ENGINE PERFORMANCE MONITORING USING SPARK PLUG VOLTAGE ANALYSIS

Spark plug based engine combustion diagnostics have the advantage of s implicity and easy access. Over the years there has been considerable interest in developing and applying spark plug ionization probes to mo nitor the in-cylinder combustion process. In this paper, alternative a pproaches are presented using the spark plug as the primary sensor. Th ese methods are based on the analysis of the spark voltage and a secon dary high-voltage discharge. A series of experiments have been conduct ed to evaluate their potential in the measurement of combustion qualit y and the detection of misfire. It is found that the spark voltage dec ay time is related to the initial flame kernel development and may be used to detect misfire and deteriorating combustion quality in the ini tial flame development. The results also show that the analysis of sec ondary voltage decay time could be an effective means of monitoring th e combustion quality and detecting misfire during the main combustion period.