US Patent 7500475 Engine and method for operating an engine

A method of operating an engine is provided. The engine may include a housing having a combustion chamber, a piston disposed adjacent the combustion chamber, a crankshaft connected to the piston, an intake valve associated with the combustion chamber, and an exhaust valve associated with the combustion chamber. The method may also include opening the intake valve after a power stroke of the piston begins and closing the intake valve before the exhaust stroke ends. Furthermore, the method may include causing the exhaust valve to be open for part of an intake stroke of the piston and closing the exhaust valve at least about 30 degrees of crankshaft rotation after the intake stroke begins.