What is engine knocking?
2 Answers
Engine knocking refers to the metallic knocking sound that occurs when the pressure rise rate in the automobile cylinder is too high. The following are relevant explanations: 1. Causes of knocking: When the piston is near the top dead center during the compression stroke, the piston's tilt and the change in side force direction cause the contact surface between the piston and cylinder to shift from the secondary thrust side to the main thrust side, resulting in lateral oscillation. This causes the engine to periodically produce the knocking sound of the piston striking the cylinder. 2. Types of knocking: Knocking is divided into combustion knocking and mechanical knocking. The sharp metallic knocking sound near the top dead center caused by combustion reasons is called combustion knocking or hot knocking. If operation continues under this condition, the engine's maximum combustion pressure will abnormally increase, thermal stress on components will rise, mechanical load will also increase, and under impact forces, moving parts will wear excessively and lead to damage. The dull heavy knocking or friction sound caused by abnormal clearance between moving parts and bearings, occurring at or near the top and bottom dead centers or when passing through the middle, is called mechanical knocking or cold knocking. 3. Solutions for knocking: Remove the cylinder head, extract the piston, and replace the cylinder liner, piston, piston rings, and connecting rod.
I still remember when driving my old car, I often encountered sudden knocking sounds from the engine - that's called piston knock, like a hammer striking inside the cylinder block. It's mostly caused by abnormal combustion due to low-quality gasoline or aging ignition systems, especially prone to occur when climbing hills or in hot weather. If left unchecked, the pistons and connecting rods can be damaged, leading to skyrocketing repair costs. Prevention is key: insist on using 95-octane or higher gasoline, and regularly replace spark plugs and air filters. Once when my car had this issue while climbing a hill, I immediately slowed down and went to a repair shop. After cleaning the carbon deposits, the engine has been running smoothly ever since. Remember, older cars require even more meticulous maintenance - otherwise, a small noise can escalate into major trouble.
