An HHO or Brown gas generator is an interesting and often misunderstood technology.
The Brown gas generator uses electrolysis to split water (H2O) into it´s base molecules, 2 hydrogen and 1 oxygen molecule.
This is why it is often referred to as an HHO gas generator.The HHO in itself is not an alternative to gasoline but a additive
to boost the efficiency of the engine. Gasoline engines are unfortunately not burning gasoline to its full potential. See http://en.wikipedia.org/wiki/Engine_efficiency
The average gasoline engine in a car is about 18% to 20% efficient. That leaves a lot of room for improvement and Brown gas is one good way of improving the efficiency. The reason for this is simple, the hydrogen is highly flammable much more so than gasoline so when your engine ignites the hydrogen the explosion ignites the gasoline with much better results (cleaner, less waste and fewer emissions) than it would otherwise have done.
Some basics the burn speed of hydrogen is 0.098 to 0.197 ft/min (3 to 6 cm/min) compared
gasoline´s 0.00656 to 0.0295 ft/min (0.2 to 0.9 cm/min).
The hydrogen explosion is so fast that it fills the combustion cylinder at least 3 times faster then the gasoline explosion and subsequent ignites the gasoline from all directions (it is like putting flue on a fire), instead of just a spark in one end of the combustion cylinder, and we would like to do that because the gasoline only has a short time in the combustion cylinder and if its not fully burnt in that short amount of time then it just goes out the exhaust and is lost.It is also preferable to ignite all of the gasoline when it is under maximum compression in combustion cylinder to get the maximum amount of energy out of it (this is a small time window),whonce the piston starts going down the energy transfer from the explosion to the engine becomes less efficient.
The hydrogen´s higher burn temperature and explosive force is such that it cleans the soot that collects in the engine (it is like having the engine consistent maintains) and with a cleaner engine you get better mileage and fewer oil changes .