HHO Effects on an Engine

by Richard Rowe

"Brown's Gas," oxyhydrogen or HHO; whatever you want to call it, this gas burns with as much controversy as heat. HHO generators use electric current passing through water to split the water molecule into its component parts, oxygen and hydrogen. While the science of its production is sound, HHO's effects on an engine remain a hotly debated topic.


Engines require air and fuel to make power. Almost all engines burn some sort of hydrocarbon, in which the active ingredient is hydrogen. This hydrogen combines with oxygen to produce an explosion, which forces the piston down and turns the engine. So, the logic behind introducing a pure mix of oxygen and hydrogen is sound, and should lead to ultra-efficient combustion and the cleanest possible emissions.


HHO generators use electricity produced by the engine's alternator to make their gas, which is where the problem lay. Whether you want to call it "perpetual motion" or the more scientific "over-unity," getting more energy out of a substance than it took to make it is physically impossible. The best case scenario from a physics standpoint is that the HHO generator makes just enough gas to offset the power required to make it. When factoring efficiency losses through the alternator, HHO generator and the engine itself, you're more likely to see a drop in fuel economy than a rise. That's the theory, anyway.

As a Supplement

True, the combination of HHO gas and hydrogen cannot (in and of itself) increase fuel economy, but there is another possible avenue for efficiency increases while using the gas. HHO itself contains 1/3 oxygen by volume and 2/3 hydrogen (which has an octane rating of 130). Those two factors alone can help the engine to more efficiently burn the gasoline it normally ingests. More gasoline burned means less going out of the tailpipe. Some engines can sense combustion efficiency by "listening" to the sound of the combustion event in the cylinder; if such an engine were to detect the presence of a high-octane fuel and oxidizer, it might well increase ignition timing to capitalize on it. Increasing ignition timing makes horsepower, which can increase fuel economy.


The oxygen generated by HHO systems could theoretically reduce emissions for the same reason they may improve fuel economy. More oxygen in the cylinders more thoroughly combust the fuel, so there are fewer unburned hydrocarbons exiting the tailpipe. Another aspect to consider is that the HHO actually displaces some of the natural air that would otherwise enter the cylinder. Earth's atmosphere contains 78 percent nitrogen, which converts into harmful nitrogen oxides (NOx) emissions in the cylinder. Less normal air means less nitrogen in the cylinder, meaning there is a very real possibility that HHO generators could help to reduce NOx (nitrogen oxide) emissions.

Other Effects

HHO generators have no known harmful effects on healthy engines. HHO generator manufacturers often assert that oxyhydrogen helps clean carbon deposits from the engine's valves, but that's unlikely since HHO gas has no solvent effect whatsoever. Large amounts of quick-burning HHO in the cylinder itself may help to burn off some oil residue from the piston and cylinder head, but this premise hasn't been tested thoroughly enough to confirm.

About the Author

Richard Rowe has been writing professionally since 2007, specializing in automotive topics. He has worked as a tractor-trailer driver and mechanic, a rigger at a fire engine factory and as a race-car driver and builder. Rowe studied engineering, philosophy and American literature at Central Florida Community College.

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