A method has been developed for the acquisition and analysis of electrical signals, called combustion signals, from the cylinders of spark ignition engines based on using the spark plugs as ionization probes.
A correlation has been established between the simultaneously recorded combustion and cylinder pressure signals based on which combustion signals could be used to identify three types of burns. These burn types were called good burns, slow burns, and misfires.
The statistical occurrence of these burn types was also correlated with the hydrocarbon exhaust emission levels for engines operating under dynamometer simulated decelerations and for engines operating with various amounts of exhaust gas recirculation (EGR). Both production and experimental engines have been investigated.
It was found that during both decelerations and operation with EGR, the degradation from good burns followed the same pattern irrespective of engine type. Good burns gradually turned into slow burns, then into misfires as decelerations became more severe or as the EGR rate was increased.
Based upon the data from the various degradation measurements, slow burns and misfires were found to contribute 3-13 and 18-24 times the amount of hydrocarbons in the exhaust.