Undercar: The Science Behind Traction And Braking
Knock and ping noises mean something bad has happened in the combustion chamber. This video is sponsored by Autolite.
I have and ASE G1 Test question for you:
Technician A says detonation sounds like a “knock.”
Technician B says detonation sounds like a “ping.”
Who is correct?
Both technicians are correct. Knock and ping noises are subjective terms and have different meanings depending on the person and even the engine. Both noises mean something bad has happened in the combustion chamber.
The noise is caused by detonation and is the result of two flame fronts colliding in the combustion chamber. What that means is that the air-fuel mixture has been ignited almost simultaneously in two locations within the combustion chamber. One flame front was probably ignited by the spark plug, while the second front was ignited spontaneously by hot spots in the combustion chamber that could be caused by carbon deposits. But, most common causes of detonation octane that is too low for the application.
Retarding or advancing the ignition timing is how the engine prevents detonation. In modern engines, the most appropriate timing is determined by the Engine Control Unit, which uses a number of sensors and inputs, including a knock sensor to determine when to retard the timing.
If a detonation problem is left unchecked, detonation can cause serious engine damage, such as broken or bent valves. Other signs are the spark plug’s insulator is cracked, chipped or broken, and the ground electrode may also exhibit damage.
This video is sponsored by Autolite.