Method of controlling internal combustion engine exhaust hydrocarbons

摘要

A method for reducing hydrocarbon emissions exhausted from an internal combustion engine includes timing the opening and closing of valved intake and exhaust ports to overlap for a predetermined time period, and introducing at least one of a pressure decrease at the intake passage during said overlap and a pressure increase in said exhaust passage during said overlap to reduce late hydrocarbon emissions during the overlap. Preferably, a pressure transducer such as an acoustic transducer may be driven to provide an increased pressure pulse at the exhaust port during the overlap period. Alternatively, a preferred implementation of reduced pressure at the intake port includes the operation of a throttle bypass valve that reduces fluid flow to the intake port. Either or both of the pressure increase at the exhaust port and pressure decrease at the intake port during the valve overlap may be employed in practicing the present invention, and the pressure change may be signalled in response to at least one of the signals sensed or controlled by the electronic engine control module employed in operating the internal combustion engine.