A hydrogen direct injection engine includes a cylinder and a combustion chamber positioned at a center of the cylinder, where an axis of the combustion chamber is approximately identical to an axis of the cylinder. The hydrogen direct injection engine also includes one or more intake valves positioned around the cylinder, one or more exhaust valves positioned around the cylinder, a cylinder head mounted across a top surface of the cylinder, and a fuel injector positioned vertically at the center of the cylinder. The hydrogen direct injection engine further includes a piston disposed within the cylinder, and a spark plug positioned between the one or more intake valves.