As I understand it, Volvo's early variable cam timing is controlled by a variable pulse width modulated oil feed, and then a separate sensor on the cam to provide feedback to the ECU.
Assuming this is correct, it is obviously more complex - and more difficult to control - than the old on/off of an early VTEC or MIVEC.
My question is: what happens if you go with a crude on/off change over? Either not powering the solenoid or just giving it the 12V. Or maybe less than 12V when its on, to look after the solenoid.
Obviously this loses a bunch of 'niceness' and leaves the cam fully advanced or fully retarded - but will it work?