Editing AFM (section)

==Operation of an AFM==

(Info adapted from a Toyota training guide but principles are the same)

The AFM converts the amount of air drawn into the engine into a voltage signal.

The [[ECU]] needs to know intake air volume to calculate engine load.

This is necessary to determine how much fuel to inject.

The air flow meter is located directly in the intake air stream, between the air cleaner and throttle body where is can measure incoming air.

[[Image:Afm5.JPG]]


The primary components of the AFM are a thermistor, platinum hot wire, and an electronic control unit.

[[Image:Afm6.JPG]]


The thermistor measures the temperature of the incoming air.

The hot wire is maintained at a constant temperature in relation to the thermistor by the electronic control unit.

An increase in air flow will cause the hot wire to lose heat faster and the electronic control circuitry will compensate by sending more current through the wire.

The electronic control circuit simultaneously measures the current flow and puts a voltage signal in proportion to the current flow

[[Image:Afm7.JPG]]