Sulzer ZG9 was a pre-World War II opposed-piston two-stroke diesel engine by Sulzer. The engine was available with a choice of two, three and four cylinders (2ZG9, 3ZG9, 4ZG9); the two-cylinder version developed 120 bhp. It used a piston scavenge pump. This was mounted vertically above one rocker, driven by a bellcrank from the main rockers. This engine is sometimes cited as an inspiration for the Commer TS3 design.