mean pipe pressure. If the blowdown time.area is insufficient, this increased pressure will enhance the problem of exhaust gases entering the transfer ducts.
A smaller restrictor will also increase the exhaust gas temperature, and hence the resonance frequency of the exhaust pipe. If the pipe was too short already, switching from too big a restrictor to a 'correct' restrictor size will cause a loss of power and power band.

That's two-strokes for you: they seem simple :D.

333115

Thank you Frits, very good information, as always. My engine is an NSR50, so is limited in blowdown time.area with a single oval exhaust port. It's water cooled of course, and happily over-revs to 14000 for short periods without exceeding water temp of 65º during a race. However, as you suggest, because I'm using such a big restrictor, the gas temperature and pipe pressure will both be low and this is borne out by the pipe length Lmax being only 678mm for an ex duration of 192º.
Lots of work to be done.

One more question, if I may: Your formula for Lmax features the constant 88, whereas I would have expected 83.3.
Is your constant adjusted for the fact/likelihood that the mean reflection point from the baffle cone is not at the pointy end of it?

[Frits Overmars]

Your formula for Lmax features the constant 88, whereas I would have expected 83.3.
Is your constant adjusted for the fact/likelihood that the mean reflection point from the baffle cone is not at the pointy end of it?I did not want to badger aspriant-tuners with the whereabouts of a reflection point; the 88 is just a factor that ought to work good together with an assumed speed of sound of 550 m/s. That speed of sound itself is the value that can be varied by the concept's users according to their findings.

[lodgernz]

I wonder: how did you arrive at 83,3? I think I've seen this value before, but I can't remember in what context.

Time for 1 rev = 60/RPM secs
Ex is open EDº = ED/360 of a rev
so Ex is open for ED/360 * 60/RPM = ED/(6*RPM) secs
in that time, sound wave must travel 2 * Lmax at V m/s
So Lmax = V * ED/(12 * RPM) * 1000 mm = V * ED * (1000/12)/RPM mm
and 1000/12 = 83.3

[mr bucketracer]

Time for 1 rev = 60/RPM secs
Ex is open EDº = ED/360 of a rev
so Ex is open for ED/360 * 60/RPM = ED/(6*RPM) secs
in that time, sound wave must travel 2 * Lmax at V m/s
So Lmax = V * ED/(12 * RPM) * 1000 mm = V * ED * (1000/12)/RPM mm
and 1000/12 = 83.3can you make my 50 fast as you are blowing my mined

[lodgernz]

can you make my 50 fast as you are blowing my mined

Based on my performances so far.... no.
Ask me again in a coupla years.

[crbbt]

quick question (I guess for wob)

I have my non power jetted carb (Keihin PJ) 'sorted' I am happy with the performance through the rev range.

I recently acquired a SPJ carb. other than running a smaller main jet. would it be correct to run the same sized slide cutout and main needle?

[ken seeber]

This just shows old blokes are not necessarily stupid:

https://www.mxlarge.com/2017/10/28/decoster-bring-back-2-strokes/

[husaberg]

quick question (I guess for wob)

I have my non power jetted carb (Keihin PJ) 'sorted' I am happy with the performance through the rev range.

I recently acquired a SPJ carb. other than running a smaller main jet. would it be correct to run the same sized slide cutout and main needle?
wob mentioned ealier adding the Power Jet and MJ size together to arrive at the corect size in relation to a non Power Jet ML size.

[F5 Dave]

Thank you Frits, very good information, as always. My engine is an NSR50, so is limited in blowdown time.area with a single oval exhaust port. It's water cooled of course, and happily over-revs to 14000 for short periods without exceeding water temp of 65º during a race. However, as you suggest, because I'm using such a big restrictor, the gas temperature and pipe pressure will both be low and this is borne out by the pipe length Lmax being only 678mm for an ex duration of 192º.
Lots of work to be done.

One more question, if I may: Your formula for Lmax features the constant 88, whereas I would have expected 83.3.
Is your constant adjusted for the fact/likelihood that the mean reflection point from the baffle cone is not at the pointy end of it?

Build the pipe. I'll find the Dyno time for you.

[TZ350]

333133

Bit of a production run of 28 rwhp Bucket racing Suzuki GP/NSR110cc engines.

Following on from Nath88's idea of using a Piezo element to sense a pressure pulse as a way to know if the motor has fired and Flettners idea of timing the sensing point to coincide with a selected period of crank angle.

333134333135

I took a look at a Piezo switch and thought that I might be able to use the exhaust pulse instead of a finger press to activate it.

333136

A NO circuit is fairly easy and to time it to a selected area of crank angle all I need to do is use a winding on a pole in the right place on the alternator to turn on another NO transistor switch.

Then if both NO switches wired in series are closed there will be a pulse that the EFI will see as an engine firing event.

[RomeuPT]

I know it was discussed before here, but can't find :/

333137

in the pic this was done just because of offset ring position and should be grind symetrical or has something to do with performance? i can't be sure...

Cheers

[lohring]

That picture is from the paper below.

Lohring Miller

333138

[RomeuPT]

That picture is from the paper below.

Lohring Miller

333138

Thanks. I think I have this document in a hardrive somewhere, got to put all of this on google drive or something

[wobbly]

In the paper the two hook positions were part of the experiment matrix.
The two positions gave different results, but in some older RS125 cylinders the pin is offset,and grinding the boost port septum's symmetrical gives
more power when used with the later pistons that have the pin at 6 o'clock.

The PJ and SPJ jet quite differently due to the length difference,if you are running a race 125 then the stock Honda jets in the SPJ are a good start point.

[lodgernz]

Build the pipe. I'll find the Dyno time for you.

Thanks Dave. I'll call you

[Lbracing]

Wobbly I sent you a pm last week , got it ?

[trevor amos]

Frits,
If you are still wondering where you once saw the reference to 83.3 as Lodgernz calculated, it can also be seen in Gordon Blair`s books shown his pipe calculation formulas.

[Nath88]

I took a look at a Piezo switch and thought that I might be able to use the exhaust pulse instead of a finger press to activate it.

333136

There is a 100Meg resistor across the piezo sensor which acts as the load, piezos need high impedance on the output to measure low frequencies, so that's fine. However the next 100Meg resistor and 100pF capacitor form a low pass filter of 15hz. This acts to smooth and slow the input, probably so it works decently as a switch instead of flicking on and off with any variation of pressure applied to the piezo. It may work, I would expect a delay between the pressure input and when the mosfet has enough voltage at it's input (gate) to 'switch'. The switch threshold would be set by the gate voltage of the mosfet combined with the filter.

My pulse sensor gives clear indication at high rpm light throttle, which was the problem area with the pressure sensor used earlier. At 7700rpm the exhaust pulses are the strongest, so that's probably the peak resonance of the pipe. However at around 4600rpm the indication is poor, not a big difference between full throttle and closed throttle. The exhaust pulse from the port is probably being cancelled by the existing wave, why at 4600? It's giving me a headache so I've made the maps the same below 5000rpm, low rpm response was never an issue.

[Frits Overmars]

Frits, if you are still wondering where you once saw the reference to 83.3 as Lodgernz calculated, it can also be seen in Gordon Blair`s books shown his pipe calculation formulas.Thanks Trevor and Lodgernz. It was in my own notes from when I developed the 'simple exhaust concept'. I knew it looked familiar :p.

[Greg85]

In the paper the two hook positions were part of the experiment matrix.
The two positions gave different results, but in some older RS125 cylinders the pin is offset,and grinding the boost port septum's symmetrical gives
more power when used with the later pistons that have the pin at 6 o'clock.

The PJ and SPJ jet quite differently due to the length difference,if you are running a race 125 then the stock Honda jets in the SPJ are a good start point.

hello wobbly, do you also work with flowbench when you work your cylinder? according to the document yamaha jaros it says that 0.325 RFC is the maximum after the admission and exhaust systems are more suitable, I think that there is a lot of parameters that are taken into account to operate a good high RFC cylinder cranckase compression, inlet, carb, Time area, sta, what do you think about wobbly? thank you sorry google translation

[katinas]

In the paper the two hook positions were part of the experiment matrix.
The two positions gave different results, but in some older RS125 cylinders the pin is offset,and grinding the boost port septum's symmetrical gives
more power when used with the later pistons that have the pin at 6 o'clock.

