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Trigger Issues / Trigger Filtering

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So I have an issue with the RPM on the log jumping around at higher revs. The engine is a bmw m50 turbo and the original crank trigger wheels gap used to line up almost bang inline with the cam trigger so I have changed the crank trigger wheel for another to move the two apart, I hoped this would solve my issue but it hasn't.

The two triggers are both vr type sensors. I have watched the webinar on trigger issue and tried to setup my arming thresholds to suit a third of the voltage but anything past 2000rpm I need a value greater than 7 but the link g4+ ecu wont let me put a value in greater than 7.

I have noticed there is also another setting called trigger filtering but the help file doesn't give any clear information on when to use this, is this a setting I should try adjusting to help with my rpm jumping around? Is there anything else i can look at that could be causing this?

The ignition timing I have seems to be a lot lower than others I can find in the internet which was another point to trigger issues in the webinar

I have attached a log, my map and a scope at 2k

any help appreciated





Scope @2k:


I dont see any signs of trigger issues in the log you attached. There is really only one short burst to 6000RPM in the posted log so that may not tell the whole story, but dwell is well controlled and the Engine speed ROC parameter is pretty stable - both of which suggest the ECU is getting good consistent trigger info.

I was comparing my engine rpm and engine speed roc (in the upto 6k run) to the one in the trigger error webinar and in the log he shows his roc barely goes above 250 yet mine is going way over 500 and my rpm curve is no way near as smooth? Which he mentions means I have trigger issues??

I havent watched the video you are talking about but it sounds like you are taking it out of context. Engine speed ROC (Rate of change) is how quickly your RPM is changing. I suspect the "rarely goes above 250" example that you saw is probably from a controlled ramp run on a dyno - in that case if the dyno is working well and the trigger is working well then the ECU will report whatever ROC the dyno was programmed to allow the engine to accelerate at. In contrast your log was done on the road in an uncontrolled manner. In your case, bumps in the road, clutch slip, tyre slip, soft engine mounts, the tune, your right foot and many other factors will all greatly influence the engine acceleration and hence the logged Eng speed ROC value.

Of course your recorded RPM will never be as smooth as a computer controlled dyno ramp run either.

So back to my original comment, there are no signs of a trigger problem in the short log you attached, it appears to be working well.

Yeah I was comparing mine to one done on the dyno. I just though it weird my rpm going down with a steady 100% throttle on a ramp run. Plus I felt my ignition values were a bit low but that was just comparing to other tables from the internet with no info on the build. Thanks for the help

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