Quad-Turbocharged Diesel Inline-Six in BMW 7-Series' Future
Oil-Burner Will Approach 600 lb-ft from 3.0 Liters
Slated for the next-generation 7-Series flagship sedan, BMW is developing a new quad-turbocharged diesel I-6, at least if a report from Autocar is to be believed. The engine will produce at least 400 hp and 590 lb-ft, a healthy increase over the output of the existing tri-turbo 3.0L diesel I-6.
That motor, which produces 376 hp and 545 lb-ft of torque, currently appears in the performance-oriented BMW M550d xDrive, X5 xDrive50d M Performance. The existing I-6 (codenamed N57S) may serve as the basis for the new quad-turbo I-6, which could add an electric turbo to the existing exhaust-driven turbos for quick low-end response. Its estimated outputs would be more than enough for the 2016 7-Series, which weighs about 200 pounds less than an equivalent 2015 model.
Autocar’s appraisal of the N57S is positive. Even with “only” three turbos, throttle response is excellent, and the sequential snails deliver boost at varying rpms to provide strong performance throughout the diesel engine’s limited rev range. With an added electric turbocharger, BMW could incrementally increase the sizes of the exhaust-driven turbos to give the engine even more flexibility and power.
The engine is likely to be earmarked for the M Performance version of the 7-Series, the first such application of BMW’s performance brand on the large sedan. It could also show in M Performance versions of the BMW X5 and X6 crossovers, giving them excellent performance without sacrificing fuel economy (as you might on the X5 M). We’d expect the hi-po diesel to achieve at least a combined 30 mpg in the 7-Series (the gas version is shown in photos here).
Diesel fanatics have always known that oil-burning engines can produce prodigious, gasoline-beating amounts of torque, but with the advanced breathing and fuel techniques used by BMW and other automakers, diesel is finally starting to rival gasoline in terms of pure power and accelerative force. It also seems like efficiency is still a huge part of the diesel game, resulting in a real “have-your-cake-and-eat-it-too” situation for economically or ecologically minded enthusiasts.