A conventional car engine takes four piston movements, or strokes, to go through intake, compression, combustion, and exhaust. In a two-stroke cycle ... long list of 1 and 2 percent improvements ...

On a 4 stroke, the piston will travel from TDC to BDC four times to turn the crankshaft one time around during a combustion cycle. On a 2 stroke, the piston will travel two times to do the same thing.

the opposed-piston 4-stroke (OP4S), 50.1%; and the opposed-piston 2-stroke (OP2S, the Achates engine), 53%. They selected five mode points to assess the OP2S efficiency advantage over a simulated ...