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Thread: Speeduino 2T EFI Project

  1. #211
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    Thankyou, I'll take one.

  2. #212
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    .

    Ok. Another bump in the road. The Pesudo MAP thing works pretty well BUT .... there seems to be another issue that comes up when the throttle is closed ie TPS = 0%.

    With the pseudo crankcase pressure MAP (Phigh - Plow)*3 I get a range of 0.2 bar, TPS = just open and motor firing to 0.9 bar, TPS fully open and engine firing. The motor responds to changes in MAP value just like you would expect.

    But with the throttle fully closed ie TPS = 0% the pseudo MAP value is 0.6 bar when it should be 0.2 at most. I think this is due to the atmospheric pressure at the stinger/muffler tip overcoming weak suction by the pipe and pushing exhaust gas back into the crankcase. And without the suction action of the pipe the residual average pressure in the crankcase is higher than it would be if the throttle was a little open and the motor firing well enough to get some suction action going in the pipe.

    The 0.6 bar is the result of (Phigh - Plow)*3 working on contaminated gases filling the crankcase whereas as soon as the motor fires properly the pipe sucks on the crankcase and the pseudo MAP value drops back to 0.2 bar.

    The EFI CPU can't work with 0.6 bar for two entirely different situations.

    The fix might be to bring the TPS into the mix and when it is = 0% then force the pseudo map to be 0.2 bar. Easy enough and I hope to try it soon. There is another interesting project on the dyno at the moment so it might be a week or so before I can get back to the 2S EFI project.


  3. #213
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    I've nothing to add, but my thanks for documenting all of your work, warts and all.

    actually i do have something to add, i'm not really surprised that TPS data would be needed!

  4. #214
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    I am no expert on this but would expect both throttle position and later also rate of throttle change to be part of the control loop.

  5. #215
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    Quote Originally Posted by Vannik View Post
    I am no expert on this but would expect both throttle position and later also rate of throttle change to be part of the control loop.
    I think thats the key, rapidly shutting off a throttle and rapidly opening a throttle have very different fuel requirements.
    For instance diaphragm Pumper carbs as used on Jet skis and Karts keep pumping due to crankcase pressure, even when the throttle is closed. This results in over run over fueling. (the way to avoid this is not shut off completely which is not practical on a bike)
    a conventional carb needs the airflow a open carb sees when the throttle is open. Consequently this doesn't happen.
    Even with the map sensor i am not sure if the difference will be enough without, a throttle closing or opening rate of change comparison.
    I dont have the brains to figure out how to do this. But you would have to set up a table showing greater or lessor over a time frame, maybe over a few corners to see what is the norm.
    Maybe it just needs the two sensors airflow and map. Or a additional maps only for overun or acceleration much like a carb how it has a different circuit for acceleration (ie accelerator pump)and lean cruise circuit.
    All i know GM spends 100's of millions doing stuff like lean cruise and overrun down hills etc.
    I am only spit-balling this, as I hope it isnt, as Rob is doing some very neat stuff and sharing it openly, i certainly dont want to sound like its criticizing him or the approach.



    Kinky is using a feather. Perverted is using the whole chicken

  6. #216
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    It it wasn't for the impressive and neat things Rob is doing we would not be able to have this discussion.

    The automotive engineering world use terminology that if you are unfamiliar with it you can miss important publications, maybe it is well known but was strange to me:

    Throttle opening: Tipp-in
    Throttle closing: Tipp-out

  7. #217
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    Quote Originally Posted by Vannik View Post
    It it wasn't for the impressive and neat things Rob is doing we would not be able to have this discussion.

    The automotive engineering world use terminology that if you are unfamiliar with it you can miss important publications, maybe it is well known but was strange to me:

    Throttle opening: Tipp-in
    Throttle closing: Tipp-out
    Well i had never seen it mentioned.
    Intersting stuff tipp-in
    the period it checks throttle delta is probably about 10hz, and I've found it is hard to get it to activate more than about 2 times per second. If it fires off once, it seems like there is a delay period before it is allowed to fire off again.

