What Does Engine Knocking Sound Like?
2 Answers
Knocking typically occurs when the throttle is fully open in high gear, manifesting as a metallic tapping sound from the engine. Knocking is an abnormal combustion phenomenon where pressure irregularities occur in the combustion chamber. Specifically, during flame propagation in the combustion chamber, unburned mixture gases far from the spark plug are compressed by the expanding burned mixture gases, causing localized mixture gases to auto-ignite prematurely before the normal flame front, forming multiple flame cores. The phenomenon where flame propagation speed and flame front shape change abruptly is called detonation, and the external reaction produced is knocking, which generates a metallic tapping sound inside the cylinder. Prolonged engine knocking can easily lead to issues such as piston sintering and piston ring breakage, accelerating the wear and tear of engine components.
The sound of engine knocking is really noticeable, like a tiny hammer constantly tapping metal under the hood, especially when you stomp on the accelerator to speed up. I've driven many cars, and this noise sounds like 'pinging' or 'rattling' abnormal sounds, sometimes mixed with slight popping noises. The reason is often insufficient fuel octane rating or improperly adjusted ignition timing, causing the air-fuel mixture to self-ignite prematurely. Having this sound for a long time isn't good—pistons or cylinder walls may wear out faster. I recommend using the recommended high-octane gasoline, regularly checking spark plugs and timing belts, and avoiding aggressive driving under high load.
