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Erratic engine speed at 2K RPM


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Hi guys,

I'm still working on my calibration. The full loads have been tuned on dyno and road by a pro and I'm finishing the transitions, cold start and other 'side' parameters. I intend to do another session to set the knock detection as well as the charge temp approx table that is still blank.. (I know we will have to rework the fuel table after that..) and maybe add a little more boost^^ A last session will then be done later for the E85. (I want to replace all the fuel hoses first since the car is almost 30 yo)

Anyway, since I own this car (tuned by the previous owner through a professional, retaining the genuine ECU) I always had an hesitation under low load around 2200 RPM. It got worse with the new mapping.

I richen the spot and it improved but I'm wondering if it's the right way to do it or if I should also work the timing or other parameters?

I attached a log of the phenomenon and the 'improved' tune. 

Also I find I have a lot of pop and bangs at the lift off. Overrun fuel cut is activated and I set the activation delay to 0 so if you could have look and let me know if you find something unusual I would be interested.. (I know some are looking of that but as far as I'm concerned I only want the engine to be safe)





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Yeah that's a bit of an unusual one, nothing too obvious there.  Can you try changing the orange cells in your ignition table to match the example below as a test.  This will probably make it feel a bit lazy but I just want to see if it is torque related or misfire related.  

And the other thing I would try is making it a lot richer in that area - like change the target to say 0.9lambda as a test.  It maybe that one or two cylinders are leaner than the rest and start to misfire when trying to target stoich.  

Can you try turning the purge output off as a test as well.

How come it is running wasted spark?  



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Thanks Adam, spot on reply as usual :)

I’lol try that next weekend is it not raining too much…

Concerning the ignition, I ditched the distributor (retaining only the phase sensor) and installed a triple coil pack from a VR6 engine.

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Hi Adam

I tried with the reduced advance as you suggested (with a lambda target to 1) and the phenomenon is reduced but still present. So I put more advance but not as much as initially and set the target at 0.9. Then I leaned to find the good limit. It’s way better now.

Reading other topics I realized that using modeled fuel I should have disabled the IAT fuel correction and zeroed the warm up enrichment table.. so I also did that in the process.

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