I was looking at the readings for MAP on my Preditor hand held to see what kind of pressure I was getting at different speeds. It was anywhere from 6.9psi to 12.4psi depending on throttle position and engine load.
Ok so the question is, when the engine is turned off and the "real time diagnostics" is running, the MAP shows 14.4psi. That's jsut about right if your measuring static atmospheric pressure. If that's true, and the sensor is measuring "static" atmosphere, am I to believe that my SC is not producing any boost as the numbers are less than static atmosphere? Am I still in vacuum? Can anyone help me with this mystery?

Thanks.

 

The stock MAP does not read or measure boost. It is used for diagnostics and a back up to the MAF.

 

The reason behind this is that the stock MAP sensor is a 1 bar (1 atmosphere) sensor and only reads vacuum - 1 atmosphere (which is what you see at WOT on an NA car). If you had a 2 bar MAP sensor, you could read boost, but it would be preported as boost + atmospheres (14.7 + your boost).

 

i always look at my map reading in KPA. 100kpa is with the motor off(atmospheric). anything in vacume is under 100kpa and anything in boost is over 100kpa. 200kpa is about 14.7psi(boost).

seems to me what you are thinking is correct. if that reading is under 14.7 then you are not seeing boost. the stock map will not read boost. once you get far enough into it that reading should max out around 14.7psi wich is just 0psi even though you will be seeing boost.

 

Guess I should just get the damn boost gauge installed! LOL