To my knowledge the PCM checks the atmosferic pressure at start up (BARO), this using the MAP.
At WOT (I'm not sure if at a certain load or a certain TPS) the BARO value is also updated.

With the supercharger I noticed that the BARO value is updated at partial throttle too, as soon as the intake pressure is higher than the pressure at start up ( I saw that already at 40% TPS), it was still cell 15 and not in PE.

The max pressure that my stock map can see is 104 kPa and as soon I hit that pressure the BARO will have that value.
A normal value is 95 kPa, 104 kPa is about 10% higher.

When the BARO value rises LTFT's go negative (-5% up to -10%).
Is there a way to let the PCM check for BARO only at start up?

When I turn off the car and let it cool down LTFT goes back to the normal values. If restert the car with a warmed up engine the BARO is not updated, but it keeps the last value.


Thanks - Stefano