• Toyota Variable Valve Timing. Evolution
VVT actuator housing (inner splines) is connected to the pulley, central gear (outer splines) is connected to the intake camshaft. There is a movable piston with inner and outer splines between them. During the axial movement of the piston the shaft rotates relative to the pulley.
ECM controls the oil flow to pulley chambers by solenoid, based on the signals of the sensors.
ECM switches on solenoid to shift the spool. Engine oil under pressure is supplied to piston and moves it. When moving at helical splines, the piston turns the camshaft in the advance direction. When ECM switches off solenoid, the piston moves back and the camshaft returns to its basic position.
At high load and low to medium rpm, the early closing of the intake valves improves the volumetric efficiency. This increases the torque at low and medium rpm. At high rpm later closing of the intake valves (when VVT is off) helps to increase the maximum output.