Sensors

These sensors detect the mass of air sucked into the manifold from the engine and are mounted after the air filter and before the throttle (if installed).

The information detected by this sensor enables the engine control unit to calculate the proper air/fuel ratio, thus helping to minimise toxic products in the exhaust gases, as well as ensuring good performance of the engine.

The MAF detects the air flow by measuring the electric current necessary to keep the temperature difference constant between a thermodependent heated resistor (“hot wire”) and a resistor which measures the temperature of the air flow (“cold wire”). The heat exchange between the hot wire and the air flow which tends to reduce the temperature is compensated by the electronic circuit which keeps the temperature of the resistor constant by increasing its electrical power. 

RPM sensors are normally installed near a phonic wheel, also called flywheel.

They detect the variations of the magnetic flow produced by the alternation between the presence and absence of the tooth or cam of the flywheel which generate an electrical signal. This signal is sent to the engine control unit whereby, depending on the phonic wheel where the sensors are installed, the detected signal indicates:

• The revolving speed of the drive shaft (Crankshaft Rotational-speed Sensors)

• The top dead center by detecting the position of the drive shaft (Crankshaft Position Sensors)

• The ignition sequence/timing by detecting the position of the camshaft (Camshaft Position Sensors)

Screwed onto the cylinder block of the engine, usually below the intake manifold, knock sensors detect if the outbreak of the mixture in the cylinders of the engine occurs incorrectly - that is, in detonation conditions.

Detonation can be caused by excessive pressure/temperature or the use of a fuel with an inappropriate octane rating and can lead to a deterioration of engine performance and serious physical damage to the cylinders.

Electronic control unit determines the engine cylinder where the detonation occurred, through the signals emitted by the knock sensors, and reacts by reducing the pressure in the cylinder or reducing speed and combustion temperature using a variation of the mixture enrichment.

Temperature sensors measure the air temperature in the intake manifold of the engine.

Information on air temperature is  necessary for some electronic fuel injection systems, in order to indirectly calculate the quantity of sucked air and then establish the correct dose of petrol. This guarantees low emissions and good engine performance.

Air temperature in the collector is converted by the sensor into a proportional voltage and sent to the engine control unit, which processes it, also taking into account the absolute pressure of the air and the number of engine revolutions.

Absolute air pressure value is information necessary for some electronic fuel injection systems in order to indirectly calculate the amount of air sucked in by weight and then establish the correct fuel dosage.

Air pressure measuring sensors convert the inlet pressure in the intake manifold into a proportional electrical signal that is transmitted to the engine control unit, which processes it, also taking into account the air temperature and the number of engine revolutions.

These sensors are divided into two types:

  - MAP (absolute pressure): a transducer that measures the absolute pressure, with reference to an ideal vacuum

  - MDP (differential pressure): a transducer that measures the pressure differential between two points 

Throttle position sensor (or throttle opening angle sensor) is fixed on the throttle body that regulates the amount of air fed to the engine depending on the accelerator pedal position.

This device measures the rotation angle of the throttle valve to control gasoline engines.

Functions of the throttle position sensors vary, from a simpler system that only manages the idle speed, fuel injection cut and the full load regime, to more complex ones that carefully control the acceleration phases, optimising both power and ignition advance.

WSS sensors (wheel speed sensor), also known as ABS sensors, are the latest addition to the Facet range.

Their function is real-time detection of the state of rotation of the vehicle's wheels (especially useful in systems with ABS) and can also be used to detect the speed and the distance travelled.