Analog EFIE Installation Instructions

It would be a good idea to familiarize yourself with what an EFIE is by reading the following two documents:

Oxygen Sensor Adjustment - General Information

EFIE: Electronic Fuel Injection Enhancer, Described

If you are installing a Wide Band EFIE, then please go to: Wide Band EFIE Installation Instructions. If you are installing our new Digital EFIE, then you will still use these instructions, but first read the Digital Narrow Band Installation Instructions.

If you are installing one of the bare circuit boards or rubber dipped circuit boards then first see the document, Notes For Installing Circuit Board & Basic EFIE Models.


0. 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 burn.

1. Locate the oxygen sensor signal wire

The easy way to do this is to look it up in your Haynes, Clymer or Chilton manual for your car. If you don't have one of these, then see this article: Wiring Diagrams. I have also found a resource at where you can find sensor information and diagrams for many vehicles.

If none of these options are available, you'll need to locate the oxygen senor and then locate the signal wire by testing. The sensor can have 2, 3 or 4 wires, and you have to know which one is the signal wire. If you have 4 wires they will be:

  • Heater 12 Volts +
  • Heater ground
  • Oxygen sensor signal +
  • Oxygen sensor signal ground

If you have 2 or 3 wires, then you can have a common ground, or no heater wires etc. The simplest setup is a single wire, which is the signal wire and the sensor get's it's ground from the exhaust pipe. You can use the following procedure to narrow down which wire is which:

  1. Stick straight pins into the sensor's wires and measure them to ground with then engine running. One of these will show 12 volts, and this will be power for the heater.
  2. Next find any wires that produce 0 volts. These will be ground wires. The remaining wire should be your signal wire.
  3. Measure the signal wire to ground with the engine running. The voltage on this wire will vary from nearly 0 to about 1 volt. Since your meter will not be fast enough to see the lows and highs, it will average them out to about .2 to about .8 volts. The fluctuations will be so fast you have a hard time reading the numbers. Note, that you have to let the engine warm up a bit before you will get these voltages from the sensor.
  4. Cut this wire at a convenient location for connecting the EFIE. We'll call the sensor side of this cut the sensor wire, and the other side of the cut, the computer wire.

Note: rarely an oxygen sensor wiring harness will have more than 4 wires. In this case, the sensor is possibly a "wide band" oxygen sensor. In this case you need an EFIE from our Wide Band series, and you'll want to follow the instructions: Wide Band EFIE Installation Instructions.

Once you have determined which is the sensor's signal wire, you want to get it located up close to the computer. If you used a manual, or wiring diagram, you probably have already located the wire at the computer's wiring harness. If you had to figure out the wires at the sensor itself, then try to find the same wire at the computer's wiring harness. Test it with an ohm meter to be sure. Sometimes they use the same colors for different things. Even if it's a pain now, it's worth it to get the signal wire located up by the computer. This makes cutting into it and hooking up the EFIE much easier. There is no electrical reason for locating the EFIE connection close to the computer. It's only a matter of convenience, and if it's not convenient then locate a place that makes it easy for you to access the wires.

Special Note: Once you have determined the signal wire, you should always test it. The most common reason for installation failures is an incorrectly located signal wire. To test the wire, you want to have the engine running, and you want to measure the voltage between the signal wire and ground. Please watch the following video to see what these voltages look like: Sensor Voltages Video

2. 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. It's not that the unit couldn't run 100% of the time, it probably could. But it would slowly drain your battery.

Most of the fuel efficiency devices need switched power as well, and you can often piggy back onto them. Note that the EFIE draws negligible power. You can attach it to any 12 volt DC voltage source. The best choice is your fuel efficiency device, such as a Hydrogen generator. That way the EFIE only activates when the generator is turned on. Note that when power is shut off to the EFIE, or the EFIE's switch is turned off, the original connection between the oxygen sensor and the computer is re-established. If connecting to your fuel saver's power is inconvenient or inappropriate, just use any circuit that is accessory key switched. Your electrical diagram can come in handy here, and if you don't find another device attach to, you can usually find a spare circuit in the fuse box (you may have to add a fuse).

