Monday, June 7, 2010

BMW ActiveHybrid 7

The new ActiveHybrid 7 is part of BMW's new line of hybrid cars. Unlike the more complex dual-mode system in the ActiveHybrid X6, the 7's system is designed to get the most from hybrid technology's ecological and fuel economy advantages while reducing the power, weight, and space penalties of more complex systems.
BMW ActiveHybrid 7
BMW ActiveHybrid 7

As a result, the car is only 165lbs heavier than a normally equipped 7, and the lithium ion battery takes up only 1.4 cubic feet of trunk space. However, this limits the system's electric capabilities. While the X6 has two large motors that can push the car on electric power alone at low speeds, the 7 makes due with a single small motor and cannot move without using the gas engine.

The 8-speed ZF transmission is the same as found in the regular 7, but a smaller torque converter and higher gear ratios have been fitted to take advantage of the electric motor's low-speed torque. The motor itself sits between the engine and transmission adding 55 hp and 65 ft-lb torque for a total of 440 hp and 455 ft-lb torque when combined with the car's twin turbo V8. While it shares this engine with the regular 750, the ActiveHybrid can reach 60 mph half a second faster than its non-hybrid stablemate. EPA figures have not yet been released, but it's expected that this car will get 15% better fuel economy than base 7.

The gas engine runs when the car is first started, allowing start-stop mode only once the car has moved. The switch between regenerative and friction braking is seamless, something rarely seen in even the best hybrids. When this happens, the tach turns blue, indicating power regeneration instead of revs.

Unlike other hybrids, exterior cues identifying this model are limited to special aerodynamic wheels and a small "ActiveHybrid" badge on the rear. A new electric air conditioning system has been added with coolant lines running to the battery to keep it cool while also keeping passengers comfortable while the gas engine is off. Oddly, the ActiveHybrid doesn't have electric power steering. Whenever the wheel is turned, the engine has to start up to provide power for the steering pump, using fuel and giving a brief feeling of heaviness to the wheel.

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