AEM Infinity ECU E46 M3 Standalone Programmable ECU

It wasn't so long ago that the BMW performance community rejoiced at the advent of the first handheld tuning devices that allowed enthusiasts to install previously uploaded software from the device into their ECU. While this was a step forward, the software was only as good as the pre-loaded, generalized maps.

As we know, not all modifications were created equal and generalized maps can leave power on the table if they don't account for all your hardware. For instance, if the handheld tuner had a map for "M3 bolt-ons," it would need to work with all bolt-on combinations in every geographic location and all grades of gasoline. So how can one pre-loaded map work for all scenarios? It's generally a conservative tune to improve performance over stock for most cars in most situations. Specifically, ignition timing and cam timing are dialed back and the air/fuel ratio is richer in the name of safety.

So what about the enthusiasts who want to maximize their engine output for the utmost performance?

Next came expensive universal standalone computers and ECU reflashes. Both were steps in the right direction but neither was perfect. The stock E46 BMW M3 ECU, for example, has a flash-life of about 15 flashes. So once you reach your last flash, the ECU is ruined - an expensive proposition at about $1500 to replace it.

Most universal standalone ECUs, while delivering increased tuning control and flexibility, require additional wiring and, in many cases, need an experienced tuner to create the base maps to run the engine.

Time and technology marches on and, thanks to companies like AEM Electronics, E46 M3 fanatics can have their cake and eat it too.

"We wanted to create a plug-n-play standalone ECU that could snap into place, mounted in the stock ECU location, that would work with the car's CAN-BUS system (Controller Area Network) to control everything the stock ECU can and more," Lawson Mollica from AEM Electronics said.

Yes folks, welcome to the next BMW tuning revolution: the AEM Infinity plug-n-play, standalone, programmable computer for the E46 M3.

According to Lawson, the mission was simple: spend the time to create the correct device for owners of track-driven E46 M3s who wanted full tuning control, including the VANOS, drive-by-wire (DBW), timing, fuel trim, and something that can communicate with the CAN-BUS system.

It was only natural to focus their attention on the E46 M3 because AEM is run by gearheads who, like us, understand the third-gen M3 is the performance bargain of the century. But before we delve into AEM's super-computer and its installation, we should explain it was designed for "off-road use" only. It hasn't been approved for street use, so if you run it in your road car, you do so at your own risk. And while it might mount in the stock location and is virtually undetectable, AEM emphasized that it's not street-legal.

Not just for race teams

"ECU reflashes have their place in the industry, but they're $400-500 a pop and after 4 or 5 updates over a couple of years to keep pace with new mods, the cost adds up. Then at some point you'll run out of flash-life, and after that your OEM ECU will be toast," Mollica explained.

So if you're continually tweaking your M3, you can spread the cost over a series of flashes or simply opt for the Infinity up front. But if you opt for the flashes, eventually replacing the stock ECU isn't cheap.

But enough about the dollars and cents, what really matters are the Infinity's capabilities, where even cars with bolt-ons should see significant power gains when making the switch. "We have full control over the VANOS system, which gives tuners the ability to tweak the cam timing to build lots of cylinder pressure. This should result in massive under-the-curve gains with nice increases at redline as well," Mollica said.

Having control over the VANOS should mean more power everywhere. Don't believe us? Look at the accompanying dyno graphs from the FSR Motorsports-tuned GoGoGear.com/UTI S54-powered E90 Pro Touring Car entered in the USTCC and WTC series last season.

This racecar used a virtually stock E46 M3 motor yet saw gains of 17hp and 18 lb-ft at the wheels over the stock ECU, simply because FSR was able to maximize the cam and ignition timing as well as the air/fuel ratio (AFR).

Power & adjustability

The AEM engineers took advantage of the processor and packed it full of items like wideband oxygen sensors and CAN-BUS technology. This means the ECU communicates with the OEM systems to add unique features like drive-by-wire and programmable outputs.

"The E46 BMW M3 was never known for its part-throttle drive-by-wire mapping. The engine is best at wide-open throttle (WOT), so we spent a lot of time working with part-throttle tuning on the base map," Mollica said.

In "Normal" mode, the throttle response is better than stock, but poke "Sport" mode for heightened throttle mapping and it comes alive. This is all thanks to the Infinity's full control over the factory drive-by-wire system.

"We also incorporated a three-step launch control system, a two-position user-defined traction control and an eight-map toggle system that allows drivers to switch between multiple maps based on boost, lambda and ignition targets, multiple VE tables, blended maps for cam position and gear, or flex fuel ignition and more," Mollica said.

All of these CAN-BUS features are controlled from the factory buttons on the E46 M3 steering wheel, which means you can toggle between "rain" or "dry" traction control settings on the fly, dialing in your preferred launch control setting for the road conditions.

Having multiple rev limits also comes in handy for burnouts at the strip, or you can set a pit-lane speed limiter at racetracks where speed is strictly enforced.

VE tuning

The accurate 3D ignition maps and individual fuel trims are impressive, but what most tuners will enjoy is that AEM uses volumetric efficiency (VE) as the basis for the tuning. "VE is extremely quick and effective for tuners because we did a lot of the hard work and calculations with our S54 base map," Mollica continued.

In basic terms, VE is the amount of air your engine will move. The easy-to-use software prompts the user to calculate the injector size, desired AFR and engine's airflow; the computer then calculates the rest. This means less tuning, resulting in less dyno time and the opportunity for owners to tune their own vehicles.