Cylinder from 1987 Honda RS-250, last model without power valve.

[katinas]

In the paper the two hook positions were part of the experiment matrix.
The two positions gave different results, but in some older RS125 cylinders the pin is offset,and grinding the boost port septum's symmetrical gives
more power when used with the later pistons that have the pin at 6 o'clock.

The PJ and SPJ jet quite differently due to the length difference,if you are running a race 125 then the stock Honda jets in the SPJ are a good start point.


Cylinder from 1987 Honda RS-250, last model without power valve. Thicker wall between right B and C. Right B transfer have deeper pocket near wall with C than left B transfer.

[wobbly]

I have given up trying to interpret the results from flow bench tests,as I believe its only a small part of the overall scavenging regime.
Same with using CNC Jaros type scavenging machine results - this gives the opposite effect, in that is it shows the velocity and vector directions
but takes no account of bulk flow.
The best setup is that used by DEA, a pulsed flow visualizer, but im not that rich.
Here is the best example I can give re the flow bench result.
A reed cage with a nice smooth aerofoil type splitter in front of the reed tips flows way more air than the modified cage I have developed with a thin splitter
and a flat wall,perpendicular to the flow directly under the reed tips.
Guess which setup makes way more power.
VHM show big gains in flow with a flat top piston and a timing edge radius, but the dyno result though near on 1 Hp in near on 50 is nowhere near as significant a result as you would expect.

[RomeuPT]

Cylinder from 1987 Honda RS-250, last model without power valve. Thicker wall between right B and C. Right B transfer have deeper pocket near wall with C than left B transfer.

They come all that way.

I have 3 std client factory RS125 cylinders 91, 97 and 01.

It would be plausible that the 01 cylinder (dif case bolt pattern) might had came with dif transfer port angles etc after the SAE 1999... I have spent some time looking and the only dif I can be sure is that the 01 has more 0.5mm height, which puts all ports lower and thus helps keep the transfer not has high has the 97 cylinder, more blowdown?!

I even putted some water flush to see if I can see dif flow patterns, transfer ports angles, areas, exhaust port look very the same.

[RomeuPT]

I have given up trying to interpret the results from flow bench tests,as I believe its only a small part of the overall scavenging regime.
Same with using CNC Jaros type scavenging machine results - this gives the opposite effect, in that is it shows the velocity and vector directions
but takes no account of bulk flow.
The best setup is that used by DEA, a pulsed flow visualizer, but im not that rich.
Here is the best example I can give re the flow bench result.
A reed cage with a nice smooth aerofoil type splitter in front of the reed tips flows way more air than the modified cage I have developed with a thin splitter
and a flat wall,perpendicular to the flow directly under the reed tips.
Guess which setup makes way more power.
VHM show big gains in flow with a flat top piston and a timing edge radius, but the dyno result though near on 1 Hp in near on 50 is nowhere near as significant a result as you would expect.

If the reed port flows less how can it make more power?

[wobbly]

Simple answer, the flow bench measures constant bulk air flow by looking at the pressure drop ( say 28" ).
A two stroke reed valve opens and closes the petals every revolution, so is nothing like a constant depression value.
My take on the power increase is that the flow "dissrupter " face is turning the flow just as it exits the cage, and this opens the reed petals quicker.
Thus more area at initial opening of the reed curtain exit.
Exactly the same power increase as you see from a 4T with better low valve lift flow.
This is exactly the point I was making - just looking at flow bench numbers is very misleading.

[Greg85]

I have given up trying to interpret the results from flow bench tests,as I believe its only a small part of the overall scavenging regime.
Same with using CNC Jaros type scavenging machine results - this gives the opposite effect, in that is it shows the velocity and vector directions
but takes no account of bulk flow.
The best setup is that used by DEA, a pulsed flow visualizer, but im not that rich.
Here is the best example I can give re the flow bench result.
A reed cage with a nice smooth aerofoil type splitter in front of the reed tips flows way more air than the modified cage I have developed with a thin splitter
and a flat wall,perpendicular to the flow directly under the reed tips.
Guess which setup makes way more power.
VHM show big gains in flow with a flat top piston and a timing edge radius, but the dyno result though near on 1 Hp in near on 50 is nowhere near as significant a result as you would expect.

thank you wobbly for the answer, yes the bench jaros is nothing significant jan me had already said also in a previous post, a professional near me has a jaros I tested several cylinder TM by comparing the RFC 1 was good and the other worse by testing the cylinders in the dyno with the same time area I had almost the same hp 0.3hp here are some pictures of the tests, vhm yes already tested the flat piston then gain 0.5hp crest nothing of significant seen the price nothing better than tm 4 degres.good your reed box you are in full test reed box also there are gains to make a pretty sensitive point as I could see it on modena mkz333166333167333168333169333171

[Greg85]

333175333172333173333174333176333177
thank you wobbly for the answer, yes the bench jaros is nothing significant jan me had already said also in a previous post, a professional near me has a jaros I tested several cylinder TM by comparing the RFC 1 was good and the other worse by testing the cylinders in the dyno with the same time area I had almost the same hp 0.3hp here are some pictures of the tests, vhm yes already tested the flat piston then gain 0.5hp crest nothing of significant seen the price nothing better than tm 4 degres.good your reed box you are in full test reed box also there are gains to make a pretty sensitive point as I could see it on modena mkz333166333167333168333169333171

[wobbly]

I suggest you look at the IAME piston,that has a 5* angled edge for around 7mm that then becomes a flat top.
This setup in a TM with a new insert ( with the plug alot closer to the piston and a very flat bathtub ) makes better power than the 4* TM setup ( same cc ).

[TZ350]

333187

Got a Piezo switch today, 24V 200mA max.

333188

Tried it out on my trusty PLC test bed. Piezo switch works great, pulse output non latching. Will check later how it goes with 12V and how square the wave form looks on a scope.

[Greg85]

I suggest you look at the IAME piston,that has a 5* angled edge for around 7mm that then becomes a flat top.
This setup in a TM with a new insert ( with the plug alot closer to the piston and a very flat bathtub ) makes better power than the 4* TM setup ( same cc ).

thank you wobbly for the information, I tested the new housing modena mkz it is more power on the whole curve I controlled the changes brought then more volume of low crankcase we arrive at 520cc atdc before 490cc inclination of the angle for the reed box 2 degrees down and another shape inside what do you think wobbly changes made? thank you333208333209333210333211333212

[wobbly]

Remove around 3mm of material in the side of the duct outside of the reed cage - this helps flow from the petals that exits sideways from the cage ( not directly out the tips).

[Frits Overmars]

Remove around 3mm of material in the side of the duct outside of the reed cage - this helps flow from the petals that exits sideways from the cage (not directly out the tips).Here are a couple of pics that may clarify your point, Wob.
333214 333215

[wobbly]

Thanks Frits.
This spillover flow out the sides is very apparent when using the style of stuffer as is used in KZ engines.
I discovered this when velocity testing the flow of the SKUSA CR125 reed cage.
As the carb is offset upwards and also angled to the side there is a huge amount of extra flow on the right side petal exits.
There is a higher velocity out sideways than directly in line.
I adjusted the petal backup stiffeners to even out the differences, and picked up over 2 Hp thru nearly the whole powerband.
The only other comment I would have is that a big taper out into the transfer ducts as is shown in the RH pic does not seem to work.
Keeping the area in front of the reed box as small as is possible ( by reducing especially the vertical height ) seems to be better.
I think that making a real effort to fill in the roof and floor, then making extra area to the sides, to help the angled reed cage flow would be the go.
But in KZ we cant add material.

[crbbt]

do you want me to send over my reed block for the RS wob :laugh:

[F5 Dave]

Jeez Louise some of this stuff is not intuitive.

