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Widebands: What you think you know, but don't.

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Old 09-14-06, 01:39 AM
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Widebands: What you think you know, but don't.

A lot of people are confused regarding widebands. This post will hopefully set everyone straight.

A "Wideband 02" (AKA "WB02" or just "WB") is a system. Unlike the common narrowband O2 sensors that everyone is used to, Widebands need more than just the sensor to work.

There are two parts to a WBo2 system. The sensor and the controller.

The sensor looks much like it's narrowband counterpart. It screws into the exhaust and has wires coming out of it. The way the WB sensor works, though, is much different than a narrowband.

A controller is required to operate the WB sensor. Unlike the stock narrowband sensor, which simply generates a voltage based on A/F ratio, the WB sensor requires sophisticated circuitry to measure A/F ratios. There is no wire you could tap off the sensor and have it put out a voltage like the narrowband sensors do.

A Bosch or NGK Wideband o2 sensor is useless without a controller

The WB controller connects to the WB sensor and reads the A/F ratio. The controller can then do anything it wants with the data. Depending on the brand/type of controller you buy, it could do one or more, or all of the following:
  • Output the A/F Ratio to a built in display
  • Output the A/F Ratio to an external screen
  • Output digital data to a serial port for display/datalogging with a PC or PDA
  • Output analog data (a voltage representation of the current A/F ratio) to a wired output.

Analog outputs
Many controllers have one or more analog outputs. These outputs generate a voltage based off of the current A/F ratio reading and can be scaled in different ways. Most WB Controllers have two outputs, one "Simulated Narrowband" (I'll use SNB for short) output and one "Wideband" output.

The SNB output is generated by the controller by scaling and manipulating the signals from the Wideband sensor to simulate the 0-1 volt output of the stock narrowband. Because of this scaling and manipulation, the SNB output is typically not useful for reading accurate A/F ratios, but it can be used in place of the stock narrowband sensor. This would allow you to eliminate the stock sensor. In order to do this, you would remove the stock narrowband sensor and connect the SNB output wire to the ECU via the wire that the stock sensor was connected to. The SNB output will act just like the stock narrowband o2 sensor and keep the ECU happy. It is worth noting that the stock O2 sensor location is typically not suitable for the WBo2. Refer to the instructions of your particular WB for information on proper location.

The WB output is typically a 0-5 volt representation of the A/F ratio. This output is scaled, but not manipulated like the SNB output so it can be used to accurately read A/F ratios. Different controller brands scale this 0-5v output differently. Some controllers allow you to program how you want the output scaled, others have a fixed scale. Most controllers have a linear output, meaning the output is directly proportional to the A/F ratio. It is important to know if the controller you are buying has a linear output.

So you have this 0-5volt output, what do you do with it? You connect it to an engine management system that can convert the output back to a human-readable A/F ratio.

Connecting to the Rtek Stage 2
In order to connect a WBo2 to the Rtek, as stated above, you need a WB *system*; A sensor and a controller. The controller must have a linear 0-5volt analog output. The particular scaling that the controller uses is not an issue as the Rtek7 PocketLOGGER software can be configured to convert any linear scaling back to an A/F ratio. The important part is that the 0-5volt output must be linear or the PocketLOGGER software will display inaccurate A/F ratios.

So, by connecting the 0-5v output of the WB02 controller to the Rtek ECU, the ECU will convert the voltage into digital data. Once the ECU has this data, you can use the Rtek PocketLOGGER software to display and datalog actual A/F ratios.

Instructions for connecting the WB to the ECU are in the Rtek7 Stage 2 instruction manual that can be found on our site.

-Mike

Last edited by turbo2ltr; 01-25-08 at 05:04 PM.
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