BY ALISA PRIDDLE
BMW is back with another rendition of its ActiveHybrid system—this time in its flagship 7-series—with the world debut of the BMW Concept 7-series ActiveHybrid in October at the 2008 Paris auto show.
The automaker pairs the car’s twin-turbo, direction-injection, 4.4-liter V-8 engine with an electric drive for what is known as a mild hybrid—meaning the car cannot operate on electricity alone. Rather, the electric motors reduce fuel consumption and emissions—BMW claims by 15 percent—through such means as an automatic start-stop function that turns the vehicle off when it otherwise would be idling.
The idea is to make the car more efficient without compromising performance. The conventional version of the new 2009 7-series with the V-8 offers 400 hp and 450 lb-ft of torque and BMW says that is not diminished—in fact, the 20-hp electric motor will boost acceleration. Combining the two powertrains should produce about 415 hp and 605 lb-ft of torque, we are told. Channeling the power is an eight-speed automatic transmission.
Energy captured in brake regeneration will be used to power many of the car’s features, leaving the fuel free to make the car go fast. BMW says enough energy can be stored to power substantially more electric components than in past vehicles—which seemingly makes it possible for an endless list of creature comforts. The energy is stored in lithium-ion batteries that are located in a trough in the trunk.
The components of the mild hybrid system come from a cooperative effort with Daimler. BMW first showed the fruits of these labors in the X5 Vision unveiled at the 2008 Geneva auto show. Mercedes introduced similar technology in Geneva with the Vision GLK BlueTec and S400 mild hybrid concepts.
Each luxury automaker insists its individual systems have been tweaked to reflect their brand images—a claim we’ll need to verify when we can drive their respective vehicles. A BMW source says the two automakers pooled their efforts for the first two steps of the development of the shared technology, at which point the work veered off in brand-specific directions. “Now we are at the fifth step of the technology,” he says. The source says BMW is using the technology to improve dynamics and performance, while Mercedes views the system as a means for better energy management—a claim Mercedes may or may not dispute.
Hybrid 5-Series Expected, Too
The mild-hybrid project is not part of a larger collaboration of BMW, Daimler, Chrysler, and GM to develop a full or two-mode hybrid system that can power a vehicle on electricity alone. BMW is more likely to put the two-mode system in its utility vehicles, such as the Concept X6 ActiveHybrid while the mild hybrid system is expected to make it into the next-generation 5-series.
The 7-series hybrid concept follows the design direction of the new 2009 sedan. Specific to the hybrid concept is an aluminum dam that stretches across the front end to control air flow for better aerodynamics. The lower air intake is partially covered by the dam. To bookend the look, a similar strip is integrated into the rear and accentuates the wide, flat shape of the tailpipes. The car is dressed with 20-inch alloy rims with a V-spoke design.
BMW says two models with the mild ActiveHybrid system will go into production in 2009, which we expect to be the 7-series and 5-series. Even though BMW showed the system in the X5 Vision, it coupled the electric motors with a four-cylinder turbo-diesel, and officials tell us they likely won’t offer an expensive mild diesel hybrid, nor does BMW see enough benefit of a hybrid system with a smaller engine (gasoline or diesel).
