What Causes Engine Knocking?

[Bill]

Engine knocking causes: 1. Overly advanced ignition timing: Excessively early 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 combusts, resulting in knocking. 2. Excessive carbon buildup in the engine: Severe carbon deposits in the combustion chamber not only increase the compression ratio but also create high-temperature hot spots on the carbon surface, leading to engine knocking. 3. Overheating engine: Operating in excessively hot environments causes elevated intake air temperatures or poor engine coolant circulation, both contributing to engine overheating and knocking. 4. Incorrect air-fuel ratio: An overly lean fuel-air mixture raises combustion temperatures, which increases engine temperature and makes knocking more likely. 5. Low fuel octane rating: Octane rating indicates a fuel's resistance to knocking. Higher octane fuels have better anti-knock properties. High-compression engines with greater combustion chamber pressure are prone to knocking when using low-octane fuels with poor knock resistance.