Comment Vapor... (Score 2, Interesting) 379
This sounds exactly like what Smokey Yunick claims to have engineered back in the day.
http://www.legendarycollectorcars.com/featured-vehicles/other-feature-cars/smokey-yunicks-hot-vapor-fiero-51-mpg-and-0-60-in-less-than-6-seconds-see-and-hear-it-run-in-our-exclusive-video/
Basically it uses hot gas vapor to improve fuel efficiency. It basically doubled the mileage of the Fiero's iron duke motor.
Link to diagram: http://farm4.static.flickr.com/3190/2738903116_71abf7785c.jpg