Purpose

Varying octane levels in todays gasoline may cause detonation in some engines. Detonation is caused by an uncontrolled explosion in the combustion chamber. This uncontrolled explosion could produce a flame front opposite that of the normal flame front produced by the spark plug. The raffling sound normally associated with detonation is the result of 2 or more opposing pressures colliding within the combustion chamber. Though light detonation is sometimes considered normal, heavy detonation could result in engine damage. To control spark knock, a Knock Sensor (KS) system is used. This system is designed to retard the spark timing when a spark knock is detected in the engine. The KS system allows the engine to use the maximum spark advance for optimal driveability and fuel economy.