The Crower six-stroke engine is a concept devloped by Bruce Crower. Two extra strokes are added to an engines Otto cycle and are called the "steam stroke". After the exhaust stroke, the intake valve stays closed and water is injected directly into the combustion chamber, creating steam and another power stroke, removing the excess heat of the combustion stroke with the exiting steam. Because of this, the engine requires no cooling system (the idea is to use the energy that's normally wasted by sending it out of the cooling system). Crower claims 40% reduction in fuel consumption and fewer exhaust emissions.