Patent ID: 7726277

Claim:
A method of operating an internal combustion engine in a four-stroke combustion cycle, said engine including a direct-injection fuel system, a spark-ignition system, and a variable volume combustion chamber defined by a piston reciprocating within a cylinder between top-dead center and bottom-dead center points, intake and exhaust passages, and intake and exhaust valves controlled during repetitive, sequential exhaust, intake, compression and expansion strokes of said piston, said method comprising: determining engine temperature within a predefined warm-up temperature region of engine operation, said warm-up temperature region including predefined non-overlapping low, middle and high temperature regions of engine operation; controlling intake and exhaust valves within said warm-up temperature region of engine operation to effect a partial-lift, negative valve overlap of about 180 to about 200 crank angle degrees; and in said low temperature region of engine operation, injecting a low temperature region predetermined total fuel mass comprising a low temperature region first injection terminating at about 350 to about 360 crank angle degrees before top dead center combustion and a low temperature region second injection terminating at about 270 to about 300 crank angle degrees before top dead center combustion; in said middle temperature region of engine operation, injecting a middle temperature region predetermined total fuel mass comprising a middle temperature region first injection terminating at about 270 to about 300 crank angle degrees before top dead center combustion; and in said high temperature region of engine operation, injecting a high temperature region predetermined total fuel mass comprising a high temperature region first injection terminating at about 370 to about 440 crank angle degrees before top dead center combustion and a high temperature region second injection terminating at about 25 to about 50 crank angle degrees before top dead center combustion.