Patent ID: 8096108

Claim:
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: selectively implementing ones of a plurality of operating modes in response to predetermined catalyst and engine temperature conditions, wherein said selectively implementing comprises: monitoring a catalyst temperature; monitoring an engine temperature; if said catalyst temperature is less than a threshold catalyst temperature, operating said engine in a high-lift cams, spark ignition mode including a near stoichiometric air/fuel ratio and full lift and duration valve events; and if said catalyst temperature is not less than a threshold catalyst temperature and if said engine temperature is greater than a threshold engine temperature, operating said engine in a homogeneous charge compression ignition mode.