If you produce hydrogen with the elcetricity of the alternator, you should going down in efficiency because of the inefficiency of the alternator in producing electricity and of combustion in producing mechanical energy. In a perfect world the net change would be zero, as energy isn't free...
Choke point at 65% of inlet valve diameter seems to work the best for high performance motorcycles. This is SMALLER than stock, yet seems to yield better results all the way trough the powerband. Unbelievable? Decide for yourself: www.mototuneusa.com/thanx.htm, check out high velocity...
According to
http://www.steamengine.com.au/ic/engines/vapour/
just about any spark ignition engine can be run on at least crankcase oil by preheating to the point of vaporization, which i would think to be somewhere close to crude oil.
The whole page is interesting, but for the specific part...
