[IanDrake]

The only ICE advancement that really seems interesting to me is adding an extra cycle to inject distilled water into the cylinder for an extra power stroke.

The idea being that the heat from the prior explosive power stroke is used to turn the water into steam. Now you're using wasted heat energy and removing the need for cooling components.

[mikepurvis]

I saw an article about that idea a few years ago, and wondered if it might be possible to combine it with a rotary engine. I ended up creating this rather odd-looking model:

http://sandbox.mikepurvis.com/design/engine.svg

Completely impractical, but an interesting experiment. There's some more general info on Wikipedia: http://en.wikipedia.org/wiki/Six-stroke_engine

[phkahler]

One downside to that is that cooling everything will add to NOx in the emissions. A nice hot exhaust is needed for the catalyst to complete clean combustion. Not that it's a bad idea, just that it has an emissions tradeoff.

[ams6110]

Distilled water is corrosive to an engine. Otherwise an interesting idea.