    I think there is probably a watchdog thread that watches the output value of the map. The map is checked as a normal thread on a periodic schedule, constantly updating the value. If the value is not zero when the watchdog is run, it triggers a special routine to buzz the injectors the appropriate amount, then starts a countdown timer so it cannot be triggered again for 1/2 second or so. This is just from experience logging and listening to the buzzing. I haven't bothered trying to look at it in detail in disassembly because I don't feel there is a need.
    http://www.romraider.com/forum/viewtopic.php?t=1735



    Kinky is using a feather. Perverted is using the whole chicken

  8. #218
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    Quote Originally Posted by Vannik View Post
    I am no expert on this but would expect both throttle position and later also rate of throttle change to be part of the control loop.
    Quote Originally Posted by husaberg View Post
    I think that is the key, rapidly shutting off a throttle and rapidly opening a throttle have very different fuel requirements.
    Yes I think so too. Pretty much any EFI CPU is for a four stroke and they typically have two provisions for rate of change of throttle position. One for rate of change of opening (accelerator pump) and another much cruder one for rate of change of closing for over run lean out, usually to reduce wet fuel and bore wash.

    I have a TPS and the rate of change of throttle position maps are already built into the four stroke EFI CPU I am using and I can modify their characteristics easily. These maps would be normal for any typical four stroke EFI CPU and all off this works Ok with my two stroke.

    A typical simple four stroke EFI CPU expects to see:-

    RPM
    Crank Position.
    Cam Position (but not always essential).
    Exhaust O2. (good to have, but not all that essential either).
    IAT (inlet air temperature).
    CLT (coolant temperature).
    TPS (position and rate of change).
    MAF (manifold absolute air flow)
    or
    MAP (manifold absolute air pressure). MAP is what my four stroke EFI CPU is looking at to judge how much air flow is passing through the motor.

    In a 4 stroke, MAP is at a minimum when the throttle is closed and at its highest when the throttle is fully open. MAP is a good indication of air flow and has a huge influence on the amount of fuel delivered each cycle.

    I am trying to run my two stroke with a simple four stroke EFI CPU that expects to see MAP.

    And my problem is to measure the fluctuating two stroke crankcase pressures that occur each cycle and present that as a pseudo MAP value to the four stroke EFI CPU in a way that the CPU understands. My fluctuating two stroke crankcase pressure has to look like a steady four stroke MAP value. That is where my pseudo MAP co processor made from an Arduino Nano comes in.

    With pseudo MAP = (Phigh - Plow)*3 I am almost there. It is the high crankcase pressure at closed throttle that is a problem and I think you are right, I will have to also use TPS here too. But just to tell the pseudo MAP co processor that the throttle is closed and instead of measuring the crankcase pressure the pseudo MAP value should just be at its lowest.

    Click image for larger version. 

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    Speeduino four stroke EFI CPU (top) with Arduino Nano co processor (bottom) for the pseudo MAP value and vari pot to simulate TPS for the EFI's CPU. The LED's are there to replicate the Injectors and so I can see what is happening.


  9. #219
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    Quote Originally Posted by Vannik View Post

    Throttle opening: Tipp-in
    Throttle closing: Tipp-out
    I like it. Very easy to visualize.

    Quote Originally Posted by husaberg View Post
    Interesting and very familiar.


  10. #220
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    Loving the project!

    are you having any problems with the jumper leads losing signal because of the vibrations?

  11. #221
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    Quote Originally Posted by crbbt View Post
    Loving the project! are you having any problems with the jumper leads losing signal because of the vibrations?
    No not really but it is all very temporary and when the basics are sorted everything will get a tidy up. Working on the CVT sidecar at the moment, hope to get back to the 2S EFI project maybe next week.


  12. #222
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    More reading for EFI addicts two stroke enginehttp://suw.biblos.pk.edu.pl/resourceDetailsRPK&rId=4079

  13. #223
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    Click image for larger version. 

