M800 Cranking comp applied when the RPM is high

[Vassili Wang]

Hi Guys,

Need your help on this one.

I have an M800 on my ktm 690 DUKE single cylinder engine，fitted a supercharger to it and using a hall sensor to detect intake rocker arm as sync signal. I'm using Throttle position as Efficiency point on the inj map, Successfully get engine to run and no other problems when idle, but when I try to tune the map on higher efficiency(at around 40% TP, 120kpa), strange things happened.

the engine discontinuously miss fire and RPM signal gets more unstable(sometimes out of range) when the boost pressure gets higher(sometimes out of range), the software shows error sync signal when this occurs. We captured several Ref/sync samples and it shows no problem.

Data shows that cranking comp applies almost every time it happens,(No other fuel comp was applied during that period), so the fuel pulse width gets very high in that particular moment(IJPU 10 msec but fuel effective pulse width reached 35 or higher) but RPM remains absolutely above cranking RPM(3500 and higher).

This happens almost every time when the engine load get higher, and it only happens when the boost pressure gets higher (close to 120 kpa). This seems to happen regardless of RPM, just when increasing the engine load.

Another strange thing is that RPM signal gets more and more unstable when engine load increases which is very obvious in the data.We have our ref and sync shielding wire connected to the ground but the problem still remains.

The instability of RPM signal is less obvious on the captured images of ref/sync signal, It turns to be stable and easy to recognize. Does anyone know why？

I'm wondering if there is anyone else facing the same problem with me, looking forward to your help.

Any suggestions would be incredibly helpful.

[Sean]

Upload your log and ecu file will make it easier for diagnosis. What sensor are you using for the sync?

[Vassili Wang]

Upload your log and ecu file will make it easier for diagnosis. What sensor are you using for the sync?

NPN Hall sensor, I'll upload the files later.

[David Ferguson]

I would expect that the Cranking Comp would only happen when the Engine RPM was below the Run RPM. What is the Adjust->General Setup->Misc Setup->Run RPM value? Log Engine RPM at a 200 hz and see if that catches it.

Perhaps some combination of ignition timing, or fuel injection timing at that particular load is causing interference with the Ref/Sync signals and thus it is having trouble. I would get the engine running, clear all errors and watch for ref/sync diagnostic errors when this occurs for clues. Make sure you are logging the Diagnostics Error Group 6 and Group 14.

Look at your Ref & Sync filter tables, does adding more filtering help?