BMW looks at steam hybrids

BMW is developing a 'turbo-stamer' that reclaims the heat lost from the engine's exhaust system. It reminds me of the early stages of regenerative braking. It looks like they have a ways to go, though. An extra 220 lbs plus the space to fit all of the components for it makes this a hard pill for any carmaker to swallow. But a 15% drop in gas reward is pretty good.

BMW’s Hybrid Vision: Gasoline and Steam - Popular Science

Certain parts of a car’s engine can reach temperatures in excess of 1,500˚F. With this in mind, the engineers at BMW developed a way to boost efficiency: Transform that otherwise wasted heat into energy the engine can use. The resulting Turbo- steamer reclaims more than 80 percent of the heat lost from the engine’s exhaust and cooling systems. It uses this surplus heat to generate steam that helps drive the engine. It boosts power and torque by 10 percent and cuts fuel consumption by 15 percent without using a single additional drop of gasoline. At around 220 pounds, the Turbosteamer will have to shed some weight before it meets BMW’s weight-distribution standards, but expect to see a version on the road within the next decade.