Combined cycle engine

摘要

A method of operation of an internal combustion engine to minimize NOx emission in exhaust gas involves detection of load on the vehicle engine as either a low load or a high load. While a low load is detected unthrottled air and a quantity of fuel providing for lean combustion are mixed with injection of fuel adjacent top dead center in the compression stroke. While a high load condition is detected, throttled air and a quantity of fuel governed by sensed oxygen content of the exhaust gas are mixed in an approximate stoichiometric ratio with injection of the fuel much earlier than injection at low load, preferably during the intake stroke.