The problem with the hho scammers is the ridiculous claims they make.
Rusty, as you said, adding hydrogen can have an effect on the efficiency of the engine.
But just a few %.
It is just VERY difficult, if not impossible, to get a scientific study result.
The only one I ever found, and it is linked by the aardvark chap, is this one:
http://www.fisita.com/students/congr...apers/sc11.pdf
The scammers also like to point to such studies, as they like the conclusion, but they neglect the numbers.
Yes, it improved efficiency, but at 240l/h of hho for a small 1 cylinder diesel engine of a couple hp (6 or 7, i believe), at 1500rpm.
That's just not practically feasible. Translate that to an average 4cyl. diesel of around 120hp, you would need a ridiculous amount of hho.
On a diesel, you're better off with adding an lpg tank for the same effect. Prins autogas has such a system for big trucks.
They did not want to do this with a passenger diesel car, as they could not make it cost effective. I asked
But hey, if someone were to invent a system that actually works, gives 5% better economy without having to invest large amounts of money that you would never get back in fuel savings, I would be very interested.
I would still like to first get better proof than what I've seen so far...