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Rich spike on throttle change


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I'm just wondering how much deviation in lambda is acceptable  on throttle transients, my situation is that i can tune all the cells with a reasonably close AFR at a steady state but soon as i release the throttle a tiny bit it instantly  goes rich say from 14.7 to 12-13 afr and shutting the throttle completely makes the issue worse. I get as you shut the throttle this is closing the air off to the cylinder resulting in a rich afr but seems much richer than it should be.

Just wondering if there are any work around to this or not?

ecu is a v9 wrx plugin running a ej207 ID1050X injectors 

Thanks Robert 

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Following this. I having a similar issue where it goes rich for a moment after stabbing the throttle. I found adjusting the accel hold to 2 INJ events helped my engine setup. Try some adjustments on the accel sense and decay? I'm going to try adjustments in the clamp table this week, starting with lower rpm first so I don't possibly run into a lean spike during full throttle gear shifts. 

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It is to do with "TAU" , wall wetting, fuel puddle are some of the names for what is going on. Our ECU does not have a correction model for this so this will always happen. If you tune to steady state targets it will only be right at steady state, if you accelerate through the map it will be lean and if you are backing off it will be rich all due to TAU.

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