Operation

This Hall effect type sensor is fitted on the cylinder and is facing the camshaft pulley (exhaust). There is an opening in the pulley which allows the timing sensor to detect the engine timing position and signal it to the injection control unit.

The injection control unit uses the timing sensor signal to recognize TDC at the end of the compression stroke.

Operation

A semiconductor layer, through which a current flows, immersed in a normal magnetic field (lines of force perpendicular to the direction of the current), produces a difference in power known as Hall voltage.

If the intensity of the current remains constant, the voltage produced only depends on the intensity of the magnetic field; therefore if the intensity of the magnetic field simply varies periodically this produces a modulated electrical signal, whose frequency is proportional to the speed at which the magnetic field changes.

To produce this change, a metal ring (inner part of the pulley) with an opening passes through the sensor.

As it moves, the metal part of the ring covers the sensor blocking the magnetic field with a consequent low output signal; conversely, by the opening where the magnetic field is present, the sensor produces a high signal.

This signal, together with the signals relating to the rpm and TDC, allow the injection control unit to recognize the position of the pistons and determine the injection point.

AIR FLOW METER

The flow meter is located on the air inlet hose and is the hot film type. The intake air temperature sensor is incorporated inside the flow meter.

Operation

The operating principle is based on a heated diaphragm in a measuring duct through which the intake air which enters the engine flows. The hot film diaphragm is kept at a constant temperature (about 120 °C higher than the temperature of the inlet air) by the heating resistance.

The mass of air passing through the measuring duct tends to remove heat from the diaphragm therefore, in order to keep the latter at a constant temperature, a current is passed through the resistance.

This current, being proportional to the mass of air which flows to the engine, is measured using a Wheatstone bridge and the signal obtained is sent to the injection control unit.

1. Covers
2. Electronic card
3. Sensor
4. Support plate
5. Support
6. Seal (O-Ring)
7. Temperature sensor