Tested: AEM’s new X-Series OBDII Wideband w/HP Tuners on C700 ‘Vette

C700 lead art fInalOur 2015 Z51 Stingray sure has come a long way. Project C700, as we’ve nicknamed it, has made substantial progress from where it began – not only in terms of horsepower, but in handling and overall character as well. Between the aggressive exhaust, the attention to stance and handling, and (most recently) the addition of ProCharger’s exclusive i-1 Supercharger, we’re pretty happy how our C7 is shaping up.

Tuning C700 to take advantage of all the mods is crucial to extract every last bit of performance out of our C7 on steroids. To accomplish this task we chose AEM Performance Electronic’s all-new UEGO wideband air/fuel ratio gauge christened the X-Series OBDII Wideband AFR Controller Gauge and HP Tuners VCM Suite.


C700 on dyno getting ready to do some logging.

For noobs, guys that don’t do their own tuning, or don’t know much about what it takes to get an engine to run at peak performance, it all starts with fuel and timing. Having the ability to tweak those two variables at just the right time and just the right value is one of the most critical things a tuner can accomplish.

The reason AEM’s wideband is cool–and why you should care–is that the faster and more accurate the gauges and sensors are that feed the ECU or display accurate information to your tuner, the better the car can be set-up to run and make maximum horsepower.

What’s unique about this gauge is that it’s designed to be used with piggyback programmers and open source tuning software, like the HP Tuners system we use on Project C700. It includes a pass-through OBDII connector that you plug into the OBD port, and you then connect your OBD connector from your laptop or programmer into the AEM pass-through connector.

The OBD stream treats the AEM wideband like any other computer on the car and sends AFR data with the vehicle’s other OBDII channels at 100 samples/second. This is much faster than gauges that people adapt using serial-to-USB connectors, which transmit at 10 samples/second. And, you don’t have to create a voltage offset table to scale the sensor so it transmits AFR correctly. AEM has done all the work already. The Bosch 4.9 sensor uses the factory resistor calibration, but you can also free-air calibrate the sensor using the buttons on the faceplate if you prefer.

If we use the analogy of digital photography, with higher resolution we get commensurately better detail and clarity of an image. The same can be said of AEM’s wideband controller as the “snapshot”  it takes of the air to fuel ratio is at the highest resolution available, giving a clear picture of the air to fuel ratio of the engine, not just at idle but when under load or during hard acceleration, part-throttle or full-throttle. Achieving good, reliable power is all about precision, and a high resolution wideband controller is the tool that’s going make air-to-fuel ratio nirvana happen.

Increased speed usually means increased costs. Every racer or performance enthusiast understands that. Going fast, or making power reliably doesn’t come cheap. The quality of wideband controller you select will be the most important decision you make. With that said, put the money where it matters and get the best sensors/controllers you can afford for your build. It will save you money in the long-run.


What’s In The Box? The AEM UEGO Wideband Controller comes with a full set of components to get you going: gauge, gauge faces – Lambda & air/fuel with a choice of colors including white faces and silver gauges, sold separately; wiring for power and light source to the gauge, long cable to attach to the sensor, Bosch 4.9LSU sensor, mounting bung and miscellaneous hardware.

Install Is Easy And Only Requires (Mostly) Common Hand Tools

Because everything is included with the kit, it’s simply a matter of attaching the sensor and plumbing the wiring and setting up the gauge.

Drill a hole for the bung near the receptacle for the factory 02 sensor. Now you're ready to weld in the bung.

First off, remove the exhaust manifold and disconnect the factory O2 sensor. Drill a hole in the exhaust manifold and weld in the bung–if you can’t do this your local muffle shop can help. Screw in the Bosch sensor to the bung. Be sure and position the sensor at a greater than 10 degree angle to prevent condensation.

Aside from some welding, the install is super easy. Right - You can see the two factory 02 sensors and where we installed the bung for the Bosch wideband sensor.

Wire the harness from the vehicle’s electrical system and connect it to the back of the gauge. Feed the long cable from the sensor through the firewall and plug into the the other gauge connection on the back of the unit. Position the gauge in the A-pillar or wherever makes the most sense or is easiest to read. The gauge comes with two thumbwheel screws to aid in securing to an interior surface.

We weren’t sure where we wanted to attach ours, so we used a cup holder until we decide where the gauge will live permanently.

NEW diagram

The Softer Side

Throughout this project we’ve been using HP Tuners VCM Suite to dial in the factory ECU with the help of Cunningham Motorsports. If you are not familiar, tuning on modern Corvettes like the C7 is flash-based. Installing performance “chips” on the ECU’s motherboard went out with the TPI and early LT1s. The HP Tuners proprietary scanner plugs into the OBD-II port and a Windows-based laptop with HP Tuners software. Tunes are downloaded, modified, and uploaded in this manner.

