System functions: Super-knocking

Super-knocking designates irregular combustion that occurs in engines operating with high-boost forced induction. When this condition occurs the combustion pressure rises from roughly 100 bar up to levels as high as 200 bar. This condition stems from contaminants in the combustion chamber (oil, residual gases, carbon particles) that ignite the mixture before the actual firing point. It is thus impossible to combat super-knocking by intervening in the ignition timing.

When the DME digital engine electronics system detects super-knock it responds by reducing output to protect the engine. Transient super-knocking can be caused by isolated contaminant particles. Super-knocking results in deactivation of the injection (for 3 to 6 cycles) on the affected cylinder. A fault (DTC) is also entered in the fault memory.