Volvo is using the VVT on exh on turbos and intake on the non-turbos.

On the turbos the VVT is activated to advance cam on cold start for a period during warm-up. Advancing the exh cam allows exh valve to close sooner decreasing overlap and reducing the raw fuel escape that occurs during rich mixture while at the same time opening the exh valves sooner to allow some escape of flame that will contribute to combusion of the raw fuel left in exhaust from last exhausting cylinder. After the warm up period the cam goes back to std position except at idle where it is advanced 7-10 degrees for better idle emissions. Exh cam range is 0-30 crank degrees advanced.

On the non-turbo the int cam is continuously variable w/o respect to temp. It is regulated for emissions optimization and HP and torque optimization based on engine speed and throttle position.

The range is 40 crank degrees but I don't know what the "standard" position is within this range.

The control is done via a hub on the cam that carries the belt gear. In the hub is a piston with an internal helical gear (piston is keyed to hub and can rotate, only move laterally). The external helical gear is inside the int helical gear and bolts to cam. As the oil pressure is regulated to be higher on one side of piston or the other the piston moves back and forth and changes the relative position of gear to the cam.

The oil pressure is regulated by a duty cycle operating pulse from ECM to an oil pressure solenoid providing the oil feed to the cam gear hub.

The cam having the VVT has a cam position sensor that gives a signal of cam postion to ECM that it compares to the RPM sensor that is tracking crank position and speed. This allows the ECM to pulse width control solenoid to obtain cam position desired.