Air intake pressure sensor (ManifoldAbsolutePressureSensor), hereinafter referred to as a MAP. It is connected to the intake manifold with a vacuum tube. With different engine speed loads, it can sense the vacuum change in the intake manifold, and then convert the change of resistance inside the sensor into a voltage signal, which can be used by the ECU to correct the injection amount and ignition timing Angle.
In the EFI engine, the intake pressure sensor is used to detect the intake volume, which is called D injection system (velocity density type). The intake pressure sensor detects the intake volume is not directly detected like the intake flow sensor, but indirectly detected. At the same time, it is also affected by many factors, so there are many different places in the detection and maintenance from the intake flow sensor, and the fault generated also has its particularity
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 amount according to the size of the signal voltage.
There are many kinds of inlet pressure sensors, such as varistor type and capacitive type. Varistor is widely used in D injection system because of its advantages such as fast response time, high detection accuracy, small size and flexible installation.
Figure 1 shows the connection between the varistor intake pressure sensor and the computer. FIG. 2 shows the working principle of the varistor type inlet pressure sensor, and R in FIG. 1 is the strain resistors R1, R2, R3 and R4 in FIG. 2, which form the Wheatstone bridge and are bonded together with the silicon diaphragm. The silicon diaphragm can deform under the absolute pressure in the manifold, resulting in the change of the resistance value of the strain resistance R. The higher the absolute pressure in the manifold, the greater the deformation of the silicon diaphragm and the greater the change of the resistance value of the resistance R. That is, the mechanical changes of the silicon diaphragm are converted into electrical signals, which are amplified by the integrated circuit and then output to the ECU
