Wiring connector

The air flow meter is the hot wire type where the flow rate is measured at source. The upper part has a duct parallel to the main flow inside of which there is the heated wire. One part of the intake air flow is introduced into the duct and, after having passed through it, it flows out of the opposite part, returning to the main flow.

Consequently, only part of the mass of air which passes through the flow meter is measured: this quantity is, however, proportional to the total mass in the flow meter.

The electrical voltage leaving the flow meter is therefore representative of the total flow rate which is calculated by applying suitable proportional parameters.

This type of flow meter has two advantages compared with the full flow type:

• considerable insensitivity to the phenomenon of air column pulses, particularly present at low speeds and heavy loads;
• less fouling of the wire, thanks to the reduced mass of air coming into contact with it; in effect the control unit does not have any wire cleaning strategy (burn-in).

1. Flow meter casing
2. Air intake into the duct
3. Air outlet from the duct
4. Outlet air
5. Intake air
6. Air measured

Wiring connector