What you need to do is get away from piston engine...try using a gas turbine engine like they use in hydroplanes.... and rather than convert water to hydrogen.... just spray water into combustion chamber then hit that with a radio frequency..... there is a video on utube of some guy burning water.... which in truth he has actually found the resonant freq. of the hydrogen which ignites.... there you have it... an engine that will run on water and be efficient....

For those of you SOOOO sure that "over unity" is not possible, remember this in your hubris.

The week before the Wright Brothers flew their airplane at Kitty Hawk, a PEER REVIEWED SCIENTIFIC PAPER was published showing that it was "scientifically impossible" for man to fly heavier-than-air vehicles.

In fact, for several years after they flew, the Wright Brothers had to contend with scientists calling them "hoaxers".

Put THAT in your pipe and smoke it!