Map sensor reading to high

[xpro]

Hello,

My evo 8 with 3 bar map sensor ( think bosch sensor), currently set up as 15# kpa delco 300kpa it appears to be reading quite high, on full load when the car is boosting 1.8 bar ( taken from greddy BC) the ecu shows that car is boosting at 2.1 bar which i think is wrong . Any ideas please? is it possible that my sensor is gone faulty?

Also the previous owner had set up the BAP channel to run of the map sensor, both channels were using the same output?? is this normal?? i just changed the bap channel to use oem BAP sensor which is now reading as it should

thanks in advance

[RossB]

It may be that the sensor calibration in the ECU is not correct for the sensor. You need to check exactly which sensor is fitted and use the correct calibration for it.

Are there any BAP compensation values in the BAP COmp table? If there are and it has been tuned with BAP set up on the MAP sensor this will have an effect on the tuning. It is not normal to have both BAP and MAP calculated with the same input!

Likewise if the engine has been tuned with an in-correct MAP sensor calibration and you change it the tune will be affected.

[xpro]

Thanks for your reply Ross.

The sensor installed is delc300kpa. and the calibration used is #15 delco kpa 300.
Sensor reads fine when ignition off, same as OEM bap sensor around 99-100kpa.
I pressure tested it yesterday at 0.5bar on the test gauge, and Map sensor is reading 150kpa which equals to 1.5 bar??
Also the BARO comps are not set up.

The map sensor is used for efficiency calculations and on full boost im hitting 260kpa zones in the fuel/ignition maps but my car only boosts at 1.8 bar, does that mean i should be only reaching 180kpa zones max??
Im getting confused here now

cheers Philip

[RossB]

It sounds like you are getting mixed up between absolute pressure and guage pressure. Absolute pressure is the actual air pressure and we need to use this for tuning because the engine will often be opperating with manifold pressures below ambient air pressure ("manifold vacuum"). Guage pressure is pressure above ambient air presure and is often used for things like oil pressure and when referring to the boost pressure of an engine. I assume that your pressure tester reads zero until you apply pressure? Zero on your tester is actually 100 kpa absolute so when you pump it up to 50 kpa (guage pressure) you will have 150 kpa absolute.
The same applies for your boost measurements. Normally a boost guage shows guage pressure so 1.8 Bar guage pressure is actually 280 kpa.

[xpro]

Thanks Ross
I was getting confuse there for second.
Its all good now, live and learn