Can an on-the-fly water electrolyzer linked to the air intake improve fuel efficiency of a gasoline engine?

Question

This article initially seems to investigate so-called water powered cars. The final few paragraphs of the article however branches off into discussion about a system where (as I understand it):

1. A car's electrical system (powered by its alternator) is used to power an electrolyzer of water, which
2. Generates hydrogen and oxygen gas, which
3. Is fed into the engine's air intake, and
4. Improves the way the gasoline burns, thus maybe increasing overall fuel economy (ie km/litre or miles per gallon)

Obviously (to anyone who knows their laws of physics anyway) any improvements in the way the fuel burns would have to more than make up for the inefficiency of producing the extra electricity to split the water into hydrogen/oxygen. However, in cars where the fuel burns inefficiently in the first place, maybe there is the potential to improve overall fuel economy? This seems less likely to be possible in modern cars where more effort has been put into designing an efficient engine.

The article is old (2008), and suggests that further work would be done, but provides no link. Can anyone shed light on whether this research has been pursued and what the results were?

Answer 1

No.

While you're not going to find a scientific study on the matter, Dateline commisionned an assessment of a very expensive ($1800) system with all of the bells and whistles (fuel heaters, tuning to make the car run a leaner air:fuel mixture, fuel line magnets(?), etc.)

They had the cars performance measured before and after at an EPA accredited facility and with a couple of steady-state cruising tests. From the video transcript:

We brought the car back to that government-approved lab and manager Robert DePalma for two more road tests. Robert DePalma: We got no significant difference in anything. Fuel economy, emissions – basically what it was last week, without the device installed. Thirty-four miles per gallon before, 34 miles per gallon after, and no change in emissions.

This test was done with the assistance of Popular Mechanics' Mike Allen, who also wrote about it:

The total improvement in fuel economy after $1800 plus of expenditure? Bupkis. Too small to measure. Nada. In fact, if you look at the EPA tests with the system switched on and then off, there's a tiny increase in fuel consumption when the system is turned on. I attribute this to the 15 amps or so of current the electrolysis cell consumes to produce hydrogen. That current uses horsepower to spin the generator, and that consumes gasoline. The hydrogen "boost" couldn't even compensate for its own losses.

This agrees with the chemistry/physics that the amount of hydrogen generated is simply to small for there to be any significant effect, even with a sufficient and properly managed flow of Hydrogen gas. Mike Allen discussed this in a separate column:

Properly managed H2 enrichment seems to increase the burn rate of the hydrocarbons in the cylinder, extracting more energy. However, these studies only suggest increases in fuel economy by a few percentage points and don't apply unless the engine is running far too lean for decent emissions. That's a long way from the outrageous claims of as much as 300-percent improvements in economy that I see on the Internet and in my mailbox.