[jbiplane]

333175333172333173333174333176333177

Hi Greg. Just wonder what DOS-software generates pictures of flows in cylinder? Is it realistic enough?

[Greg85]

Hi Greg. Just wonder what DOS-software generates pictures of flows in cylinder? Is it realistic enough?

hello, yes DOS software but the version I do not know there are several versions for the bench jaros? you know this type of bench?

[Greg85]

Remove around 3mm of material in the side of the duct outside of the reed cage - this helps flow from the petals that exits sideways from the cage ( not directly out the tips).

wobbly thanks for your analysis i will do it, as you said the inlet design for a 30mm carburetor is super important to have a good flow and look for the 50 HP but complicated to reach ...

[Greg85]

Here are a couple of pics that may clarify your point, Wob.
333214 333215

Thanks frits for your explanation

[Flettner]

Ok, anyone here know anything real about the smart carb?
Have been told by a convert that the SC will atomize fuel better than a modern fuel injector. I don't believe it but someone here will have the 'real dirt' on these carburetors.

[husaberg]

Ok, anyone here know anything real about the smart carb?
Have been told by a convert that the SC will atomize fuel better than a modern fuel injector. I don't believe it but someone here will have the 'real dirt' on these carburetors.
its a lectron Ei, Quicksiver, posifuel, lake injector, rehash.

[Flettner]

American company? Excellent marketing then.:laugh:

[husaberg]

American company? Excellent marketing then.:laugh:
1968-1969: The Lake Injector prototype and final production model carburetor.
· 1970-1971: The Pos-A-Fuel prototype and final production model carburetor.
· 1971: The Pos-A-Fuel with remote float bowl production model carburetor.
· 1973-1974: The Lectron prototype and final production model carburetor.
· 1976-1977: The E.I. Prototype and final production model carburetor.
· 1978: The Blue Magnum production model carburetor.
· 1980: The Bank of Four Blue Magnum model carburetor.
· 1981-1982: The Qwik Silver prototype and production model carburetor.
· 1982: The Qwik Silver Bank of Four carburetor wins Daytona super-bike race.
· 1993: The Qwik Silver II production model carburetor (sold to Edelbrock).
Wob was doing something with one a while back 4 years or so.


https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1130842057#post1130842057
https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1130255542#post1130255542
https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1130812466#post1130812466
https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1130437168#post1130437168
there is more but KB search is not working properly maybe due to the thread being split a few times. poll etc

[wobbly]

The Smartcarb does a few things really well, but they would not listen to me re the shortcomings.
The flat cutaway needle from the Lectron is used, and yes it does atomize fuel smaller than conventional FI.
This makes the carb much less tuning sensitive.
The bore is egg shaped at the slide, giving very good throttle response at small openings.
And it has a pressure sensing setup in the top of the bell mouth ,that varies the depression above the fuel in the bowl.
This has the ability to correct the fueling on the run when it encounters differing air pressure.
Works really well at Pikes Peak with a huge variation in elevation.
And they has won several classes of Quads with engines/pipes I have done.
But its big downfall is that unlike a Lectron it does not have a secondary main jet circuit ( power jet ) than can be fine tuned to alter the top end jetting.
This means its all but impossible to correctly jet a twin to get equal egt, as just like a Lectron moving the needle up and down doesnt affect the main jet fueling.
They dont make needles in fine enough increments to change the egt say 30* F,and thats a real hassle even in a single cylinder application.

[Flettner]

And sonic flow engines? Part of smart carb I believe?
Oil less engines if I read it correctly?

[Frits Overmars]

American company? Excellent marketing then.:laugh:Yes, the kind of bragging that never fails to irritate me. However, I must say the Smartcarb performed really well on the dyno. But it gave some problems on the track,
whereupon its patent holder made an appointment to come over to Europe, insisting to meet me in person. He was scheduled to arrive early October. Still waiting...

[DoldGuy]

Red Edmonston

http://investorshub.advfn.com/boards/read_msg.aspx?message_id=100142794


Frits, hope this will end your waiting as I don’t think he will be showing up this life’s journey.

[DoldGuy]

Google images of: george boswell carburetor

I have heard motors run with these carbs back in the nineties & they where VERY responsive & crisp.

The brains behind this had accommodations elsewhere for a while, but has since thought of another avenue for the carburetor...

Google: PWK stic metering block

[Frits Overmars]

Red Edmonston http://investorshub.advfn.com/boards/read_msg.aspx?message_id=100142794 Frits, hope this will end your waiting as I don’t think he will be showing up this life’s journey.Thanks DoldGuy, I get your point; I edited my previous post, replacing spiritual father with patent holder.

[guyhockley]

"unique result", they say...
https://transmoto.com.au/bike-dissected-yamaha-yzr500fi/

[marsheng]

Going by the name of steve james, he is wrecking a MBR250 and wants to know if
I need any parts. Just to confirm that he 'has' the bike, he shows me a
picture of it. It is a picture of the bike in my back yard. Ha Ha. I don't
think the lift goes to the top in this one. Just how many MBR250s are there? Not a trick question, one.

Anyway as a security check, I always get a contact number that I call that is
registered to an address backed up with a Whitepages entry or web page.

I think I will string him along for a ride for a while. Darwin award ?

[Grumph]

Going by the name of steve james, he is wrecking a MBR250 and wants to know if
I need any parts. Just to confirm that he 'has' the bike, he shows me a
picture of it. It is a picture of the bike in my back yard. Ha Ha. I don't
think the lift goes to the top in this one. Just how many MBR250s are there? Not a trick question, one.

Anyway as a security check, I always get a contact number that I call that is
registered to an address backed up with a Whitepages entry or web page.

I think I will string him along for a ride for a while. Darwin award ?

Certainly an award for something, Wallace. But it's obviously a very rare and expensive bike....
Is the payment to go to Nigeria ?

[ken seeber]

Question: Is there a phone app (Android) that one can stick on a phone in one’s pocket and do a (straight line hopefully) acceleration run and this is recorded. Essentially the output will be velocity vs time or preferably, acceleration rate vs speed. Don’t care whether it is just GPS based or utilizes the phone’s accelerometer.

Why? I have been working on the sliding cylinder engine https://www.youtube.com/channel/UCg24eWF2LE0nEmf8YrX0RYQ and have tried to run it against a water brake dyno. So far, I just can’t make it work, seemingly the engine power curve exceeds the absorption curve at some point and the engine just revs of to infinity (well, just over 70,000 rpm). Figuring I don’t want to be developing a dyno, I reckon that for cheap thrills I am just going to wack it onto a kart and drive up some bitumen road or track.

Given this, if I could record the accel (at varying cylinder height steps), it’d be extremely useful. I can back calc the engine rpm from the kart speed.
The few apps I have looked at seem to have things like 0 to 60 mph, 1/8 mile, ¼ mile test ranges, but I just want to be able to press start, do a run and then press stop and have an accel run log.

Any ideas?

[wobbly]

https://play.google.com/store/apps/details?id=ch.perfectpower.PerfectPower&hl=en

[diesel62]

Is the GPS refresh rate good enough for that on a phone?

Sent from my SM-G900F using Tapatalk

[SwePatrick]

They are using the acceleratorsensor in the phone.

I´m using this one:

https://play.google.com/store/apps/details?id=com.perfexpert&hl=en

[Frits Overmars]

Is there a phone app (Android) that one can stick on a phone in one’s pocket and do an acceleration run... Figuring I don’t want to be developing a dyno...
https://play.google.com/store/apps/details?id=ch.perfectpower.PerfectPower&hl=en
Quote from the above website: "It will also allow you to perform motor development with efficiency thanks to its perfect regularity"I don't doubt the perfect regularity of the app, but what about the regularity of track conditions, wind, tires? Building an inertia dyno can be quite simple, there will be hardly any need to develop it as the necessary software and electronics can be found all over the internet, and it will be a much better tool for engine development.

