When we tested the BMW X5 M last month, we thought it was a seriously mean machine. But now we've met its brother, the 2010 BMW X6 M, and found something even nastier. The X6 M is a piece of automotive engineering that shouldn't exist, its total lack of practicality suggesting it is more about art than function, the automotive equivalent of Mount Everest--BMW built it because it could.
If you stripped away the body, you would find a car nearly identical to the X5 M, the same 4.4-liter V-8 surmounted by twin turbochargers, which is sort of like putting bow ties on puppies. They're already cute; they don't need the embellishment.
Upholding its engineering reputation, BMW fits the 4.4-liter V-8 with its double-VANOS continuously variable valve timing and direct injection, making for an engine that produces plenty of torque at low speeds. The twin turbos, one for each bank of four cylinders, force air into the engine at 22 psi, cranking up overall engine output to 555 horsepower and 501 pound-feet of torque.
The result is a thrumming, barking beast under the hood that gives the X6 M breathtaking acceleration. BMW claims 4.7 seconds to 62 mph, and we more than verified that timing by hitting 60 mph in 4.38 seconds, using the car's M mode and putting the six-speed automatic transmission into Sport. On another run, manually shifting with paddle shifters, our time was 4.68 seconds, showing that we can indeed be replaced by a mechanical device.
During a typical timed run, we lined the car up, then mashed the gas pedal. Unlike some cars with complicated suspension and traction control technology, the X6 M unhesitatingly leapt forward. Acceleration continued on a smooth and linear path, with no turbo-lag. At each gear shift, the exhaust let out a deep bass rumble as the engine rapidly changed speed. During our manual-shifting tests, tapping the right side paddle produced a quick upshift, but we frequently didn't catch it in time, as the tach needle quickly headed into redline territory.
Given the similar power train and chassis, the X6 M should be virtually identical to the X5 M. But here's the difference: where the X5 M sports the passenger and cargo-friendly body of an SUV, the X6 M's roofline, sloping radically down toward the hatchback, tortures rear-seat passengers with minimal headroom. Cargo space is also limited to things that can lie flat.
The X6 M seems designed with the sadist in mind, a person who would welcome people into the back seat, grin, then proceed to drive like a madman until the rear-seat passengers were suffering neck pains that would keep a team of chiropractors in business for 50 years. And on arriving at a destination, said sadistic driver would look in the cargo area and say, sorry, couldn't fit your suitcases in, guess you'll have to live in those clothes for the next few days.
This purported sadistic driver will be able to do plenty of damage to the rear-seat occupants, as the X6 M can maintain grip at amazing speeds in the corners. Driving it over wet mountain roads, the car craved speed, begging for more power on every turn. On a long sweeper we got it up to what we felt was a comfortable speed, but, as the X6 M started to lean, we pushed the gas harder, making it regain its flat cornering poise. On the tight corners, rising hairpins, and the like, the X6 M eagerly scrambles up and around. It's a big dog but it gets around like a terrier.
How does BMW make a car weighing more than 5,200 pounds handle so well? The answer is something called Adaptive Drive, a technology that monitors, in a matter of milliseconds, side and longitudinal g-forces, speed, steering angle, and ride height. It takes this data and adjusts the antiroll bars and dampers to counteract forces that threaten to get the X6 M sideways when it is being pushed hard.
Of course, this car also features the M button on the steering wheel, which immediately sharpens throttle response and makes the suspension more sport-worthy with a simple touch. Fitting the high-tech theme of the X6 M, this button is kind of like a macro: you can program it through the car's settings menu. In this menu, you can make the M button put the dynamic stability control, electronic damper control, and power into sport modes, while having the head-up display change from showing just speed and navigation information to a colorful virtual tachometer.
The six-speed automatic transmission also has a sport setting, but it's not controlled by the M button. You need to pull BMW's funky-looking shifter from Drive to Sport yourself, which also substantially affects the car's performance. Where Drive mode feels benign and sluggish, Sport uses sensors to look for opportunities to downshift. Get up speed in a straight, then bang on the brakes as you plow toward a turn, and this transmission puts itself into an appropriately low gear, usually second, and holds it as the tachometer pushes redline, shifting up only before fuel cutoff.