Auto-ignition gasoline engine combustion chamber and method

A combustion chamber for an internal combustion engine comprising:

• a closed end cylinder having an inlet port and an exhaust port formed therein with valve members disposed in the ports for controlling the flow of air and products of combustion to and from the combustion chamber, a gasoline fuel injector having a spray tip and a spark ignition source having a spark gap, the cylinder having an axis and positioned to receive air and fuel injected directly from the fuel injector;
• and
• a piston mounted for reciprocation in the cylinder, the piston including a generally flat rim having an inner edge surrounding a recessed bowl into which the fuel is primarily injected, the bowl having a floor and a surrounding side formed by an arcuate surface connecting tangentially with the floor and extending to the rim inner edge;
• the spark plug having a centerline through the spark gap and being offset to one side of the cylinder axis with the spark gap extending into the combustion chamber toward the axis;
• and
• the injector being offset to an opposite side of the axis with the spray tip aimed to direct a generally conical fuel spray into the piston bowl with a portion of the fuel spray passing near the spark gap;
• wherein the spark plug centerline is spaced inward from the bowl side arcuate surface by a minimum distance in a range of 6 to 10 mm.