A couple of examples of simplicity:

[paul gane]

The 250G cylinder has much more modern transfer ports and ducts than anything previously.
Thus you could do the mods as per the Eckerold cylinder but using waisted studs allows the inlet to go even wider ( with a bridge of course ) allowing two extra boost ports
and you then dont have to add an Exhaust bridge as going 3 port is easy.
Turning the cylinder around is also easy and this makes the pipe headers straight, and then the inlet becomes dead straight onto the reed blocks with the carbs sitting horizontally.
The 350 period engine going into the LSR streamliner is as above, but uses a Banshee 58mm crank/115 rods with 61.5 Kawasaki pistons, making it a not so big overbore and close to square.

The 350 in the LSR streamliner, using the Kawasaki H1 61.5 pistons you used, were they the two ring road bike type, or special single ring one offs. I am interested in building a 350 based on the 61.5x58bore and stroke, did the engine perform up to expectations, any advice appreciated....

[wobbly]

The Wossner H1 pistons are two ring, but we only used the top ring as its pinned at 6 o'clock.
This ran over a welded in central port bridge that had added boost ports down each side.
The key to the whole engine is the 13mm locked in place studs, that can then be ground away to enable the added Aux ports
plus a huge intake.
The cylinder was reversed as well, as this took most of the piston thrust off the inlet,and made pipe routing easy.
Porting/pipes were set up in EngMod, and its performance exceeded all expectations with more than enough power to break the Pre 81 - 350cc records easily.
The setup was optimized to make 100 crank Hp at 11500 on 110 octane.
It ran overeving to 12,000 in 5th gear, as the shift mechanism would not select 6th under load,but would have gone at least another 15mph faster hitting peak power rpm in 6th.

[paul gane]

[QUOTE=wobbly;1131070937]The Wossner H1 pistons are two ring, but we only used the top ring as its pinned at 6 o'clock.
This ran over a welded in central port bridge that had added boost ports down each side.
The key to the whole engine is the 13mm locked in place studs, that can then be ground away to enable the added Aux ports
plus a huge intake.
The cylinder was reversed as well, as this took most of the piston thrust off the inlet,and made pipe routing easy.
Porting/pipes were set up in EngMod, and its performance exceeded all expectations with more than enough power to break the Pre 81 - 350cc records easily.
It ran overeving to 12,000 in 5th gear, as the shift mechanism would not select 6th under load,but would have gone at least another 15mph faster hitting peak power rpm in 6th.[/QUOTE


Wobbly, thanks for the info. I don't get the 13mm studs locked in place, how do these work.
This was a reed valve converted cylinder, what reeds did you use ?
Thanks for sharing......

[Nath88]

Any ideas?
I remember an app called GPS logger, I think it logged the other sensors as well. Produced a .csv file you could process later with excel. Hopefully the data rate of the phone GPS is enough to give you useable numbers.
If you could log wheel speed with something it would probably be a bit more accurate.

Very interested to see this thing under load. What are the port timing limits on the slide?

[wobbly]

Here is a pic of the oversize studs in place.Just the normal M8 threads screw into the case,with M8 female in the top.
The reeds were VeeForce replacements for Honda RS125 late model, and the rubber manifolds were used as well.

[paul gane]

Here is a pic of the oversize studs in place.Just the normal M8 threads screw into the case,with M8 female in the top.
The reeds were VeeForce replacements for Honda RS125 late model, and the rubber manifolds were used as well.

Thanks Wobbly, thats all clear now. Looks to be well worth all the effort.
Many Thanks......
P. G.

[JanBros]

Any ideas?

for some time I used my Starlane GPS laptimer as a dyno. not that it would give me HP-numbers, but it did gave me very accurate time vs speed grahps and in the end that is all that matters.
just made a "track" on the roads arround my house that included a long stretch of road that's hardly used. once passed the "starline" it started counting, then I simply stopped on the straight and did a "drag-pull", always from the same starting point.

in the starlane software you can very accuratly determine the point where speed rises from zero, and than it gives you the time between any 2 points. you can lay different runs on top of each other and compare them directly.

[koenich]

Previously MicroDyno was free but maybe it still helps: https://play.google.com/store/apps/details?id=com.pledlstefan.siphorsepowerdyno&hl=en

[shnaggs]

I have been looking for something like this also, RE. the smart phone dyno. I was under the impression that these apps needed to be hooked up to the vehicle via OBD2 port? I have PerfExprt for my car but have never used it. I will have to investigate these more. The mircrodyno looks interesting, cause it was created for 2 strokes and is capable of reading RPM via frequency.

[lohring]

Microdyno looks like it uses the same method the software on an inertial dyno uses to calculate power. That makes me wonder if it could be tricked to work on an inertial dyno.

Lohring Miller

[adegnes]

Simpledyno
https://sites.google.com/site/simpledyno/home
+ a hall sensor on the wheel and an arduino based tiny computer in your pocket should work great.

Not as quick and cheap as just an app though.

[Greg85]

That A-kit paper is from 1992. You can tell by the picture and the drawing that show the coolant hose nipple still attached to the cylinder.

Cutting the steps out increases the duct volume, which is bad. You may remember my bicycle-pump metaphor.
Filling in the steps until there is a smooth transition to the header is good.

hello frits, I would like you to tell me about your bicycle pump methapor, the theory between the difference between the up and down the good ratio case / comp following a certain volume of combustion chamber, the ex duct height also has an influence the said wobbly. thanks

[Frits Overmars]

hello frits, I would like you to tell me about your bicycle pump methapor, the theory between the difference between the up and down the good ratio case / comp following a certain volume of combustion chamber, the ex duct height also has an influence the said wobbly. thanksGreg, I'd be glad to oblige, but I hate writing the same thing twice, so I started looking for the original 'bicycle pump' text. I gave up after 20 minutes; forum search functions never seem to do what I need.
Then I remembered that I wrote about it on another forum and I even had a fairly good idea where exactly: http://www.pit-lane.biz/t117p375-gp125-all-that-you-wanted-to-know-on-aprilia-rsa-125-and-more-by-mr-jan-thiel-and-mr-frits-overmars-part-1-locked.

Your question about "the theory between the difference between the up and down the good ratio case / comp following a certain volume of combustion chamber,the ex duct height also has an influence the said wobbly" is too complex for me; I do not understand what it is you are asking.

[Greg85]

Greg, I'd be glad to oblige, but I hate writing the same thing twice, so I started looking for the original 'bicycle pump' text. I gave up after 20 minutes; forum search functions never seem to do what I need.
Then I remembered that I wrote about it on another forum and I even had a fairly good idea where exactly: http://www.pit-lane.biz/t117p375-gp125-all-that-you-wanted-to-know-on-aprilia-rsa-125-and-more-by-mr-jan-thiel-and-mr-frits-overmars-part-1-locked.

Your question about "the theory between the difference between the up and down the good ratio case / comp following a certain volume of combustion chamber,the ex duct height also has an influence the said wobbly" is too complex for me; I do not understand what it is you are asking.

thank you frits for the links pit lane, excuse me I badly formulated my question, I would like to know if there is a report with crankcase compression and compression? I mean balancing the top and the bottom for example decompressed for not braked the piston up and decompressed the case to not brake the piston down to have the right ratio, I saw in a wobbly post and you (p1230) an image showing a calculation for chamber combustion and engmod software asks the crankase compression for that I ask you apparently it's bound as the exhaust duct height thank you( sorry Google traduction)

[RomeuPT]

I have given up trying to interpret the results from flow bench tests,as I believe its only a small part of the overall scavenging regime.
Same with using CNC Jaros type scavenging machine results - this gives the opposite effect, in that is it shows the velocity and vector directions
but takes no account of bulk flow.
The best setup is that used by DEA, a pulsed flow visualizer, but im not that rich.
Here is the best example I can give re the flow bench result.
A reed cage with a nice smooth aerofoil type splitter in front of the reed tips flows way more air than the modified cage I have developed with a thin splitter
and a flat wall,perpendicular to the flow directly under the reed tips.
Guess which setup makes way more power.
VHM show big gains in flow with a flat top piston and a timing edge radius, but the dyno result though near on 1 Hp in near on 50 is nowhere near as significant a result as you would expect.

