Wide Band EFIE Installation Instructions

Install your fuel efficiency device

The EFIE is not intended to be a fuel saver by itself. You should install a device that is designed to get more energy out of the same fuel, such as a hydrogen gas electrolyzer, a fuel vapor production unit, fuel heater, or other device that gets more power out of the same fuel by increasing the efficiency of the petroleum's burn.

Locate the wide band oxygen sensor current wire

The most important point in installing any EFIE, is to correctly identify the wire on the sensor that must be connected to the EFIE circuit. This is also the most common mistake made when an installation is not successful.. In general, the easiest way to locate the correct wire is by use of a wiring diagram. If you don't have a set of wiring diagrams that includes your oxygen sensor wires, then see this article: Wiring Diagrams. Once you think you have found the correct wire, I still recommend that you test it to be sure. The correct wire will often be marked "A/F+", or perhaps "IP+".

Often times the wiring diagram will not tell us specifically which wire we need, but will show which wire is paired with which. The 2 current pump wires will always be paired with one another in the diagram, and that's usually all you need to know to identify them. Then you can measure the 2 wires in the pair, with the engine running, and you will select the one that has the higher voltage. One other trick, is that on 4 wire wide band sensors, the wire colors on the sensor itself are often standardized as black, black, blue, and white. In these cases the blue wire is the one you need.

Please see Wide Band Oxygen Sensors for information on identifying and testing your sensor wires. This article describes how to find the wire you'll need to attach to your Wide Band EFIE without a diagram. You are looking for the "current pump" pair of wires, which should be around 2.7 and 3.0 volts, or 3.0 and 3.3 volts. The wire we need is the one that has the higher voltage of this pair. We will call this the "current return wire", and this is the one that we will connect the EFIE's signal wire to.

Locate 12 volt power and ground

You need to ensure that you have switched power, not power directly from the battery. You don't want the EFIE running 100% of the time. Most of the fuel efficiency devices need switched power as well, and you can then piggy back onto them. Note that the EFIE draws negligible power. You can attach it to any circuit. The best choice for a voltage source is a fuel efficiency device, such as a Hydrogen generator. That way the EFIE only activates when the fuel efficiency device is turned on. Note that when power is shut off to the EFIE, the signal from the oxygen sensor to the computer is not affected. The EFIE has no affect on this circuit when it's powered off.

Ground should be to a wire that leads back to the battery. Bonding to the body is sometimes problematic in that the body is sometimes not well bonded to battery ground. However, you can usually find a good ground wire existing that you can tie into. Just make sure that whatever you choose to use for ground has a negligible resistance when tested against the negative battery terminal of your car.

Our Original Wide Band EFIE:

The wide band EFIE has only power and ground connections, and one output wire for each sensor. Below is a picture of a Dual Wide Band EFIE. It is shown with just the lugs and no wires attached, but the colors indicate which wire color plugs in at each location. The white and blue wires are the output wires, and each of these will be connected to a wide band oxygen sensor's current return wire. Note, if you are installing a dual EFIE and only have one wide band sensor to handle, then only use one of the output wires. Leave the other one disconnected.

Photo of Wide Band EFIE

The EFIE's signal out wire connects to your wide band sensor's current pump return wire, as located in the step above. In your wiring diagram, the current return wire will often be labeled AFS+ or IP+. Connect the white wire to one wide band sensor's current return wire, and the blue wire to the current return wire of your other sensor. These EFIE wires are tapped into the sensor's current pump return wire. The original path of the current return wire between sensor and ECU is maintained, and the EFIEs signal wire is also connected to that wire, forming a "Y".

The signal out for both wideband outputs is controlled with a single pot. When turned counter-clockwise all the way to the stop, it has no effect. When turned clockwise all the way it will add about 1.5 milliamps. This is the full lean position and you should never need to set your EFIE this high. Most vehicles use between 1/4 and 1/2 of the EFIE's full output. This means you wouldn't set the pot past the 12 o'clock position when first setting the EFIE.

Our New EFIE Models:

The following images show our new series of wideband EFIEs that include both wide band and narrow band EFIEs. These models allow you to treat both the upstream and downstream sensors using one device. The first images show the wiring keys for the Wideband Quad and Wideband Dual EFIEs, as well as how you wire into the sensor circuit.

Wideband Quad EFIE
Wideband Dual EFIE
Wideband Quad Wiring Key Wideband Dual Wiring Ket
Wideband Quad EFIE Function Diagram
Wide Band and Narrow Band Connection Diagram

The Wideband Dual EFIE has the same controls as the Wideband Quad EFIE.

