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I was wondering if anyone has some advice for tuning the super high vacuum cells entered when decelerating and momentarily tipping into the throttle while in those cells. I am seeing some huge swings rich/lean and sometimes I hear back fires. When I try adjusting the cell so that it doesn't go too rich (reduce engine efficiency) upon decel, I get a huge lean spike when tipping into throttle. Until it goes into the next cell up where engine efficiency is much higher.
Motec m150. FA20.
I try and keep the decal cells around 14.5-15, it's generally very smooth with this value and no backfire
The process I follow is to tune as much of the high vacuum area as possible in steady state. You'll find that you can only get down so far before the engine doesn't make enough torque to drive the dyno. You can complete a little more of the map by using 1st or second gear to multiply the engine torque further. If you complete the low load area of the map using this technique and you're thorough then you should find that the performance during off/on throttle is pretty seamless. I'd also recommend extrapolating the trends you're seeing in the areas of the map you can tune down into the lower areas you can't reach for completeness. If you've got all of this tuned correctly then you also need to focus on the fuel film model in the M1 for good transient throttle control of the fuel delivery.
Note that you will see a lean spike as you go off and on the throttle as the ECU will apply an over run fuel cut when the throttle is completely closed. This is normal and nothing to worry about.