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Mercedes-Benz broke the cone of silence on the AMG GT Four-Door Coupe (known as a “sedan” outside Germany) at the Geneva auto show on Tuesday. The Affalterbach-bred sports sedan gets a choice of the new 429-hp, 384-lb-ft 3.0-liter I6 in the GT53 model, a 577-hp, 553-lb-ft twin-turbo V8 in the GT63 or 630 hp, 627 lb-ft from the same V8 in the GT63 S model. All get nine-speed automatics. The I6 comes with a torque converter automatic; the V8s replace that torque converter with clutches in Mercedes’ MCT transmission; all get 4Matic all-wheel drive. Top speed is 174 mph for the six, 193 mph for the GT63 and 195 for the GT63 S. The short version: Speed won’t be a problem.

Balancing that speed will be a touch of efficiency. That sixer gets Mercedes’ new EQ Boost starter/alternator that can add 21 hp and 184 lb-ft in short bursts, along with a 48-volt electrical system.  The V8 versions come with AMG cylinder management, which can deactivate up to four cylinders, depending on conditions, to save fuel. We don’t know how much fuel yet because we don’t have EPA figures.

Mercedes is calling this its first four-door sports car. It follows the company’s “sensual purity” design philosophy with a long hood featuring two power domes, a low greenhouse and AMG’s new grille and “shark nose” front bumper. Blacked-out side window frames elongate the profile, as does the raked rear window. Both front and back lights are slim and the rear gets an extendable spoiler.

The bodyshell was developed alongside the company’s race cars, using motorsport analysis and simulation methods to reinforce the structure where necessary for “maximum performance.” In the center and tail end, Mercedes uses carbon-fiber-reinforced plastic to save weight and improve stiffness, giving an “optimum basis for high lateral dynamics potential.”

All AMG GT four-doors get adaptive damping. I6 models come with steel springs, while the V8s get the company’s multichamber air suspension. Mercedes adds that the electronically controlled locking rear differential (standard on GT63 and GT63 S, not available on the GT53) has a new reinforced mount to lower noise, vibration and harshness. The 4Matic plus AWD system uses an electromechanically controlled clutch to connect the front and rear axles. The system varies the torque as necessary depending on driver input. Like the E63 AMG, the GT four-door gets a drift mode where all the power is sent rearward. Drift mode is standard on the S, optional on the GT63 and not available on the American-spec GT53.

Additionally, the V8 models come standard with rear-wheel steering, using the same setup as the rest of this new breed. At slow speeds, the rear wheels point in the opposite direction to tighten turning radius; at higher speeds, they turn in the same direction to increase stability using two electric actuator motors.

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Like all good AMGs, the GT four-door comes with drive modes for slippery, comfort, sport, sport-plus and race that affect the steering, power application, transmission and traction control. As you turn the knob toward race, you get more power, quicker shifts and less intervention from the safety systems.

As for the most important safety system, the brakes, Mercedes has you covered. V8 models get six-piston front calipers and single-piston floating calipers at the rear. The GT63 gets red clampers, the GT63 S gets yellow. The GT53 has smaller discs but still a six-pack of pistons in front inside silver calipers. Ceramic brakes are offered, in bronze. Surrounding those brakes are 19-, 20- or 21-inch AMG-specific wheels.

Moving from the corners to the interior, the GT four-doors get a new steering wheel with controls for infotainment and drive modes, turbine air vents like its two-door counterpart, two 12.3-inch widescreen displays and the usual central controller with swipe and pinch motions. A program called AMG Track Pace can keep your lap times, check your sprint times and log your lateral and longitudinal g-forces.

Elsewhere inside, buyers will be offered the usual array of Mercedes stuff, including diamond quilting on the seats in leather or microfiber, carbon-fiber or brushed metallic accents and an executive rear seat package that comes with a touchscreen between the back seats for calling up dynamic data via the AMG menu, controlling the ambient lighting or adjusting the climate control and seat heating.

The first AMG GT four-doors come in early 2019; the I6-powered GT53 comes later next year.