Different MAP sensors showing different readings....

[kaptainballistik]

So, my weird one for the day..

As I haven't got a 3 Bar capable subaru/Denso on throttle body map sensor suitable Map sensor and i'm planning on running 20 ish pound o boost I've fitted a GM 3 bar unit. Do the usual run a Calibration and all good. The car is 1/2 tuned so what the heck, lets change stuff.

Car runs, all good.. BUT.. Its reading 2.5 kpa Higher than the old map sensor when the motor is stopped...., Mind you, Sticking on another known Subaru MAP sensor it reads 2kpa LOWER than the original. ( And yeah, recalibration performed, triple checked the MAP types, googled the Map sensors ect...).

Is this actually "normal" Heuristics for different MAP sensors? (The sensors should be calibrating to match the internal map.. shouldn't they? 

[Vaughan]

The MAP calibration function looks at the BAP value and applies a small offset to make the MAP match the BAP when the engine is off. To confirm you are using the ECU Controls -> MAP Sensor Calibration function each time you change sensor?

[kaptainballistik]

Yep, I tis doing the Cal every time.

Its not a big thing , (Heck, it was a daily issue in one of my previous careers.....) But if its something unexpected i'll go hunting a Ground leak or if I have a 5v+ issue..... The Car seems to be a much happier thing with the GM sensor!
 

Cars..... why do we do this......

[Adamw]

MAP with engine off and BAP will vary from day to day with the weather and tides etc.  As long as it always matches BAP with key on, engine off it is normal.