The arsenal of technology required to make a 5.05m-long, 2.1-tonne car handle like a smaller, lighter, lower-slung sports car takes some wrapping your head around. The GT 4-Door Coupé does without the lightweight spaceframe construction of its two-door namesake, instead relying on Mercedes’ MRA monocoque car platform – and that’s why it weighs so much, and why there is so much physics for all that tech to overcome.
Our GT63 4Matic+ test subject – the current entry-level derivative for the UK market – is powered by Affalterbach’s 4.0-litre biturbo V8 engine. The ‘hot-vee’ configuration of the motor’s twin turbochargers should be familiar, but the use of so-called ‘anti-friction’ bearings inside those turbochargers is new and helps to sharpen the motor’s responses. In the GT63, the V8 makes a peak 577bhp and 590lb ft, the latter spread from 2500rpm to 5000rpm.
The upper-level GT63 S 4Matic+ derivative, meanwhile, makes fully 630bhp and 664lb ft. In either case, and true to form, AMG plainly hasn’t risked under-endowing its four-seater debutant. The car deploys its firepower to all four wheels via AMG’s nine-speed multi-clutch transmission (in which a wet clutch in place of a torque converter helps reduce weight and inertia) while an electromechanically controlled clutch rallies torque from the permanently driven rear axle forwards as required.
The AMG’s suite of cutting-edge drivetrain and chassis technology doesn’t end there. There’s a torque-vectoring, actively locking differential at the rear axle; four-wheel steering as standard; active aerodynamics similar to those found on the GT R coupé; lightweight alloy wheels; and an electromechanical steering rack with a passive variable ratio. A multitude of drive modes and corresponding selectable traction and stability control programs (the latter dubbed AMG Dynamics) are also present to allow the driver to fine-tune the handling to a level that, AMG claims, isn’t possible on its lesser cars.
For suspension, V8-powered GT 4-Doors make use of a pseudo double-wishbone arrangement at the front and a multi-link configuration at the rear, along with air springs and AMG’s Ride Control adaptive dampers. Anti-roll bars derived from those of the GT R help reduce the weight of both axles.
On that subject, however, our fully fuelled GT63 weighed 2135kg on our test scales, with that mass split 54:46 front to rear. For perspective, the front half of it weighed 1155kg – 10kg more than an entire Volkswagen Polo. The BMW M5 we tested last year was almost 200kg lighter. Not the best omen for the car’s handling – but also not one beyond AMG’s established powers to recover from.