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AEM Wideband

Updated on April 8, 2011

AEM Digital Wideband UEGO Gauge

Thanks in part to improving technology, the modern auto enthusiast enjoys access to a wide variety of once out-of-reach auto parts that were simply to expensive for the average consumer. A vital addition to any tuned car, a Wideband O2 gauge informs the driver of the engine's current air/fuel ratio (or "AFR"). In modern high performance turbo and supercharged engines, the air/fuel ratio is king, and must be set appropriately to ensure maximum performance and reliability.

Today's market features a variety of inexpensive aftermarket wideband O2 systems, most of which come as a complete package, featuring all wiring, connections, sensors and gauges. With so many options, it becomes difficult to decide which wideband O2 gauge is the right choice. Recognizing this, AEM developed the popular AEM Wideband UEGO gauge, a full standalone wideband system featuring the industry recognized Bosch 4.2 wideband O2 sensor, which allows for accurate air/fuel ratios as close to 0.1 AFR

The Wideband UEGO gauge features both silver and black faces to match any gauge or interior configuration.
The Wideband UEGO gauge features both silver and black faces to match any gauge or interior configuration. | Source


The single most beneficial feature of the AEM Wideband gauge is the ability to interface properly with all major engine management systems, as well as with all major dyno systems. The UEGO features 0-5v analog outputs for gasoline, ethanol, E85, and methanol. This integration allows logging of air/fuel ratios during dyno tuning. This complete integration feature provides a tuner with more information about how the car is responding to changes, allowing for a better tune, more power and improved reliability and fuel economy.

Thanks to the highly accurate Bosch 4.2 wideband O2 sensor, the UEGO can read air/fuel ratios as low as 10:1, and as high as 20:1. The Bosch 4.2 Sensor is factory calibrated by Bosch, and does not require re-calibration, unlike several other available wideband O2 sensors.

The AEM UEGO gauge features both silver and black face plates (both come with the gauge, no additional purchase is required) that allow the gauge to suit any gauge or interior setup. Featuring a digital "analog" style sweeping LED display, as well as a central red AFR readout, the outputs are easy to read and easy on the eyes under all conditions. Currently, red is the only available color for the central AFR display, as red is easiest on the eyes for night driving.

Frequently Asked Questions

"Should the sensor be located before or after the catalytic converter?"

  • In applications with one or more catalytic converters, the O2 sensor should be placed before the catalytic converter(s). Because catalytic converters alter the contents of the exhaust gasses, placing the sensor after the catalyst will report incorrect readings to the sensor.

"Which direction should the O2 sensor face?"

  • Because condensation builds up on the O2 sensor, the sensor should be mounted on either the side or top of the exhaust piping. This prevents condensation build up, which can and will cause the sensor to fail prematurely.

"Where do I mount the O2 sensor?"

  • Many aftermarket exhaust systems now come with optional bungs designed to accept a wideband O2 sensor. If your exhaust does not have a bung, you will need to weld a bung in. The AEM Wideband UEGO gauge comes with a bung, should the addition of one be necessary.

"What should my air/fuel ratio be?"

  • Appropriate air/fuel ratios vary widely from engine to engine, and even from country to country. For example, in North America, someone tuning a turbocharged engine may aim for 11.5:1 AFR under full boost, where in Japan an AFR of 10.5:1 may be more desirable (albeit with more ignition timing dialed in to compensate for the richer mixture). The Stoichiometric air/fuel ratio (the number where the most complete burn is accomplished) is 14.7:1, but no engine will run 14.7 all the time. After installation of a wideband O2 gauge, the driver will notice the number constantly changes; This is normal. It's best to talk to a local tuner about the topic air/fuel ratios.

One of the most oft-asked questions relating to the AEM wideband system is the O2 sensor, or more specifically, "where should the sensor be placed in the exhaust?". There are a few different answers to that question, which we will tackle below.

Installation of Bosch Wideband Sensor on turbocharged applications

  • To ensure long service life, the sensor should be placed at least 36 inches (91 centimeters) away from the turbocharger. The sensor will work if placed closer, but will run hotter, which will decrease the service life of the sensor unit.

Installation of Bosch Wideband Sensor on supercharged applications

  • On supercharged engines, the wideband O2 sensor should be placed no closer than 18 inches (46cm) from the exhaust port. In applications with a catalytic converter, avoid placing the sensor to close to the catalytic converter to prevent premature O2 sensor failure (catalytic converters run very hot and give off lots of heat).

Installation of a wideband sensor on naturally aspirated applications

  • Similar to a supercharged application, you want to place the O2 sensor no closer than 18 inches (47cm) from the exhaust ports. You should also be mindful of the catalytic converter if your application has one.

AEM Wideband UEGO gauge in action

The video above demonstrates the wide AFR range the AEM UEGO gauge is capable of displaying.  As far as aftermarket gauges go, a wideband should be high on your list, especially if you are running a turbocharged engine setup, which require pinpoint air/fuel accuracy for the most power and reliability.  With more competition stepping up to the plate, AEM has been forced to lower their prices to stay competetive.  It's never been a better time to buy a wideband O2 gauge!


The author of this article does not work for or represent AEM in any way.  He just likes to write about car stuff.


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      Sham 2 years ago

      Ignition module works for me if it gets too hot, it makes it tough to start. There shluod be a heat conducting gel under the module, I have no idea how long it is supposed to last, but it would be a quick and cheap fix if all you had to do was clean off the old gel and add some new stuff.