BMW has released the details of its flagship 7-Series saloon which will go head to head against arch rival Mercedes S400 BlueHYBRID, unveiled last week. The 7-Series concept hybrid follows the previous Vision EfficientDynamics diesel hybrid based on the X5 and concept X6 ActiveHybrid showin in 2007.

The BMW Concept 7-Series ActiveHybrid is based on the 4.4 L V8 750i model unlike Mercedes S400 which is based on a smaller 3.5L V6 powerplant. The 4.4L V8 produces 407 bhp and is mated to an electric drive motor with 20 bhp and 210 nm of torque. The car features the ’standard’ hybrid features like regenerative braking system, efficient aerodynamics, auto start-stop function and will also feature the same efficient Lithium-ion batteries like the big benz.

BMW claims the new ActiveHybrid will improve the economy by upto 15% while Mercedes claims a more substantial 21% improvement in economy with is BlueHYBRID S400.

The new 7-Series hybrid will go on sale late next year and features BMW’s version of the modular two-mode hybrid system with twin electric motors located with in the transmission which reduce drag from auxillary components like the starter motor and the alternator.  The system provides electric only propulsion at low speeds and performance ‘boost’ at high speeds and has been  jointly developed with Daimler, Chrysler and GM.

Jump over for the BMW Concept 7-Series ActiveHybrid gallery.

Gallery: BMW Concept 7-Series ActiveHybrid