Do you think this would work on the V-force 2/3? flatening the fins?

Do you have any simple PDF/paper regarding Aerodynamics for motorcycles? Something like newbie concepts etc?

Cheers

[peewee]

thank you frits for the links pit lane, excuse me I badly formulated my question, I would like to know if there is a report with crankcase compression and compression? I mean balancing the top and the bottom for example decompressed for not braked the piston up and decompressed the case to not brake the piston down to have the right ratio, I saw in a wobbly post and you (p1230) an image showing a calculation for chamber combustion and engmod software asks the crankase compression for that I ask you apparently it's bound as the exhaust duct height thank you( sorry Google traduction)

i believe the crankhouse compression ratio should be around 1.32 (+/- .02). compression ratio above the piston will depend alot on the fuel type and perhaps even engine cubic capacity since small engines seem to tolerate high ratios better. maybe less piston surface area has something to do with it ?(standard low grade petrol, racing petrol, , e85, methanol, nitro etc)

[Frits Overmars]

I would like to know if there is a report with crankcase compression and compression? I mean balancing the top and the bottom for example decompressed for not braked the piston up and decompressed the case to not brake the piston down to have the right ratio.No, balancing the pressures above and below the piston is not a point of consideration. You want a downward-moving piston to push on the con rod as much as possible, so you do not want the crankcase pressure to slow down a downward-moving piston. But after BDC the piston must be accelerated upwards, which requires negative work via the con rod; now you want the crankcase pressure to help accelerate the piston as much as possible.
In short: when the piston is moving down, you want a low crankcase pressure, i.e. a large crankcase volume, and when the piston starts moving upwards, you want a high crankcase pressure. But when the crankcase volume is small, the crankcase pressure will drop fast because of the rising piston, so that is one more argument in favour of a large crankcase volume.
However, all the above factors are unimportant against the requirement for mixture transfer: a large crankcase volume from which the exhaust pipe can suck up as much mixture as possible.

Above the piston, things are much simpler. Let's just look at an engine without ignition and combustion. On its way towards TDC the piston is slowed down by the compression pressure, so this pressure is applying negative energy. But after TDC that same compression pressure is accelerating the piston downward, applying just as much positive energy. In short: compression pressure above the piston is energy-neutral.

Of course, with combustion, things become more biased: a low compression ratio equals a low expansion ratio, leaving more energy in the exhaust gas. And this energy is used by the exhaust pipe in the same way that a turbo would: the more the better.

[Greg85]

No, balancing the pressures above and below the piston is not a point of consideration. You want a downward-moving piston to push on the con rod as much as possible, so you do not want the crankcase pressure to slow down a downward-moving piston. But after BDC the piston must be accelerated upwards, which requires negative work via the con rod; now you want the crankcase pressure to help accelerate the piston as much as possible.
In short: when the piston is moving down, you want a low crankcase pressure, i.e. a large crankcase volume, and when the piston starts moving upwards, you want a high crankcase pressure. But when the crankcase volume is small, the crankcase pressure will drop fast because of the rising piston, so that is one more argument in favour of a large crankcase volume.
However, all the above factors are unimportant against the requirement for mixture transfer: a large crankcase volume from which the exhaust pipe can suck up as much mixture as possible.

Above the piston, things are much simpler. Let's just look at an engine without ignition and combustion. On its way towards TDC the piston is slowed down by the compression pressure, so this pressure is applying negative energy. But after TDC that same compression pressure is accelerating the piston downward, applying just as much positive energy. In short: compression pressure above the piston is energy-neutral.

Of course, with combustion, things become more biased: a low compression ratio equals a low expansion ratio, leaving more energy in the exhaust gas. And this energy is used by the exhaust pipe in the same way that a turbo would: the more the better.

thank you frits for your answer, ok in summary have a large crankcase volume I think around 1.33 for a reed valve is a good base as the said pewee. after us in karting we have a volume respected 13cc minimun so by calculating the theoretical compression ratio is effective it is far from arrived like the RSA which was 14.88: 1? the question is how to do more power with a low rate compression? by increasing the trapping effiency of the cylinder? a better combustion chamber? exhaust adjustement? what do you think about frits? thanks

[Greg85]

i believe the crankhouse compression ratio should be around 1.32 (+/- .02). compression ratio above the piston will depend alot on the fuel type and perhaps even engine cubic capacity since small engines seem to tolerate high ratios better. maybe less piston surface area has something to do with it ?(standard low grade petrol, racing petrol, , e85, methanol, nitro etc)

hi peewee yes single cylinder 125cc and benzin sans plomb 98 total yes you're right it takes a high compression ratio but in karting we have a minimum volume respected 13 cc volume chamber, a low compression ratio, so yes I think be a good base 1.32 1.33 crankcase compression ratio thanks for answer peewee

[katinas]

Honda NS250/400 std. cylinders from factory have free space under EX duct, but after drilling two holes can be very easy filled with coolant. It looks like Honda engineers wanted filling cooling all around EX duct, but for some reasons decided block passages in casting.
Maybe it looks too much, but that open space under exhaust duct and transfers A, gave much better power and 1500 rpm more (on standing bike without load before was max 13000rpm , now 14500rpm ). On the road, before modification, power drop after 12000 rpm , now after 13200 rpm. But not tested in 5 and 6 gears. Angle, head, carb, reed all is the same.
Bottom and mid power not changed , but after 11000rpm feels stronger. I dont know why, but maybe, like Frits wrote, more volume for exhaust suction, or maybe temperature under exhaust duct. And power feels better with longer load , but maybe in 5 and 6 gear would be different.
Maybe someone had experience.

[wobbly]

Many engines have the water inlet directly under the Ex port duct.
Jan tried the idea of stopping flow directly cooling the duct bottom, by filling it with epoxy,and the engine lost power and detoed badly.
Franco at TM has decided to not use at all the holes in the case and cylinder that would allow ALL of the flow into the cylinder to enter under the duct.
I cant believe that he did not test this back to back against the original method of supplying water from the case via a hose that enters up high above the Ex port.
I am about to do this test, along with ceramic coating the duct,as there is still a belief by some that a hot duct will help the pipe work better.
This is very wrong in my opinion,as overheating the duct will overheat the plugging mixture pushed back past the rising piston, but the only way is to test this back to back.
My other test will be to do the cooling "properly ",that is to have the cold water enter the cylinder at the back ( opposite the Exhaust ) then flow over the transfers,cooling the Ex last.
In the TM homologation papers there is no hose shown, so having one around the back is not going to be illegal.

[katinas]

Many engines have the water inlet directly under the Ex port duct.
Jan tried the idea of stopping flow directly cooling the duct bottom, by filling it with epoxy,and the engine lost power and detoed badly.
Franco at TM has decided to not use at all the holes in the case and cylinder that would allow ALL of the flow into the cylinder to enter under the duct.
I cant believe that he did not test this back to back against the original method of supplying water from the case via a hose that enters up high above the Ex port.
I am about to do this test, along with ceramic coating the duct,as there is still a belief by some that a hot duct will help the pipe work better.
This is very wrong in my opinion,as overheating the duct will overheat the plugging mixture pushed back past the rising piston, but the only way is to test this back to back.
My other test will be to do the cooling "properly ",that is to have the cold water enter the cylinder at the back ( opposite the Exhaust ) then flow over the transfers,cooling the Ex last.
In the TM homologation papers there is no hose shown, so having one around the back is not going to be illegal.

Thanks

Exactly in this cylinder cold water enter at the back then flow over the transfers to EX.
Yes, heated mixture not good thing and that why higher power surprised me. But maybe on long run power will change.

[peewee]

wob do you think ktm got it all wrong with cold water going in under the exh passage first, then around the cylinder sides to the rear and exiting at the front of the head ?

[wobbly]

Well that is how dozens of motors have the water flow.
But TM could do that, and have plugged the holes - opting to have the flow in above the Exhaust duct.
Why that is I will know soon.
But as I said, the best way I believe is to cool the transfers first and I can easily do that by rerouting the side hose to a fitting on the back.
But as Jan found out, not cooling under the duct sufficiently causes power loss and big time deto, so I plan on trying to drill out the plugs to say 5mm
and see if that makes any difference ,along with the main flow in at the rear.

