1999-01-0855 A Crank Angular Velocity Based Method for Engine IMEP Measurement for Idle Quality Investigation and Adaptive Ignition Time Trimming to Improve Idle Quality

Idle quality as perceived by vehicle occupants is closely linked with engine combustion variability. This is usually represented by variability in indicated mean effective pressure (IMEP). IMEP is derived from measured cylinder pressure. This paper describes an alternative method for quantifying IMEP at idle condition based on crank angular velocity measurement. Compared with the traditional method, this technique has the advantages of simple set-up, easy measurement and little requirement on data storage. The technique has been used successfully in idle quality investigations. Based on the correlation, an EMS (engine management system) strategy has been developed which significantly reduces the cylinder to cylinder combustion variability by means of adaptive ignition trimming of the individual cylinders. The implementation of the strategy has virtually eliminated 1/2 order vehicle vibration caused by combustion variability on a 90° V8 engine.