crazy MAF numbers??
03-30-2007, 01:49 AM
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crazy MAF numbers?? i just did head/cam swap, ported/polished TB, ported/polished MAF ends. now after all that, been having some issues of course getting my idle down pat, but while logging, i found that my MAF reading where way above my table. so i went to logging and adjusting my MAF table according to what it was actually reading. the crazy thing is that the more i adjust the MAF table, the higher the numbers have gotten in the logging. the more i adjust the MAF, the more it is evening out in the logs but the harder it is becoming to get the idle correct. is it that imparitive to have the MAF table set to very close to what it is logging? and is this what is causing me some grief in getting the idle correct? if i get the idle smooth in park, it wants to hang in gear, and i notice that the GEAR setting seems to affect the idle in park more and the P/N seems to affect the in gear idle more, is this normal?
03-31-2007, 08:48 AM
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the g/sec the MAF is reading is always higher than what the MAF table is calibrated for. everytime i inch it up to what it is actually reading, the MAF reads alittle more than the last time. i cant seem to catch up unless i raise it quite a bit. should it be really close to the same or always reading a gram or 2 more?
03-31-2007, 08:30 PM
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How are you getting the MAF g/sec to compare to the table? Are
you looking at the reported frequency and the indexed table value, \
vs the g/sec logged MAF airflow?
There may be some funny predictive stuff going on (PCM trying to
comp out the lag in the MAF, etc.).
I don't think you want to be adujsting the MAF against itself; you
want some other, impartial reference to work against.
you looking at the reported frequency and the indexed table value, \
vs the g/sec logged MAF airflow?
There may be some funny predictive stuff going on (PCM trying to
comp out the lag in the MAF, etc.).
I don't think you want to be adujsting the MAF against itself; you
want some other, impartial reference to work against.
04-02-2007, 10:08 AM
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I don't know how this works exactly, but EFI Live has the following description in one of their tables:
During steady state airflow scenarios less than 4,000 RPMs (stock value unless otherwise modified), the PCM calculates a dynamic airflow value based on the MAF sensed airflow and MAP calculated airflow. There's a correction factor that is updated based on the difference between what the MAF says and what the PCM calculates. Over 4,000 RPMs, the PCM uses the MAF exclusively to calculate grams of air per cylinder.
That correction factor is probably the reason why your MAF never matches the number you're looking at assuming your VE was never tuned or is tuned incorrectly.
During steady state airflow scenarios less than 4,000 RPMs (stock value unless otherwise modified), the PCM calculates a dynamic airflow value based on the MAF sensed airflow and MAP calculated airflow. There's a correction factor that is updated based on the difference between what the MAF says and what the PCM calculates. Over 4,000 RPMs, the PCM uses the MAF exclusively to calculate grams of air per cylinder.
That correction factor is probably the reason why your MAF never matches the number you're looking at assuming your VE was never tuned or is tuned incorrectly.