Airflow Meter

All engine air is drawn through the airflow meter. The meter is basically a tunnel with similarly shaped measuring flap and dampening flap (offset 90° on same casting).

The measuring flap swings on an axis in air stream against reverse pressure of a spiral spring and is connected to a potentiometer. The potentiometer transmits an electrical signal proportionate to the angular displacement of the measuring flap to inform the ECU of engine load. See Figure .

In addition to monitoring airflow, the meter also controls fuel pump operation and idling. At idle, the measuring flap is almost closed due to spiral spring pressure. An idle air by-pass receives air from main airflow through a small hole, the size of which is controlled by the idle mixture screw. This adjustable air by-pass influences CO levels at low engine speeds.