Camshaft Position Control (VVT Variable Valve Timing) System Description
The VVT system is an electronic control system which continuously vary and optimize the intake valve timing in
response to the engine operating condition.
The optimized intake valve timing produce such an air intake with high efficiency that both the higher power generation
and lower fuel consumption can be attained in the whole engine speed range from low to high. In the area of the
average engine load, low emission of nitrogen oxides (NOx) and high fuel efficiency can also be attained by making
the valve opening overlap between the intake and exhaust valves longer.
For the brief of the system operation, the intake valve timing is varied by the cam timing sprocket (1) which varies the
rotational phase between the intake camshaft (3) and sprocket. The rotor (2) in the cam timing sprocket is actuated by
switching or adjusting the hydraulic pressure applied to the chambers for the timing advancing (7) and/or retarding (6).
To switch or adjust the hydraulic pressure appropriately, ECM operates the oil control valve (12) with detecting the
engine speed, intake air value, throttle opening, engine coolant temperature and camshaft position (angle).
4. Oil passage to chamber for timing retarding
5. Oil passage to chamber for timing advancing
Most advanced timing
60˚ (variable angle)
Overlap of valves
8. Oil filter
9. Oil pump
Most retarded timing
10. Oil pan
11. Control signal from ECM