[Matt@TYGA]

Interesting about the water inlet position, flow and so on. Especially the bit about cooling the plugging mixture.

Having the cold water cool the transfer ducts makes sense, as does tapping off the inlet flow to also flow in under the exhaust duct.

Wobbly, you've shown your 3 port exhaust duct design, with a length of 2x the bore diameter. So how much of this duct are you looking to cool? All of it? Let's suppose the first part of the header pipe was also jacketed and cooled, would you then be cooling the pipe too much? Change pipe dimensions to suit?

Much testing required I suspect, and as always creates more questions than answers.

[Frits Overmars]

Having the cold water cool the transfer ducts makes senseIt would certainly make sense if we had cold water, Matt. But apart from outboard engines, the coolant temperature may well be higher than the temperature of the fresh mixture in the crankcase.
The transfer duct walls are heated by thermal conduction from the hottest cylinder part, the exhaust duct. So if we take away the heat there, the transfer ducts will benefit as well. And it is a lot simpler than convincing the coolant to flow from around the transfers to the underside of the exhaust duct and then upward without mixing with the 'cold' coolant that enters the cylinder from behind.
In most good cylinders, only the roofs of the transfer ducts are wetted. And in the best of 'm, some of the water that enters the cylinder under the exhaust, is directly guided through the inner transfer duct curvatures before it has had time to be heated by the exhaust duct.


Wobbly, you've shown your 3 port exhaust duct design, with a length of 2x the bore diameter. So how much of this duct are you looking to cool? All of it? Let's suppose the first part of the header pipe was also jacketed and cooled, would you then be cooling the pipe too muchOnly the part of the exhaust duct that gets temporarily filled with washed-through fresh mixture, needs to be cooled. If we cool a length of exhaust duct, long enough to hold a mixture volume equal to the cubic cylinder capacity, we'll be all right. Cooling the remainder of the exhaust tract would needlessly raise the coolant temperature and entail a loss of exhaust gas energy, reducing the good work of the pipe.

[Matt@TYGA]

Very good points there Frits, and plenty of food for thought.

[RomeuPT]

Only the part of the exhaust duct that gets temporarily filled with washed-through fresh mixture, needs to be cooled. If we cool a length of exhaust duct, long enough to hold a mixture volume equal to the cubic cylinder capacity, we'll be all right. Cooling the remainder of the exhaust tract would needlessly raise the coolant temperature and entail a loss of exhaust gas energy, reducing the good work of the pipe.

I guess it's exacly where the wet part of exhaust flange/header looks taking an exhaust off while doing a plug chop.

On my case the wet part now is exacly the lenght of the Aluminium flange.

If this end fresh gases are cooled better, do you think the engine will tend to run richer or leaner?

[Frits Overmars]

If this end fresh gases are cooled better, do you think the engine will tend to run richer or leaner?How would a difference in temperature change the air-fuel ratio of a mixture that was already prepared in the carburetter, Romeu?

[SwePatrick]

As i´m building a new pipe for my 211cc engine, could it be worth it to build a waterjacket, say first 100mm on the header?

[shnaggs]

As i´m building a new pipe for my 211cc engine, could it be worth it to build a waterjacket, say first 100mm on the header?

I had this same idea, would love to know also.

[shnaggs]

Also, going back to the dyno talking point quick. I noticed that aprillia used an inertia dyno, is this correct Jan? In a 2 stroke application is there any pro's and con's to using an inertia dyno versus a loaded dyno, like a water brake or eddy current?

I have used both dyno's before, I wont name the manufactures names, but the one dyno was so bad at giving me good data plots that my runs were just not repeatable and believable. The current dyno is an eddy current dyno that works well, and gives me good data plots per run, but I am loading the engine quite a bit.

It just caught my eye what you guys were talking about with inertia dyno's. Would love to know the experts opinions on the matter.

[lohring]

I'm a long way from an expert, but we used an inertial dyno for all our 26 and 35 cc model boat race engine development. The story of the 35 cc engine development is here (http://www.modelgasboats.com/magazine/tech-articles-mainmenu-608/244-cmb-35-record-engine). The big advantage is that the runs are very short allowing a lot of testing of various ideas without wearing out the engine. Also due to the short run, we saw beginning failures sometimes before they destroyed the engine. However, we also completely destroyed an engine that seized. An over run clutch might have helped disconnect the inertia wheel more quickly than the clutch. I would always include an over run clutch for larger engine testing. The run time was chosen to approximate the run up to the timing trap for speed events or the time of acceleration from a corner down the straight in oval racing. We held the ultimate gas RC boat speed record of 109+ mph from 2004 to 2016.

Lohring Miller

[RomeuPT]

How would a difference in temperature change the air-fuel ratio of a mixture that was already prepared in the carburetter, Romeu?

If charged with cooler mix the engine makes more power, more power going to exhaust, means it will cause greater depression/pressure, may cause lower pression below piston, then suck more fuel?!
Also hotter gases may change a little the plugs appearance and burning temp?! Too much guessing probably....

[Sandokan]

Only the part of the exhaust duct that gets temporarily filled with washed-through fresh mixture, needs to be cooled. If we cool a length of exhaust duct, long enough to hold a mixture volume equal to the cubic cylinder capacity, we'll be all right. Cooling the remainder of the exhaust tract would needlessly raise the coolant temperature and entail a loss of exhaust gas energy, reducing the good work of the pipe.

Has it ever been tried to thermaly isolate the exhaust from the cilinder?
I suppose most heat transfered from exhaust gas is passed to the metal of the pipe by Radiating.

[Frits Overmars]

Has it ever been tried to thermaly isolate the exhaust from the cilinder?Ages ago, with asbestos gaskets.

[Matt@TYGA]

As i´m building a new pipe for my 211cc engine, could it be worth it to build a waterjacket, say first 100mm on the header?

A friend of mine has fitted a 110cc boxer engine into a homemade surfboard. Running just straight pipes, into a silencer box, and out the back of the board. We jacketed the pipes, basically to try to keep the temperature down inside the engine compartment. How much is jacketed and how much water runs through the jacket makes a big difference on the power output.

But then again, he's also been playing around a lot with the prop pitch and nozzle diameter that it's a bit difficult to keep up with it all!

[jbiplane]

Hi guys

I produce my own cylinders by cnc milling and coat them by nikasil which works ~250 hours at 8000 rpm.
Tried to make nitrided steel liners of 40cr, survive just 50 hours.

Could anyone recommend me something better, but realistic for small production
- best possible for coating
- best possible liners material?

Valery
Aviamech llc
jbiplane@gmail.com

[Frits Overmars]

Hi Valery, there are many ways of preparing cylinder bores, but I have no personal experience with them, apart from chrome (not usable in combination with chromed piston rings) and nikasil.
But I wonder: why use steel liners? You can chrome or nikasil those too, but the contact surface between the liner and the cylinder casting will form an undesirable thermal resistance. And even if you use wet liners, the steel itself will form a thermal resistance.

[jbiplane]

why use steel liners? You can chrome or nikasil those too, but the contact surface between the liner and the cylinder casting will form an undesirable thermal resistance. And even if you use wet liners, the steel itself will form a thermal resistance.

My objective is create lightweight hybrid electric-ICE engines. The best numbers I achieved is 26hp ICE with 5kw alternator-starter which weight 9000 grammes and low resource. Want make something better...

[Tunisti]

Tried to make nitrided steel liners of 40cr, survive just 50 hours.

Could anyone recommend me something better, but realistic for small production
- best possible liners material?

Hi,

I'd recommend using GGG50 aka. EN-GJS-500-7 ductile cast iron bar. If I've understood right the steel liners have problems with lubrication, especially when used in two-stroke applications. Cast irons have self lubricity due to the graphite witch is distributed in the metal matrix. In this case the graphite is in nodular form, but it can also be in flake-like form, ie. GG25 grey cast iron. The self lubricity of grey cast iron is a bit better, but on the other hand it's mechanical properties aren't so convincing.

