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Since I wrote the original article pointing out how the claims that by creating HHO gas, you could "run your car on water" were a clear violation of the laws of thermodynamics, I've had a lot of correspondence from people who say "that's not how it works".
They claim that these HHO schemes don't violate the laws of thermodynamics because the extra fuel savings gained comes from the way HHO gas improves the thermal efficiency of your car's engine by altering the way regular gasoline and diesel is burnt.
They claim that the injection of HHO into your vehicle's air intake significantly increases the speed with which the air/gasoline mix inside the cylinder burns and therefore more of the fuel is burnt than in an unmodified engine. That extra fuel-burn means extra power or lower fuel consumption.
Well I always try to keep an open mind about these things so I thought I'd do some research to see if this was really true.
I Googled the web to try and find some sound-science that supported the claims of the pro-HHO community and I found an interesting paper (PDF) published at the 2004 FISITA world automotive congress in Barcelona.
The testing methods seem sound and the results/conclusions presented in this paper are indeed very interesting. They seem to lend credibility to the claims of those pushing HHO systems.
However, on closer inspection it all falls apart.
Yes, the addition of H2 and O2 the intake of an engine does appear to improve the thermal efficiency by (in the case of the tests cited) an astonishing 15%.
However, the following destroys the claims of the HHO fans.
So, as is so often the case with these scams, this one does have some very tenuous link to scientific principle. Unfortunately, what they don't tell you (or probably don't even understand) is that the very tiny amounts of this gas they're injecting into their engines will have almost no effect whatsoever on the combustion efficiency of their engines -- and what improvement there is will be more than lost to the extra load put on their alternators.
I've actually done the calculations based on the energy-cost of electrolysis and the gains to be had from this hydrogen-enrichment recognized in that paper.
One thing that should be noted however, is that vehicles with an electronic engine-management system and computer that displays fuel use in MPG can become confused when even trace amounts of H2/O2 are injected in the manner the HHO proponents suggest.
This can cause erroneously high MPG figures to be displayed, even though they're not actually being attained and (even worse) they can cause your engine to run very lean -- effectively risking damage and creating increased emission of nitrous oxides.
And if you're someone who's certain that you're getting improved mileage from your HHO system, here's an experiment for you to try...
First, make sure you can turn your electrolysis cell off and on while driving.
Now with the cell turned off, drive at a constant 60mph for a minute or two, so that the engine reaches a steady temperature. Don't use cruise-control, just use your foot to position the gas-pedal so your speed remains constant.
Without moving your foot (the one on the gas pedal), turn on your electrolysis cell.
Now if all the claims for HHO are true, your engine will be developing 20%-30% *more* power than it did with the electrolysis cell turned off -- so you should notice your speed increase to around 70-75mph as the HHO gas starts flowing.
If you don't get this increase, then it's *not* working.
Or you could do this the other way...
Ensure your electrolysis cell is energized and drive along at a steady 60mph.
Now turn off the cell without moving the gas pedal up or down.
Your engine's power should drop noticeably -- since the combustion efficiency will (according to the pro-HHO people) now be much lower than before. THis means your car or truck should slow down quite noticeably -- perhaps to as little as 45mph.
If you try these experiments and don't see the changes you should then you can be pretty sure that the fuel-efficiency you think your seeing is just the placebo effect or your engine's electronic management system being fooled into running your vehicle dangerously lean (with a high risk of damage).
Here's another question -- does your engine's idle increase by 40% as the HHO gas starts being generated after you start it? If not -- why not?
If the fuel is burnt 40% more efficiently then the amount of fuel that produces an idle of (say) 1,000 RPMs should produce an idle of 1,400 RPMs when the gas kits in. If it doesn't then there's your proof that this system doesn't work.
Update: I've now asked over 100 HHO scammers to perform these tests and report their observations. Not one has done so. That's because the vast majority of those claiming it works don't even have a system in their vehicles, they're only in this scam for the money they earn from it.
And another worrying aspect of these HHO conversions has been brought to my attention...
All of those who are *actually* seeing a small improvement in fuel efficiency after fitting one of these kits have one thing in common.. they've messed around with the O2 sensor in their engine. The rationale here is that the extra oxygen from the electrolysis is causing the O2 sensor to return a reading that will cause the engine computer to increase the amount of gasoline injected -- so the O2 sensor should be disabled or adjusted to compensate.
This is utter rubbish. The O2 coming from the electrolysis cell will be totally consumed when it oxidizes the hydrogen during combustion.
What happens when you fool with the O2 sensor is that you trick your engine computer into forcing your engine to run lean -- far leaner than it's designed to run -- and that's bad.
Yes, you *may* save a few dollars per tank in fuel costs but you'll pay dearly for it a little further down the track in the form of burnt valves and damaged piston-crowns.
When you allow your engine to run lean, the internal operating temperatures soar, as does the exhaust gas temperature. This has a huge effect on the life of the valves and valve-seats, as well as promoting pre-ignition and the damaging effects that can produce.
And if you are someone who's done this and claim extra mileage, try disconnecting your HHO system without further touching the O2 sensor. Guess what, your fuel efficiency will *increase* even further! The HHO system has *nothing* to do with the fuel-economy you're seeing, it's simply the over-lean setting you've fooled your engine's computer into delivering.
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