At the 2007 Frankfurt auto show, German automakers had hybrid cars and concepts on display. Up until now, European automakers seemed uninterested in employing hybrid technologies, but Mercedes-Benz, BMW, Porsche, and Audi have all stepped up to the plate. Mercedes-Benz has an actual hybrid SUV ready for production, while the other automakers have concepts that strongly indicate future hybrid powertrain development.
Wayne Cunningham
Wayne Cunningham reviews cars and writes about automotive technology for CNET's Roadshow. Prior to the automotive beat, he covered spyware, Web building technologies, and computer hardware. He began covering technology and the Web in 1994 as an editor of The Net magazine.
BMW built its hybrid system into its new X6 concept vehicle. BMW refers to the X6 as the first-ever Sports Activity Coupe, although we count too many doors to call it a coupe. The X6 is supposed to be what you get when you mix a BMW sport coupe with a BMW X-vehicle. Given the current trend in crossovers, there is momentum for BMW to bring the X6 to production. The ActiveHybrid version of the X6 is supposed to get 20 percent better fuel economy.
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BMW has been working on its Efficient Dynamics program for many years, but the X6 ActiveHybrid represents a concrete step towards a production car. The car uses the two-mode hybrid system jointly developed with Daimler-Chrysler and GM. We've driven a Chevy Tahoe with the two-mode hybrid system, and it works as well as, if not better than, Toyota's system. BMW hasn't offered engine specs for the X6 ActiveHybrid, but a 3-liter straight six is a safe bet.
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Another product of the two-mode hybrid joint development program, Mercedes-Benz builds the system into its ML-class. Unlike the other cars here, Mercedes-Benz promises the ML450 hybrid will come on the market in 2009, potentially making it a 2008 model. At the same time, Mercedes-Benz will bring out a hybrid S-class, which could be the first sedan to use the two-mode hybrid system.
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As evidence of how close this vehicle is to production, Mercedes-Benz has already designed and implemented the power flow diagrams that show when electricity is being used or generated. The two-mode hybrid system is designed to use a continuously variable transmission at low speeds, and fixed gears at high speed or heavy load. When starting out with a light touch on the accelerator, the car runs under electric mode to as fast as around 30 mph.
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As implemented in the ML450, the two-mode powertrain is made up of a 279 horsepower V-6 and a hybrid module with two electric motors that produces 61 horsepower, making a combined 321 horsepower. Mercedes-Benz claims the ML450 should get 31 mpg, an impressive feat for an SUV.
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Porsche promises the Cayenne hybrid will be available by the end of the decade. The company is already testing prototypes of this car, using a hybrid system developed independently. Porsche can claim a lot of history with hybrids, as Dr. Ferdinand Porsche built a hybrid car in 1900.
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For this effort, Porsche designed a parallel hybrid system, which can run the car under electric power at speeds of 75 mph. The Cayenne hybrid's powertrain is made up of a 3.6-liter engine, a 38-kilowatt electric motor, and a 288-volt battery pack. Porsche claims current test car mileage of 24 mpg and is working to get that up to 26 mpg.
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Audi forgot to put a car on its hybrid powertrain, but still displayed its work to date. Similar to Porsche, Audi is developing a single-shaft parallel hybrid, with the motor between the engine and transmission. Audi suggests one configuration could use its 2-liter, turbo four-cylinder engine, producing 210 horsepower, a 32-kilowatt electric motor, and an eight-speed automatic transmission. Audi offers no dates when this hybrid could go into production.
