Just a year after the introduction of the controversial X6, BMW rolled out the X6M.
As if the 407bhp of the X6’s regular V8 engine wasn’t enough, the M version’s engine produces a whopping 555bhp.
Not surprisingly, the X6’s (more sensible) genetic twin, the X5, also spawns an identical M version that has identical mechanical specifications, right down to the 2.3-tonne kerb weight and performance figures.
Rather uncharacteristic of the M division – which has a habit of replacing the entire engine, transmission and driveline to make an M car out of a standard BMW model – the X6M receives a heavy revision to the existing components to qualify it as an M car.
The V8 block and cylinder heads are unchanged but the standard exhaust manifolds have been tweaked.
Instead of feeding the exhaust gas from both cylinder banks to the two turbochargers, there are now four separate exhaust manifolds leading from sequentially firing cylinders into the turbines.
This arrangement assures a continuous flow of exhaust gas to each of the turbos – and all eight cylinders – to deliver a quicker response to the throttle.
The power hike over the standard V8 didn’t come from BMW installing bigger turbochargers.
Instead, it’s from raising the boost pressure on the standard turbos to 1.5 bar.
So efficient is the power delivery from the twin scroll design that it’s hard to detect any lag, despite the lift in boost pressure and power.
Torque is up to 680Nm (versus 600Nm on the X6), which swells from a remarkably low 1500rpm right up to 5650rpm.
Curiously, it has a carbon dioxide rating of 325gm/km, so it’s a cleaner car than the X6 xDrive50i (329gm/km).
Although the dual-clutch transmission is available for use, it was finally decided that the X6M would rely on an automatic box from ZF, as it’s better able to cope with the enormous torque.
With the inherent torque-amplifying effect of the torque converter, the result is a downright explosive character that suits the extreme machine well.
This is most evident during take-off and kickdown, where the torque surge is especially potent.
By left-foot braking while launching, the engine revs rise and this momentarily gives a significant lift in torque, which provides a tremendous launch surge right from standstill as one steps off the brakes.
This translates into a 0-100km/h time of 4.7 seconds, an astonishing achievement for a behemoth that tips the scales at 2380kg.
So muscular is this powerplant that the X6M almost feels like it only weighs half as much.
But the laws of physics will not be violated.
On top of the car’s considerable weight is its tall stance and resulting higher centre of gravity.
While its adhesive grip in corners is tremendous (especially considering it is not on some quasi-track tyres like the rest of the M family), transients are not so easily performed.
That said, it is much better than the normal X6, thanks to the tweaked suspension that lowers ride height by 10mm and bumps spring rates up by about 15 percent.
The rear features an air suspension set-up – instead of the steelies on normal X6 models – for self-levelling when the car is towing.
Huge compound brakes with the floating rotor design also help sharpen braking response and soak up the huge energy this X6M is capable of producing in remarkably short distances.
Surprisingly, the M division has chosen to shod one of its M-badged vehicles with what appears to be run-of-the-mill Bridgestone run-flat tyres (RFT).
This is because none of the usual suppliers like Pirelli or Michelin were able to supply such a size and load specification with their quasi-track compound tyres.
Surprisingly, the RFTs held up their end around the Road Atlanta race circuit far better than expected, showing just how far the second-generation RFTs have come.
Compared to the wild scream of the M5’s V10, the X6M is almost too polite.
But this is perhaps necessary in order for the car to pass the forthcoming EU noise regulations.
But it does make an entertaining burble at each full throttle gear change (it actually comes from the ignition of unburnt fuel that sneaks pass the spark plugs in the split-second needed for gear change to reduce torque).
Around the track, the X6M is perhaps the easiest of the M machines to pilot, thanks to the forgiving nature of the active X-drive all-wheel-drive system.
It ensures that too much torque or braking effects do not overwhelm all four contact patches.
The engine’s wide spread of torque pretty much ensures one is always in the power band, unlike the naturally aspirated M engine that demands you be in the correct gear and rev band at every corner to get maximum attack.
While certainly capable on the track, the X6M is not going to challenge an M5 or M3 in terms of the alacrity and sense of sportiness, but it does lift the capabilities of these X cars from quick to exciting.
Perhaps it is better to think of the X5M or X6M as the prefect nemesis to Mercedes’ ML63 rather than against what an M3 or M5 delivers on the track.
As usual, the independent M division comes up with solutions that run contrary to what mainstream BMW is peddling.
Take, for example, the steering-mounted shift paddles that are arranged with a plus paddle for upshifts on the right and a minus paddle for downshifts on the left.
This is certainly more intuitive than the pull for upshift and push for downshift on either paddles in the standard BMW car.
Also the M division does not fit the variable ratio Active Steering system, and only tweaks the electro-assisted steering to be light at parking speeds and heavier on the move.
With an iDrive programmable M-Dynamic Mode (MDM) button on the steering, one can set the parameters of steering, engine, suspension and transmission responses to default.
So just by engaging the MDM, one transforms the X6M from mild to wild.
When it is not being hurled around the racetrack, the X6M is an easy-going machine on the open road.
The ride is a tad firmer but not far off the standard set by a normal X6.
Obviously, it is not BMW’s intention to make a track vehicle out of the X6M.
And while the car is capable in that environment, it is on real roads that it proves itself as a fast vehicle with tremendous ability to reel in tarmac.
The way the X6M gains speed is one of its outstanding traits.
And if the limited 250km/h top speed is just on the slow side for you, there is an optional M Driver’s Package which, among other things, raises top speed to a governed 275km/h.
Some may argue that the X6 is already at the very fringe of social acceptability, and the X6M might cross that moral line.
But as BMW does so often, it makes a truly compelling machine on the basis of sheer driving pleasure alone.
Yes, it confounds by being such a large and heavy vehicle.
But on several fronts, the X6M seems to make sense (especially in the United States) and is BMW’s way of covering all niches.
2009 BMW X6M 4.4 (A)
Type V8, 32-valves, turbocharged
Bore x stroke 89mm x 88.3mm
Compression ratio 10:1
Max power 555bhp at 6000rpm
Max torque 680Nm at 1500-5650rpm
Power to weight 233.2bhp per tonne
Gearbox 6-speed automatic with manual select
Driven wheels All
0-100km/h 4.7 seconds
Top speed 250km/h (governed, 275km/h optional)
Front Double track arm struts, coil springs
Rear Multi-link, coil springs, active dampers
Front / Rear Ventilated discs
Type Bridgestone RE050 RFT
Size 275/40 R20 (front), 315/35 R20 (rear)
Traction aids ABS, DSC
Kerb weight 2380kg
Turning circle 12.8m
Price incl. COE To be advised
Warranty To be advised
+ Tremendous power, handling and grip, comfort not compromised
– Even heavier than regular X6, pricey, restricted rear view