Green Car Congress reports on Cyclone Technologies' update to the steam engine, which could be a practical power plant for cars. The Cyclone steam engine has been engineered for efficiency and, according to the article, delivers 3 horsepower for every inch of displacement, double that of the average gasoline engine. And unlike the behemoths of yesteryear, these steam engines are compact. The article makes them sound pretty clean, since steam is used to push the cylinders, but there still has to be some kind of fuel to heat the water. Also, with operating temperature of 1,200 degrees and pressure of 3,200psi, the engine would probably be very dangerous in a crash or during a failure.