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.

3. Mount the EFIE

You can use the mounting ears to screw down the EFIE to a suitable location on the vehicle body or firewall. Some people like to mount the device inside the passenger compartment of the car. I personally like my EFIE under my hood, because once I have it set, I don't mess with it.

4. Attach the wires

The EFIE multi-conductor wire has 6 colors: red, black, white, green, blue and brown. Connect the red to your power source. Connect the black to ground. Connect the green wire to the oxygen sensor. Connect the white wire to the computer. For Dual EFIE units, the brown wire goes to the 2nd oxygen sensor, and the blue wire goes to the 2nd sensor's computer line. Hopefully you've been able to locate all these wires up by the computer in an easily accessible location. But if so, be sure not to cut them too close to the computer so that you have plenty of slack to work with them.

You should solder them and use heat shrink tubing to insulate the connections from other wires. If you don't have heat shrink, you can use electrical tape. I personally always use heat shrink. It's more professional looking, and less likely to unravel later into a sticky mess.

I'm sometimes asked about what wire size you should use if you have to extend the EFIE's wires. Well, any wire will do. The power drawn by a an EFIE is minimal. We usually use 24 or 22 gauge wire which is more than enough copper to handle the minimal currents involved. I also prefer stranded wire, because it is less likely to being damaged by moving it around. But that's a preference. Solid or stranded wire will both work fine electrically.

EFIE Connection Diagram

EFIE Photo

5. Adjust the EFIE

You will now need to adjust your EFIE. They do not come from the factory with a particular starting voltage preset, so you'll have to set the initial voltage. I have found that .200 volts (200 millivolts) is a good starting point. The controls of the EFIE are shown and further described below:

EFIE Controls

EFIE Controls

The picture above shows a Single EFIE Deluxe, with the controls marked. The toggle switch turns the EFIE on/off, and the red LED glows only when the EFIE is on and has power. Note that when the EFIE is powered off, it makes the connection between the oxygen sensor and the computer, the same as it was before the EFIE was installed. If you ever have need to reconnect the oxygen sensor directly to the computer, just turn the EFIE (or Dual EFIE) off, and this will be accomplished. Also, if power is shut off to the EFIE, you'll get the same result regardless of which position the switch is in.

The red and black test points will accept and hold in place the electrodes (probes) from a multi-meter. The black point is attached to the oxygen sensor lead, and the red point is attached to the lead that outputs to the computer. Just push the leads in and they will be held in place by spring loaded clamps. With your probes in the two test points, you'll be reading the voltage offset being supplied by the EFIE, and this is the setup you need for EFIE adjustment.

The adjustment screw adjusts the voltage offset between the signal from the sensor, and what the computer "sees". Turn the screw in a clockwise direction to increase the offset, and counter-clockwise to reduce the offset, and your multi-meter will be reading the offset amount. The signal adjustment potentiometer (or "pot" for short) is designed to turn 18-20 full revolutions. This is so that the voltage offset can be tuned to a fine degree of control. Adjustments as small as a few millivolts can be made.

Most computers will see 425 millivolts from the EFIE, plus the sensor's voltage as high all the time. In other words even when the sensor is putting out it's lowest voltage, when the EFIE adds 425 millivolts, the computer will think the sensor is reading high. The computer will think the sensor is damaged, because it reads high all the time, and will ignore it's data. If this occurs you may or may not get a check engine light alerting you to the "defective oxygen sensor", but for sure your gas mileage will get very bad. So you should never operate your EFIE this high. The exact voltage is .45 volts to the ECU. Above that voltage is "high" and below that voltage is "low". The ECU must see transitions from low to high several times per second or it will "know" that the sensor is bad and then just start merrily adding gas.

It is possible to damage the adjustment pot by turning it past it's lowest or highest values. However, I've turned them at least 10 full revolutions past the end with no ill effects. But there is a limit to how many times you can turn them, and I have ruined one once by turning one too far. The thing to do, is only turn them with your multi-meter hooked up. When you get down below 50 millivolts, and further turning doesn't change the amount, stop. And the same applies at the top end of the scale. In actual practice you should never need to be at the extremes.

