Misfire Monitoring

Misfire Monitoring

General Description

Measure Principle

Segment period acquisition







The acquisition of the segment period is performed through an angular range of 180 degrees crank angle.

NC_CYL_NR is the number of cylinder.

The segment starts NC_MIS_PHA degree CA before TDC.

To compute an engine roughness value for a 4 cylinder engine, n = 9 contiguous valid segments are required.

Physical background
Misfire induces a decrease of the engine speed, therefore a variation in the segment period. The misfire detection is based on the observation of this variation of segment period.

Main causes of misfiring: injector shut-off, fuel pressure problems, fuel combustion problems, ignition cut-off...

Limits for the strategy application
Variation in the engine torque caused by phenomenon other than misfiring must be recognized in order to inhibit misfiring monitoring.

For example:
- negative torque
- trailing throttle / acceleration transition
- ignition retardation without change limitation
- air-conditioning compressor activation
- rough road detection
- cylinder shut-off (ex: for engine speed limitation, vehicle speed limitation)
- crankshaft oscillation

Algorithm







Statistics: Fault Processing