A car makes more electricity then it needs. That is wasted energy. If you could recycle that surplus into fuel the argument that it would be ineficient loses its value. After all it would be free energy.. Or am i missing something.
Not to start a flame war or something, but just wondering if that would make a difference at all.
I do remember reading somewhere that one of these silly devices is actually real, I think it only worked for diesel, and it provided a very small boost in fuel economy by somehow causing the engine to combust the fuel more fully, emitting less unburnt fuel in the exhaust, thereby getting more "bang for the buck". But it was nowhere near a 33% fuel-mileage gain.
One British scientist did actually find a boost in mileage just as you described. Problem is, it wasn't a closed loop system. The hydrogen came from an external supply. The actual gain was around 6%--not insubstantial--but (and this is what all the looney-tunes advocates ignore) the hydrogen was not generated by hydrolysis, it came from a tank. Why is this important? . . . see again the laws of thermodynamics.