What are the causes of engine knocking?
1 Answers
Automobile engine knocking occurs due to the following reasons: 1. Excessively advanced ignition timing: To ensure the piston receives power immediately upon entering the power stroke after reaching top dead center (TDC), ignition typically occurs before TDC. However, excessively advanced ignition causes most of the air-fuel mixture to burn while the piston is still in the compression stroke. The remaining unburned mixture then undergoes extreme pressure and spontaneously ignites, resulting in knocking. 2. Severe carbon buildup in the engine: Excessive carbon deposits in the combustion chamber not only increase the compression ratio (generating high pressure) but also create hot spots on the carbon surface, leading to engine knocking. 3. Overheating engine: High intake air temperatures in hot environments or poor engine coolant circulation can cause the engine to overheat and knock. 4. Incorrect air-fuel ratio: An overly lean air-fuel mixture raises combustion temperatures, which in turn increases engine temperature, making knocking more likely. 5. Low fuel octane rating: The octane rating indicates a fuel's resistance to knocking. Higher octane fuels have better anti-knock properties. High-compression engines generate higher combustion chamber pressures. Using low-octane fuel with poor anti-knock properties increases the risk of knocking.
