Dealing With Oxygen Sensors

Last Updated: Feb. 7, 2017

Oxygen Sensor Adjustment - General Information

Almost all modern vehicles employ oxygen sensors to tell the vehicle's computer if the air/fuel mixture is too rich or too lean. The computer uses the information from the O2 sensor to determine if more or less fuel should be added to the mix in order to maintain the correct proportion.

Gas vehicle engines (as opposed to diesel engines) are designed to operate at an air/fuel ratio of 14.7 to 1. When these proportions are being supplied to the engine, a certain amount of oxygen will be detected in the exhaust by the O2 sensor, and this information is fed into the vehicle's computer. If more oxygen is sensed, the computer thinks the mixture is too lean (not enough fuel), and adds fuel to the mix. Likewise, if less oxygen is sensed, the computer thinks the mixture is too rich (too much fuel) and cuts back on the fuel fed to the engine.

There's a big problem with this scenario as soon as you start adding a system that increases the efficiency of the petroleum combustion. There are many different systems that can do this, with HHO being the most popular. What happens is that for any given air/fuel ratio, burned more efficiently, the oxygen content in the exhaust will rise. The oxygen content rises as the fuel is burned more efficiently for a number of reasons. Chief amongst these are a) less fuel is being used to produce an equivalent amount of engine revolutions, and b) less oxygen is being consumed to create carbon monoxide in the exhaust. The bottom line is there is more oxygen in the exhaust as the fuel burning efficiency is increased.

Note: Many people new to the HHO industry think that the "O" part of the "HHO" is what is causing the problem. In actual fact, the amount of oxygen that is being added to the intake in a supplemental hydrogen system is so small that it is virtually undetectable by the sensors. This has nothing to do with the need for sensor adjustment. There is thousands of times more oxygen being drawn into the intake from the outside air. Consider a system that produces 2 LPM of HHO. 1/3 of that volume will be oxygen, or .66 LPM of oxygen. An average V8 engine will draw in about 2,000 LPM of oxygen from the outside air. So adding a fraction of 1 LPM to 2000 LPM will have no effect on the sensor's signal. However, the hydrogen will cause the same petroleum fuel to now turn the engine 35% more times. This causes the oxygen from the intake to increase by 35%, from 2000 LPM to 2700 LPM. This is what is causing the problem. And that is why any other type of system that improves fuel combustion efficiency has the exact same problem.

So, now that we have spent time and money to install an HHO system, and we are getting a more efficient fuel burn, what does the vehicle's computer do? It dumps gas into the mix in an attempt to get an oxygen reading in the exhaust equal to it's earlier, inefficient setup. This will then tend to negate the fuel savings of our new system, and in some cases will actually cause an increase in fuel consumption.

The Solution

The handling for this situation is simple. The signal coming from the 02 sensor needs to be adjusted to compensate for the increased fuel efficiency being achieved. Basically the added oxygen in the exhaust fools the computer into thinking the mixture is too lean, causing it to (incorrectly) richen the mix. We need to un-fool the computer so it continues to give us the same amount of gas as before. We do this by making it think there is less oxygen in the exhaust than there actually is.

The oxygen sensor produces voltages to communicate the oxygen content to the computer. When the sensor reads below .45 volts, that means it's lean, and when it reads above .45 volts, it's saying the mix is rich. If you connect your voltmeter to an oxygen sensor signal wire and ground, while the engine is running, you'll see the voltage is constantly changing, and you'll probably see voltages in the range of .3 to .7 volts or so. In actual fact, the voltage is changing back and forth from about .1 volt to about 1.0 volts, once or twice per second. A hand held meter is not usually not quick enough to show this, is all.

The EFIE adjusts the sensor's voltage so the computer "sees" a richer condition. This causes the computer to provide less gas. Many people think we're trying to fool the computer with an EFIE. That's actually not accurate. The extra oxygen in the exhaust because of a more complete combustion is what's fooling the computer. It's making the computer think the mix is too lean, and it's compensating by adding gas that is not needed. The EFIE is un-fooling the computer. All we want to do is get it back to giving us a 14.7 to 1 air/fuel ratio again.

It should be noted that an oxygen sensor handling device, by itself, is not a fuel efficiency device. It possibly could be used to control the vehicle's computer, and make the engine burn a little leaner, and this could possibly give an increase in gas mileage. But this is not what it was designed to do. It was designed to complement, and in some cases make possible, increased gas mileage when using an HHO dry cell system.

So, depending on your vehicle's oxygen sensor configuration, we have EFIE devices available to handle the oxygen sensor signals. We have different complete Wet Cell and Dry Cell kits that come with an EFIE (each one specific to your vehicle's oxygen sensors). We have an article to help you determine your sensor configuration, here: What Type of Sensors Do I Have? If you need to purchase an EFIE separately, you can find them in our store, here. By using a properly tuned EFIE with an HHO Wet Cell or Dry Cell System, you can dramatically increase your mileage and decrease harmful emissions.