[t vago]

Originally Posted by euromodder

It's inefficient because of the way the hydrogen is being generated, but it has advantages over injecting water in that the hydrogen can be combusted whereas the water cannot be.

Traditional water injection is a mechanism by which you inject a mixture of 50% water and 50% methanol into the intake manifold. The methanol is added primarily to sure that the mixture does not freeze up at colder temperatures, and it also serves as an additional fuel source.

This mixture is injected such that you'd get anywhere between 30:1 to 60:1 concentration in the intake manifold. This is then mixed with gasoline in the usual way, and the resulting mixture is then sucked in and burned as normal. Both the water and the methanol perform very well in their task of cooling off the combustion, and the methanol is also combustible. It has an octane rating of 100, IIRC, and it requires about 1/3 as much spark energy to ignite, compared to gasoline. Finally, last time I checked, a gallon of methanol costs somewhere in the range of $1.50.

So, you have this mixture that moves combustion away from detonation by virtue of cooling off the combustion chamber, and you have something that allows (almost necessitates) a leaner-than normal gasoline combustion. The only thing you have to do is periodically provide a 50/50 mix of water-meth solution. Of course, in some peoples' eyes, that itself was too much to ask.

Energy consumed by the water injection mechanism itself is limited to the pump, solenoids, and whatever control electronics you care to install. Much less inefficient than electrolyzing water.

Thus, I again maintain that HHO injection is simply a dangerous and inefficient form of water injection.

Originally Posted by euromodder

The gains of adding LPG, CNG to diesel or H2 to gasoline engines, is that like water they reduce combustion temperatures (good for reducing NOx), but unlike water they also replace part of the chemically complex liquid fuel by something that burns more easily. This in turn helps the combustion of the reduced amount of gas or diesel, which becomes more efficient, leading to less emissions - beyond what is achieved by substituting the simple additional fuel.

Hydrogen actually burns hotter and faster than gasoline at stoich, it burns much faster than gasoline at a wide range of lean concentrations, it tends to have a much thinner boundary layer than gasoline (meaning it is much more likely to combust right at the surface of the combustion chamber and melt that surface), and because its molecules are much smaller than gasoline molecules, it has this annoying tendency to leak past intake and exhaust valves as it burns. This is in addition to the HHO electrolyzing chamber and plumbing necessary to carry HHO from the chamber to the engine, which is going to be very leak-prone due to the nature of hydrogen. Not sure I'd want to have HHO...

Originally Posted by euromodder

The idea of mixing in an easily combustable gas definitely has merit.
The way the H2 is generated, less so.

So there are probably good engineering safety-related reasons as to why hydrogen-assisted gasoline cars have not been introduced, then. This is in addition to the reason why water injection never really caught on, when it was actually introduced by GM way back when.

I'm not saying that hydrogen assisted gasoline engines don't have merit. Heck, NASA experimented with hydrogen assist and found a benefit. I'm just saying that HHO is rather dangerous and rather inefficient way to implement water injection.