For those who find the larger X6 M and X5 M ungainly and unwieldy, BMW have released two compact alternatives as the faster Sports Activity Vehicles of their lineup. The new X3 M and X4 M bring their slimmer proportions as well as the all-new 3,0 S58 six-cylinder engine to the category. In its basic version, the high-revving powerplant produces 473 horsepower and 442 lb-ft of torque, and for those who want even more, the Competition variant of the TwinPower Turbo engine delivers 503 horsepower, making it the most powerful six-cylinder engine BMW has ever offered to the public.
A Sophisticated Powerplant
In typical M-fashion, the powerplant incorporates a slew of new technological advancements. Thanks to a lightweight forged crankshaft and reduced rotating mass, the redline sits at at a lofty 7,200 rpm. Increased power comes thanks to a closed-deck design, with improved combustion. The engine’s overall weight has been trimmed thanks to the use of 3D printing in its development. In fact, through the 3D printing technology, engineers were able to cut the weight of the new engine’s cylinder head core and allows its coolant ducts to be routed in a way that optimizes temperature management.
As a true sports activity vehicle, turbocharging does not deprive the S58 of any response. Two single-scroll turbochargers are fitted with upgraded compressor wheels and an electronically controlled wastegate for quick spooling, and a new, more efficient water-to-air intercooler system reduces incoming air temperatures for additional power. The Valvetronic fully variable valve timing and the Double-Vanos variable camshaft timing technologies further contribute to the increased output. As a result, the inline-six makes an incredible amount of thrust across a mile-wide rev range; producing its peak torque of 442 lb.-ft. between 2,600 and 5,600 rpm and between 2,600 and 5,950 rpm in the X3 M Competition and X4 M Competition models. It generates maximum horsepower output at 6,250 rpm and sustains its potent power delivery until the 7,200 rpm redline. A heavyweight sports vehicle needs to pull like a train, and this motor does just that.
These figures amount to a 0-60 time of 4.1 seconds, and the Competition models hit the mark in 4.0 seconds. The top speed is limited to 155 miles an hour, though selecting M Driver’s Package bumps top speed to 174 miles an hour with the standard models, and 177 miles an hour with the Competition models.
For healthy running temperatures after long sessions on track, the car employs a large central radiator and two smaller radiators positioned on either side of it, as well as an engine oil cooler and a separate transmission oil cooler. To ensure the mill remains lubricated during hard cornering a lightweight oil sump containing two chambers and an integrated suction chamber is fitted. Oil starvation, even with an SUV capable of hauling the kids to soccer practice, is a non-issue.
The unique appeal of these BMW SUVs is that they are genuinely quick on the track, and not just a powerful people carrier. To help the car in a variety of situations, the M xDrive intelligent all-wheel-drive system has a rear-wheel bias which blends stability and the natural agility offered by rear-wheel drive. Torque is only transferred to the front when the rears exceed their limit, much like the ATTESA-ETS system functions.
It gets more interesting. The M Dynamic mode allows the driver to shuffle torque front to rear to their liking. With this, the driver is given to the access to the M xDrive 4WD Sport option. This sends even more power to the rear wheels, enabling controlled drifts. DSC Off mode (with DSC deactivated), meanwhile, has been optimized for dynamic track driving situations and can be combined with the standard all-wheel-drive setting 4WD, or with 4WD Sport mode.
The active rear differential can vary lockup between 0% and 100% to ensure an efficient deliver of power depending on the grip required. This ensures enhanced traction, agility and directional stability, especially when the SUV is being driven in a very sporty manner or on roads with differing levels of grip.
Naturally, these two enjoy the sort of footwork deserving of an M badge. Electronically controlled dampers, M-specific Servotronic steering, and beefier brakes (15.6″/14.6″ front/rear) are standard, and the suspension mounting points enjoy additional bracing for greater stiffness. The front end is also braced with an A-strut, which has been incorporated into the front section near the firewall, with two further struts increasing stiffness between the shock towers and the front of the car.
The double-joint spring strut front suspension benefits from greater negative camber and incorporate bespoke swivel bearings, torque arms and wishbones. In the rear, a five-link rear suspension features model-specific bushings that help deliver precise wheel location and directional stability. Both axles are kept level with anti-roll bars, which are of a larger diameter in the Competition variants.
These two SUVs might divide the audience with their mixed aims, but the truth is, they’re only going to impress the avid enthusiast. As the X5 M and X6 M held their own on the track, these two—with their compact proportions, revised suspension, and trick engine—might be able to show their older, heavier siblings their own quad tailpipes.