ENGINE MECHANICAL (M13 ENGINE) 6A2-5
Variable Valve Timing (VVT) System Description
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 gen-
eration 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 var-
ies 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 cam-
shaft position (angle).
4. Oil passage to chamber for timing retarding 8. Oil filter 10. Oil pan 12. Oil flow
5. Oil passage to chamber for timing advancing 9. Oil pump 11. Control signal from ECM
1
4
5
13
10
8
9
2
7
6
12
11
3
12
60˚ (variable angle)
Most retarded timing
Most advanced timing
Exhaust valve
Intake valve
Crank angle
Overlap of valves
Valve lift
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