This is a little out there, but I recently read in one of the automotive engineering journals about a new power boosting, variable displacement and variable compression ratio design. They put a linked rod between the crankpin and the connecting rod. The link is moveable with (hydraulic control maybe?) Anyway they can change the stroke of the motor while it runs. Also the piston lingers longer at TDC, so there is more complete burning of the mixture - more power and better efficiency.