content: Care to explain how you would make an internal combustion engine more efficient than it already is? Only 1 stroke of a 4 stroke engine helps you move forward. The rest is wasted energy adding new air/fuel and expelling the exhaust. While 2 stroke engines give you more power strokes per crank rotation, they don't burn efficiently and waste a ton of fuel. Unless you're talking about completely redesigning how engines function (which at this point makes no sense might as well just go electric) I don't see how you can make them MUCH more efficient.