Is Baro locked in at key on or not?

[Dan Stewart]

I just can't find anything that determines if this is so or not.

The whole BARO-MAP thing just doesn't make sense. Why would you trim the MAP reading based on a one-time calibration? The VE table does not change and therefore the current reading from the MAP would always be accurate.

If the MAP is trimmed based on a key-on BARO reading, then the whole theory behind "Massflow = (VE * MAP * RPM * Displacement) / IAT" is useless because you are not accounting for the actual amount of vacuum in the engine.

I also read in another post that redhardsupra was not too sure about the whole key on BARO vs. MAP trimming and wanted to test it out, but there was never another post in that thread.

[striker754]

Don't worry about BARO unless you are trying to log boost. That is all.

[Chris@HPTuners]

baro can be adjusted during engine operation for NA applications using a single MAP sensor. it is set at key on and then during operation if any MAP reading is higher than that it is updated. There are also tests to lower baro during operation during moderate load, mid/low RPM operation.

For boosted apps you need another MAP sensor, this is commonly called the Supercharger Inlet Air Pressure (SCIAP) sensor.

Baro is not used for the GM speed density calculation, the VE table is referenced to absolute MAP.