When Daniel Wennerberg was preparing his BMW E46 M3 to compete at the NASA National Championships, he went beyond the stock engine management system, installed the new AEM Infinity system, then took it to AEM headquarters in Hawthorne, Calif., to dial it in.
Wennerberg, who owns BMW specialist shop Pure Performance Motors in Laguna Hills, Calif., wanted the car to make all its power below the factory redline, to get the most of out of the engine while decreasing the load on the rotating mass.
Using the Infinity software on their laptops — called InfinityTuner Wizard — they were able to alter the cam timing to make the horsepower and torque peaks earlier. Infinity can control the timing of up to four cams. AEM engineers set up the power curve just the way he wanted it. InfinityTuner Wizard shows it all graphically and numerically on its many user screens.
“Those plot windows, they scroll,” said Tyler Hara, engine management systems engineering manager for AEM. “This is like an EKG. This is just data going by. This is a snapshot in time. You can see where he shifted gears and that’s the beginning of the dyno pull.”
According to AEM literature, “The Infinity EMS represents a quantum leap in technological capability over virtually all existing programmable engine management controllers available today and eases the tuning process for even the most sophisticated engine combinations. It is quite possibly the most advanced programmable engine controller available.”
The system allows tuning based on volumetric efficiency using airflow calculation models. Although Wennerberg’s car runs on regular old race gas, the Infinity system compensates for flex fuels and handles multiple-fuel strategies. Hara explained tuning based on volumetric efficiency this way: A perfectly efficient 3.0-liter six cylinder would draw a half a liter of air per cylinder on the intake stroke. That would make calculating how much air and fuel to deliver a snap at 14.7:1, what’s called the stoichiometric ratio. Real engines, however, are not perfectly efficient.
“So what we’re assuming is, if this is a half-liter cylinder, if it were perfect wide-open throttle, we’d match the proper amount of fuel to that half liter,” Hara said. “In reality, though, there are restrictions in the system. There’s your throttle blade, there’s your valves, the camshafts opening and closing valves, so within that half a liter, you’re actually pulling kind of a vacuum.
“I like to think of it like a big syringe,” he continued. “If you pull a syringe real quick, it’s kind of springy because you’re pulling a vacuum inside there. If you pull it slowly, and leave it at the bottom, then you’ll have it at full volume at perfect air. In reality, there’s a restriction, so that’s what volumetric efficiency is, what percentage of that half liter do we have? Is it 100 percent? Is it 90 percent? At idle when the throttles are closed, it’s much lower, about 60 percent. It’s a measure of how efficient the engine is at filling that swept volume.”
The Infinity controller measures the air-fuel ratio through its dual internal wideband controllers, a technology in which AEM has been an industry leader for more than a decade. But that’s just a portion of what the Infinity can do. For example, it has 100 channels of data logging with playback and controls synchronization.
It will power up to 12 peak-and-hold injector drivers and 12 ignition coil igniters. It can process up to six analog temperature inputs, up to 17 analog voltage inputs and two knock sensors. It has inputs for two knock sensors, up to eight digital inputs, six VR/Mag inputs and up to 13 configurable outputs. It even can control one or two drive-by-wire throttle bodies and includes auto calibration for DBW sensors.
So, with all that capability, is it possible to control the air-fuel mixture down to the nearest tenth at any given rpm range?
“You sure could,” Hara said. “We control the fuel injectors, how long they stay open and what the fuel pressure is behind them. We can then target that ratio, whether it’s 14.7:1, 12.5:1, anything.”
The Infinity ECU calculates injector pulse width in units of one tenth of a microsecond (0.0000001 second). Individual cylinder fuel trim is included and user adjustable versus engine rpm. It’s also compatible with most factory and performance aftermarket sensors, and includes a two-channel controller area network. What that means is you can program functions into a vehicle’s OEM controls.
On our visit to AEM for Wennerberg’s dyno tuning, AEM’s marketing and PR director Lawson Mollica showed us a E36 M3 road car in which they were installing an Infinity system, which uses the steering-wheel-mounted cruise control buttons to switch back and forth between street and track tunes. Pretty slick.
As slick as the engine management system is, the software you use to program it is equally cool. For example, its airflow model based systems greatly reduce the amount of time it takes to set up and tune an engine by eliminating many of the lookup and correction tables necessary in previous generation ECUs.
InfinityTuner software features several three-dimensional ignition trim maps based on coolant and air temperatures, and its back-end timing code is tested to 100,000 rpm. Individual cylinder ignition trim is included and is user adjustable versus engine rpm. The system is incredibly detailed and technical.
“When it comes to the tuning, you’ve really got to know what you’re doing,” Mollica said. “They understand this, so they’re able to take this and take your vehicle and get it to perform the way you want it to and set it up with all the features.”
In truth, the Infinity does a lot more than can be explained in a magazine feature. It’s a hugely powerful system. AEM’s website provides resources for finding authorized dealers and knowledgeable tuners who can work with the sytem.
Wennerberg got his M3 dialed in and trailered it to the National Championships two weeks later. So, how did he do? He scored a second place podium finish in GTS4 and ST3.
“This is a really powerful tool for you to be able to achieve maximum performance from what you’ve done to your vehicle,” Mollica said.