Seen on CNN: Hydrogen used to Increase Mileage

[TheEnemy]

No, but in their conclusion,

2. Hydrogen addition would lead to higher NOx emission if spark timing is not optimized. Also, hydrogen enrichment was found to be not good for engine efficiency improvement at unchanged spark timing—actually it obviously dropped when 50% hydrogen was added in this study. Unburned HC emission always decreased with the increase of the amount of hydrogen added no matter whether spark timing was changed or not.

[euromodder]

Originally Posted by Crazyrabbit

It appears there is a preponderance of scientific journal papers saying it works.

Adding an easily combustable gas will certainly help a diesel - it's being done with LPG and CNG.

It works if you add H2 from a bottle - but it'll be a fairly large and heavy bottle for it to hold any substantial amount of H2.
H2 has great power to weight, but lousy power to volume.

It won't work out anymore if you use engine power (inefficient) to generate electricity (alternator losses), then electricity to H2/O2 (more losses) before burning the generated H2/O2.

The inefficiency of the engine and alternator are so big that the minor gain from injecting H2 will vanish.

The noted increases in NOx formation point to the temperature and pressure of combustion being raised substantially.

And to more acid rain ...

[UFO]

Originally Posted by TheEnemy

ScienceDirect - International Journal of Hydrogen Energy : On-board fuel processor modelling for hydrogen-enriched gasoline fuelled engine

Calculated that for on board generation the generator would have to operate at a 90%+ efficiency for an improvement.

And this is patently impossible. Hydrogen generation by electrolysis includes losses in your alternator and the heat losses in the hydrogen generator. By the way, the linked article has nothing to do with hydrogen generation by electrolysis of water, and as such has NOTHING to do with the topic at hand.

[dcb]

I think reading too many HHO sites isn't good for you

[TheEnemy]

I was trying to link scientific papers, almost all that I could access showed little to no improvement in overall energy efficiency while injecting H2 from a tank. The highest I saw was 6% improvement, but I couldn't access the paper.