Originally Posted by blau928

Hi Tuomo, The MAF sensor will give the mass (weight) of the air as you described. However, To calculate the mass of air in a MAP system, you need the temperature to convert it to Kpa (absolute pressure). Temperature is affected with density (pressure), and vice versa.. a la boyle's law.. If I know the temperature and the mass of air at the temperature it was measured by the MAF, then I can calculate what the absolute pressure is of the mass of that air at the given temperature. When I do that, I will be able to get the MAP values, and easily convert the MAF voltage in CFM/KG per min etc to Kpa, as the MAF voltage value will tell me what the mass of air is at the given temperature... I already know the engine's swept volume per cylinder, total displacement etc.. So, if I can get this measurement, I can have a MAP - MAF converter scale and see where the engine actually is compared to the calculated values and VE etc... I am trying to understand the factory calibration for < 100Kpa values, or the fatory calibration using MAF values, but converted to MAP with the help of mssrs Boyle-Mariotte... Hope that helps with my reason for wanting the temperature..

Originally Posted by ptuomov

Yes, you definitely need the temperature to convert pressure to density and mass flow. However, I don't think you need to know at which temperature the above MAF function was measured. It's invariant to temperature. You only need to know the temperature at the time you take the pressure reading. That's at least how I've reasoned this in my head.