Quad-turbo BMW M550d xDrive is ultimate diesel Q car | CAR Magazine

Quad-turbo BMW M550d xDrive is ultimate diesel Q car

Published: 26 April 2017

► BMW M550d xDrive revealed
► Four turbos, four-wheel drive
► Saloon or estate available

Say hello to the fastest diesel-powered BMW 5 Series yet: the BMW M550d xDrive. It’s an oil-burning Q car with a quad-turbo six-cylinder diesel engine and a 0-62mph launch time that’s enough to make sports cars flinch.

The M Performance-fettled 3.0-litre straight-six has 395bhp and 561lb ft of torque to play with, which is brought to you by a suite of four turbochargers on board that kill any thought of turbolag dead in its tracks. 

Woah… FOUR turbochargers? How does that work?

This isn’t some sort of half-pretend electric turbo system seen in the likes of the Audi SQ7 – it’s an evolution of the all-mechanical tri-turbodiesel engine seen in the previous-generation M550d xDrive. Instead of one low-rpm turbocharger curtailing lag from low revs, two mini turbos work in unison to provide even more pressure at low speeds.

BMW M550d xDrive Touring rear quarter

These two small turbos and one of the larger, second-stage turbos are always on regardless of throttle input or engine rpm, while the second of the larger units fires up over 2500rpm.

So how fast does this wizardry make the M550d?

Thanks to the multi-stage turbocharging, around 332lb ft of torque is available from just 1000rpm. All that shove is fed through an eight-speed automatic ‘box and BMW’s xDrive four-wheel drive system, so what you have here is a 5-series that can launch to 62mph in 4.4 seconds (4.6 for the Touring estate) – the same sprint time as the previous-generation, petrol-powered F10 M5 – and on to a limited top speed of 155mph.

BMW wants to stress that these are just provisional numbers for now, but those numbers are enough to worry a Lexus RC F, a Porsche 718 Cayman and an Audi TT S.

The engine isn’t the end of it, either: the M550d xDrive has tech like rear-wheel steering, a performance exhaust and performance brakes.

BMW M550d xDrive door sill

So, if it’s a bona fide Q car, how can I make one out?

With relative difficulty. The M550d looks like any old M Sport at first glance, but the signs are there – namely the new 19-inch ‘Double Spoke’ alloy wheels and flashes of matte grey on the front grille housings and side sills. That and an M aerodynamics package, of course.

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By Jake Groves

CAR's deputy news editor, gamer, serial Lego-ist, lover of hot hatches