BMW’s Scorching New M3 Has Hybrid Side – Sort Of
August 14, 2007

By Bill Visnic

Over at Edmunds.com’s Inside Line, they’re in a lather about the sizzling performance of BMW’s all-new M3, which marks the first time the company’s famed Motorsports Division-tuned 3 Series has used V8 power.

But down deep in the specs for the 2008 M3’s new 420-horsepower, quad-cam 4-liter V8 is a nod to environmental awareness that portends of a coming trend: an innovative energy-management system that enables BMW to subtly eke out a little extra fuel economy without looking like an eco-weenie in front of the autobahn performance gods.

BMW calls the system Brake Energy Regeneration. And although this sounds a lot like the “regenerative braking” we’re always hearing about with “full” hybrid-electric vehicles, such as the Toyota Prius, the Bavarians’ BER system is much more a variation of the “mild” hybrid theme we’re going to be hearing more about in the coming months.

AutoObserver is told several automakers and major suppliers plan to unveil a host of similar new mild-hybrid components and systems at September’s Frankfurt Motor Show. Fuel-efficiency and reduction of carbon-dioxide emissions (cutting CO2 is Europe’s persistent bugaboo) are expected to be headline themes at the Frankfurt confab. These new innovations are geared toward delivering hybridlike benefits at a more palatable cost.

The BER system, says BMW, is part of its Efficient Dynamics engineering initiative that seeks to optimize how energy is used by the engine and various components throughout the vehicle. In the case of the M3’s new V8, the BER system hinges on an electronically controlled alternator and a special battery.

The typical alternator is driven by the familiar belt we all see at the front of the engine. The belt is itself turned by the engine crankshaft. A conventional alternator –- a generator, actually, that keeps the battery charged and supplies power for the vehicle’s electricals –- always is running, and the drag saps power from the engine, leaving less of the fuel’s energy for propelling the vehicle.

The problem is, most of the time your vehicle doesn’t require anything near the alternator’s full output -– so it’s spinning away, wasting fuel to generate electricity you don’t need.

The electronically controlled BER alternator, however, runs only when engine power isn’t required to motivate the car -– usually, when braking or coasting, BMW says. When electricity isn’t required, the alternator is switched off via a clutch, reducing the drag on the engine, which boosts fuel economy.

Or leaves more power for turning the wheels, the part the performance fanatics will appreciate.

The system also uses BMW’s new Absorbent Glass Mat battery, which is “able to handle far greater loads than conventional lead acid batteries. An AGM battery holds the acid content in microglass-fiber mats between the individual layers of lead, thus retaining its ability to store energy even when charged and discharged frequently,” says BMW press material.

Throw in a special sensor and some software that always monitors and optimizes the battery’s state of charge, and you’ve got what most hybrids really are all about: harnessing energy normally wasted by most vehicles.

BMW hasn’t yet quantified just how much fuel BAR is expected to save, but says it “developed Brake Energy Regeneration for petrol and diesel engines of any size, regardless of engine capacity and number of cylinders. This ensures that this innovation will be available to all (model lines) early on and that as many customers as possible will be able to profit from its benefits, leading to a positive effect on the fuel consumption of the entire fleet.”

Although it’s a part of the M3’s hot new V8 recently launched for the press in Europe, a BMW North America spokesman says the BAR system’s first application came earlier this year for European-specification 5 Series models. The spokesman cannot yet say whether or when U.S. versions of the M3 (hitting America later this year) or other U.S.-spec BMWs will offer BAR.

BAR notwithstanding, you’re not likely to see any new M3s parked in front of the Sierra Club’s headquarters: the M3’s fuel economy, measured on the European urban driving cycle, is 13 mpg -– although highway economy is a less-scandalous 26 mpg.

About the Author

Bill Visnic is a nearly 20-year veteran of automotive journalism. He started at Car & Driver magazine, spent 13 years covering automotive technology for the Ward’s Automotive Group, and now is one of the press corp’s leading authorities on automotive powertrains and technology.

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