Setting the Wide Band EFIE:

I'll start this section with a word of caution. Setting too high can cause your engine to run too lean and this can cause the valves to overheat. So you must be careful. If you set this EFIE above 1/2 power, be very careful you do not have any signs of an over-lean condition, such as loss of horsepower or misfiring at any engine speed. Some vehicles will tell you right away when you have set the EFIE too high. The engine revolutions will lug down and the engine may misfire. However, many modern ECUs are programmed to never allow this. They use inputs from other sensors to set minimum fuel levels that will be provided, and no matter how high you set the EFIE the engine will not lug down. The statistic you will use to set the correct level of adjustment on your EFIE will be the fuel mileage gains as described below.

We should review a little of the basic theory of why we are using an EFIE: When you add a fuel efficiency device, such as an HHO generator, one of the results will be that there is more intake air in the exhaust per amount of fuel. This equates to more oxygen, that the oxygen sensor then detects. The additional oxygen means that the air/fuel ratio appears lean to the computer, and it will react my adding more gas. This causes you to lose some of the gains you should be getting from your fuel efficiency device. The purpose of the EFIE is to counteract this effect. The EFIE makes the signal look richer than it is, causing the computer to lean the mix. The point of this is, that all we are trying to do with the EFIE is to counter the effect caused by your HHO. We're not actually trying to lean the mix. We just don't want the HHO to cause it to run rich.

So take it easy in setting this device on your car. I think you'll find that the correct setting will be between 1/4 and 1/2 power. Some cars will go over 1/2. The thing to do is to start low, and test your mileage. Then raise it a bit and see if you've mileage improves. Continue to test in this way until you get no increase of mileage, or a decrease. Then go back to the last point that increased mileage. That's where you want to be.

Setting The Analog (Downstream) EFIEs

Downstream sensors must be treated with narrow band type EFIEs. Analog EFIEs work better on downstream sensors than digital EFIEs due to the nature of the signal they generate, so our downstream EFIEs are analog. But narrow band EFIEs work differently than the wide band EFIEs and must therefore are adjusted differently.

To keep things simple, all of our EFIEs make the mix leaner when you turn the adjustment screw clockwise, and richer when you turn the adjustment counter clockwise. When you turn the wide band EFIE's pots clockwise, the mix gets leaner. When you turn the narrow band EFIE's pots clockwise the voltage at the test points goes higher, and the mix gets leaner. When adjusting the down stream sensors, we recommend using your volt meter in the 2 test points so you can see what voltage you are adding. You can, if you wish, use pot positions to keep track of your EFIE settings. However, I find using a volt meter to be more precise and easier to keep track of in my notes.

We recommend starting out your rear sensors at about 200 mV. Once again, you will need to experiment with the settings on these sensors, and make adjustments based on your fuel mileage gains. In general, you shouldn't ever need to go above 350 mV on any analog EFIE. We also recommend fine tuning the front EFIEs first, with the rear EFIEs set at about 200 mv. Then, you can try experimenting with raising the rear EFIEs to see if you get better results. But realize that the bulk of your results will come from the front sensors.

For more information on setting analog EFIEs, see Analog EFIE Installation Instructions.

Our New 2-Pot Adjustment System:

Note that our newer EFIEs use 2 pots instead of one for each adjustment. This is so we can have a course and a fine adjustment pot, and therefore have finer control of the associated EFIEs. The course adjustment works the same as the original pot in the old system. The fine adjustment pot will change the EFIEs output 1/10th the amount of the course adjustment. Here's a picture of a pair of pots:

Dual Pot Tuning System

The way to set these is to set the fine pot at center, and then make your initial adjustments with the course pot only. Later, if you need to make small changes in the setting, you can do so with the fine pot.

Because the wideband outputs are so difficult to read with a meter (as they are very tiny), its difficult to see this 2 pot system in action on the wideband EFIEs. However, the narrowband EFIEs work in exactly the same way, and these can be easily read with a voltmeter. Just connect your voltmeter to the test points for the downstream EFIEs. Then power up the EFIE - you'll need to wait 60 seconds for the built in delay. But then you'll see the voltage that the EFIEs are set at. Now when you make changes to the course pot, you'll notice big changes on your meter. But when you make changes with the fine pot, the voltage changes very little. Turn both pots all the way off, then all the way on. See how almost all of the change occurs by use of the course pot, and the fine pot makes very tiny changes.


If you run into trouble or have can't understand these directions, please contact support@fuelsaver-mpg.com. We can use your questions and comments to improve the instructions for others. Also log into our forum at www.fuel-saver.org. We have created a forum specifically for our Wide Band EFIEs, where you can read what others have discovered using these devices, and get help and suggestions for your own project.

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