Detonation
Uncontrolled combustion where the air-fuel mix ignites from pressure/heat instead of the spark plug. Causes knock and can destroy engines.
Why it matters
Detonation is the most dangerous combustion event. It creates pressure spikes that can crack pistons, bend rods, and blow head gaskets.
What to look for
Indicated by knock sensor activity and timing retard. Often caused by low octane fuel, excessive timing advance, high IAT, or lean conditions.
Related terms
When the ECU detects detonation (uncontrolled combustion), it pulls ignition timing to protect the engine. Any amount above 0 degrees means knock was detected.
How many degrees before the piston reaches top dead center the spark fires. More advance = more power, but too much causes knock.
The temperature of air entering the engine. Hotter air = less dense = less power and more knock risk.
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