If you’re a serious gearhead that likes to get the best performance from your vehicle, there’s a good chance that you already know about the best wideband gauges, also known as AFR gauge or Lambda gauge, but with them being able to tell you so much about your engine’s performance, I personally think all vehicles should have them fitted!
You’re only going to fit a wideband oxygen sensor and gauge if you’re intending on tuning your engine. Although ‘tuning’ could be anything from serious modifications to optimizing the fueling for economy, but modifying your cars fueling strategy takes some serious hardware and know-how, unless you’re driving an old classic with a carburetor.
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The Job of a Wideband Gauge
To give it the technical name, a wideband oxygen sensor measures the AFR (Air to Fuel Ratio) of a vehicle. And 100% of new cars use them as a way of monitoring and adjusting fuel for emissions and best performance. The difference here is that instead of talking to the ECU (Electronic Control Unit), the sensor is connected to a gauge, which gives you a live reading of the fueling.
The ideal figure is called the ‘Stoichiometric’ ratio, which for a gasoline engine, equates to 14.7%, that’s 14.7 parts of air to 1 part fuel. Simple right?
Not quite … the 14.7% figure is based on ideal conditions, with the engine in a ‘no load’ status. A modified engine being driven hard will easily see that drop to around 10.8%, and a race motor could be even lower still, but there does come a point where fuel saturation overcomes running.
Going the opposite way, a figure of 19% will mean that the engine is running too lean … too much air entering the engine, and performance will suffer, as well as the increase risk of damage from overheating – the fuel does have a cooling effect, despite quite literally exploding in the combustion chamber. Typically, you’ll be within 20% of the stoichiometric figure, depending on load state.
You may have taken your car to the shop for some work and seen that they use a gas analyzer, it’s pretty much the same thing, but due to the nature of being needed to swap from vehicle to vehicle, it will be a probe that slides into the exhaust through the muffler.
A decent wideband gauge will come with a weld-on boss to fit to the exhaust, as close to the engine as you can, while still measuring all cylinders – so at the point where the manifold collects and all cylinders exhaust. If you’re running a Vee engine, you may want to consider fitting one gauge per bank.
Fitting the boss is relatively easy, especially if you have mechanical know-how (and why wouldn’t you if you’re tweaking your fueling?) - think about the location of the sensor when it’s fitted – you don’t really want it at the lowest point in the system, nor facing straight down where it can get knocked or bashed, you also need to the think about the permanent wiring and the route that takes.
The Best Wideband Gauges
Spending a little time searching online, you’ll find quite a few different gauges. But for what it’s worth, I’ve already selected two of the best, and they’re right here! And both products are manufactured by AEM Electronics.
What makes the so good? Read my review on them to find out.
1. AEM (30-4110) UEGO Air/Fuel Ratio Gauge
First up, it should be noted that none of the AEM wideband sensors need a ‘free air’ calibration, meaning you don’t have to go to the trouble of removing them every so often to calibrate them in clean air, which is a big plus point – saves a lot of time and effort.
The 30-41110 wideband gauge has a lot of neat functionality, including the ability to swap bezels and faces – black or chrome for the bezel, and black or white for the face. Sounds like a nothing, but you stand a chance of it matching your existing dials.
Getting a little more technical, this gauge has a 0-5v analog output for datalogging or ECU control, and will read between 10 – 20% AFR, which is all you’re really going to need unless you’re having some major issues.
The thing I like about the 30-41110 gauge is that it uses a digital readout to give you actual numbers. Some of the more inferior gauges just give a series of color coded LEDs which are OK, but for proper tuning, you need to know exactly where the fueling is. It also has a neat digital, sweeping ‘needle’ on the rim of the gauge, which is color coded. This is easy to see an approximate AFR at a quick glance.
The sensor is a standardized 2 1/16 inch diameter, which means it should fit in to most gauge pods on the market. Overall, the kit comprises everything you’ll need to make it happen – sensor, wiring, weld-in boss, gauge … you’ll literally just need to the welder and drill bit!
2. AEM 30-0300 X-Series Wideband Gauge
Let’s just remind you … like the 30-41110 kit, this won’t need a free air calibration process, ever.
Although similarly priced, the X-Series gauge seems to be for the more professional user … it has more outputs, including the 0-5v analog, an RS232 serial output and the AEMnet (CANbus) output.
AEM also say that it has a faster response time, with a reduced ‘dead’ time zone, which means that the time taken between reading and displaying the data has been reduced. While this in theory sounds great, sometimes it’s easier to work with a ‘damped’ gauge. So it isn’t jumping all over the readings every few milliseconds, but giving you a smoother reading, and an input that’s easier to use when remapping.
The great thing about the X-Series is the digital readout size. Equipped with a new 7-segment center display is 87% larger than the 30-41110, which makes a huge difference to being able to read it quickly – either when you’re out on the street, or driving a rolling road – visual clarity is really important.
AFR & Fueling
Putting aside the need for the hardware, if you’re unsure about why you’d need an AFR gauge, or how changing the fueling will affect your ride, then really, talk to a professional first … Getting the fueling wrong isn’t just a minor problem that can be easily rectified, it could destroy your engine – melted pistons, burnt valves, blown turbos, dropped valve seats … literally scrap.
Having said that, if you know what you’re doing, and have the appropriate hardware, tuning your engine from standard could see a huge improvement in performance, especially with some mechanical work. However you choose to do it, a wideband gauge is an essential part of the toolbox needed, don’t even attempt it without.