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      07-02-2009, 06:21 PM   #1

Drives: 2007 335i
Join Date: Sep 2008
Location: West Chicago, IL

iTrader: (5)

AEM analog A/F UEGO gauge Review....LOOKS STOCK!!

AEM – Analog Wideband Air/Fuel Gauge
Part Number: 30-5130

Project car: 2007 BMW 335i
Author: Eric Gaudi of AMS performance

Recently we had the opportunity to try out AEM’s new wideband Air/Fuel Gauge in our shop BMW 335i. Having searched around we wanted to find the best balance between functionality, reliability, cost and aesthetics. Our search landed us right to AEM’s new analog wideband Air/Fuel gauge. The benefits of a quality wideband gauge in a car are many but for those that are a little new to this particular instrument let me answer a few questions:

What is a wideband air/fuel gauge?
A wideband Air/Fuel Gauge is an instrument that accurately displays the ratio of air to fuel in your engine. It typically reads how many parts of air to one part of fuel. For example a reading of 14.7 would translate into 14.7 parts of air to one part of fuel. It does this by using an additional oxygen sensor that samples the mixture.

Why do I need one?
Well the reasons are many but in short this sensor will accurately display how your car is running in regards to fuel mixture. You have heard people comment on if their car is running lean or rich...this is a tool used to find that out. The higher the number reads the leaner your car is running. The lower the number the richer your car is running. Tuners have been using these for years to help dial in a cars fuel mixture to optimize performance while retaining reliability and safety.

Why can’t I simply use a cheaper non wideband air fuel gauge?
The term wideband comes from the sensors sampling range. Standard air fuel ratio gauges piggyback the factory O2 sensor and translate it into a rough reading. The problem is that translation is done in the form of a vague colored light range. No actual number is given. Not to mention that factory sensor is a narrow band sensor. The factory sensor has a sampling range of 0-1 volts whereas a wideband sensor has a sampling range of 0-5 volts allowing it to be MUCH more precise. This would be like comparing a cup and a string to an actual telephone…night and day. The AEM system features a Bosch sensor with an accuracy of .1 AFR, making it among the fastest and most accurate widebands available.


What first drew us to the AEM line is there track record. We have been using AEM UEGO wideband digital gauges for years and its quite possibly the best all around wideband gauge. Easy installation, precise readings, quality construction all packed in a very aesthetically pleasing part. We knew this analog model would be just as accurate and well made.

Installing an AEM UEGO Gauge could not really be much simpler. As far as gauges go this is pretty straight forward. The hardest part is routing the O2 sensor but even that is very basic. Wiring again is very simple. You have power, Ground and signal. There is also an optional output wire but we will get to that later.

I won’t get into the specific wire to wire details on where to mount this gauge because for each user that will vary. Because you only have to pick up a power and a ground this gauge can really be mounted wherever you see fit. I chose to remove the factory ashtray and cigarette lighter and mount my AEM UEGO gauge there. In order to do this I had to build a custom carbon fiber panel. Obviously this is one of the more labor intensive areas to put this gauge in a 335i but I wanted something that looked very clean and factory like.

Wiring was a breeze! I simply tapped into the power, ground and dimmer wires already going to my cigarette lighter. Being that the gauge was only about 6” from the factory wiring it allowed for a clean easy install. One of the really nice features are the integrated output wires on the gauge. Should you choose to use them you can have the AEM output that same 0-5v signal to any form of logging device you might be using. This is very convenient for those using the UEGO for tuning as you can actually see point by point on your logging software your fuel mixture.

Routing the wideband sensor through the firewall was a little more difficult than the wiring of the gauge. Even this was not really difficult. Most cars have either rubber grommets on the firewall near the pedal assembly. In addition the steering column usually passes through the firewall with a rubber boot. Robber grommets were in an awkward place on the 335i so I chose to make a small incision in the rubber boot on the steering column. I then simply passed the harness through and routed it below the car using existing factory brackets and ties already holding in factory wiring. So far the install was going pretty easy. Now comes the only 'hard" part of the install. In order for the sensor to work it has to be in the exhaust stream. In order to achieve this a bung needs to be welded in the exhaust. AEM recommends about 2-3 feet from the turbo. On the BMW there are two dedicated exhaust pipes so you just need to install it in one of the two pipes. VERY IMPORTANT: if you have catalytic converters in the car the sensor MUST be installed BEFORE the cat in order to get a proper reading.

With the gauge installed and the sensor hooked up its time to see how she works. The first thing that stands out if the color range, instead of choosing a predetermined color AEM actually has a fine dial on the back of the gauge. This allows you to dial in the color of the gauge to match your factory instruments. I was able to match the factory BMW instrument cluster EXACTLY! It literally looks STOCK! This was a huge plus for me as I am very particular about how gauges match in a car. To top if off AEM even gives you two different bezel options (gloss black and silver) I chose black as it seemed to look the most OEM.

Now the real reason to buy a wideband A/F gauge is functionality. AEM does not disappoint! Most wideband A/F gauges on the market read primarily numerical. This is hard to read during real time as a series of numbers will rush by until it levels off. With an analog or needle based gauge you can watch the needs as it sweeps. This gives you a much better way of monitoring how A/F is changing in real time. With the needle you can see how fast the needle sweeps and if it dips or spikes. AEM actually developed this just for tuners so they can not only log and review A/F from the 0-5v output but also monitor it in real time. The needle is VERY responsive and smooth, so much it actually had me questioning the countless other needle based gauges that I have used in my car career. AEM got it PERFECT!

In summary we are very impressed with the AEM UEGO analog wideband air/fuel gauge. AEM never seems to disappoint with quality products that don’t break the bank. We plan on using other AEM gauges for our project 335i and we will continue to report back on them in the future. For more information or to pick up one of these for yourself visit AMS HERE! or at any AEM distributor.