A waste heat recovery system (100) for an engine (101) comprises a fluid supply (104); one or more evaporators (120, 121) adapted to transfer waste heat from the engine (101) to fluid from the fluid supply (104) to heat the fluid to a superheated vapor; a condenser (134); a bypass circuit (130) in fluid communication with an outlet on the one or more evaporators (120, 121) and an inlet on the condenser (134); and an injection port (465) in fluid communication with the fluid supply (104) and the bypass circuit (130) and adapted to inject fluid from the fluid supply (104) into the bypass circuit (130) to cool the superheated vapor in the bypass circuit (130). A waste heat recovery system (100) for an engine (101) also comprises one or more evaporators (120, 121) adapted to transfer waste heat from the engine (101) to fluid from a fluid supply (104) wherein the engine (101) generates the waste heat with the fluid.