[beef_bourito]

that looks like a very interesting concept. it would be interesting to see the cam tuning in something like this, you wouldn't really want to get rid of all the exhaust in the chamber and might actually want to close the exhaust valve BEFORE TDC to keep some extra hot gasses and allow more water to be turned into steam.

One definite problem i can see with this would be the fact that steam is passing through the exhaust. this could cause problems with mufflers and might force people to use straight through mufflers in order to reduce the water that gets stuck. also, i wonder how efective the cool down period would be at removing this water, because in cold climates you definitely don't want water freezing in your muffler.

another thing would be lubrication. does anyone know how this would affect lubrication?

it would be really cool to hear one of these go though, the sound would be completely different from any normal vehicle you see nowadays. i also wonder, if it was made and improved upon, what kind of revs it could achieve. i doubt it would be able to get very high revs, but it'd be interesting to see.

edit: one possible solution to the steam in the exhaust would be to use one valve for your regular exhaust and one valve for the steam exhaust and have two separate systems of disposal. this would make the system more complex and might hurt exhaust flow or make the heads strange or complicated but would solve the problem.