Abstract

A variable cam timing phaser including a housing, a rotor coaxially located within the housing, a phase control valve, a switching valve, and a passage connecting the first advance and retard chambers. The housing and the rotor define at least two chambers, a first chamber separated by a first vane into the first advance and retard chambers, and a second chamber separated by a second vane into the second advance and retard chambers. The switching valve has a first position in which fluid may flow freely between the passage connecting the first advance and retard chambers and fluid flow from the phase control valve to the first advance and first retard chambers is blocked. In the second position, the passage connecting the first advance and retard chambers is blocked and fluid may flow freely between the phase control valve and the first advance and first retard chambers.