XC70 L5-2.5L Turbo VIN 59 B5254T2 (2003)
Variable Valve Timing Actuator: Description and Operation
Variable Valve Timing Control
Variable valve timing control
Continuous variable valve timing (CVVT) control, general
The engine combustion can be improved by changing the shift angle of the camshaft. This reduces emissions, gives lower fuel consumption and better
performance. The shift angle of the camshaft is controlled by the control module which changes the pulse ratio of the reset valve. The pulse ratio of the
reset valve affects the variable valve timing unit which changes the camshaft position compared to the crankshaft position (CKP). This ensures quick and
precise control of the shift angle of the camshaft.
Definition of "Camshaft shift angle" (X)
When the camshaft (A) is set at the factory it is aligned to top dead center (TDC) on the crankshaft which is 0° (B). The camshaft position when aligned
to the crankshaft TDC is the camshaft 0 position (0°). With continuous variable valve timing (CVVT) the camshaft 0 position is offset, the value of the
offset of the camshaft 0 position is the camshaft shift angle (x°).