We already know everything there is to know about the second-generation BMW X6, which was recently launched for the 2015 model year, but its high-performance version, the X6 M, is still somewhat of a mystery. What we do know about it, though, is that the Germans have been testing prototypes since early 2014. Now that yet another test vehicle has surfaced, this time around on the Nurburgring track, we know for a fact that development is well underway.

How do we know we're looking at the upcoming X6 M? Well, that's very simple, despite the fact that the SUV->ke145 is still wearing a serious amount of camouflage. The first hint lies in the front bumper, where a couple of large air intakes can be spotted. Then there's the rear diffuser, which isn't available on the standard X6, and the redesigned, more aggressive side skirts. If you still have doubts, then the hostile exhaust note coming with the video above should convince you.

Speaking of which, the X6 M will retain the turbocharged, 4.4-liter V-8 currently residing under its hood. The unit is now rated at 547 horsepower and 501 pound-feet of torque, but it's unlike for BMW to let those numbers untouched. Expect output to increase to around 560 ponies to keep up with the Porsche Cayenne Turbo S.

Alongside an upgraded engine, the second-generation X6 M is also in for a revised aerodynamic body kit, the updated headlamps and taillights of the 2015 X6, and a revised interior with updated technology and new trims. The unveiling is expected to take place by the end of 2014.

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