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    I have been fighting a bit of a battle with the PesudoMAP sensors software thinking there was something wrong with it but after extensive testing with the simulator and oscilloscope I am very confident with it. The issue is that the PesudoMAP value drops away over 8,000 RPM or so as seen in the picture above (Yellow line).

    Currently my code can make a sensible reading every 8 deg at 13,000 RPM and with a bit of clever coding it could make a reading every 2 deg. 8 deg is good enough for the three high pressure readings I make at 15 deg intervals. 115, 130, 145 deg ATDC. If the software code is good then the issue must be with the crankcase pressure sensor.

    Click image for larger version. 

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    So I put the oscilloscope on the crankcase pressure sensor tonight, purple line, yellow line is the ignition pulse. I wanted to see what sort of signal it produced and what it looked like compared to EnginMod's prediction. Pretty close I recon. The next move is to try and capture a trace at 12,000 rpm.

    I have been having problems with the MAP value dropping away above 8,000 RPM and suspect either the pressure sensor is not keeping up or the speed of response from it is so slow that the indicated pressure peak moves away from my last measuring point at 145 deg ATDC.

    Click image for larger version. 

Name:	2S Crankcase Pressure Traces.png 
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  14. #224
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    What Husa said about GM reminded me of a point Rob might appreciate. They cheat on throttle closing. Most of the auto EFI systems have a damper on the throttle linkage which regulates the rate of closure over the last few degrees of throttle plate movement.
    When that area between working throttle and reducing to idle is a constant in terms of rate of change, it's much easier to map.
    Reason is a tool - remember where you left it..... The late, great, John Clarke

  15. #225
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    Quote Originally Posted by wobbly View Post
    TeeZee , the comment about ignoring the absolute value , just measure the delta between high and low values is a valid one.
    Yes, it is my intention to only measure the delta between high and low, then multiply it by a simple correction factor to increase its magnitude to something similar to what a regular four stroke MAP value would be.

    That way I can use a regular common after market four stroke type EFI CPU unit and traditional Alpha-N and VE volumetric efficiency mapping. It has taken a bit of work to figure out how to do this, not quite there yet but I feel I am closing in on it.

    Click image for larger version. 

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    On my two stroke GP/NSR110. 3 times the Delta crankcase pressure roughly equals the MAP reading you would expect to see from a four stroke's inlet manifold.

    Click image for larger version. 

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    This is an actual scope reading at about 11,500 rpm of a MAP sensor reading the crankcase pressure of my GP/NSR110. The yellow spikes are the ignition trigger pulses.

    The purple steps are the sensors output each milli second. The sensor outputs its last (averaged??) reading every milli second for a milli second, hence the steps.

    It is easy to see that the low pressure is around TDC and the high pressure at BDC as seen by this pressure sensor. I think processing delay shifts the timing from reality a bit. But that is not a problem as it is consistent.

    My mission is to capture the readings with my Arduino Nano, process them and then pass a pseudo MAP reading to the EFI's CPU.

    The Arduino Nano can easily take the two readings required every cycle, in fact it takes three high and three low and picks the best. Then averages them over ten readings, finds the delta and multiplies it by 3 and finally outputs it as an analog pseudo MAP reading. I have successfully simulated the fluctuating crankcase pressure and tested the pseudo MAP software on the scope to 15,000 rpm.

    Click image for larger version. 

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    Theoretically it is technically simple to do but it is just taking me a bit of time to achieve it in working practicable reality on my bike.

    KTM

    Quote Originally Posted by monkeyfumi View Post
    A small tube in the back of the cylinder is connected with an intake pressure sensor, which supplies pressure data to the control unit. .... https://www.ktm.com/en/enduro/150-ex...engine-exhaust
    I think KTM have got it sorted and are doing something similar on their latest EFI 2S bikes.

    Quote Originally Posted by Flettner View Post
    I think so, you might find KTM and TM are spying here. KTM were certainly aware of my work documented on TSM.


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