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Posts Tagged: detonation

Pre-ignition versus detonation (knock)

Pre-ignition versus detonation (knock) — what’s the difference? Many car “experts” use the terms pre-ignition and detonation interchangeably or blame pre-ignition on low octane fuel. Let’s set the record straight; pre-ignition and detonation are not the same, they occur in different phases of the four-stroke process and only one is caused by using low octane fuel. What is pre-ignition? Pre-ignition is defined as starting the combustion process BEFORE the spark plug fires. It occurs during the compression stroke. Pre-ignition is caused when a hot object/area in the combustion chamber ignites … Read More


What is detonation? Many people confuse the terms detonation and preignition. Both may cause engine damage, but the root cause is different. Preignition, as the name implies is a combustion event that happens before the ignition system has provided a spark. The combustion can start from a hot spot within the combustion chamber and usually begins at low pressure, like at the very beginning of the compression stroke. Detonation, happens AFTER spark generation. What causes detonation? The number one cause of detonation is low octane fuel. If an engine is … Read More

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