An internal combustion engines keeps the pistons at or near the Top Dead Center (TDC) for the whole time or most of the time that fuel is burning or while fuel is injected into the engine. A scotch yoke embodiment includes a curved slot to extend the piston's time at TDC. A second embodiment includes a cam on the crankshaft and a follower. The shape of the cam extends the piston's time at TDC.