Im not sure if any of you have ever heard of the 6 stroke engine, but i was reading about it the other day and it seemed like a pretty good idea. Its a basic 4 stroke engine, but with 2 more strokes added. at the top of the 4th stroke, they inject water, the water turns to steam, expanding causing the piston to go down. the 6th stroke is just to remove the steam.
Here is a link
http://www.autoweek.com/apps/pbcs.dl...THISWEEKSISSUE
http://en.wikipedia.org/wiki/Crower_six_stroke
it is supposed to use wasted heat energy. you would probably have to use stainless steel parts to prevent corrosion. Just an idea to ponder on.