Originally Posted by DelboyTurbo
hmmm.....surely MAP can only be as accurate if the car stays at the same height (above sea level)
Map sensors accuracy will deviate as a car goes up a hill (i mean a big one lol). MAF will always compensate for this as it measures the mass of the air. Thats why manufacturers (especially japs because of their environment) tend to use MAF sensors.
Or so i would imagine.
depends if the MAP sensor measures just the pressure that it sees (known as the guage pressure), or includes the atmospheric pressure too (known as absolute pressure sensors).
even in the case of gauge sensors, when the ignition is switched on before the engine is cranking, the ecu can do a quick reading of the MAP sensor to effectively read atmospheric pressure and compensate for it. however, if you drive up or down a big hill, or into a storm or whatever, without switching the ignition off and on to recalibrate then it will not be able to compensate for the pressure change.