Among the detailed mechanical changes over the standard SLS is a lightly fettled engine boasting improved breathing properties. The naturally aspirated 6.2-litre V8 kicks out an added 18bhp, with 581bhp developed at 6800rpm. Torque remains the same, swelling to 469lb ft at 4750rpm.
Accompanying the boost in power is a reworked seven-speed gearbox that uses new, in-house-developed software algorithms for an improved shift action. The dual-clutch unit, supplied by Getrag and located within the rear axle assembly, is described as being more direct and spontaneous on up-shifts in manual mode. It has also been programmed to provide a more pronounced blip of the throttle and double-declutching action during downshifts.
Most of all, it is the changes brought to the suspension that help define the hardened character of the SLS GT.
The double wishbone arrangement with variable damping control retains the same basic geometry and ride height as the SLS, but the elastokinematic properties have been altered to provide the car with a more focused nature.
Despite the suspension upgrade, however, the SLS GT rides on the same wheels and tyres as the standard SLS, with 265/35 profile rubber on 19-inch alloys up front and 295/30 on 20-inch rims at the rear.
The first clue to the SLS GT’s added potency comes the moment you hit the starter button. The reworked engine, which sits well back in the engine bay on the same hydraulic mounts, fires with greater urgency, and as you get up to speed the signature baritone exhaust note is even more alluring than that of the standard SLS.
The naturally aspirated engine lacks the low end explosiveness of other turbocharged mills but it provides tremendous mid-range punch. With a 0-62mph time of 3.7sec the GT is quicker off the line than the standard SLS, but only by 0.1sec in coupé guise. While there’s little to indicate the engine’s added reserves in terms of outright acceleration, the hardcore soundtrack at the business end of the rev range has always been at the root of the appeal of the SLS, and so it is here.
It delivers on the dynamic front, too, in line with the head of AMG development Tobias Moers' assertion that the SLS GT operates on a much higher level than the earlier SLS.
Even at moderate speeds at part throttle there’s a noticeable improvement in the action and overall efficiency of the gearbox, with a crisper and faster action.
This is more apparent on full-bore up-shifts and lunging downshifts, which are fired off in a more efficient action with less of a pause between the declutching of one gear and the engaging of the next.
The improvement has been achieved with the adoption of new software, although there is no word yet on whether it will be made available to existing SLS owners as a running change.
Moers also indicates that AMG has made detailed changes to the SLS’s hydraulically actuated steering. There remains a small area of slack around the straight ahead, but the speed sensitive system is more responsive off centre, and weighting has been wound back a tick at the extremities of lock to give the SLS GT a more fluid and confidence-inspiring character.
With larger diameter anti-roll bars, new bushings and firmer springs and dampers, the ride is stiffer than the standard SLS's and there are greater levels of tyre noise at low and high speeds — none of which adds to the car’s hard-earned reputation as a fantastic long distance proposition.