Method for rich pulse control of diesel engines

A method for controlling fuel injection to provide a rich combustion mixture for periodically regenerating a lean NOX trap disposed in the exhaust system of a diesel engine in which exhaust gas is recirculated and fuel is injected by pilot and main injections during each combustion cycle, said method comprising:

• sensing engine speed;
• sensing an operating parameter correlative of engine load;
• providing a map of the engine operating regime;
• delimiting a region of the engine operating regime in which low temperature combustion is desired to provide a fuel rich combustion mixture;
• increasing exhaust gas recirculation when the engine is operating in said delimited region;
• reducing intake air when the engine is operating in said delimited region;
• increasing the volume of fuel injected during the main fuel injection of the combustion cycle when the engine is operating in said delimited region;
• advancing the timing of fuel injected during main fuel injection when the engine is operating in said delimited region;
• decreasing exhaust gas recirculation when the engine is operating outside of said delimited region;
• reducing intake air when the engine is operating outside of said delimited region;
• increasing the volume of fuel injected during main fuel injection when the engine is operating outside of said delimited region;
• and,
• retarding the timing of fuel injected during main fuel injection when the engine is operating outside of said delimited region.