Abstract

A variable camshaft timing phaser for an internal combustion engine having at least one camshaft comprising a plurality of vanes in chambers defined by a housing and a spool valve. The vanes define an advance and a retard chamber. At least one of the vanes is cam torque actuated (CTA) and at least one of the other vanes is oil pressure actuated (OPA). The spool valve is coupled to the advance and retard chamber defined by the CTA vane and the advance chamber defined by the OPA vane. When the phaser is in the advance position, fluid is routed from the retard chamber defined by the OPA vane to the retard chamber defined the CTA vane. When the phaser is in the retard position, fluid is routed from the retard chamber defined by the CTA vane to the advance chamber defined by the CTA vane.