Improving Misfire Diagnostic Through Coupled Engine/Vehicle Numerical Simulation

Numerical simulation can be effectively used to reduce the experimental tests which are nowadays required for the analysis and calibration of engine control and diagnostic systems. In particular in this paper the use of a one-dimensional fluid-dynamic engine model of an 8 cylinders high-performance s.i. engine coupled with a vehicle and driveline model to simulate the effects of misfire events on the engine angular speed is described. Furthermore, the effect of cycle-to-cycle combustion variability was also evaluated, in order to take into account variations in the combustion process that can substantially increase the engine speed fluctuations under normal operating conditions, thus hindering the misfire detection. Finally, a comparison with experimental data obtained on a chassis dynamometer was carried out. After this accuracy assessment, the numerical simulation could be used to analyze different techniques for misfire detection, thus reducing the required experimental tests.