Introduction

The BMW X4 Sports Activity Coupe is structurally similar to the compact X3, but it's topped by a seductively curved roof that almost sends it into another category. 

The X4 has four doors, so it's not really a coupe. Taking the X3 that serves as its foundation, BMW developed a roofline that tapers toward the rear. More intriguing in appearance than its taller cousin, the X4 loses some interior space and functionality. 

The X4 was launched as a 2015 model. For the 2017 model year, two versions of are available, the X4 xDrive 28i and the new X4 M40i. 

2017 X4 xDrive 28i models now come standard with Wireless charging and a wi-fi hotspot with enhanced USB and Bluetooth. Navigation has been upgraded to iDrive 5.0 on 2017 BMW X4 models. A turbocharged 2.0-liter four-cylinder develops 240 horsepower and 260 pound-feet of torque. Surprisingly spirited, the X4 28i can reach 60 mph in six seconds. 

The new BMW X4 M40i model supplants the former xDrive35i. Ranking as an authentically potent performance vehicle, the M40i holds a 3.0-liter turbocharged inline six-cylinder engine that generates 355 horsepower and 343 pound-feet. That one accelerates to 60 mph in a mere 4.7 seconds. 

Both engines mate with a smooth-shifting 8-speed automatic transmission and xDrive all-wheel drive. Adhering to BMW tradition, each promises taut, confident handling talents, helped by an independent suspension similar to the one used in the X3. Electronic steering offers variable effort and an alterable ratio. Three driving modes are available: Eco, comfort, and sport. 

Befitting its performance qualities, the X4 M40i gets a specially calibrated transmission and xDrive system, as well as quicker steering, 20-inch wheels, and sportier suspension tuning. In order to achieve suitable sounds of power, a resonator sends some engine noise right into the cabin. 

Neither the National Highway Traffic Administration nor the Insurance Institute for Highway Safety has crash-tested the X4, though the X3 earned a five-star overall rating. 

Lineup

The 2017 BMW X4 xDrive 28i ($45,550) comes with the 2.0-liter engine, SensaTec simulated-leather upholstery, wood trim, a power liftgate, moonroof, Bluetooth and USB connections, automatic climate control, power front seats, 18-inch wheels, adaptive headlights, paddle shifters, variable sport steering, rear parking sensors, and a leather-wrapped steering wheel. Leather upholstery is optional ($1,450). Also available: an M Sport package ($2,300) with sport seats, M steering wheel, and an aero body kit. An xLine group includes 19-inch wheels and copper gloss trim. 

M40i ($58,100) comes with the six-cylinder engine, plus a Harman Kardon surround-sound system, the M Sport package, Dynamic Damper Control, keyless access, aluminum interior trim, front/rear parking sensors, and 19-inch wheels. 

A rearview camera and head-up display make up the Driver Assistance package, but a Plus version adds surround-view cameras, blind-spot monitoring, and active-safety features. An optional Parking Assistant lets the X4 steer itself into a parallel parking spot. 

Walkaround

To create the X4, BMW designers essentially shaved down the back end of the upright-profile X3, resulting in a gracefully curved profile for the X4. Visually effective at a glance, the design has drawn criticism from some quarters, notably for the bulging haunches surrounding its wheelwells. Breaks at the C-pillar and shoulder line, evidently intended to suggest performance potential, come across better. 

Dimensions don't differ much between the X3 and X4. The X4 is about half an inch longer, but 1.5 inches shorter. The center of gravity is almost the same in each body style, too. 

Interior

Only a glance at the X4's profile is needed to realize that back-seat space and cargo capacity are compromised. A price must be paid for that shapely roof, in contrast to the squared-off roofline of the X3 model. 

Fitted with aluminum and wood trim, the X4's interior design resembles that of the X3 that spawned it. While the X3 is a full-fledged five-passenger model, the reduced backseat head clearance and deeply contoured bucket seats of the X4 make it more logical for four occupants. Rear leg space also loses a couple of inches, compared to the X3. Six-footers can survive in the rear compartment, but not by much. 

As for cargo capacity, whereas the X3 boasts 27.6 cubic feet, luggage space in the X4 shrinks to a skimpy 17.7 cubic feet. Folding the back seats down increases that volume to 49.4 cubic feet, again, not exactly a voluminous storage compartment. 

Driving Impression

For a vehicle of its size, the X4 behaves athletically. When breezing through a corner, body motions don't become excessive, and little nosedive is evident. 

Braking power is markedly less delightful, as the weight of the X4 becomes noticeable right away when attempting to slow down in a hurry. The M40i does better when quick braking is needed, thanks to upgraded front brake rotors that raise their ability to curtail forward motion. 

Sport mode tends to be the most effective choice for most driving conditions, when the X4 is fitted with adjustable dampers, part of Dynamic Damper Control. The X4 driver can also select from Normal and Sport Plus modes. Making a choice affects steering feel, transmission shift points, and the feel of the gas pedal when starting off (throttle tip-in).
BMW's xDrive system splits engine power 40/60 percent, front/rear. When alteration becomes necessary as traction conditions change, the system can transmit full power to the back wheels. However, the performance controller is able to divide torque between the two rear wheels, to improve overall stability and cornering capability. Unlike many all-wheel-drive systems, BMW's xDrive is performance-focused, and not intended to make challenging off-road treks possible. 

Fuel economy is similar to that of the X3. The BMW X4 xDrive28i is EPA-rated at 20/28 mpg City/Highway, or 23 mpg Combined. As expected, the six-cylinder X4 M40i is less frugal, EPA-rated at 19/26 mpg City/Highway, or 21 mpg Combined. 

Summary

Crossover SUVs with gracefully sloping roofs are mainly the province of premium-vehicle manufacturers. Rivals to the X4 include the Range Rover Evoque and Porsche Macan. No matter how enticing an X4 looks, you can't get away from that limited back-seat space. (The same goes for similar vehicles.) Like most BMWs, too, the X4 has a substantial list of options and packages that can raise the price sharply. 

Driving impressions by Aaron Cole, The Car Connection. James M. Flammang contributed to this report.