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HHO Gas Generators for Cars

Now, please suppress the grins 'n snickers for a few moments and indulge me.

Has anyone heard much about HHO (on demand) gas generation technology to improve efficiency of internal combustion engines e.g. cars? The claims range from "Run Your Car on Water" .... to ..... "double you car's MPG". Some of the more 'down-to-earth' claims are interesting when explained in technical terms. One outfit offers free download DYI plans for constructing an HHO generator that appears to be pretty simple. It's made from a short section of 4" PVC pipe and claims an MPG improvement of 20%. However, an external $50.00 - $100 EFI device is needed to fool the O2 sensor's output to compensate for the change in the exhaust gas mixture of fuel injected cars. These guys could actually be in the business of selling 'do nothing' EFT devices.

Essentially, these 12v powered devices produce HHO (hydroxy) gas from water electrolysis that is then fed into an engine's intake. The HHO gas produced is too small to ever actually run a car sized engine on HHO alone. Instead, HHO gas when mixed with normal vaporized gasoline, is claimed to improve combustion efficiency by increasing combustion temperatures. The improved efficiency is supposed to more than offset the energy needed (i.e. the 12v power) to produce the HHO resulting in a net MPG improvement together with cleaner exhaust gas'.

In my view, even if these things do work, the increased combustion temps would mean accelerated engine wear, possible exhaust valve burn holes and catalytic converter damage etc. unless the engine were designed to operate at elevated temps.

Here's a nay sayer's POV: Sad
Here's info supporting HHO: Smile

Comments? Smile
This one has been kicked around on several science forums - I've done some of the kicking myself.
In short, I believe this is hogwash.

Let's start with the basics. It is obvious that you cannot extract more energy than you put in (basic Thermodynamics).

The electrolysis of water to produce hydrogen and oxygen is about 80% efficient in industrial systems, much less in this type of DIY kit (probably around 50%). That means that 50% of the energy provided by the alternator to electrolyse the water is lost in friction, heat, and other mechanical inefficiencies. Then you need to consider that the engine driving the alternator is itself only about 20-odd percent efficient.
So, you use a very large amount of energy to produce a very small amount of hydrogen and oxygen, which you then burn to recover a fraction of that energy.

Now, the proponents know this (or the ones with a physics O level do) so they insist that what is happening is that the efficiency of combustion is being improved by the addition of the Brown's gas, and that this accounts for the extra MPG. I think that is hogwash.

I was trying to setup a test about a year ago, using a dynamometer and a couple of different cars, but it never happened. However, I do know that one of the chaps at 'Popular Mechanics' did setup a proper test. Hang on......yep, got it.

The results (to my complete and total lack of surprise) were no noticable difference.
^From that article:
(Which was, by the way, very annoyingly redirecting me to an ad page every 30 seconds or so.)
I spent a good hour on the phone yesterday with Fran Giroux of He tells me that the HHO injection is only an enabler for other devices and changes. The fuel savings doesn't come from the energy contained in the hydrogen as it's burned, which is what I've asserted all along was implausible. Giroux sells a system of modifications that disables the engine management's computer and makes the engine run extremely lean—as lean as 20:1. That's far from the normal 14.7:1. The hydrogen is necessary to let the ultralean mix burn completely, he claims. There's also a heater for the fuel to promote complete vaporization, and some additives for the fuel and oil to complete his system.

This mirrors what I've heard. You have to make other modifications, usually changes to the engine electronics, to see any improvement.

I had a teacher who tried this. He also found that he didn't get any gain from just the hydrogen. BUT, after adding in an electronics modification kit specifically made to change his truck for HHO systems, he did get better gas mileage, bringing the old 14.5 up to 16.
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