Combustion chamber for reverse tumble spark ignition direct injection engine

A combustion chamber for a reverse-tumble spark-ignition direct-ignition engine, the combustion chamber comprising:

• A piston having an outer diameter and a head end with a raised pedestal thereon having dual shallow upwardly angled intake and exhaust faces intersecting at a linear peak, a shallow bowl formed primarily in the intake face and extending from an outer side adjacent an edge of the head to an inner side slightly beyond the peak, wherein, relative to the piston outer diameter, the bowl has a depth below the outer side in a range from about 9 to 10.5 percent, a width between lateral sides in a range from about 48.5 to 53.5 percent, a mixture preparation surface between a fuel spray portion adjacent the outer side and an ignition portion adjacent the inner side, the mixture preparation surface having, relative to the piston outer diameter, a radius of curvature in a range from about 27.5 to 30.5 percent, a bowl lip re-entrant angle on the inner side in a range from about plus 10 to plus 15 degrees and bowl lip re-entrant angles along the lateral sides in a range from about minus 15 to minus 20 degrees, the bowl lip re-entrant angle on the inner side having, relative to the piston outer diameter, a length in a range from about 20.5 to 26 percent;
• a cylinder having a closed end, the piston being reciprocable in the cylinder wherein the combustion chamber is defined by the closed end of the cylinder and the head end of the piston, the piston having a top center position at which the combustion chamber has a minimum volume, the cylinder closed end including a raised combustion chamber roof with dual shallow upwardly angled intake and exhaust surfaces opposing the intake and exhaust faces of the piston, the dual roof surfaces intersecting at a linear peak, a valved intake port opening through the roof intake surface opposite the outer side of the piston bowl and a valved exhaust port opening through the roof exhaust surface opposite the exhaust face of the piston, a spark plug extending through the roof with a gap adjacent the inner side of the piston bowl and a fuel injection spray nozzle extending through the cylinder closed end adjacent the outer side of the piston bowl, the injection nozzle having a fuel spray cone angle of about 90 degrees;
• wherein at piston top center, the distances from the spark plug gap to the adjacent piston bowl lip and the cylinder roof peak are in ranges from about 7-8 mm and from about 6 to 8.5 percent of the piston outer diameter, respectively, the combustion chamber roof exhaust surface and the piston exhaust face form an inwardly closing squish angle in a range from about 6-10 degrees while the roof intake surface and the piston intake face are approximately parallel, and the exhaust side squish clearance at half cylinder radius is in a range of about 3-4 mm while the intake side squish clearance at half cylinder radius is in a range of about 2-3 mm.