Cam phasers are specially designed, computer-controlled cam gears that automatically optimize camshaft timing based on the current engine rpm. Engine oil is pressure fed to the cam phasers through a series of passageways in the cylinder heads and camshafts. The engine computers control solenoids that adjust this oil flow into and out of the phaser's control chambers, giving the ability to retard the cams up to 60 crank degrees.
