Abstract: In a fuel injection system and method for a diesel engine with compression induced ignition, NOx emissions are reduced by providing a supplemental fuel injection from a supplemental injection nozzle, in addition to the primary fuel injection through a primary injection nozzle. The supplemental injection nozzle injects a supplemental quantity of fuel onto a vaporization surface such as an exhaust valve, a flame ring area, or a top surface of the piston, in the combustion chamber, whereupon the supplemental fuel vaporizes and forms a lean air/fuel mixture. Thereafter, the primary injection nozzle injects the main fuel charge into the combustion chamber, to produce a rich air/fuel combustion mixture, which is then ignited and combusts.