Of course there are these fancy spun cast industrial liners, but they're not available in Finland - so we use 3000*60mm EN-GJS-500-7 round bar. It costs about $250 including shipping&taxes, so material cost for one liner is less than $10.

About 60kg

https://tunisti.kuvat.fi/kuvat/Random%20Pics/DSC00346.JPG/_smaller.jpg (https://tunisti.kuvat.fi/kuvat/Random%20Pics/DSC00346.JPG)

Machining

https://tunisti.kuvat.fi/kuvat/Random%20Pics/IMG-20170706-WA0124.jpg/_smaller.jpg (https://tunisti.kuvat.fi/kuvat/Random%20Pics/IMG-20170706-WA0124.jpg)
https://tunisti.kuvat.fi/kuvat/Random%20Pics/IMG-20170706-WA0125.jpg/_smaller.jpg (https://tunisti.kuvat.fi/kuvat/Random%20Pics/IMG-20170706-WA0125.jpg)

Ports etched

https://tunisti.kuvat.fi/kuvat/Random%20Pics/DSC00748.JPG/_smaller.jpg (https://tunisti.kuvat.fi/kuvat/Random%20Pics/DSC00748.JPG)

I'd love to hear if someone has tried "thougher" nodular cast irons, ie. GGG60 or GGG70? I reckon that the self lubricity decrease too much, even though the mechanical properties are enhanced?

By the way, when cutting off the transfer duct openings from the liner above, I decided to do a little testing. I cut off two 25mm*25mm*2,5mm pieces of that curved wall. I tried to forge the other piece, but it just went flat and got a bit thinner at the edges, no fractures found. The other piece was bent with two pliers, first straight and after that about same amount of curvature in the "negative" direction, until it snapped into two pieces. It was hard to believe that it could take so much violence before cracking. The cheap (grey?) cast iron cylinders tend to crack at thin places if you just look at them with a wrong eye.

Sadly the track season is over in Finland. Some few months ago we built this bucket style 77cc track moped. In the video it only has about 10rwhp, since the quite DIY-style suspension was just being adjusted. We managed to build 13,5rwhp technique with worn out clinder, but got to drive it just once...

https://tunisti.kuvat.fi/kuvat/Suzuki%20S%20Track%20Moped/DSC00798.JPG/_smaller.jpg (https://tunisti.kuvat.fi/kuvat/Suzuki%20S%20Track%20Moped/DSC00798.JPG)

https://www.youtube.com/watch?v=QBXu6W8BLoA

Now we are waiting that the ice on the lakes is thick enough..:rolleyes:

https://tunisti.kuvat.fi/kuvat/Random%20Pics/IMG-20170207-WA0039.jpg/_smaller.jpg (https://tunisti.kuvat.fi/kuvat/Random%20Pics/IMG-20170207-WA0039.jpg)

[wobbly]

LA sleeve and several others make blank spun cast iron liners in a huge range of sizes.
This machines really well,and works perfectly.

[jbiplane]

Thanks for advices guys. I want to make experimental liners of metal powders by plasma coating 3d printing or whatelse.
This should result porous composite structure.

Once my friend cast very porous aluminum cylinders (and cover by nikasil) which leaks oil through everythere, but were very durable.

[JanBros]

I have this idea to use a blank liner in an oversized cast iron cylinder to get it back to 50cc, and at the same time use the liner to turn the single exhaust into a double. how thick do you recon the liner has to be for the bridge in the exhaust port to be "safe" ?
or should I first weld the exhaust port so the bridge has material behind it that gives support ?

[husaberg]

Thanks for advices guys. I want to make experimental liners of metal powders by plasma coating 3d printing or whatelse.
This should result porous composite structure.

Once my friend cast very porous aluminum cylinders (and cover by nikasil) which leaks oil through everythere, but were very durable.
John Tice here (http://forums.everything2stroke.com/threads/49513-How-It-s-Done-Projects-around-the-Shop/page9) and here (http://forums.everything2stroke.com/threads/49513-How-It-s-Done-Projects-around-the-Shop/page19) here (http://forums.everything2stroke.com/threads/49513-How-It-s-Done-Projects-around-the-Shop/page35) shows how to make the paterns for cast sleves, i believe he used to supply them for a few manufacturers.

[SwePatrick]

Has it ever been tried to thermaly isolate the exhaust from the cilinder?
I suppose most heat transfered from exhaust gas is passed to the metal of the pipe by Radiating.

I used an other approach then Frits.
Just for testing, and dragracing, no need for long serviceintervals.

Let´s see if i can explain in text:

As my duct is quite worn for the pipefitting in cylinder, i bored it out 0.5 millimeter bigger.
This way i can fit an bit of a tirehose on the part that holds the o-rings on the pipe.

I also let the hose 'hang over' the end of the fitting so it made a thermal barrier 'axial' against the duct in cylinder.
As the hos is flexible it didn´t hang freeley, it 'shrunk' and made an axial seal, hard to explain.

Well,, like putting a condom on a.... ;)

As i run methanol i had no issues with burning the rubber.

Rgds.

[Haufen]

'hang over'
putting a condom on
no issues with burning the rubber.

Rgds.

just practicing my selective reading skills :)

What I was wanting to ask - did you notice a difference between the isolated and the non-isolated pipe on the dyno?

[Frits Overmars]

John Tice here (http://forums.everything2stroke.com/threads/49513-How-It-s-Done-Projects-around-the-Shop/page9) and here (http://forums.everything2stroke.com/threads/49513-How-It-s-Done-Projects-around-the-Shop/page19) here (http://forums.everything2stroke.com/threads/49513-How-It-s-Done-Projects-around-the-Shop/page35) shows how to make the paterns for cast sleves.Quote from that forum:
After the sleeve is in & aligned a weight is put on top to hold things in place. If you don’t weight the new liner it will raise like you squeeze your tooth paste tube.Been there, done that and learned that it doesn't work.
When the cylinder is cooling down and the sleeve is picking up heat, they grab each other at some point and from then on, the cylinder top deck will creep further down along the liner, towards the point where the two first grabbed. You'd need a giant weight or better still, a press, to move the sleeve further down in order to keep its top collar in contact with the cylinder deck.

I'm avoiding sleeves, but if I still had to fit one, I'd slide it in the hot cylinder, line the windows up and then immediately put a damp cloth on top of the cylinder,
making sure that the deck cools faster than the rest of the cylinder. That way the sleeve is grabbed at the top first and the cylinder deck won't creep down on it.



I used an other approach then Frits. Just for testing, and dragracing, no need for long serviceintervals.
As my duct is quite worn for the pipefitting in cylinder, i bored it out 0.5 millimeter bigger. This way i can fit an bit of a tirehose on the part that holds the o-rings on the pipe. I also let the hose 'hang over' the end of the fitting so it made a thermal barrier 'axial' against the duct in cylinder. As the hose is flexible it didn´t hang freeley, it 'shrunk' and made an axial seal...Using asbestos exhaust gaskets was not 'my' approach Patrick; it was common practice back in the day when we did not yet have an environment and asbestos was considered a cure for everything.
Having said that, your condom solution works fine. We used to use a similar approach on the old Yamaha TZ-cylinders (with butyl rubber muffs instead of an inner tube, because in roadracing it had to last a bit longer than in dragracing). Especially the axial buffering that you describe was favourable because it protected the heat-softened aluminium exhaust stubs against the hammering of the pipe flanges.
333309 333310

[SwePatrick]

just practicing my selective reading skills :)

What I was wanting to ask - did you notice a difference between the isolated and the non-isolated pipe on the dyno?

Sadly i never tested 1-2-1 testing with that.
But as i added more and more tricks my powerlevel climbed upwards the whole time.
This was worth about 1.2hp
It might be worth more with petrolengines, but i haven´t tested that.
But,,, it might be that hangover and burned rubber again when pushing it too hard ;)

[TZ350]

333324

Building another Suzuki GP100 NSR 110 hybrid using a re plated but standard NSR250 cylinder.

