MAF & RELATION WITH AIR DENSITY

AS WE LEARN THE MAF MEASURE THE AIR MASS :

BUT AS WE KNOW MASS AIR FLOW = V * D

MY QUESTION ABOUT THE (D)

D= 2.7 (P/T)

WE KNOW (T) BECAUSE ITS FITTED IN MAF

BUT WHAT ABOUT (P) PRESSURE ???

THAT MEAN WE CAN'T USE MAF WITHOUT KNOW THE ATMOSPHERE PRESSURE Or is it inaccurate !!!!

The MAF sensor measures the Mass Air Flow directly. The physics of the sensor design and calibration account for the Density and Volume, but it does not have an output for Pressure. For that we use an absolute pressure sensor.

I'm not so sure about other brands but for instance Evo's MAF is built in such way when all three sensors are combined in one unit close to each other (pins 52,64,65 for Evo 7 GTA with automatic transmission).