Unstable engine speed M142
Posted: Sun Feb 02, 2025 5:51 amI have an M142 on a Cummins ISX diesel engine and I cannot seem to get a stable reading of engine speed. It is much noisier than I would call satisfactory and it is impacting fueling, timing, etc - any table that is a function of engine speed. I have done an input capture and the signals look great. I've attached input capture and a log where you can watch engine speed and fuel mass fluctuate. The engine is being held at a constant 800 RPM.
I have noticed that engine speed and engine speed reference instantaneous both seem to read the same thing, which seems odd. Which one is used for pulling from tables? Is there a way to filter engine speed reference instantaneous to feed engine speed?
I am using the 'Scania SGL12A' Reference mode. Falling edge for both cam and crank active edge. I have tried changing threshold voltages, hysteresis, pitch threshold's etc to try and get a more stable reading with no success.
Some help would be appreciated, thank you
I have noticed that engine speed and engine speed reference instantaneous both seem to read the same thing, which seems odd. Which one is used for pulling from tables? Is there a way to filter engine speed reference instantaneous to feed engine speed?
I am using the 'Scania SGL12A' Reference mode. Falling edge for both cam and crank active edge. I have tried changing threshold voltages, hysteresis, pitch threshold's etc to try and get a more stable reading with no success.
Some help would be appreciated, thank you