Low emission two-stroke engine and engine operating method for reducing engine emissions

摘要

Disclosed herein is a method of operating a two-stroke internal combustion engine so as to promote reduction in engine exhaust emissions, which two-stroke internal combustion engine includes a combustion chamber, a pump operable to periodically pump air unmixed with fuel into the combustion chamber, a fuel injector communicating directly with the combustion chamber and operable to periodically inject fuel unmixed with air directly in the combustion chamber to provide a fuel charge, an ignition system operable to periodically ignite the fuel charge in the combustion chamber, and an exhaust system including an exhaust manifold communicating with the combustion chamber and operable to produce, in the engine exhaust gas, a thermal reaction so as to reduce engine exhaust emissions, which method includes the steps of pumping air unmixed with fuel to the combustion chamber, injecting fuel unmixed with air directly into the combustion chamber so as to provide a fuel charge and at an injecting timing which is retarded from the optimum injection timing for minimum fuel emissions and fuel consumption in an engine without thermal reaction within the exhaust system and in an amount so as to provide an air to fuel ratio which is richer than the optimum air to fuel ratio for minimum HC emissions without a thermal reaction in the exhaust system, and igniting the fuel charge at an ignition timing which is retarded from minimum spark advance for best torque.