RomRaider

I was curious as to how a subaru ECU measures atmospheric pressure.

I would imagine that the ECU uses a sensor that measures absolute pressure somewhere post turbocharger for use in its tables. I just don't understand how it could use that sensor to find the local atmospheric pressure for the conditions.

Does the engine have a second external sensor outside of the intake piping that measures local air pressure? (Doubtful i think) or is there some code/calculations involved using other sensors?

There's a second sensor.

IIRC the second sensor is located in the ECU, other than models with an air pump.

And if car has airpump? Is atmospheric pressure sensor in airpump?

Bumping old thread... (Really old) but I need/want to know this aswell, I'm @ sealevel and according to my car, atmospheric Pressure is 21.76, I don't know what refrences this control wise, but it would obviously be very wrong.

I have an 07 STi, and it HAD a secondary air pump on it that has been removed.

I saw a thread somewhere, can't recall now of the steps to remove the air pump and what needed to be compensated for so the ECU would still read ATM. I think the thread was on the legacygt.com forum. They a search there for the air pump removal how to.

How much fluctuation does everyone see in atmospheric pressure? I've checked mine a couple times in the past and always saw 14.36. Only recently did I start displaying it as a gauge and have noticed it bounces from 14.22 to 14.65.


Here is the thread on air pump delete.

http://legacygt.com/forums/showthread.p ... 40259.html

That's typically what I see where I am too. The pressure only changes with the weather or if you are on a cross country tour doing mountain passes and all.