ESE's works engine tuner

[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 .

[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.

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.

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.

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.

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.

[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.

Did this workout on the Aprilia RSA?

One more thing to try

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 use

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.

[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]

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.



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.



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.



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