Camshaft to control valve timing

Abstract

A camshaft for a multiple cylinder four-stroke internal combustion engine is described wherein peak lift of a first exhaust lobe is angularly displaced relative to peak lift of a second exhaust lobe by an angle of cam rotation greater than an angle defined by a full revolution of the camshaft divided by the number of cylinders of the engine. By increasing the angle between peak lift of exhaust lobes associated with physically adjacent and successive firing cylinders, the exhaust port of an earlier firing cylinder begins to close earlier than a conventional symmetric arrangement and opening of the exhaust port of the subsequently firing cylinder may be delayed. As such the crossover or overlap period when two exhaust ports are open may be reduced, which thereby reduces the transfer of exhaust gas from one cylinder to another.