Abstract

A variable cam timing system for an engine with at least one camshaft comprising: a housing, a rotor, and a controlled bypass. The housing has an outer circumference for accepting drive force and chambers. The rotor has a connection to a camshaft coaxially located within the housing. The housing and the rotor define at least one vane separating a chamber in the housing into advance and retard chambers. The vane is capable of rotation to shift the relative angular position of the housing and the rotor. The controlled bypass provides fluid communication between the chambers. When the valve is closed, the valve blocks passage between the chambers and when the valve is open fluid flows through the passage extending between the advance chamber to the retard chamber. A method for reducing the valve event is also disclosed.