Curious car, this one. Despite a massive temptation to ask just how such a thing ever made it past the idea stage, car companies, particularly German ones, don't tend to make things that they haven't already established someone will probably buy. Which means that, when asked by the researcher with the clipboard and fixed smile, more than one person must have said "Yes, actually, there is an X6 M shaped hole in my life". Who these people are and what sort of lives they lead is anyone's guess but, having driven the X6 M, I can only suggest that they are conflicted. Very conflicted.
Because the car is, too. Quite apart from the fact that BMW's M division a few years ago swore that they would never use 4WD, a turbocharger or an automatic gearbox, and the X6 M features all three, there's also the glaring issue of, what the hell is it for? I spent most of a day thrashing the bejesus out of one at Road Atlanta racetrack trying to find out and ran the thing out of petrol before I could come up with a convincing answer.
It's not that it wasn't fun on the track, it was. It monstered its way around the circuit, consuming kerbs and curves, hitting almost 150mph down the long back straight and stopping straight and true, lap after lap. It was more the constant nagging that it was all a bit ridiculous and that a car with half the weight and half the power - such as the original M3 - would have been more entertaining and less complicated to explain.
Whatever. The first thing you need to know is that the X6 M is as fast as the current V10 M5 in a straight line. That's very fast. Both do 0-62mph in 4.7secs and run on to limited top speeds of 155mph. The second thing you need to know is that the X6 M does a similar lap time (8mins 30secs) to an E46 M3 - the one before the current one - round the Nerdbirdthing. And that's just absurd. Because going fast in a straight line isn't that hard with plenty of power. Going fast around a circuit is.
The reason for the X6 M's super saloon speed is simple in a very technically and typically complicated BMW way. I'll simplify: they take the stock 4.4-litre V8 motor, drop a pair of twin-scroll turbochargers into the V, bolt on a couple of intercoolers and, voilà, another 155bhp is born. This brings the maximum available power under your right foot to a round 555bhp and torque to an equally neat 500lb ft. But as nice as that is, it's not the clever bit. To ensure the power doesn't arrive in one almighty tyre-shredding peak, there is a new-fangled exhaust manifold that links cylinders on opposite sides of the engine. This ensures the blowers are constantly kept spinning smoothly and allows you to control your speed precisely.
This new pipework completely strangles the V8 sound, which is disappointing, but otherwise, so far so good. The reason for the X6 M's handling abilities takes a little bit more explaining. Building on all the clever chassis technology already fitted to all X6s, the M dept has thrown every single electric toy you can imagine into the mix. So, on top of the xDrive 4WD system and the M-tuned Dynamic Performance Control (DPC), which distributes power to each wheel based on things like available grip, direction of travel, etc, there's also MDM.
MDM stands for M Dynamic Mode. This allows you to create a maximum death setting for the chassis and drivetrain. And it's brilliant.
When you are feeling a bit tasty, you just press the M button on the wheel and the car changes immediately from a quick truck into an angry attack vehicle. On congested British roads where it's ‘go now or stay behind the caravan for another 50 miles', with MDM you will always go now.
And thanks to some spectacularly massive brakes - 15.6 inches at the front, 15.2 inches at the rear - you can always stop pretty much immediately when you need to, too. Even after six laps of racetrack abuse, the pedal did get a bit softer but never failed to stand the two-tonne plus X6 M on its nose. So no complaints there.
Likewise, the chassis, however complicated it might be, is pretty amazing. Ignoring the fact that the company created the problem they now claim to have solved, the X6 M is still very easy to drive very fast. Unlike the Porsche Cayenne Turbo S or GTS, in which you can feel all the electrical systems heaving and straining to keep the car heading where you want, the BMW feels comparatively mechanical. It still gets understeery if you take your eye off the ball or get into a corner too fast - two tonnes is still two tonnes however many systems you have -- but it's still miles faster through the curves than any other SUV-type vehicle, other than the mechanically identical X5 M.
Ah, yes, the X5 M. It's hard enough to make a case for the X6 M on its own, but against the slightly cheaper, bigger capacity, four-door X5 M it's nigh-on impossible. So it all has to come down to taste and character, or maybe lack thereof. And that's when it starts to make sense. Perhaps the X6 M is not for us Brits at all. Perhaps it's for other countries like the US and the Far East. Places where just being different is enough to make it desirable. Maybe that M on the X6 is not about motorsport so much as marketing. Look at it like that and perhaps the X6 M is not so curious after all.