A piston for a lean-burn gasoline engine

A piston for a lean-burn gasoline engine comprising a cylinder, an air inlet and an exhaust outlet, wherein the air inlet and the exhaust outlet are arranged about a longitudinal axis of the cylinder, the piston comprising:

• a circular peripheral wall having a central axis, wherein the peripheral wall is configured so that the central axis is substantially aligned with the longitudinal axis of the cylinder in use;
• and
• a working surface comprising:
• a central dished portion;
• an outer sloped portion, wherein the outer sloped portion surrounds the central dished portion;
• a first pair of valve pockets located in the outer sloped portion on a first side of the central dished portion;
• and
• a second pair of valve pockets located in the outer sloped portion on a second side of the central dished portion opposite the first side of the central dished portion,
• wherein the central dished portion comprises a ramp protuberance located on the first side of the central dished portion between the first pair of valve pockets, and wherein the central dished portion is configured to promote tumble of air flow into the cylinder from the air inlet, in use during an intake stroke of the piston.