Flow sensor is one of the key components of efi system, it directly affects the vehicle's normal driving cars use air flow sensor is hotline flowmeter, the effect is measured by sensors of air flow within a certain time, and the air flow signal to ECU. ECU according to the signal to monitor the working condition of engine, the calculation of fuel supply. Air flow is big, show that the engine is accelerating; Air flow is small, indicates the engine in slow or idle running.
Working principle: when enter the body of a throttle air flows through the sensor, and part of heat away, the greater the air flow, the more heat away. To keep the temperature of a sensor at a constant temperature, it needs additional current to heat induction. By measuring the voltage of the current sensor to determine the size of the air flow.
Air flow sensor in the hotline is made from metal platinum, near to the throttle body of air passage. The air flow sensor adopts the huis bridge principle, in the air flow in electric hotline for air cooling effect and make the resistance change, bridge and so out of balance, control circuit automatically increase the voltage, current through the hotline increase, make the hotline resistance varies with temperature rise and rise, bridge to regain balance. In the process of regulating, air flow sensor to voltage signal of electronic engine control module (ECU), along with the change of air traffic in recent hot line of the air flow will also include a compensation resistance wire, so as not to make a bridge with the change of air temperature out of balance.
Hotline after fouling the air flow sensor, ECU to voltage signal will not, the dirt will affect the radiation, the lower the cooling effect. When the air flow rate increases, the hotline to cool slowly, its electrical resistance variation also reduced accordingly, so the voltage and can't accordingly increase the current through the hotline, so that to the ECU signal voltage on the low side, mixture too thin. Although the hot-wire air flow sensor with a burning net circuit, namely at every time of downtime, ECU automatically to the hotline at high temperature of 1000 ℃ heat 1 s, in order to burn off the dirt and dust on the hotline, but in some parts, especially in remote areas in China due to the use of fuel quality is too low, tempering inlet pipe, caused by excessive impurities and carbon deposit cementation on the metal platinum wire, so the single heating hotline purification device can also be difficult to remove. Therefore, you must remove the air flow sensor directly spray cleaning, to return to its normal function.
