Engine detonation refers to spontaneous combustion of the remaining fuel/air mixture in the chamber after normal spark-initiated combustion.
Article based on ‘What is Engine Detonation?’ Amsoil Blog , July 21, 2021 | Links added by National Synthetics Staff
The terms “pre-ignition” and “engine detonation” are often thrown around interchangeably to describe the phenomenon that causes engine knock. While pre-ignition refers to early ignition of the fuel/air mixture prior to the spark plug firing, what is engine detonation? Another abnormal combustion event, engine detonation refers to spontaneous combustion of the remaining fuel/air mixture in the chamber after normal combustion is initiated by the spark plug.
In a properly running engine, spark-triggered ignition typically occurs a few degrees before the piston reaches top dead center (TDC). This careful timing ensures the downward force of the exploding fuel/air mixture works in tandem with downward piston momentum, resulting in optimum efficiency and power.
Engine detonation, however, can be caused by excess heat and pressure, leading to engine knock. Computers in modern vehicles can detect engine knock and compensate by adjusting engine timing. While this saves your engine from destroying itself, performance and fuel economy can suffer.
Causes of engine detonation
While a myriad of factors can cause engine detonation and knock, these are three of the most common.
1) Carbon deposits
Carbon deposits in the combustion chamber can be damaging if they get hot enough to ignite any residual fuel from the combustion event or if they clog injectors and impact spray patterns, leading to excessive residual fuel.
While all gasoline sold in the U.S. must be formulated with a lowest additive concentration (LAC) level of detergent additives, it takes a very low level of additive to pass the tests. The low levels of detergent additives in modern gasoline allow deposits to build up on critical fuel system components.
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2) Coolant/cooling system
An overheating engine is more likely to experience the effects of engine detonation. Check your coolant level. If it’s low, top it off. If that doesn’t work, inspect your cooling system to make sure everything is in working order. Keep an eye out for a bad water pump, missing fan shroud, a thermostat that’s too hot or slipping fan clutch.
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3) Incorrect spark plugs
In addition to producing spark, spark plugs withdraw heat from the combustion chamber and into the head. They are designed to operate within a certain heat range, and using spark plugs different from OEM recommendations can lead to engine knock.
Make sure you’re using the correct spark plugs to help avoid detonation.
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