How HHO Works

Last Updated: Jun. 07, 2014

How does HHO work? We get asked this question a lot. And yet, this is the most important point to understand, especially if you want to make your car more fuel efficient by using this Hydrogen Assist technology. The physics and chemistry of this subject can be very complicated. But, fortunately, the basic concepts are very few and extremely simple.


The most common misconception is that these hydrogen generators are producing enough HHO to be a stand-alone fuel source, and that burning this HHO delivers all the needed fuel to skip the trip to the pump! Or even, that the device will allow a vehicle to run purely on water.

Here are the properties that are involved in the conversion of water to fuel:

  • Mechanical to Electrical (the vehicles alternator makes electrical energy)
  • Electrical to Chemical (the Hydrogen Cell Unit makes HHO from the alternators electrical energy)
  • Chemical to Mechanical (the HHO burns in the engines combustion chamber to make mechanical energy)

The apparent problem here, is that there are three energy conversions occurring, and each one loses some energy. It is a basic fundamental of physics, that in any conversion of energy from one form to another, there is going to be some loss. There is no such thing as 100% efficiency. In some of these conversions there is quite a bit of loss. So if this is all there was to the picture, then the system would actually lose mileage when it was used. We have even seen this mistaken idea expressed in magazines and television news coverage of the technology.

What Really Is Going On

A vehicle's alternator can and does more energy than is consumed by the electronic components (e.g. stereo, headlights, 12v accessories) installed by the manufacturer. This “extra” energy, while not infinite, is in most cases enough to serve the purpose of supplying the needed power to disassociate the water molecule “H2O” into “2 H2 + 1 O2” (that's 2 Hydrogen molecules and 1 Oxygen molecule). This process/reaction is performed through electrolysis. To explain further, the water is subjected to two charged electrodes (inside the Cell Unit) and the reactions that occur are a reduction at the cathode and an oxidation at the anode. This effectively separates the water molecule into two gasses (hydrogen and oxygen) and it is the gasses that are now available as an ignitable power source in the vehicles combustion chamber.

Ok, so how is HHO able to improve fuel economy? In actual fact, when HHO is added to the air/fuel mixture going into the engine, the petroleum fuel we buy at the pump burns more rapidly. It is scientifically proven that HHO addition will considerably increase the flame speed of the petroleum mixture for a more “complete burn”. This means less waste of unburnt petroleum fuel leaving the combustion chamber. And it is this fact that sums up the primary way in which HHO improves fuel mileage.

When the flame speed of the fuel mixture is increased, more of the fuel is burned during the power stroke of the piston. Less fuel is being burned after the power stroke, and during the exhaust stroke, which actually works against the turning of the engine. And, less unburned fuel is being expelled from the engine as waste and pollution. Thus, a relatively small amount of HHO will have a dramatic impact on the amount of power a given amount of gasoline will produce. It will also dramatically reduce the amount of harmful emissions the engine produces.

A Problem, And Its Solution

Back in the good ol' days, before there were computers in cars, experimenters were able to add HHO to their engines and get remarkable mileage gains and huge decreases in emissions. No other handling was needed to get excellent results. Similarly, diesel engines today even get excellent results with HHO and need no other handling.

However, with the advent of the vehicle onboard computer, fuel injection, oxygen sensors, and other sensors used to control the air/fuel ratio, a problem is introduced into this simple technology. The problem starts like this:

  1. When hydrogen is introduced, and the engine is turning more times with less gas, one of the results from the more efficient burn is that there is less unburnt hydrocarbons and more oxygen coming through the exhaust.
  2. This is reported to the computer by the oxygen sensor(s) that are installed in the exhaust pipe(s)
  3. The computer reads then reads this additional oxygen as a "lean" air/fuel mix
  4. It then promptly adds more gas, until it "sees" the same exhaust conditions it was programmed to expect
  5. However, it is now incorrectly adding fuel even though the engine would be running more efficiently

People with modern fuel-injected cars, who put in HHO, often report that their vehicle runs smoother and has a dramatic increase in horsepower. But, they also often report that they are not seeing any increase in fuel mileage. This is because the vehicle's computer, by default programming, tells the fuel injectors to pump more fuel than is actually needed (to make up for the aforementioned exhaust readings) with the addition of HHO. So, what we need to do in order to receive all the gains available from this technology, is to somehow compensate for this additional oxygen in the exhaust.

A device was created that does just that…It's called an EFIE, which is short for Electronic Fuel Injection Enhancer. You can find out more about this device, and how it works in our EFIE Information Page. Basically, this device manages the vehicle's computer to compensate for the additional oxygen appearing in the exhaust. By interfering with the signal from the oxygen sensor in the exhaust to the onboard computer (ECU) we allow the computer to tell fuel injectors the information needed to reap the benefits when an HHO system is installed.


There is a remarkable simplicity to this technology. If you add HHO to your engine, you will get an increase in combustion efficiency. That is just science, and it works as certainly as turning on a light switch. But to get your gains, in a vehicle that is equipped with oxygen sensors, you will most likely have to compensate for the additional oxygen that will now appear in the exhaust. And that is done by modifying the sensor information going to the computer. If you can do these two things, you will get a dramatic increase in fuel mileage and a corresponding decrease in fuel emissions.

Fuel economy results can range from 15% all the way up to 50%. Ordinarily, people can get a minimum of a 25% increase in MPG, and 30-35% is our expected average. Some people have gotten 50% or more mileage increases, depending on their vehicle. By proper application of this simple technology, you can get these increases for your vehicle too. If your ready to start saving money with a Hydrogen Assist System, allow us to search our database for the best fit. We have kits for all vehicles and all budgets.