Tri-turbos are sooo last season. Aiming to keep up with fashion BMW is reportedly working on quad-turbo engines, according to Autocar.
The company already fielded a tri-turbo design in the X5 xDrive50d M Performance and the M550d, adding an electrically driven turbocharger for extra low-end boost pressure. The quad-turbo design could follow that with another electrically driven turbo, or BMW could opt to go the conventional route and simply add a second bi-turbo setup to the diesel inline-six.
The quad-turbo inline-six diesel engine is expected to debut in the M750d 7-series sedan in 2016, and it could also make a cameo appearance in the xDrive50d M Performance versions of the X5 and the X6 in the near term.
Just how much power is the quad-turbo 3.0-liter diesel unit expected to pump out? Autocar says we could see more than 400 hp and 590 lb-ft of torque. That'll be well north of the 255 hp and 413 lb-ft of torque that the outgoing 740Ld xDrive model -- the first diesel 7-series sedan sold in the States -- produced when it arrived for the last model year of the F01-generation, whose run ended this year. That said, it remains to be seen whether the quad-turbo diesel will make it across the pond.
The 2016 BMW 7-series was revealed in June and is expected to go on sale in the U.S. by the end of 2015. The U.S. will receive just the long-wheelbase versions of the 740i and the 750i xDrive models, with the former using a 320-hp, 3.0-liter turbocharged straight six and the latter powered by a 4.4-liter twin-turbo V8 good for 445 hp and 480 lb-ft.