Abnormal Combustion Diagnosis and Combustion Period Based Phase Estimation with a Modified Form Tandem Ion Current Detection System on SI Gasoline Engines

Abstract

Researches on typical ion current signal analysis and characteristics were studied on a 1.3L four-cylinder turbo-charged gasoline engine with a modified form tandem ion current detecting system. Analyses for knock condition and misfire condition were based on single cycle. The integral of ion current can enhance the accuracy rate of knock diagnose, reached 87.2%. Furthermore, aiming at the recognition of knock level, ion current peak value (Ionmax) and mean value (Ionmean) have a linear correlation with knock intensity. Weighting algorithm can be employed to optimize the correlation coefficient between newly defined parameter ion current knock key value (Kion) and engine knock intensity from 0.811 to 0.843. For totally misfire and late combustion condition, the diagnose accuracy rate was 100%. However, combustion phase estimation with ion current parameters was based on combustion period, not single cycle. Results show that coefficient of variation of integral of ion current based on combustion period, or 10 cycles, was below 4% under normal operation.