Porsche did it with the Panamera. Aston Martin did it with the Rapide. The concept of the 4-door high-performance "sport coupe" continues to catch on around the world, and now BMW continues the trend as it expands its M6 lineup for 2014 with the addition of the 4-door M6 Gran Coupe. It joins the automaker's existing 2-door M6 Coupe and Convertible, and comes equipped with the same beefy, twin-turbocharged 560-hp V8. Sitting on the M5 platform and borrowing many of its components from the 640i/650i Gran Coupes, which debuted a year earlier, the M6 Gran Coupe blends the functionality of a 4-door sedan with the sporty styling of the 6 Series and the high-performance powerplant of a track-worthy M sport coupe.

In addition, BMW introduces a new Competition Package for 2014. Available for all three M6 trims, the package boosts horsepower for the V8 to 575 and features retuned chassis components and an upgraded Active M differential designed to deliver optimal performance and handling.

The M6 Gran Coupe artfully combines the best features of a sedan and a coupe, melding them into a functional yet very fast vehicle. The Gran Coupe can seat 4 passengers comfortably in a 2+2 arrangement, and a fifth person can squeeze into the center rear seat (emphasis on "squeeze"), resulting in what BMW calls a 4+1 configuration. And those 4 or 5 passengers better make sure they lock their seatbelts firmly in place, because the M6 Gran Coupe rockets from 0-60 mph in just 4.1 seconds. Needless to say, this is not your father's family sedan.

All that power comes from the 4.4-liter M TwinPower Turbo V8, which pumps out 560 hp up to 7,000 rpm, and features such technologies as double-VANOS infinitely variable camshaft timing and high-precision direct injection, which help the engine eke out every available pony. In addition, the V8 produces a whopping 500 lb-ft of torque over a broad range from 1,500 and 5,750 rpm, with a rev limit of 7,200 rpm. With that much power available at such a low rpm, it's no wonder the Gran Coupe jumps off the line as quickly as it does. The V8 drives the vehicle's rear wheels through a high-torque 7-speed M double-clutch transmission, borrowed from the M5 and M6 Coupes. BMW offers a 6-speed manual transmission as an option. The drivetrain also includes an Active M Differential, which distributes power to the wheels in a balanced fashion for optimal performance. BMW limits top speed to 155 mph.

The M6 Gran Coupe borrows its chassis and suspension from the M5, but BMW adds a number of upgrades, including reinforced chassis mountings, aluminum suspension components and an aluminum rear axle subframe bolted to the body, ensuring a rigid structure and precise handling. BMW also includes its M Dynamic Damper Control system with electronically controlled shock absorbers and driver-selectable Comfort, Sport and Sport Plus modes, each offering a progressively stiffer suspension. M-specific Servotronic speed-sensitive hydraulic power steering, rather than the electronically controlled systems found on some competitive vehicles, also includes Comfort, Sport and Sport Plus settings, allowing drivers to choose the level of steering precision and feedback.

The advanced Dynamic Stability Control (DSC) system, which works in conjunction with damper control, features an M Dynamic Mode, which overrides the system for drivers who prefer to toss the vehicle around the corners. An M brake system includes 4-wheel ventilated antilock disc brakes with blue metallic 6-piston calipers, although buyers can add M carbon-fiber ceramic composite brakes, which help reduce weight and have a greater resistance to heat. A standard Brake Energy Regeneration system converts kinetic energy into electrical power for use throughout the vehicle. The Gran Coupe rides on 20-inch double-spoke light alloy wheels, while the M6 Coupe and Convertible get 19-inch forged alloy wheels. All trims receive run-flat performance tires.

