2006-2010 Suzuki DF150 / DF175 4-Stroke Outboards Service Manual, Page 90Get this manual
ENGINE CONTROL SYSTEM
VVT (Variable Valve Timing) SYSTEM
The VVT system is designed to continuously vary intake valve timing to best fit the engines current operating condition The intake cam timing sprocket assembly (VVT actuator) is located at the front end of the intake camshaftThe timing sprocket' internal rotor is operated by engine oil pressureSince the rotor and intake camshaft is bolted together, the rotor and camshaft move togetherVarying the intake valve timing is accomplished by changing the intake camshaft phase angle relative to the intake cam timing sprocket using pressurized engine oil applied to the rotor through an ECM controlled oil control valve The oil control valve (OCV) directs engine oil pressure to the advance chamber or retard chamber inside the intake cam timing sprocket assembly (VVT actuator)The oil control valve operates on duty cycle controlled by the ECM The ECM determines the optimum valve timing (advance angle) under various operating conditions based on engine speed, throttle opening and cylinder wall temperatureThese input values are then used to control the position of the oil control valve (OCV)The ECM also detects the actual advance angle from the CMP sensor inputs to perform feedback control and accurately maintain the target advance angleVVT actuator