Efi Gasoline Engine Fire Theories And Methods Of Diagnosis

The emission of the vehicle has been the biggest pollutant in our country, so the emission regulation becomes more and more strict, and the Europe III regulation will be implemented in whole China. The Europe III regulation prescribes that the EMS must has the function of the On-Board Diagnostic(OBD) to detect the faults including the engine's many systems and mechanism components and the circuit, which can reduce the emission. The misfire detection is an important part of the OBD system. The researches with misfire detection internal and oversea have many troubles at high speed to make sure the misfire occurs or not in every circle. And the misfire detection in engineering also uses the speed fluctuation in several circles then sets the threshold of the misfire detection with calibration.On the base of analysis of the relative research internal and oversea, this paper provides a new method at high speed to solve the problem of picking-up the useful fault information, which aims to the detection in cycle one by one at high speed. First, we should use the different between the amplitude of the basic frequency at misfire and normal state to make sure the misfire occurs or not, and use the sliding windows arithmetic to lighten the load of the computer, which is helpful to the detection on line. When known the misfire occurs, we use the wavelet decomposition to de-noise the waveform which is formed by the data collected in one cycle. The effect of the de-noising with different wavelets will be confirmed by calculation and then we compare many different ways and indexes, such as the signal noise ratio and the threshold of the wavelet coefficients, to select the optimal decomposition layers and the wavelet type. At last, we get the clear waveform which is what we wanted to pick-up the useful fault characteristic value. A basic diagnosis strategy is set and also the signal of the camshaft position sensor is used to judge the cylinder which misfire occurs.At last, the result of the experiment we took validates that the diagnosis strategy...