Allied to a new twin-turbocharged 5.5-litre V8 petrol engine, the lightweight structure provides it with the potential for greater performance and added handling prowess.
Power has increased by 11bhp to 529bhp endowing the car with an ultimate power-to-weight ratio of 314bhp per tonne. That’s an increase of 30bhp per tonne over the old model.
Torque is up by 73lb ft, or a whopping 199lb ft with the higher engine tune, which extends its torque-to-weight ratio by 30lb ft per tonne to 375lb ft per tonne – or 89lb ft per tonne more than the far more expensive SLS. For those who want a bit more power have the option of the SL 65 with its mammoth 6.0-litre V12 engine and 621bhp and 737lb ft of torque.
There are two driving modes, accessed by a button on the centre console: Comfort and Sport. The Comfort setting places a clear emphasis on overall refinement and all-round compliancy and is perfectly suited to city driving and loping part-throttle cruising, at which the SL 63 feels right at home, thanks to the inherent flexibility of its engine.
But it is the Sport mode, bringing sharper throttle and steering response as well as firmer spring and damper settings, that you need to have engaged to extract the best of its dynamic abilities. A further AMG mode also remaps the electronic stability control to delay the point of its intervention.
The engine is the clear focal point, and despite its inclusion of sound-dampening turbochargers, the SL 63 bellows like a Nascar racer when worked with a heavy right foot. Keep the throttle planted and you’re also treated to a heavy swirl of exhaust gas out back – something that’s further intensified when you’re running with the new car’s superbly engineered aluminium roof folded back underneath the boot lid.
Acceleration is brutal, mechanical grip is immense and the brakes – at least, the carbon-ceramic units that come with the optional Performance Package fitted to our test car – offer breathtaking levels of stopping ability. In these three disciplines, it clearly deserves its supercar billing.
However, there are points of dispute. The gearbox, a reworked version of Mercedes’s seven-speed auto fitted with a wet clutch, is tardy to respond. It is not so much the action of the gearbox itself that disappoints, because the actual shifting of gears is quite rapid. No, the problem is the lack of decisiveness between the point where you flick the paddle to the point where the electronics initiate a change of gear.
The SL 63 sits on an aluminium-intensive chassis that gets a uniquely calibrated version of the advanced Active Body Control system offered on the standard SL. Ride height varies according to the driving mode and speed, while pitch and roll are exceptionally well suppressed, even on wildly undulating roads and during all-out cornering. Begin pushing and you discover plenty of front-end bite, and the rear, which has a locking diff a, is remarkably well planted.
The overall limits of adhesion are extremely high – helped, no doubt, by track widths that are up a significant 50mm at the front and 52mm at the rear over the old SL 63’s and a wheel and tyre combo (with the Performance Package) that sites 255/35-profile rubber on 19-inch wheels up front and 285/30-profile hoops on 20-inch rims at the back. With the AMG mode engaged, the recalibrated ESP system also allows you to edge up to the point of breakaway without any premature electronic intervention.