Knock Retard
When the ECU detects detonation (uncontrolled combustion), it pulls ignition timing to protect the engine. Any amount above 0 degrees means knock was detected.
Why it matters
Knock is destructive. Even small amounts of persistent knock reduce power and risk engine damage. The ECU pulling timing is a safety intervention.
What to look for
Any knock retard above 0 degrees during WOT is a finding. Occasional 1-2 degrees may be acceptable. Persistent or high values (4+ degrees) are critical.
Related terms
How many degrees before the piston reaches top dead center the spark fires. More advance = more power, but too much causes knock.
Uncontrolled combustion where the air-fuel mix ignites from pressure/heat instead of the spark plug. Causes knock and can destroy engines.
The temperature of air entering the engine. Hotter air = less dense = less power and more knock risk.
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