Stroke 48mm Bore 54mm for 110cc ... (an NSR is 54 x 54).
Inlet opens 140 BTDC closes 80 ATDC
Exhaust opens 80 ATDC
Transfers open 114 ATDC

The shorter stroke gives me a very useful increase in blow down time area without having to do any porting at all.

333322

The cylinder sits on a 12.5mm spacer plate, the head is spigot ed 2.5mm into the cylinder and the cylinder also has 2.5mm skimmed from the top, 0.65mm squish.

333323

Using the standard head gasket so as to control the water flow around the cylinder.

333325

Yamaha RD400 2T2 rod with solid pin and flat big end bearing cage. The balance factor turned out to be 55%. I was looking for 50% so next time I will use a smaller Mallory slug opposite the bigend.

333321

The whole motivation for this engine is to have a smaller diameter inlet tract.

So I am leaving the original 24mm inlet tract un touched. Previously I would have made this as large as I could get away with. but an earlier dyno test with the variable inlet valve suggested there was not much top end in it and a noticeable difficulty in getting the carburation right at the lower end of the torqe curve just as the engine was coming onto the pipe.

333334

This is the dyno graph that has inspired me to try a smaller inlet tract. Red is the variable inlet open and equivalent to about 32mm and Blue is closed and about equivalent to a 24mm inlet tract. Top end is much the same, the difference seems to be just a little over rev.

Below are some links to the earlier Suzuki six speed, water cooled, drysump GP100/NSR hybrid.



331569 331568

The two basic items needed for adapting a NSR125 or 250 cylinder to the bottom end of your choice to make a go fast water cooled Bucket engine.




329021

How to make a decent light weight racing 12 Volt generator stator for the Suzuki GP/TF/TS RG50 from a Lifan aftermarket magneto kit.



This is Team ESE's formula for a reliable 110cc water cooled Bucket racing Engine.



The VeTec or variable inlet area story. Follow the links back to see the pictures.


I am hoping this V Tech inlet idea will add an extra 1000 or so rpm on the bottom end


Fitted the divider tonight and bolted it all up. Hopefully it lasts long enough to see if it has any merit in it.


Ok.... got the V Tec variable inlet onto the dyno.


This is the RC Servo that I am going to use to close the V Tec below 7,000 rpm.


My approach decreases the size of the inlet tract when the inlet closing point is reduced, this keeps the inlet tract gas velocity up.


Finaly got the V Tec working ...... Video of the V Tec in action http://www.youtube.com/watch?v=FeB9O6rtLXQ



241278

Tried the V Tec, works and cleaned up the carburation.

241277

Blue line inlet soft closes 98 ATDC Red line 88

It beats me how closing later picks up some mid-range and loses over-rev.



In most race applications I have found that 88* is the best compromise.
But that over 90*the troublesome carburation effects overcome any power advantages that you would expect.
As I said in another post - rotary valve tuning is as much about timing ( usefull STA ) as it is about ameliorating the issues with tract resonance affecting the A/F ratio actually seen in the case, and thus the combustion process.
Your intake is relatively long now - thus the resonance effects are seen earlier, and stronger.

[RomeuPT]

Wobbly can you provide some dimensions of KZ10 engine, piston height (after or before chanfer), rod dimensions, are the cylinder bolt fitting similiar to Honda RS?

The parts for them are not very expensive and makes a serious consideration for tunning other engines.

Cheers

[diesel62]

Have a look at www.superkart. it
Piston size is listed

Sent from my SM-G900F using Tapatalk

[wobbly]

Alot of info is within the CIK homologation papers.

And TeeZee, I have simply drilled a hole into the Mallory with a carbide drill before to correct overbalancing ie an 8mm hole in a 20mm tungsten.

[Sandokan]

Ages ago, with asbestos gaskets.

As one would expect its all been done before. :doh:
I came accros this tube video therefore the thought erupted.
https://m.youtube.com/watch?v=b_gh4R7vfkA
If its wise to isolate the cilinder from the exhaust this might be worth a try?

S

[TZ350]

And TeeZee, I have simply drilled a hole into the Mallory with a carbide drill before to correct overbalancing ie an 8mm hole in a 20mm tungsten.

Great tip, I had not thought of that, thanks.

[wobbly]

Again, Franco at TM is doing the opposite - all factory supported engines now do not run the thick gasket they used to have between the spigot and the cylinder.
And the spigot flange is recessed deeply to remove material.
This I cannot believe is an " accident " so cooling the spigot by allowing access to the duct cooling water ( that is directly behind the spigot face ) is " better ".
Seems very odd that he secretly believes that having a hot duct will be better, but in practice is doing the opposite to cool the spigot.
In my opinion the cylinder duct should be at least 15mm longer, moving the cooled zone outward,and thus increasing the volume of cooled plugging gas.
The TM has a 61mm long duct so its very little longer than 1 bore size, the volume is quite small with 78% area at the spigot face,so in this case I believe longer ( and cooler ) would be better.

[dutchpower]

Do you lose power in the lower part Wobb

[RomeuPT]

Alot of info is within the CIK homologation papers.

And TeeZee, I have simply drilled a hole into the Mallory with a carbide drill before to correct overbalancing ie an 8mm hole in a 20mm tungsten.

There is alot here yes
https://www.google.pt/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&ved=0ahUKEwiTnM3rtb_XAhWCfRoKHYUPALsQFgg4MAY&url=http%3A%2F%2Feolstoragewe.blob.core.windows.ne t%2Fwm-553616-cmsimages%2FTMKZ10C-TM32-M-24.pdf&usg=AOvVaw2899vtCWst0FWsJlgmH3ir

But not the cylinder bolt pattern.

if only you can check that :2thumbsup

[TZ350]

.
Back to the EFI thing and the problem of determining if the engine has fired or not and the subsequent fuel demand for the next stroke.

Following Nath88's suggestion of measuring the exhaust pressure pulse and Flettners suggestion of differentiating between the outgoing pulse and the return pressure wave by timing the sampling point.

333410

I brought an Arduino Micro PLC, a relay kit and some Piezo sensors all for less than $10. The plan is to have a pulse trigger on the flywheel that corresponds with the exhaust port opening and a pressure sensor in the exhaust tract close to the exhaust port. When the Arduino see's both pulses in align it opens the relay thereby switching the EFI CPU to a different fueling map.

333409

Or there are some of these Wika pressure transmitters lying around work. There is a variety of pressure ranges up to 500 bar. So I could easily measure the combustion pressure directly and when its over a certain threshold ie the engine has fired then the 4-20mA output through a small power transistor could be arranged to switch the relay.

[diesel62]

What do you need the relay for?

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[TZ350]

What do you need the relay for?

333411

The Ecotrons EFI software swaps maps when it see's this switch closed. So I was starting with the clean voltage free contacts of a relay but I really hope that I can do it with a transistor.

[diesel62]

333411

The Ecotrons swaps maps when it see's this switch closed. So I was starting with the clean voltage free contacts of a relay but really hope I can do it with a transistor.Can't you just wire directly to arduino from ecotrons ecu.? I don't think you will need the relay as there is no current

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[SwePatrick]

It will sadly enough not be a smooth transition when switching maps i guess.
This leads to hesitations etc etc.

You need to read pipe pressure dynamic and a compensationtable to add fuel related to different pressures.
Exact same way in a 4stroke turboboosted engine, but there it´s way more simple.
The mapsensor has a much easier work.

The thing is to invent a mapsensor that takes the pulses in exhaust with ease, and survives.

Rgds.

[diesel62]

It will sadly enough not be a smooth transition when switching maps i guess.
This leads to hesitations etc etc.

You need to read pipe pressure dynamic and a compensationtable to add fuel related to different pressures.
Exact same way in a 4stroke turboboosted engine, but there it´s way more simple.
The mapsensor has a much easier work.

The thing is to invent a mapsensor that takes the pulses in exhaust with ease, and survives.

Rgds.Maybe a DPF differential pressure sensor. That should work

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