Mass Air Flow
The mass air flow system uses a single sensor to compute measurement of mass air flow. Mass air flow is derived by processing the MAF sensor signal through a look-up table programmed into the ECM. A typical MAF sensor consists of a screen to break up air flow, a resistor, a heated film, and electronic module mounted on the sensor.
Air flow is directed over the heated film. The cooling effect of air flowing over the heated film in the sensor changes its resistance. Additional electrical power is then required to maintain the sensor at 165° (75°C) above the incoming air temperature. This current is measured and converted to a digital signal (30-150 Hz) that is sent to the vehicle's ECM.
The ECM uses the signal to calculate air intake in grams per second through preprogrammed information. Using calculations of mass air flow, engine temperature and RPM, the ECM calculates the exact amount of fuel required to provide a proper air/fuel ratio (14.7:1). The MAF sensor readings and fuel requirement calculations are made by the computer every 6-14 milli-seconds (approximately 160 calculations per second). See Fig 1 .