"at zero percent duty cycle, the valve directs oil to the advance dise of the vanes, which results in a fully advanced cam phaser. at 100% duty cycle, oil is directed to the retard side. this results in a timing of about 36 degrees BTDC. at 50% oil is directed to both sides, and maintains the current cam phaser position."
This link was posted on the first page of this thread 3 years ago. It contains factory training information.