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Why AFR goes richer during spool for turbo cars?

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Hi Can someone explain to me why actual AFR during spool for turbo cars will always go below or richer target map.

What is the correct way to adjust this ? I have my VE tables set pretty good on steady state dyno but when i go WOT during spool it will always go richer during spool . SHould I adjust the VE table to compensate the spool area or i should use fuel map to raise the target AFR ? For example if my Traget AFR for 1 to 10 psi is set for 12.5 AFR on steady state dyno but during WOT spool it will drop to 10.5.


That's an unusual case what you see. usually the part load range can be a bit leaner if you built boost with full throttle through a area that you tuned at steady state. As an example we reach 0.5 bar of boost at 4500rpm with only 30% throttle in steady state. but if you are acceleration after a corner with WOT, you will reach the same cell for a short time during built up of boost. This time you go through the same cell with full throttle, which means less turbulence in the intake manifold (because there is no restrictive part closed throttle) which leads to a higher volumetric efficiency. Consequently you will see a leaner mixture during WOT spool up than steady state for the same cell.

Regarding your case.

I would check if the acceleration enrichment isn't active to long. Have a look also at every other parameter, which can add a compensation. As an example inlet air temperature. Usually you see a lot higher IAT's in steady state thant on a single pull, during spool up.

Thanks i'll look into the compensation tables