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Accel Enrichment question


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I'm trying to understand an issue I'm having with my tune where I'm seeing acceleration enrichment being triggered sometimes when it shouldn't be. I'm running an E-throttle, and my acceleration enrichment setup has "Accel Mode" and "Accel Load axis" both set to TPS.

I recently got my A/C system functional, and have been trying to tune my idle controls to deal with the A/C load. While doing that, I've had situations where the engine is nearly stalling, but the closed loop idle control catches it after a bit of hunting/oscillation. In my logs I've noted that sometimes when it behaves like this, my accel enrichment gets triggered, even when my accel pedal position is sitting still at 0%AP(main) / 0%AP(sub). The TP(main)/TP(sub) values bounce a bit between 0~8% or so until the idle settles down and stabilizes.

So the question is should I consider changing my Accel Mode and/or Accel Load axis settings to MAP instead? I'm also running closed loop lambda control at idle, so the unwanted accel enrichment tends to bugger that up.

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Hi Adam, here's a link to the current tune file and a log file where the behavior occurs. Right around time index 9:44.500, you can see an accel enrichment event where the car was trying to stabilize its idle, AP was at 0% and steady. If I recall, the A/C was turned off at the time.


Looking a bit closer, it appears that the TP delta may have been triggering the accel enrichment?

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40 minutes ago, Adamw said:

I think too much idle control proportional and the idle ign control is a bit weak.  I have made a few tweaks in the attached map, see if this settles the throttle oscillation down.  If not, give us a new log.


Baseline Tune 6-01-2022.pclr 163.61 kB · 0 downloads

Thanks, I'll give that a try tomorrow and let you know how it went. Looks like the idle ignition timing end values on the +/- 500RPM error extremes are the same as what I had, but you're ramping up to those ignition timing extremes at lesser RPM errors to give the ignition idle control a better chance at stabilizing the idle error, and relying less on the idle control proportional & anti-stall gains to avoid the idle hunting?

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Yes, the torque increase you get from throttle movement is relatively slow, so it is best to have the bulk of the instantaneous torque adjustment needed to control idle to come from ign timing, then the throttle is mostly used to take care of the longer term error.   

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