In all honesty, we could write an entire article on the inner workings of the Infinity and how it turns numbers into horsepower from its algorithms, but know this: it's as thorough as standalones get.

Safety

Let's start with the failsafe systems. The trigger can be based on oil pressure, fuel pressure, air/fuel ratio, overboost protection along with a lean rev limiter, a lean ignition or fuel cut. Users can set the failsafe to trigger under defined conditions, like oil pressure or AFR against RPM, or even coolant temp against RPM. The latter can be set to prevent over-revving when the engine is cold, or activate a lower rev limit when it's too hot.

Like AEM's wideband failsafe gauges, the AFR failsafe feature on the Infinity can be set to trigger against RPM, throttle position or boost/vacuum. This means it won't false trigger under part-throttle settings where AFR can fluctuate.

The knock-control feature is equally sophisticated thanks to a system that uses a tuned microphone to monitor individual cylinders. The knock systems of old could easily be triggered by a noisy valvetrain or loud noises, but not the Infinity's. With enough tuning, the user can precisely identify the exact frequency of a knock and set the computer to recognize it like an OEM computer. The Infinity also has a self-diagnosis protocol to allow users to perform systems checks on all the sensors and parameters like an OEM unit.

We shouldn't forget the system is compatible with flex-fuel sensors as well. So switching between E85, pump and race gas won't require any changes on the driver's part because the sensor detects the fuel and automatically switches maps.

Other noteworthy features include wet and dry nitrous injection control, multiple boost control strategies, coolant temperature-based idle control for smooth idling regardless of ambient temperature, and lightning-fast data logging that can log an impressive 1KHz per channel.

Harnessing the power

The harness itself features high-grade insulated cable built to withstand heat, while the connectors are weather-tight.

The optional AEM sensors are top rate. Take the manifold air pressure (MAP) sensor, for example. It replaces the restrictive factory HFM sensor (BMW's mass-air sensor) so users can swap the HFM for a straight-pipe to improve airflow.

Note: AEM doesn't bundle the ECU, harness and connectors since one size doesn't fit all. Instead, you choose the best parts for your car.

"We worked really hard to ensure the hardware was as good as the software, because the ECU needed to fit like factory, be able to be removed or installed in under 30min and withstand the rigors of racing," Mollica said.

Testing

According to Sai-Ngarm, the Infinity's tuning capability really shines under the heavy restrictions of motorsport classes. "We know we can't increase power significantly because we'll get weight penalties, so we had to retain restrictive things like the OEM manifolds, catalytic converters, intake manifold and air box. Yet we were able to take advantage of the Infinity's incredible throttle mapping as well as multiple ignition and fueling maps to maximize traction in all conditions. So if it's slipping on corner exits, we can dial back the power based on throttle position, then ramp it back in under WOT. Or if traction is good, we can give it everything. So whether I'm working on the racecar or a 700whp E46 M3 turbo, the Infinity is a nice addition," he said.

Supreme adjustability is obviously part of the attraction, but what else makes the standalone unique? "The two onboard Lambda (wideband oxygen) sensors can each be set to run half the cylinders like the OEM setup. This delivers better consistency, economy, power and reliability because the S54 is sensitive to AFR, especially with forced induction. So we now have supreme control," he explained.

He also liked the speed of the processor, the ease of installation and removal, its many failsafes and other details like its integration with a Racepak Dash. But he felt its VE-based tuning was a huge attribute over traditional pulse-width setups. "I like tuning with VE. It's much easier. There's a reason why OEMs use VE: you simply enter the parameters and let the ECU handle it. From there you make the finite changes.

"Once VE is calculated, if you change the injectors or fuel, all you need do is update the specs in the Wizard (AEM's software) and it'll do the rest - there are no trims, so altitude, temp, cold start, etc, aren't affected," he explained.

Before wrapping up with Sai-Ngarm we asked for his final thoughts on the Infinity. "When we first started tuning BMWs, we were told there wasn't a lot of power to be had from the VANOS, but we knew that wasn't the case since the S54 has more than 50? of cam timing adjustment. We felt it only needed an ECU that could control the VANOS accurately, quickly and precisely to fully exploit it.

"Because our S54-powered E90 racecar was limited to low-quality fuel and factory smog equipment, it gave us the opportunity to spend time dialing the VANOS for optimum performance. After exhaustive and incremental tuning of the entire VANOS map, I couldn't be happier. The way you roll-in the intake camshaft makes a huge difference to power against throttle position as you drop the hammer. Sure, you can fix the intake camshaft to make the most power during a dyno pull, but by adjusting the way the camshaft advances or retards based on throttle and RPM, it fattens up the power curve.

"Interestingly, many people also said exhaust cam timing had little to do with S54 power, and while this is true of some engines, the S54 does benefit from exhaust cam adjustments, although it's in a very tight range. In this case, there was a 4-6? window where we picked up almost 10whp across the range. Any futher and it lost power. On turbo cars, being able to adjust the cam timing has helped us resist detonation, which is always a problem with high-compression turbo cars on pump gas," Ian concluded.

A new era

Admittedly, a standalone ECU isn't cheap, but neither is flash tuning over time. And when you consider the possibilities that a new ECU can unlock, it could be money well spent. Welcome to the new era of E46 BMW M3 tuning.