BMW comes up with a pair of 7s

BMW shows its new 740i and ActiveHybrid 7 at the 2010 Detroit auto show.

2011 BMW ActiveHybrid 7
The powerful ActiveHybrid 7 showcases BMW's hybrid technology. Sarah Tew/CNET

DETROIT--With Europe clamping down on CO2 emissions and Americans wanting to pay less at the pump, it would seem that big, luxury sedans would lose popularity. But BMW offers a couple of choices to keep its flagship 7-series sedan in favor. The company showed two new versions at the 2010 Detroit auto show, one with reduced engine size and a mild hybrid.

The new 740i marks a return to when the 7-series was powered by a mere 6 cylinders, rather than the 8 and 12 of recent years. But this car is no slouch, as its engine is a similar twin turbo 3-liter inline six that powers the 135i, 335i, and 535i, all very capable cars. In the 740i, that engine means 0 to 60 mph in 5.7 seconds. BMW hasn't released EPA mileage figures yet, but the 740i goes on sale this spring.

The ActiveHybrid 7 is much more complicated, and more powerful, than the 740i. With system output of 455 horsepower, it hits 60 mph in 4.7 seconds, making it the fastest hybrid in the world. BMW's hybrid system uses a small electric motor between engine and transmission, getting power from a lithium ion battery pack. This motor gives the twin turbo 4.4-liter V-8 a little extra boost, but, more importantly, enables a start-stop function. BMW claims 15 to 20 percent better mileage than the 750i. The ActiveHybrid 7 goes on sale in the second quarter.

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