Sounds like the turbo steamer (if it works financially to be mass produced) could net a substantial gain to all vehicles. It could be one of those pieces of technology that everyone begins to use if it really can capture as much waste heat as BMW's claims would have us believe. In conjunction with a mild hybrid system we could potentially see some pretty substantial gains in both city and highway mileage in the future. Definitely good news!
The turbosteamer is designed to capture wasteheat from the exhaust and coolant and transform it into usable energy. Water injection is designed to cool the intake charge to prevent detonation and allow for higher compression ratios in the engine. I think someone has proposed an engine that has an extra "water cycle" where water is injected after the exhaust stroke to be turned to steam to convert waste heat into mechanical work, but that would require a decent sized water tank. A lot of guys use water/methanol injection on their diesels to keep their EGTs down, but some of those systems really use an incredible amount of water/methanol. I think some inject over 10% water/methanol mixture v/v with diesel into the air charge. Since most guys use the windshield reservoir for this its a huge pain since it can get emptied pretty darn fast. If diesels had gone the route of water/methanol injection instead of urea injection to control Nox diesels would be more efficient, have more power, and would have cleaner valves. Bummer on that one. If a good set of tuners comes along for Chrysler's ecodiesel that allows the SCR to be shut off and a kit created to use the urea tank for water/methanol injection I would buy one in a heartbeat.
Water injection has a nasty habit of chewing up spark plug electrodes in short order. The problem is not so much corrosion, but that there is no spark plug which is of the proper heat range for when the misting is on and when the misting is off.