Knock Control System

Knock Control System:

Ignition timing is retarded by the ECA when knocking occurs. If knocking persists, and the engine is in a high-boost condition, the maximum boost is also reduced by the [1][2]turbo boost control solenoid valve to prevent possible engine damage. The boost pressure line to the actuator is split, with one line going to the actuator and the other through the turbo boost control solenoid valve to the inlet side (turbine housing) of the turbocharger. The turbo boost control solenoid valve receives its signal from the ECA. The ECA determines the position of the turbo boost control solenoid valve from signals it receives from the knock control unit which in turn receives its signal from the knock sensor. If a "no-knock" condition is detected by the ECA, the turbo boost control solenoid valve is fully open and the boost pressure is divided between the two lines. A maximum boost is set at 60 kPa (8.7 psi). If a "knocking" condition is detected by the ECA under high-speed or full throttle acceleration and continues after ignition timing is retarded, the ECA will signal the turbo boost control solenoid valve to begin to close. The turbo boost control solenoid valve closes step by step to limit the pressure vented to the inlet side (turbine housing) of the turbocharger. This reduces the needed boost pressure to open the wastegate and therefore reduces maximum boost. These closing steps will continue until the vent line is fully closed, if necessary, to limit the boost even more. With the turbo boost control solenoid valve in the fully closed position, the maximum available boost is 45 kPa (6.5 psi).