It has been barely a year since BMW's "New 7" was introduced, but what an eventful year for BMW. No mere evolutionary product, The New 7 was instead a bold statement about who BMW is, what BMW stands for, and where BMW intends to go. "With help from its suppliers," stated no less august a source than Automotive Engineering International in its March '02 issue, "BMW has produced a vehicle that blazes the engineering trail with innovations that will influence passenger vehicles for years to come. The new BMW 7 Series was selected by the readers and editors of AEI as Best Engineered Vehicle for 2002 because it points the way not only for luxury/performance sedans but also for other vehicle segments." Heart of the 760Li: A new V-12 engine of dazzling technology and performance
As BMW had offered a 12-cylinder model in the previous 7 Series, the 750iL, it was natural and expected that a 12-cylinder version of the new Series would in time make its debut.
The 750iL, offered through 2001, was powered by a V-12 of 5.4 liters with single overhead camshafts and 2 valves per cylinder; that engine's output was 326 horsepower - a figure now matched by the 7 Series' V-8. The V-12 powering the new 760Li is completely new, with 6.0 liters of displacement, dual overhead camshafts (per cylinder bank) and 4 valves per cylinder. Designated N73, it is also related to the N62 V-8 engine that powers the two 745 models, in that the two engines share key technologies and overall engineering architecture; yet it also introduces groundbreaking new technologies of its own.
The V-12 configuration has long been recognized as an ultimate power plant concept, suited for top-class vehicles. Its physics are ideal: 12 cylinders arranged in a 60° "vee" of two cylinder banks are perfectly balanced; combined with the relatively even power pulses of so many cylinders, this results in a supremely smooth propulsion unit.
This V-12 is also a supremely powerful unit, delivering a monumental 438 horsepower and 444 lb-ft. of torque; for perspective, compare this to the 325 hp and 330 lb-ft. that give the 745i its 0-60-mph capability of 5.9 seconds and you can easily envision the performance potential of the V-12!
Let's take a look now at the most significant new technology in this new engine: direct fuel injection. Indeed, this is the first direct-injected gasoline V-12 engine ever offered in a production automobile, and the first direct-injected gasoline engine to meet contemporary expectations regarding emission control.
Direct fuel injection means injection of the fuel directly into the combustion chamber, rather into the intake port as is the norm; it has been chosen and developed by BMW's power train engineers to boost power output and fuel efficiency to higher levels than could be achieved with conventional fuel injection. BMW's system operates on a stoichiometrically optimum fuel-air mixture (( = 1) and can be emission-controlled by conventional, proven 3-way catalyst technology. By contrast,
other direct-injection concepts currently under development in the auto industry (such as lean-burn or stratified-charge) can achieve greater fuel-efficiency gains than the concept chosen by BMW, but these depend on unproven "deNOx" catalyst technology and require sulfur-free fuel, which is not universally available. Thus BMW has deployed a technology that is actually usable in the real world at present.
Text and photos courtesy of BMW AG
