Which EFIE Do I Need?
Before we get into the details, please keep in mind that we recommend Digital EFIEs for about 90% of all vehicles. We recommend these units for virtually all American cars, all foreign cars older than 1997, and most foreign cars after 1997. In the rest of the article we will cover why, and also the exceptions to the rule.
Basic Types of Oxygen Sensor
There are 2 basic kinds of oxygen sensor. They are called "narrow band" and the more modern, and superior, "wide band" oxygen sensor. The most important distinction is which of these 2 types of oxygen sensors you have. An EFIE made for one type will not work on the other. However, it's usually very easy to determine which type you have.
Is your car pre-1997? Then it's narrow band. Is it an American Car? It's narrow band (we've now seen a few wide bands in 2010 American cars, but none before that). If it is a German or Japanese make and was built after 2000, then you should suspect that it has wide band sensors. Actually a very few cars started using wide band sensors in 1997, but it is only after 2000 that they are used with any regularity. But here's another test: Does the sensor have more than 4 wires? If it does, then its a wide band sensor. Note that Toyota and Honda use a 4-wire wide band oxygen sensor, so 4 wires means it could be either type. However, less than 4 wires is always narrow band.
Here's another way to tell: Open your hood. Now look up. Do you see a sticker up under the hood with technical data about your vehicle? Often if you have wide band sensors, they are noted on these stickers for the mechanics. Note that it may be called an AFR (Air/Fuel Ratio) sensor, or AFS (Air/Fuel Sensor). These are all synonyms for a wide band oxygen sensor.
One other point: If you have wide band sensors upstream of the catalytic converter, you will still have narrow band sensors downstream. As of this date (2009), we have never seen wide band oxygen sensors being used downstream of any cats. For this reason our Wideband EFIE products also have narrow band inputs for your downstream sensors. See the product description for our Quad or Dual Wideband EFIEs for more information on this.
At this point, if you have a 4 wire sensor, and still don't know what type it is, you can always measure the voltages to find out. If you look at the colors of the wires that go to the sensor, you will see that 2 of them are the same color. These 2 wires will be your heater wires and can be ignored. The other 2 wires are the ones we are interested in. If you have a wide band sensor, these 2 wires will measure above 2.5 volts and no higher than 3.4 volts. They will not change very much at all when measured with the engine running. If your sensor is narrow band, one wire will be ground (0 volts) and the other will be between 0 and 1 volt and changing constantly as the engine runs.
This point is very important to getting the correct EFIE for your vehicle. If you have any doubts about which type you have, please just write to us and ask. We need to know the year/make/model and engine size of your vehicle, and we can look it up for you. If you order one of our systems, you don't need to worry about which type of EFIE you need. You just tell us what vehicle the kit is for and we'll look it up and include the correct EFIE in your kit.
Number of Sensors
Now that we know what type of sensors we have, we just need to know, "how many sensors do you have?". V6, V8 and larger engines, usually have 2 sensors that are upstream of the catalytic converter, one on each exhaust manifold. Further, they will have 1 or 2 downstream sensors as well, with 2 downstream sensors being the norm after 1996. Note: some pre-1996 vehicles don't have downstream sensors. Vehicles with 4 cylinder engines usually have 1 upstream sensor, and 1 downstream sensor. You will occasionally run into some oddball configurations that vary from these, but these are the usual configurations.
We recommend that you treat all oxygen sensors regardless of whether they are upstream or downstream. Many manufacturers are now using the downstream sensors in their air/fuel calculations, and others are using them to check the function of the upstream sensors, causing odd trouble lights and poor mileage gains. Because this has become so prevalent, we designed our products to include EFIEs for both the upstream and downstream oxygen sensors.
For instance, the Quad Digital EFIE has 2 digital EFIEs for treating 2 upstream narrow band oxygen sensors, and 2 analog EFIEs for treating 2 downstream sensors. Using analog EFIEs on the downstream sensors was not a cost saving consideration. It has been found through much testing, that analog EFIEs work better on downstream sensors, while digital EFIEs are clearly superior working on upstream sensors. There is also a Dual Digital EFIE for cars with only 1 upstream and 1 downstream sensor, such as you would find on an American made 4 cylinder engine.
For those who have wide band sensors, we have similar products. You'll want to get the Quad Wideband EFIE, where we package 2 Wideband EFIEs combined with 2 Analog EFIEs for the 2 downstream sensors, or the Dual Wideband EFIE which has one of each type.
Have Questions? Contact Us
We know it can be a little confusing at times, trying to figure out what device is best for your vehicle. If you would like help with this, you can Contact Us with the information on your vehicle and we will see that you get the product you need. Sometimes its just not clear which EFIE you need from the information you have available. In such cases, let us help you.