New York 2009: BMW X5 and X6 M

In a first for BMW's M division, they have just introduced a pair of high-performance SUV's: the X5 M and X6 M.  BMW's M (which used to stand for "Motorsport!") division has traditionally based their models on BMW's cars, citing the purity and light weight necessary for a "real" M car.  Everyone's stretching their brand boundaries these days, though, and it was bound to happen eventually.

So let's not whine about the relatively pointlessness of these vehicles, and appreciate them for what they are: absurdly fast.  Based on the X5 and X6 SUV's, the X5 M and X6 M receive the typical M-car upgrades: more power, better suspension and brakes, interior upgrades, and bodywork differentiations.

The biggest news is under the hood.  BMW's shiny new twin-turbo 4.4L V8 has been fettled by the M technicians, with a new twin-scroll layout for the turbochargers.  The exhaust manifolds are combined into one unit with balanced, twin feeds to the turbochargers for faster spool-up of the low-inertia blowers.  Direct injection (which lowers the effective temperature of the charge) and twin air-to-air intercoolers allow for a rather loft total of 21 psi over atmospheric pressure, which is then crammed violently into the intake manifolds.  It's important to note that this engine is the reverse of what you'd expect: the intake manifolds are on the outside of the block, and the exhaust manifold and turbochargers are on the inside of the V for increased space efficiency and drastically shorter plumbing from turbo to intake, for decreased lag.  Regardless of what a maintenance nightmare that must be, the results are drastic: the new M twin-turbo V8 is BMW's most powerful production engine, rated officially at 555bhp@6000rpm and 500lb-ft of torque in a broad band from 1500-5650rpm, and increase of 155 horsepower and 50 lb-ft of torque over the regular V8 (which sees duty in the X6 xDrive50i and the 750i).

With this much grunt underfoot, BMW claims the X5 and X6 M will both reach 60 mph in a scant 4.5 seconds, which is way too fast for a  5000+lb SUV.  Thankfully, they're limited to 155mph - but that's still a lot of kinetic energy to stop.  M has seen fit to upgrade the brakes, and they're suitably huge: 15.6" ventilated discs at the front with 4-piston fixed calipers riding atop, and 15.2" ventilated discs at the rear with floating calipers bring things to a halt in a hurry.

The suspension has been upgraded as well.  The X5 and X6 M ride on modified double-wishbone front and 4-link independent rear suspension, and the spring and damping rates as well as anti-roll bar size has been increased, while static ride height is 10mm lower than the standard models.

As with any new M-car, electronics take center stage in keeping everything in check.  The X6 has BMW's unique torque-vectoring rear axle and all-wheel drive, and the limits of the stability control have been expanded to allow more lateral slip before intervention for higher cornering limits.  Both models are equipped with Active Drive, which utilizes active damping control as well as active roll stabilization to provide M-car handling characteristics.

Stylistically, the M versions look downright mean.  A gaping front fascia provides additional air for the turbocharged V8, and around back the rear fascia has been modified to accomodate the traditional quad exit exhaust pipes.  Both cars ride on massive 20" alloy wheels, with high-performance runflats in sizes 275/45/ZR20 front and 315/35/ZR20 rear - price those suckers out at TireRack!

The X5  and X6 M will be competing with prestige performance SUV's like the Porsche Cayenne Turbo, Mercedes-Benz ML63 AMG, Jeep Grand Cherokee SRT-8 (which manages to be nearly as fast with only 415 horsepower) and the odd-ball 500bhp V12 TDI Audi Q7 in Europe.