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Continental M3C ECU working strategy

EFI Tuning Fundamentals

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Hi and thanks for adding. I have questions about the working strategy of this ecu. I have an ATV / Arctic Cat Alterra 700 single banger 4 stroke and cvt transmission. It has a Keihin throttle body with tp sensor, map sensor, idle speed valve. I have two maps to airmass. One is called tp and the other pratio. I talked to some people about working strategy. They say the fuel mass is calculated in low end by pratio map and at top end via tp map. I think this statement is false. I think that's how it works. The fuel mass is 100% calculated by the tp map. The pratio map is in correlation with Spark advance map. It is at the same time a "calibration" of the map sensor. The values are dependent on real manifold pressure and decide on Spark advance. If I change these values, then the Afr in the exhaust gas go hi oder down, but it has nothing to do with the Afr of cylinders and the injected fuel mass. Which statement is correct?

best regards

Robin

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Hi Robin, I'm not sure how much help I'm going to be here as I don't have personal experience with this ECU. It's not unusual in the motorcycle tuning world to have multiple maps based on both TPS and MAP, or even individual maps per gear too. The issue with a single cylinder engine in particular is that the MAP signal, particularly at low rpm and low throttle openings, is very erratic so it's difficult to use this signal as a reliable load input. My best assumption would be that the ECU would primarily use TPS and potentially the MAP based map would be used at high throttle openings/rpm. If you're unable to find more specific information on this ECU such as a description file, the only sensible approach is to make small and specific changes in one map at a time and then test to validate the results. Sadly this is a slow and time consuming process but it's the best approach I can offer. Sadly factory ECUs are often more complex in their operation than the aftermarket (where we'd simply use TOS as the load input for both fuel and ignition)

Hi Andre, thank you very much for your reply! I made a breakout box between ecu and can log all signals. I changed the values in different maps in small steps and saw what happened. When I change the values in the tp map, then the Afr value changes in low rpm to high rpm but the power is always the same. If I change the values in the pratio map from low rpm to high rpm, then the afr value and the power change. That's the one. The other is, the for facelift Modells drive 120km/h (with Delphi ecu). Now with Continental ecu they only drive 90km/h. You can see in the pratio map that from 5500rpm and wot the values fall. I made it a straight line and now it runs over 100km/h. That's why I think the pratio map is in correlation with the spark advance. I measured the signals from the map sensor with an oscilloscope. The voltage peak is always the same (approx. 2Volts) at low and high rpm, only the altitude and frequency is different. Unfortunately, I can't exactly measure the spark advance. I could put the crankshaft signal and ignition coil signal on top of each other, but for this I would need an oscilloscope with a separate ground, unfortunately I don't have that. Do you have any idea how I could digitally log the spark advance while driving? My flywheel with timing mark is in the engine, that's not an option.

thank you and best regards

Robin

Robin Empunkt are you doing the logging and testing on the bike or are you simulation it on the bench? if on the bench are you share what tools your using?

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