The scanner (MPVI) runs $349 for the standard version and $499 for the Pro version we have, which adds four external inputs. The standard version can be upgraded later, and both can be used on any number of cars. The software itself is a free download, however, to actually tune a car you must purchase credits. The scanner and credits can be purchased in a package or separately. There are quantity discounts on the credits, too.


With HP Tuners Pro MPVI VCM Suite package you can reprogram the factory computer, manually edit hundreds of performance parameters, and build custom tunes for maximum power. Plus, you can view, chart, and log data in real-time with any VCM Suite MPVI package or VCM stand-alone scanner.

With each passing year, HP Tuners is continually upgrading its software. By the time we did this install we were on version 3.0 but 3.4 is now out with expanded applications. The team of crack engineers is hard at work to often be first-to-market with new applications. The C7 and other direct-injection GM V8 engines utilize a brand-new ECU and programming that had new challenges for the team. Thankfully by this point we have the full range of capabilities for tuning any parameter we want – like shift points and firmness on the new 8-speed 8L90E.

Since C700 often sees daily driving duties and is modified beyond the point of a handheld tuner with canned tunes, HP Tuners was the natural choice. Aftermarket ECUs certainly have their place, but they often do not integrate with factory electronics – especially electronic transmissions like the 6L80E and 8L90E – and the C7 is chock full of that. Plus, the aftermarket is still catching up to the Gen V’s direct injection system and no solutions are currently available.

Whether you actually plan to do any hardcore tuning yourself, HP Tuners can be a wise investment for any owner of a highly modified vehicle. At the very least it allows you the option to datalog using the same software as your tuner, so you can send the logs and have them easily (and quickly) correct any of those difficult to replicate issues in the tune. Plus you can alternate between tunes for race gas or methanol injection. And if you feel a little more ambitious, you can recalibrate the speedometer for tire size or gear changes. You can also use the scanner and datalogger to read trouble codes and troubleshoot mechanical problems. HP Tuners software has plenty of drop-down sections with information to help guide you, but there are also classes available from third-parties to help you learn the software.

Now, On To The Tune
Once the AEM X-Series OBDII Wideband AFR Controller Gauge is installed, the procedure for accessing and logging the data in HP Tuners is quite simple as outlined in the above video (even for a novice tuner).

You are basically going to plug into the OBDII port, let the scanner look for the wideband, then search for the particular channel and add it.

Normally, Ryne Cunningham of Cunningham Motorsports would insert the wideband plug into the HP Tuners interface, which is also plugged into the OBDII port. Then he’d click “Add Channel” and go to external inputs where he’d open “MPVI Pro” and select “a/d input (1-4).

This adds the MPVI input to the PID list, which he would then right-click and select “transform.” This, finally, brings out a list of different sensors, where he would select “air-fuel ratio” and open another list of already setup wideband sensors such as “AEM 30-(03×0,2340,5130)” that needs to be selected to make it fully functional.

By the sound of that, no doubt, you can tell that wiring in through the OEM wiring and accessing the wideband through the OBDII port saves many of these steps.

Either way, you don’t need to be a software engineer to set up the wideband, says Cunningham. “The outputs are already available, so setting it up is pretty easy. There’s nothing custom. Everything is right in there.”

CMS screen grab

Once the wideband is successfully set up in the HP Tuners VCM Scanner, you will see “MPVI.1 -> AEM 30-(03×0,2340,5130)” along the lefthand side in the PID list and in the graph bottom right (second line in green). When the car is running you will see a value – at 5,106rpm C700 was at 12.11:1 air/fuel ratio. Some of you tuners out there might think that seems rather lean for a boosted car, but keep in mind this is a direct-injection engine.

“You definitely run leaner with DI, but not a full point [as some have said],” according to Cunningham. “I usually run around 11.8-12.0 with boost, but not 12.5.” Experienced tuners will also know that at idle, the O2 sensors oscillate and during WOT the air/fuel is much more steady (thanks to Ryne’s tuning). These trends are obvious in the data logs as you look at the line for the “AEM AFR.”

It is also interesting to note the comparison between TPS % and the AEM AFR, as the two move almost totally in sync at tip-in throttle in a fraction of a second.

Thanks to AEM’s patented digital wideband technology, which was independently tested to be the fastest responding wideband versus 17 other wideband controllers (you can see the test results on their website.) This is exactly what we mean about the X-Series wideband’s digital technology allowing the sensor to react so quickly, which will help you tune out those dead spots and hesitations from lean condition at tip-in.

