The use of catalytic converters to reduce exhaust pollution, engine, oxygen sensor is an essential component. As soon as the mixture of air-fuel ratio deviation from stoichiometric, ternary catalyst on the CO, HC and NOx purification capacity will drastically decrease and installed in the exhaust oxygen sensor to detect the concentration of oxygen in the exhaust to the ECU send feedback signal, and then controlled by the ECU Injector volume change, which will control the mixture air-fuel ratio near the theoretical value.
EFI car in order to obtain high exhaust purification rate and reduce emissions (CO) carbon monoxide, (HC) hydrocarbons and (NOx) oxides of nitrogen components, must make use of ternary catalysts. However, in order to effectively use the ternary catalyst, must be accurately controlled air-fuel ratio, it is always close to the theoretical air-fuel ratio. Catalytic converters are usually installed between the exhaust manifold and muffler. Oxygen sensor has a characteristic, in the theoretical air-fuel ratio (14.7:1) is the output voltage near the mutation. This feature is used to detect the concentration of oxygen in the exhaust and back to the computer to control the air-fuel ratio. When the actual air-fuel ratio becomes higher, the concentration of oxygen in the exhaust oxygen sensor to increase lean mixture state (small electromotive force: O V) notify ECU. When the air-fuel ratio lower than the theoretical air-fuel ratio when the concentration of oxygen in the exhaust lower, while the oxygen sensor state (large electromotive force: 1 V) notice (ECU) computer.
ECU according to the electromotive force from the oxygen sensor to judge differences in the low or high air-fuel ratio, and the corresponding control fuel injection duration. However, if the device is faulty oxygen transfer to the output of the EMF is not normal, (ECU) computer can not precisely control air-fuel ratio. Therefore, oxygen sensor can cover the other pieces of machinery and wear EFI system error caused by air-fuel ratio. EFI system can be said that the only "smart" sensors.