How does the S60 control VVT? I ask because what I have seen so far seems to vary duty cycle according to a map. The ford system works differently. It doesn't actually use oil pressure. THe pulley has 2 chambers, an advance and retard chamber. The volume of oil in the chamber dictates how much the pulley moves. The soilenoid plunger effectively has 3 positions. A "hold" position where it keeps the volume of oil in each chamber constant, so the pulley is locked. The other two positions are the advance and retard. In the retard, an oil way is opened to allow oil to fill the retard chamber and at the same time drain the advance chamber. As soon as the desired amount of retard is reached, the valve moves back to the hold position. The opposite happend if we want advance.

This requires a pretty robust method of control, which will have to be closed loop for certain.

Rick.