Speeduino 2T EFI Project

[TZ350]

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The Arduino Nano co processor on a screw terminal breakout board and a 12 bit DAC for realistic analog output that is usable as a MAP signal for the EFI's CPU.

Hopefully get to try this out on the bike in the next night or two. If it looks promising I will post the code, if not its back to the drawing board.

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[TZ350]

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Arduino Nano MAP co processor setup ready to test. Hopefully tonight.

[Michael Moore]

In case it might be of help, 55641075000 is the part number for the KTM TPI MAP/crankcase pressure sensor, US$39.31, (listed with the oil pump instead of the throttle body/ECU where I expected to find it). It seems like it should be some standard bought-in component. It may be worth your getting one to see if KTM specified something out of the usual range of sensitivity compared to MAP sensors sold for 4T use. Or if it matches up to what you are using you'll know you probably aren't too far off on your setup.

There's a KTM/Husky TPI thread at advrider and the sensor seems to often get replaced when people's bikes are having problems running correctly.

cheers,
Michael

[husaberg]

In case it might be of help, 55641075000 is the part number for the KTM TPI MAP/crankcase pressure sensor, US$39.31, (listed with the oil pump instead of the throttle body/ECU where I expected to find it). It seems like it should be some standard bought-in component. It may be worth your getting one to see if KTM specified something out of the usual range of sensitivity compared to MAP sensors sold for 4T use. Or if it matches up to what you are using you'll know you probably aren't too far off on your setup.

There's a KTM/Husky TPI thread at advrider and the sensor seems to often get replaced when people's bikes are having problems running correctly.

cheers,
Michael

https://www.kiwibiker.co.nz/forums/s...post1131118311
Check out the O2 sensor price and location a few posts down
https://www.kiwibiker.co.nz/forums/s...post1131118379

[TZ350]

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Well my first try of the pseudo MAP co processing simulator did not work so well on the bike. So I have spent two weeks developing a high/low pressure simulator to mimic the fluctuating two stroke crankcase pressures and then tested the pseudo MAP co processing unit and it was a real failure as far as timing and staying in sinc with the ignition trigger. So no surprise it did not work so well.

Arduino Nano crankcase pressure simulator on the right and the pseudo MAP co processing unit on the left.

With the help of the Arduino Nano crankcase pressure simulator I made/programmed and a scope I finally got the pseudo MAP co processor sorted. The co processor is triggered of the ignition pulse and stays in sink now with the crankcase pressure changes from 500 RPM to 14,000 RPM and can clearly see both peaks and troughs. The scope display is at 12,000 RPM.

Hopefully I now have a pseudo MAP co processing unit that can sense the changes in airflow through the two strokes crankcase and interpret the changing differences between the high and low points as changes in airflow and send that as a 4T like MAP value to the EFI's CPU.

Hopefully get to try it on the dyno tomorrow night after work.

[patouille]

Hey,
I didn't give any news for a while but I was still investigating my troubles.
I replaced my hall sensor with a pwm generator to see why I was unable to make it run over 10K RPM. It turns out the injector starts messing up at ~11K, I tried a different one (CBR 125) with the same troubles at the same RPM.
Did you have the same issue ?
For me the next step is to modify the throttle body in order to add a second injector. I think I will trigger one injector after the other.

[Drew]

At some point I think ya'll are gonna have to accept that the best method is direct injection to the combustion chamber, and let it oil the way they do normally.

[TZ350]

I was unable to make it run over 10K RPM. It turns out the injector starts messing up at ~11K, I tried a different one (CBR 125) with the same troubles at the same RPM.
Did you have the same issue ?

Sounds about right. An injector small enough to give good tun-ability at lower rpm will be to small to deliver enough fuel at 11k rpm. It is time to get the job done that is the problem.

And no.... I have always used two logical injectors a small and a big in staged injection. They swap over about 7-8k rpm. Both big and small deliver the same amount of fuel (more or less) per crank cycle. It is just the big one has much less time to do it so has to really shovel it in. But then of course because it has to be open for a minimum amount of time it is to big for low rpm.

The Ecotrons injectors I have been using so far have been good to 14,000 rpm firing on each crank cycle (233 Hz).

[TZ350]

At some point I think ya'll are gonna have to accept that the best method is direct injection to the combustion chamber, and let it oil the way they do normally.

Why? and that would also limit rpm to something less than 9k because of the time it takes to evaporate the injected fuel and stir it properly into a combustion-able air/fuel mixture.

[Drew]

Why? and that would also limit rpm to something less than 9k because of the time it takes to evaporate the injected fuel and stir it properly into a combustion-able air/fuel mixture.

Pointed slightly outward from the center, the squish will take care of stirring it with the fuel.

[TZ350]

Pointed slightly outward from the center, the squish will take care of stirring it with the fuel.

No, that whole approach has proven to be dud for high rpm performance engines, just not enough time to get things done. The whole thing is RPM (read "time") limited.

[TZ350]

Video of the Pseudo MAP concept:

Some smoothing required and the bike is just idling, I need another pair of hands to video a dyno run, but for now things look promising.

[TZ350]

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Success ....... https://youtu.be/xAp77XQx9R8


I have finally got the pseudo 2S EFI MAP co processor working well with the output smoothed. Now I have something useful to work with to explore the possibilities of using MAP and a VE like table with fuel injection for a two stroke 2S. The co processor is measuring the high and low crankcase pressures and converting the difference between them to a pseudo MAP value.
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[Vannik]

This is just so great!

I was wondering in your calculation of the MAP values (I think it was (Phigh-Plow)*3) whether you should not maybe add an atmospheric based Patm to your equation? Maybe you are planning it but for now it is not an issue.

[TZ350]

I was wondering in your calculation of the MAP values (I think it was (Phigh-Plow)*3) whether you should not maybe add an atmospheric based Patm to your equation? Maybe you are planning it but for now it is not an issue.

Yes, thank you for your encouragement and I think you are right, the equation needs developing. But for now, I am happy just getting the (Phigh-Plow)*3 actually giving a meaningful result. A lot to do yet.

The great news is that the Pseudo MAP value behaves like I hoped. It increases as the motor starts making power and drops in areas where the TPS increased but the motor did not fire. You can see that in the middle of the picture where the TPS (green line) increases but the RPM (white line) decreases because the motor did not pick up and the MAP (yellow line) and rpm dropped. To the right of the graph you can see where the motor picks up and the MAP follows suit. Fueling is crap so the traces are not very neat.



Altogether it looks like the concept is going to work.