Air intake for a lean-burn gasoline engine

A lean-burn gasoline engine comprising:

• an air intake port with an air intake port inlet, an air intake port outlet, and an air channel connecting the air intake port inlet to the air intake port outlet,
• a combustion chamber with a combustion chamber inlet being connected to the air intake port outlet, the combustion chamber inlet having a throat where the air intake port outlet meets the combustion chamber inlet, and
• a movable valve comprising a bottom surface that faces the combustion chamber and a tapered top surface that faces the air intake port, the movable valve being arranged to move between a closed state for closing off the combustion chamber inlet and an opened state wherein intake air can flow from the air intake port into the combustion chamber, and wherein
• the throat comprises a tapered surface that is complementary with the tapered top surface of the movable valve, wherein a floor of the air channel is flat up to the throat, and wherein the throat provides a sharp edge with a channel floor of the air channel to separate an incoming air flow from a combustion chamber wall.