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M aficionados take note: The 2010 X6 M (and yet-to-be-tested X5 M) represents the most dramatic shift in BMW's Motorsport division since its inception – and it's not because they're the first crossovers branded with the tri-tone "M" badge. This high-riding duo are the first M machines ever to be equipped with all-wheel drive. The first fitted exclusively with an automatic transmission. And the first (and surely not the last) to pack a pair of turbochargers. M has evolved, but BMW hasn't lost the plot – it's completely rewritten the screenplay, added Michael Bay firepower and harnessed the electronic might of a supercomputer farm to tie it all together.

Purists have decried that "X" and "M" sharing a bootlid is the death of the brand, but these newest additions are just the latest in a long string of M-badged expansions. The brand's original intent – producing homologation specials tailored to die-hard enthusiasts – underwent its first conniption-inducing phase when BMW introduced the E30 M3 Convertible. Devotees cried foul, but amazingly, the brand not only survived, it thrived. Similar (if less vocal) protests were heard when the six-equipped E36 model debuted, followed by the E46 and the latest V8-powered model.
While that broken record is wearing thin, there's no doubt that the M brand is completely unrecognizable two decades later. It's moved beyond motorsport to bring power, agility and engagement to the masses through BMW's bread-and-butter models. And in the case of its fire-breathing SUVs (errr... SAVs), it's a story we've seen played out by another German automaker and its controversial introduction of a high-performance 'ute. We know how well that turned out, and now we know this: the X6 M has the goods to dominate its aging competition from Stuttgart – even if BMW doesn't want us to draw comparisons.

Packing a reworked version of the 4.4-liter twin-turbocharged V8 initially fitted to the X6 xDrive50i and later on the 2009 7 Series, the S63B44 has been tuned to deliver 555 hp at 6,000 rpm (five horsepower more than the Cayenne Turbo S – oops, we did it again) and 501 lb-ft of twist from an oh-so-low 1,500 rpm all the way through to 5,650 rpm. The party ends at 7,000 RPM, but outputs only tell a fraction of the tale.



An ingenious (and patented) exhaust manifold lies between the engine's two cylinder banks, shuttling spent hydrocarbons through four individual exhaust runners, then two tuned tubes feeding a duo of twin-scroll turbos. With a compression ratio of 9.3:1, peak boost of 7.3 psi and precise pulses of exhaust gas keeping the turbos perpetually on boil, the X6 M nearly eliminates any hint of turbo lag and sets a new bar for force-fed throttle response.

BMW claims a 0 to 60 mph run of 4.5 seconds (without launch control) and we have little doubt it's more than capable of shaving a tenth or two from that figure depending on the testing method. But straight-line performance aside, this V8 is among the quickest, most linear turbocharged engines we've ever tested and the transmission delivers shifts nearly on par with the world's best dual-clutch gearboxes.

The six-speed auto 'box is a mildly reworked variant of the ZF unit found on the standard X6, and in either automatic or manual modes, the tweaked six-speed has found a soul-mate with the twin-turbo'd V8. The amount of programming that's gone into delivering seamless shifts boggles the mind, specifically the ECU's ability – in Sport mode – to cut ignition to one cylinder while locking the torque converter to deliver a completely imperceptible suspension of torque.



Although the shifts aren't nearly as impressive when the awkward but adaptable transmission stalk is set to Auto, the steering wheel-mounted paddles are laid out as God intended – upshift on the right and downshift on the left – and they are easily snatched for passing power on demand. To lay into the throttle in Auto mode is to take a beat and feel your kidneys wrap around your spine as all four wheels grapple the tarmac and a muted, aggressive howl erupts from the quad-tipped exhaust.

While the transmission is excellent and the engine is beyond reproach, the all-wheel drive system and its assorted acronyms prove BMW has signed a pact with the Devil – one that cuts both ways and doesn't include a trip to Jenny Craig.

Originally fitted to the X6, the AWD system features BMW's torque-vectoring Dynamic Performance Control (DPC) which shuffles power between the rear wheels to maintain a constant cornering attitude no matter the conditions. It's unobtrusive and highly adaptable, accelerating the inside rear wheel when it detects oversteer, delivering more grunt to the outside rear wheel to keep understeer at bay, or sending the majority of the power to the rear wheels when nailing the long pedal in a straight line. Navigate to the vehicle settings page in the (much improved) iDrive system and passengers can see exactly which wheels are getting precisely measured delivery of torque. But it's best to avoid the desire to stare at the display, as the next corner presents itself a quickness... and you've got an unwieldy amount of mass to manhandle into submission.