Spark-ignition gasoline engine

Abstract

A spark-ignition gasoline engine having at least a spark plug, the engine including an engine body having a geometrical compression ratio set at 14 or more, and an intake valve and an exhaust valve provided, respectively, in intake and exhaust ports connected to each of a plurality of cylinders of the engine body. The intake and exhaust valves are adapted to open and close corresponding respective ones of the intake and exhaust ports. The engine further includes an operation-state detector adapted to detect an operation state of the engine body and a control system adapted, based on detection of the operation-state detector, to perform at least an adjustment control of an ignition timing of the spark plug, the control system being operable, when an engine operation zone is a high-load operation zone including a wide open throttle region within at least a low speed range, to retard the ignition timing to a point within a predetermined stroke range just after a top dead center of a compression stroke.