Air Flow Meter/Sensor: Description and Operation

Fig 1 MAFS Sectional Diagram:

The Mass Air Flow Sensor (MAFS), measures the quantity of air drawn into the engine and reports to the ECM.

The Lucas 2OAM MAFS is of the heated wire type, which measures air flow by the cooling effect of passing air over a heated platinum wire, altering the electrical resistance of that wire. The electrical resistance value is converted to an analogue output voltage signal, which is supplied to the engine control module (ECM), for the regulation of the correct air/fuel ratio.

The heated wire sensor (1) is situated in the central pillar, which is an integral part of the casing. The pillar has a central tube entry (2) and four exit slots (3) which allow air to pass over the heated wire sensor and return to the main air flow. The sensor is an integral part of the heatsink and control unit (4) which has the three pin connector (5) included in the moulding. The metal gauze screen (6) is designed to stabilize the airflow through the sensor and also serves to protect the sensor from any debris which may enter the airstream.