a gasoline direct injection engine that has an injector directly injecting fuel into a combustion chamber , a spark plug , an intake valve , and an exhaust valve and generates power by reciprocating a piston in a cylinder , may include a first cavity formed on a piston head of the piston to return at least some flow of the fuel injected from the injector to the spark plug , a protrusion protruding and off - set from the first cavity toward the exhaust valve , and a second cavity formed from the protrusion to the exhaust valve at a smaller height than the first cavity .