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Thread: Spikes in Average Air Mass and Air load on shifts

  1. #1
    Advanced Tuner bbrooks98's Avatar
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    Oct 2011
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    Gainesville, VA
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    Spikes in Average Air Mass and Air load on shifts

    Looking over some data and curious whats causing the air load to spike on a shift? Is this normal or is it something to do with the transient fueling? Anyone seen large spikes like these before?How is average Air Mass calculated and whats desired vs average? I'm assuming it's the final airflow either blended with SD or not depending on how its setup in the tune similar to dynamic airflow on a GM vehicle?

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    issue_0300Misfire_run3.hpl
    2011 Mustang GT TT A6
    1998 Eclipse GSX Awd

  2. #2
    Senior Tuner
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    Jan 2013
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    Hawaii
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    This is normal. RPM is the denominator part of the equation that turns the MAF value into a load value. On fast shifts it can drop a couple thousand RPMs much faster than airflow drops, so you get a little load spike. Because this is a reality even for a split second, this can be the cause of detonation on shifts if the spark is aggressive and the load spikes far above the tables axis value and the ecu has no other way to reduce spark enough to control peak cylinder pressure on those few cylinder cycles to avoid it.
    "We can never be right, we can only be sure that we are wrong"- feynman