The air inlet pressure sensor 274-6720 for cat 320D

The intake pressure sensor detects the absolute pressure of the intake manifold behind the throttle. It detects the change of the absolute pressure in the manifold according to the engine speed and load, and then converts it into a signal voltage and sends it to the engine control unit (ECU). The ECU controls the basic fuel injection quantity according to the signal voltage.

principle of operation

There are many kinds of intake pressure sensors, such as varistor and capacitor. Because of the advantages of fast response time, high detection accuracy, small size and flexible installation, varistor is widely used in D-type injection system.

Fig. 1 shows the connection between the piezoresistive intake pressure sensor and a computer. Fig. 2 is the working principle of the piezoresistive intake pressure sensor, and R in fig. 1 is the strain resistors R1, R2, R3 and R4 in fig. 2, which form a Whiston bridge and are bonded to the silicon diaphragm. The silicon diaphragm can be deformed under the action of absolute pressure in the manifold, which causes the change of the resistance value of the strain resistor R. The higher the absolute pressure in the manifold, the greater the deformation of the silicon diaphragm, and thus the greater the change of the resistance value of the resistor R.. That is, the mechanical change of silicon diaphragm is converted into electrical signal, which is amplified by integrated circuit and output to ECU.

Manifold Absolute Pressure Sensor (MAP). It connects the intake manifold with a vacuum tube, and with the different engine speed load, it senses the vacuum change in the intake manifold, and then converts it into a voltage signal from the change of the internal resistance of the sensor for ECU to correct the fuel injection quantity and ignition timing angle.

In EFI engine, the intake pressure sensor is used to detect the intake air volume, which is called D-type injection system (velocity density type). Intake air pressure sensor detects intake air volume indirectly instead of directly as intake air flow sensor, and it is also affected by many factors, so there are many differences between the detection and maintenance of intake air flow sensor, and the faults caused by it also have its particularity.