Patent ID: 6935104

Claim:
An engine control system, comprising: a NOx catalyst containing ammonia as a reducing agent, provided in an exhaust system of an internal combustion engine, and selectively reducing NOx from exhaust gases; a reducing agent supply providing the reducing agent to the exhaust system and positioned upstream of the NOx catalyst; a NOx sensor detecting an amount of NOx in the exhaust gases emitted by the internal combustion engine; a fuel injection system injecting fuel to the internal combustion engine in one of a main injection mode performing a main injection and a pilot-and-main injection mode performing a pilot injection and the main injection, the pilot injection proceeding the main injection; and a control unit activating the fuel injection system in the pilot-and-main injection mode to increase a NO 2 /NOx ratio in the exhaust gases when a NOx purifying efficiency (η) is equal to or below a preset NOx purifying efficiency (ηL).