1996-02-01

Fault Identification in Engine Misfire Using a Runner-by-Runner Intake Manifold Pressure Observer 960327

A nonlinear model-based method for engine misfire detection has been proposed in the earlier work [2]. Many possible reasons for persistent cylinder misfire (e.g., a burned inlet valve or other faults), however, still need to be identified. Identification of engine misfire enables engineers, vehicle operators or technicians to trace the cause of misfire and to identify the faulty components in the engine. Also, a cylinder-by-cylinder manifold model will provide a considerably more accurate estimate of individual cylinder air flows.This paper develops a model-based nonlinear intake manifold pressure observer and an algorithm to identify a burned inlet valve. The proposed manifold model is a runner-by-runner model. A nonlinear observer using this runner-by-runner model can estimate the plenum pressure and all individual runner pressures and their subsequent flows. The estimate is then used as an indication of a faulty inlet valve, one of the possible causes of engine misfire.The observer's performance is simulated on a V-8 engine model. Simulation results indicate that the observer is robust and the pressure estimation by the observer is quite accurate. Any burned inlet valve, for example, even when the burned area is very small, can be successfully detected and located using the runner pressure estimate as an indication. Cylinder-by-cylinder air-fuel ratio control also benefits from this runner-by-runner pressure observer through more accurate air flow estimates.

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