The thing is that you can produce hydrogen, but not in the volume you would need to run a car off of the cars electrical system, it just ain't happening. I had a guy that wanted me to build an HHO generator and had a several hundred page manual that was just a bunch of double speak and half truths. The schematic was simple, but the amount of energy needed would have to come from somewhere else. A car couldn't run and build up enough to keep it going for any length of time. That didn't even take into account metering it to the engine it was just a tube that led to the carburetor there was no way of throttling the outgoing gas. It was ridiculously ludicrous.

Jeff