Three is better than two, just like two is better than one. That’s the conventional wisdom, at least, disseminated everywhere from Ecclesiastes to the Arby's drive-thru menu. Evidently, BMW's into that whole thing, too. Not contented with its current triple-turbo “N57S” engine, the luxury automaker has unveiled its next-gen diesel motor. And, yeah, this puppy’s got four turbochargers.
The announcement comes from the Vienna Motor Symposium, undoubtedly the most German-sounding event in the history of Germany and possibly events. Like the outgoing tri-turbo engine, the new “B57” is a straight-six with 3.0 liters of displacement. Peak output is 394 horsepower, on tap from 4000 to 4400 rpm. Torque, as you’d expect from a diesel engine with four turbos, is healthy—561 pound-feet, available between 2000 and 3000 revs. And that’s not even exploiting the full potential; engineers had to cap the torque to keep from destroying the automatic gearbox. Because four turbos.
Technically speaking, the B57 retains BMW’s two-stage forced induction system. But whereas the old engine used a single low-pressure turbo for grunt and two high-pressure turbos in upper revs, the new engine replaces the bigger turbo with two smaller guys on a common exhaust. The result, according to BMW, is five percent better fuel economy and, because of some clever packaging, a negligible weight penalty. It also allows owners to tell everybody that their car has four freakin' turbochargers.
The new engine will make its first appearance in the flagship 7-Series sedan. BMW says that, equipped with the quad-turbo six-cylinder, an all-wheel drive 750d will do 0-60 mph in 4.5 seconds. Don’t be surprised to see the B57 in the next wave of M Performance models, too, specifically the X5 and X5 SUVs, as well as the next 5-Series. Sadly those models will almost certainly be verboten in the U.S. market.