Patent ID: 7684925

Claim:
A method of operating a four-stroke internal combustion engine including 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, a direct injection fuel system and a spark ignition system, comprising: during engine cranking at cold start conditions within a predetermined engine temperature range and for a duration thereafter until a predetermined engine temperature, operating said engine in a spark-assist start mode including: controlling said intake and exhaust valves to effect a partial-lift, negative valve overlap in a range of about 180 to about 200 crank angle degrees; controlling said fuel system to deliver a first injection of fuel during said negative valve overlap and a second injection of fuel during said compression stroke of said piston; and, controlling said spark ignition system to effect spark ignition.