Abstract: A predictive model is derived for subsequent use in a misfire detector in an internal combustion engine. Data collected using a test engine is curve-fitted using NARMAX techniques to obtain a computational formula for the predictive model which relates deviant acceleration at the accessible crankshaft section to deviant acceleration at the inaccessible crankshaft section. Thus, the model can be used during actual misfire detection to reduce the effects of the torsional oscillations.

Abstract: Irregularities in crankshaft velocity introduced when measuring crankshaft rotation at a section of a crankshaft in an internal combustion engine that is less damped to torsional oscillations than is another more accessible crankshaft section are corrected using a NARMAX-generated model to predict rotation measurements that would have been obtained at the inaccessible section based on data actually collected at the accessible crankshaft section. Thus, the effects of torsional oscillations in the crankshaft are substantially filtered away, resulting in crankshaft acceleration values that form the basis of a misfire detector having nearly maximum signal-to-noise performance.