HHO =
Water Car Test - HHO Shows Why You Can't Run Cars on Water - Popular Mechanics
and
http://en.wikipedia.org/wiki/Water-fuelled_car
"Many alleged water-fuelled cars obtain hydrogen or a mixture of hydrogen and oxygen (sometimes called "oxyhydrogen", "HHO", or "Brown's Gas") by the electrolysis of water, a process that must be powered electrically. The hydrogen or oxyhydrogen is then burned, supposedly powering the car and also providing the energy to electrolyse more water. The overall process can be represented by the following chemical equations:
2H2O → 2H2 + O2 [Electrolysis step]
2H2 + O2 → 2H2O [Combustion step]
Since the combustion step is the exact reverse of the electrolysis step, the energy released in combustion exactly equals the energy consumed in the electrolysis step, and—even assuming 100% efficiency—there would be no energy left over to power the car. In other words, such systems start and end in the same thermodynamic state, and are therefore perpetual motion machines, violating the first law of thermodynamics. And under actual conditions in which hydrogen is burned, efficiency is limited by the second law of thermodynamics and is likely to be around 20%.[9][10] More energy is therefore required to drive the electrolysis cell than can be extracted from burning the resulting hydrogen-oxygen mixture."