Brief description of components: Knock

In contrast to normal combustion, knocking combustion involves auto-ignition in the still uncombusted mixture towards the end of combustion. Operation of an engine with knocking combustion over a prolonged period can lead to serious damage.

Knocking tendency is increased by:

• Increased compression ratio (the compression ratio can also reach excessively high values due to deposits or production-related scatter)
• High cylinder charge
• Poor fuel quality (RON/MON)
• High intake air and engine temperature

On engines without knock control, these unfavorable influences must be taken into consideration in the ignition design by providing a safety distance to the knock limit. However, this results in unavoidable losses in efficiency in the upper load range.