AMG chief Tobias Moers says this 4.0-litre engine is now nearing the limit of its performance potential. Handily for him, on the basis of this road test – in the lesser of two available derivatives, let’s not forget – you have to question how much more power a four-door performance car could ever sensibly need.
With the car’s launch control program working well and the traction benefits of four-wheel drive very evident, our telemetry timed the 577bhp GT63 to 62mph in 3.4sec, with 100mph arriving after 7.7sec – a mere 0.5sec behind that of the Mercedes-AMG GT R tested in 2017.
On a cool dry surface, the car’s getaway is fantastically crisp, as fresh waves of force then jolt the car forward with each successive gear ratio dropping the tacho needle right into the sweet spot of the engine’s power band. MIRA’s testing straights are a mile long, which was enough for the GT63 to surpass 170mph with a zeal that suggests the claimed 193mph top speed is either electronically enforced or quite conservatively estimated.
The car’s standard-fit cast-iron brakes well match this whirlwind of acceleration, biting crisply but without unnecessary assistance and eliciting barely a squirm from the chassis when worked hard. The GT63 duly pulled up from 70mph just 3.9ft later than its coupé sibling, despite tipping the scales at 2135kg – some 470kg more than the GT R.
The GT63’s outright performance potential is somewhere between mesmerising and intimidating to comprehend, then, although the car can serve up its performance in a more versatile fashion when you want it to. In fact, AMG’s twin-turbo V8 has arguably found its ideal home in the four-door GT. Such a supremely characterful engine begs to be wrung out (rarely, if ever, will you disable the sport exhaust) and works with a throttle response and lack of crankshaft inertia that belies the deep, barrelling soundtrack.
The closely stacked low to intermediate gears of this well-mannered nine-speed transmission also ensure the revs rise supercar quick with the throttle wide open; but so tractive is this twin-turbo V8 that rapid progress isn’t reliant on that style. Huge torque propels the car along in a high gear with enough in reserve for easy-going overtaking. Our test car needed less than three seconds to surge from 50mph to 70mph in fifth gear, which is comfortably brisker than the W12-engined Continental GT.