When it comes to making the actual adjustments to the EFIE for your particular car and fuel saver combination, I recommend starting out with 200 millivolts. The process of adjusting the EFIE is trial and error. If you're setting the EFIE above 350 millivolts you're starting to get pretty high. Watch for symptoms of too lean a mix such as rough engine, lack of power, "check engine light" coming on, etc. When these show up, adjust it back down until the symptoms go away. Note, some computers will accept an EFIE setting of over 400 millivolts. This is not the norm however, unless you take some of the actions in Tuning For Mileage.

A couple of adjustment tips: 1) If your "check engine" light comes on, you've likely set the offset too high, and the computer thinks your oxygen sensor is on the fritz. This can also be caused by mis-wiring the EFIE, so make sure you're hooked up correctly. 2) If you lose horsepower, you've got an incorrect setting, as fuel efficiency devices should increase horsepower proportionately with the increase in MPG (as well as decrease emissions). 3) If you have a high temperature probe, run down the highway with the fuel efficiency devices turned off, long enough to get the engine up to full operating temperature, and note the temp of your exhaust pipe, near the exhaust manifold. As you increase your voltage offset, this temperature may increase. Don't let it raise more than 180 degrees from your initial test.

You will probably find adjusting the EFIE to be frustrating at first. When you turn the adjustment screw, the voltage starts raising (or lowering) and keeps on doing so long after you've stopped turning the screw. It can take up to 10 minutes for the voltage changes to settle down completely. I have learned to set EFIEs similarly to balancing a long stick on your finger. You have to turn the screw farther than you expect the final position to be to get the EFIE's voltage changing in the direction you want. Then when the voltage gets close to your target voltage, quickly start turning the adjustment screw the opposite way until the voltage stops increasing. Once the voltage is at your target value, then you just make small adjustments either way to get the voltage to settle down. But note you'll want to check the voltage some minutes later to make sure it hasn't continued to drift up or down to a different value.

Alex Roeske from posted the following advice in our forum: "Drive down the highway with a friend either adjusting your EFIE, or driving for you so you can adjust the EFIE. Just drive a normal speed on as flat an area as you can reasonably find. Don't do both by yourself. Have the person with the EFIE adjust it until the engine loses power. Take your time, maybe a 1/2 to full turn every minute or so to allow the EFIE and vehicle's ECU to adjust. Back it off until your power comes back and fine tune from there. Having a voltmeter hooked up while you do this will tell you where your EFIE is set at and helps to set both sides the same. If you can't get to the point of losing power with an EFIE adjustment then the EFIE probably isn't hooked up correctly. After you find this point some tweaking will be required to get smooth performance on both the highway and city driving."

That's the basics. If you run into trouble on your installation, you can use our Contact Page to get assistance.

Special Notes About Titania Sensors:

There's another type of narrow band sensor called a Titanium Dioxide sensor. We only see this rarely. I recently looked up a 98 Jaguar engine that had this sensor. It uses a signal wire voltage of 0 to 5 volts, and the logic of rich and lean are backwards from normal narrow band sensors. Low voltage means rich, and higher voltage means lean, which is the opposite of the more common zirconia type narrow band sensors that we almost always see. The only EFIE that we know of that will work with titania sensors is our original Dual Analog EFIE. The first thing you must do is follow the directions in this article: Range Adjustment . You want to increase the range to about 3.5 volts, from its factory range of approximately .5 volts. Because of the reversed logic of the sensor, you have to hook up the EFIE backwards. You do this by taking the wire the instructions say must go from the EFIE to the computer, and connect it to the sensor signal wire. Then likewise, connect the wire that the instructions say should connect to the sensor's signal wire, and connect it to the computer. In other words, you're reversing these 2 connections. This causes the EFIE to subtract voltage rather than add it, and will then work with this type of sensor. We don't know much about what voltages you should use with this type of installation because we just don't have much experience with it. But I would say start out by setting the EFIE at about 1 volt. I would be extremely surprised if you would be able to go higher than 3.0 volts. But other than the fact that your voltages will be different, the instructions for setting the EFIE will be the same as described in the instructions above.

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