Valve Timing Control System

In order to improve engine performance and reduce exhaust emissions, Q45 models are equipped with variable valve timing. This is accomplished through the use of intake valve timing control solenoids which are located on the intake camshaft pulleys. Intake valve opening and closing is controlled according to engine operating conditions as monitored by the ECU. Input signals from the mass airflow meter, crank angle sensor, coolant temperature sensor, throttle position sensor and park/neutral (inhibitor) switch are used to determine intake timing.

Intake camshaft pulley position is regulated by oil pressure which is controlled by the valve timing control solenoids. Intake valve timing is controlled when engine is not idling, coolant temperature is 158-230°F (70-110°C), engine speed is less than 4600 RPM, engine load is high and transmission is not in Park or Neutral. During these conditions, solenoid is energized by ECU. This causes intake valve opening and closing time to advance and valve overlap to increase.