503 HP, 4 Seconds to 60: Full M Treatment Comes to BMW X3, X4

There once was a time when BMW’s M performance variants graced only a few models, but those days are gone. The latest vehicles to get the M treatment are the X3 and X4 SUVs, whose new M variants — not to be confused with the next-rung-down M40i trim levels — can dispatch 60 mph in as little as 4 seconds flat.

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That’s if you get the Competition editions, of which the twin-turbo, inline-six-cylinder engines crank out 503 horsepower and 442 pounds-feet of torque apiece. Sans Competition grade, the X3 M and X4 M have the same engine with identical torque but 30 hp less, and it’s good for a 4.1-second sprint to 60 mph — still significantly quicker than the M40i versions of the X3 and X4 (355 hp, 4.6 seconds to 60 mph) but a few ticks slower than the rival Mercedes-AMG GLC 63 and Alfa Romeo Stelvio Quadrifoglio (as low as 3.7 seconds for the Benz and 3.6 seconds for the Alfa).

Horsepower for both models peaks all the way up to 7,200 rpm, and Competition models sustain peak torque to nearly 6,000 rpm, versus 5,600 rpm for the standard M engines. Power reaches the wheels through an eight-speed automatic transmission, which has a gear selector with buttons to toggle between three shift strategies that alter how soon and fast the shifts occur. Standard all-wheel drive sends most power to the rear wheels to maximize balance, while a dual-exhaust system with electronic flaps — continuously variable in the Competition grades — spews its contents out four tailpipes, versus the two in M40i grades.

Selectable driving modes vary myriad characteristics, with a row of buttons on the center console that allow you to mix and match how the steering effort, exhaust note and suspension behave. An M Dynamic mode sends even more power to the rear wheels through a variably locking rear differential.

Naturally, drivetrain enhancements aren’t the only difference. M models have additional front-end bracing, including a strut brace under the hood that bridges the shock towers for increased chassis stiffness. Adaptive shock absorbers are standard, and BMW claims all manner of other unique suspension components for the M SUVs, from bearings and control arms to stabilizer bars and rear bracing. Starting in August, the automaker will offer the shock-tower brace in carbon-fiber-reinforced plastic — the same material used extensively in the i8 supercar — as an option.

Twenty-inch wheels wear P255/45ZR20 tires up front and wider, P265/45ZR20 rubber in back. Competition grades have 21-inch wheels and lower-profile tires, albeit with the same width. Both sets frame enormous, cross-drilled disc brakes: 15.6 inches up front and 14.6 inches in back, or nearly 2 inches larger up front than the X3 M40i’s disks.

Versus the M40i trims, the X3 M and X4 M have rejiggered front bumpers with taller, six-sided center openings flanked by more-tapered side portals. The tails have more body coloring on the lower bumpers versus the M40i SUVs, plus unique liftgate spoilers. The side mirrors sport BMW’s signature M design, each with an extra arm up top. As with the shock-tower brace, BMW will offer certain exterior elements in carbon-fiber-reinforced plastic as an option beginning in August.

Inside, the gauges, steering wheel and gear selector have unique M treatments, while the optional head-up display can show a rev indicator with shift lights. The sport seats have M logos, while unique seats with illuminated logos are standard if you get the Competition grades.

If you’re itching to buy one, expect sales to begin in late spring. Production of the M variants begins in April 2019, and a BMW spokesman told Cars.com that sales usually commence around two months after that.

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