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

In the past, expensive and complex standalone ECUs were used almost exclusively by dedicated racecars with highly tuned motors. However, there's also another scenario. Remember earlier when we mentioned the E46 M3 ECU has a flash-life? So if you plan to keep your E46 M3 for the long haul and intend to continually mod it, the AEM Infinity might be more cost-effective than you'd imagine.

"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 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

Comparing the stock E46 M3 ECU to the AEM unit is futile because the Infinity's processing speed is lightning fast thanks to a 200Mhz processor capable of 400MIPS (millions of instructions per second). In fact, AEM claims it might be the fastest aftermarket ECU available.

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 CAN-BUS compatibility and DBW communication is amazing, but full control of the dual VANOS is even sweeter because it allows you to tweak camshaft timing to build power. "Without the ability to alter the cam timing, tuners will reach a power limit but we've seen highly tuned bolt-on cars pick up an extra 10hp up top and more in the middle from cam-timing tweaks alone," Mollica explained.

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.

By Justin Fivella
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