System functions: Super-knocking

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Super-knocking designates irregular combustion that occurs in engines operating with high-boost forced induction. When this condition occurs the combustion pressure rises from a normal level of roughly 100 bar up to levels as high as 200 bar. This phenomenon is caused by contaminants in particulate form within the combustion chamber that initiate combustion of the air-fuel mixture before the actual ignition firing point. For this reason it is not possible to prevent super-knocking by adjusting the ignition timing. When the DME digital engine electronics system detects super-knock it responds by reducing output to protect the engine. 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 in response to recurring super-knock at high engine speeds. Under these conditions a damaged spark plug can be considered as a potential problem source.

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