Scirocco L4-1781cc 1.8L DOHC (1986)
Knock Sensor: Description and Operation
The functioning element of the knock sensor is a piezoelectric crystal. Detonation (knocking) causes vibrations in the engine which cause the crystal
to generate small voltage signals. This signal is used by the ignition control computer to correct the ignition timing.
When knocking is detected, the ignition control computer will retard the timing. If the knocking stops, the timing will be advanced in .5° steps until it
reaches its normal programmed value. If the knocking continues, ignition timing can be retarded as much as 12°.
