BMW has just pulled the sheet off their latest creation, the 2010 BMW ActiveHybrid 7, in anticipation of its debut at the Frankfurt Motor Show in September. The vehicle represents a fairly typical BMW approach to the idea of a hybrid, to the point that calling this car a “hybrid” isn’t really fitting. Instead, let’s consider it a high-performance luxury sports car that has a range of efficiency options installed.
The heart of the ActiveHybrid 7′s drivetrain is a 4.4-liter V8 engine affixed with two turbochargers, same as the standard 7-Series models. At the back of the engine there is a small electric motor/generator squeezed between the engine block and the transmission, resulting in a combined power rating of 455 horsepower and 516 lb-ft of torque. This results in what’s called a “mild” hybrid system. A “full” hybrid, like the Toyota Prius, has electric motors onboard that can drive the vehicle under purely electric power, which is then aided by an internal combustion engine when the power runs out. The BMW system, developed in cooperation with Daimler (who own Mercedes-Benz), takes a different approach.
The bulk of the 7′s motive power comes from the V8 (the electric motor is only rated at 15 horsepower), with the addition of the electric motor being precisely controlled via a computer. This computer analyzes fuel consumption and then determines when adding an electric boost would be most valuable. The real genius of this system isn’t in its motive power, but rather its braking power. When you take your foot off the accelerator or apply the brake, the electric motor begins to act as a generator. Essentially, it causes a braking force on the engine’s output that generates electricity (which is fed into the lithium-ion battery) and also slows the car. The idea is that when you apply conventional brakes, you are essentially wasting energy. You spent the fuel to accelerate, and now that fuel is wasted because your speed must decrease. This regenerative braking system is designed to counteract that.
Also contributing to the 7′s efficiency claims is a Start Stop engine system. Whenever you’re sitting at a stop light, the engine turns off. A computer remembers the exact cylinder position (contributing to near-instant restart times) and when you place your foot on the accelerator, the electric motor acts as a starter, turning over the engine.
None of these technologies is particularly revolutionary. The Auto Start Stop has been found in other car offerings for a year or more. The regenerative braking system was taken from BMW’s Formula One car (where is was called KERS, for Kinetic Energy Regeneration System, and controversy over the system helped lead to BMW’s recent withdrawal from the race division). And “mild” hybrid systems have been around for a bit, as well. What makes the ActiveHybrid 7 special is that all of these features are seamlessly integrated into a superb luxury sports car. In fact, if not for the “ActiveHybrid” badge and the engine cutting out automatically at stoplights, you wouldn’t really notice the difference between a standard BMW 750i, other than the 15% increase in fuel economy (putting it in the 20 mpg combined range, although official EPA numbers haven’t yet been determined).
The seamless integration, however, does not occur without a cost. There’s a reason why BMW is utilizing this technology on an already expensive model (a base model 7-Series, non-hybrid, starts at $80,000): rich people, who will buy a 7-Series anyway and want the feel-good eco credit of owning a hybrid will shell out the extra money. And that allows BMW’s designers to build these fantastical new technologies. And the more often they are built, the lower the price becomes.
The 2010 BMW ActiveHybrid 7 represents a generation change for the automobile. A fitting comparison would be the removal of the horse as a prime method of transportation. When the automobile was first released, not everyone could afford one; only the rich could. Once the technologies and the manufacturing processes advanced, car makers could offer vehicles at a lower price, making them available for the general public. That is what the ActiveHybrid 7 is, the first step to the eventual adoption (within a decade or so, most likely) of these efficient technologies into every car. And for that, the ActiveHybrid 7 should get a big seal of approval.