Practical Evaluation and Computational Simulation of the Effect of Engine Front End Accessory Drive (FEAD) Dumpers on OBD Misfire Monitor Signal

Misfire monitoring is currently a mandatory On Board Diagnostic (OBD) regulatory requirement in most of the main automotive markets. The most common method used for misfire detection is the one based on the calculation of the derivative of the angular crankshaft velocity in which sharp variations of the derivative signal are associated to misfire events. Therefore, the misfire detection calibration is practically unique for a given engine hardware and installation.

Within this context, this Paper will present a practical evaluation and also a computational simulation of the impact of an engine hardware change (front end accessory drive dumpers) on the calculated angular acceleration signal and, therefore, on the overall misfire detection capability. The outcomes of this study will ultimately define the need of calibration changes as well as support a future development of an analytical method to predicted impacts in misfire calibration.