The M6 Gran Coupe stretches 4.45 inches longer than the M6 Coupe, giving it a distinctive side profile. Out front, the Gran Coupe displays a unique black-and-chrome M dual-kidney grille, which distinguishes it from the other M6 trims, as well as large air intakes. The HID auto-leveling headlights, standard across the line, include dynamic auto-leveling, corona rings, cornering lights and retractable headlight washers. LED headlights with automatic high beams are optional. Aerodynamic body skirts give the sidelines a concave look, while the Gran Coupe's low roofline flows easily to the shoulders and rear end, adding to its aesthetics. An aluminum hood, soft-close automatic aluminum doors, rain-sensing wipers, Shadowline exterior trim and heated power auto-dimming side mirrors are also included on the Gran Coupe, as well as on the M6 Coupe and Convertible. The Gran Coupe and Coupe are both outfitted with a lightweight carbon-fiber composite roof panel, while the Convertible gets a power-operated black softtop with a heated glass rear window, although owners can opt for a Moonlight Black or beige softtop at no additional cost. At the rear, the Gran Coupe receives a unique carbon-fiber diffuser apron, and all trims get quad chrome exhaust pipes, which complete the look.

The Gran Coupe also receives a number of unique interior features, including a bi-color leather and Alcantara headliner, 4-zone automatic climate control and available heated rear seats. All M6 trims come standard with Merino leather upholstery and 20-way power-adjustable M multi-contour heated front seats with 4-way lumbar support and memory for both the driver and passenger. The Gran Coupe also includes a split-folding rear seat. The Coupe and Convertible get automatic climate control, while all trims include keyless entry, an auto-dimming rear-view mirror, a power tilt/telescopic steering wheel, ambient interior lighting, keyless entry with a start/stop button and a leather-wrapped M sport steering wheel with paddle shifters and audio, cruise and Bluetooth controls. All M6 trims come standard with Black Carbon Fiber interior trim, although owners can add Gray Poplar or Fineline Oak wood interior trim at no extra cost. BMW also offers a variety of additional interior trims, including Dark Red Sycamore and White Ash Grain wood trims, as well as a Piano Finish Black trim.

The M instrument cluster features an integrated LED display, while the standard BMW navigation system includes a 10.2-inch display screen, 3D maps and a 200GB hard drive. A rear-view camera and Park Distance Control for both the front and rear are also displayed on the screen. In addition, BMW includes its iDrive on-board controller with 8 programmable memory buttons on all trims. For tunes, the Gran Coupe and Convertible come equipped with a 12-speaker, 500-watt Bang & Olufsen Surround Sound audio system with HD radio, SiriusXM satellite radio and enhanced USB. The Coupe gets the same system but with 4 additional speakers, for a total of 16.

The optional Competition Package, newly available for all 2014 M6 and M5 trims, adds a number of track-inspired features and components to the standard high-performance package. For starters, BMW gooses output from the V8 by 15 hp to 575 and stiffens the anti-sway bars, damper calibrations and coil springs. In addition, the automaker uniquely tunes the Active M differential and reprograms the steering system, and even makes adjustments to the DSC's M Dynamic Mode to further enhance performance and handling. Finally, the package adds unique 20-inch M light alloy wheels and a sport exhaust system with tailpipes finished in Black Chrome. An Executive Package, also available for all M6 trims, adds such features as a heated steering wheel, ventilated front seats and a head-up display, as well as heated rear seats for the Gran Coupe.

In addition to DSC, all M6 trims include such safety features as front and side-impact airbags, active knee protection, an electronic park brake with automatic hold, adaptive brakelights, brake-fade compensation and brake drying, as well as a start-off assistant, which prevents roll-back on slopes. The Convertible also includes a Rollover Protection System. In addition, BMW Concierge Services with critical calling and an Assist eCall system with emergency request and automatic collision notification come standard on all M6 trims.

Testers say the 2014 M6 Gran Coupe achieves its goal of combining the best elements of a family-friendly sedan layout with those of a road-eating world-class sports coupe. What's most impressive, reviewers say, is the way the Gran Coupe easily shifts between these two modes, offering a comfortable ride around town while opening up in exhilarating ways when pushed on the highway or around curvy roads. It's an admirable addition to the ever-growing cadre of 2-row, 4-passenger sport coupes like the Panamera and Rapide, as well as the Audi S7, the Mercedes-Benz CLS-Class 4-door coupes and the Cadillac CTS-V sedan.