Let’s face it, the art of EFI tuning is in eliminating these small issues that affect drivability. Transient fueling is one of the most difficult things to get right, so it helps to have good tools to work with from the start.


The advantage of having the AEM wideband plugged into HP Tuners is that you can data log and make changes within the same software. One of the other things you will notice in the PID list of the screenshot from Cunningham is the Equivalence Ratio (this is another term for Lambda).

By logging the wideband in Equivalence Ratio you can overlay the observed air/fuel ratio with what was commanded, then make changes to the MAF or VE tables according to the percentage difference like you would with a complete aftermarket EFI system. This takes tuning beyond the guess and see method of looking at the dyno’s AFR readings and making an arbitrary estimation of change. The end result is a game-changing level of precision.

As we continue to flog our ProCharged 2015 C700 Stingray, we will be able to do so with the confidence that we can keep an eye on perhaps the most critical indicator of our LT1’s health. These new Gen V direct-injection engines are known for two things in the aftermarket: limitations in fueling and false knock.

The former stems from the lack of aftermarket support in fuel injectors and pumps. The only parts available are the LT4’s mechanical fuel pump and the various fuel pump lobes on aftermarket camshafts that drive it – all the more reason to keep a close eye on the air/fuel ratio. Since fuel can only be sprayed within a short window of time with direct injection (instead of sprayed at the back of the intake valve for infinity), injection timing also factors in.

“When you are pushing the limits, injection timing tends to get close to ignition timing. That’s when a lot of problems happen. As long as you have enough volume, you are pretty good.” As for false knock, “the C7 computer works off calculated torque, so it picks up false knock quite a bit more. I have to crank up the sensor threshold to combat that,” said Cunningham.

The horse has been beat to a pulp, yet we must repeat: fueling is even more crucial when you have decreased the sensitivity or reaction from the knock sensors. You don’t want a slight ping to turn into a big KA-POW. A fast reacting wideband like the X-Series will help the tuner eliminate lean spots in transient fueling that would cause detonation and subsequent carnage.


Your tuner has much to assess when you bring your car in. Sending him logging data before hand puts you ahead of the game.

Even if you do not do any tuning yourself, owning the AEM X-Series wideband is an extremely valuable tool in getting critical information to your tuner. “I like having them on customer cars because they can send me a log,” said Cunningham.

Because a tuner can not drive your car in literally all situations before completing the tune, it happens quite often in highly modified cars that a few spots in the tune need to be cleaned up. If you do not have HP Tuners, you can use AEM’s proprietary free software (AEM Data).

Alternatively, you can use another type for programming software, a standalone ECU with logging capability or AEM’s AQ-1 data logger, which has free set up and analysis software that can be downloaded from their website. They even have an OBDII version of the AQ-1.

If you are utilizing fuel types other than gasoline, E85 or methanol for example, you will want to make sure you are looking at Lambda (not AFR), which you can match to the gauge display by flipping the faceplate. Displayed AFR is a calculation based upon the stoichiometric mixture for gasoline (14.65:1). The stoichiometric mixture, if you are not familiar, is the ratio in which 100% of the fuel is consumed in combustion.

With Lambda, the stoichiometric mixture is always 1.00, no matter the fuel type. For example, if we decided to run E85 on Project C700, we’d want to keep the Lambda at close to .833 as you see in this log, even though the quantity of fuel injected would be much higher.

One bit of warning, though, Cunningham did note it is important to let the sensor warm up for 10-15 seconds. Otherwise it could damage the sensor. Leaded fuel, oil, and coolant are just a few other things that can damage wideband O2 sensors. Since race fuel often contains lead, most racers just replace them over time. Especially after some catastrophic failure.

Having the ability to free air calibrate the sensor using the faceplate buttons on the X-Series Wideband is beneficial if you are at the track with an older sensor and want to verify that it is reading properly.

The AEM X-Series OBDII Wideband AFR Controller Gauge is a great tool not only for a tuner savvy owner, but also a great way to log a valuable data channel that can be viewed and logged in your HPTuner’s software or transferred to an experienced tuner.

When tweaking the parameters of your engine, having an accurate assessment of what’s  going with your mill is crucial and AEM X-Series Wideband Controller is the best, most accurate wideband on the market today.

For more, check out AEM and stay tuned to Corvette Online for additional mods to our C700 project car.


Article Sources

About the author

Dave Cruikshank

Dave Cruikshank is a lifelong car enthusiast and an editor at Power Automedia. He digs all flavors of automobiles, from classic cars to modern EVs. Dave loves music, design, tech, current events, and fitness.
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