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BACKGROUND

At the New York Motor Show in March 2010, Mercedes unveiled a GT3 racing version of the critically acclaimed SLS AMG that went on to prove itself an enormously effective machine at both national and international level.

The standard SLS base car that pre-dated the GT3 had itself arrived just six months prior as Mercedes’ long overdue Gullwing-doored successor to the iconic W198 300 SL produced between 1954 and 1957. The 52 year gap between the two cars had seen Mercedes produce a handful of super sports cars with Gullwing doors, but unfortunately these C111 and C112 prototypes had either served strictly as R&D testbeds or never made it into series production for reasons of timing and production logistics.

The issue of actually manufacturing a high end supercar was eventually circumvented when Mercedes’ F1 partner of the time, McLaren, went on to handle assembly of the jointly developed SLR manufactured between 2004 to 2010. However, sales of the wickedly expensive carbon-tubbed SLR were disappointing and the absence of Gullwing doors meant the SLR could never be considered a true successor to the original W198.

Nevertheless, the SLR proved a worthwhile image-building exercise and, mid-way through production, Mercedes began to plan for a less expensive Gullwing-doored replacement, the development and assembly of which would be handled in conjunction with AMG.

Following a successful roll out for the SLS and its GT3 spin-off, Mercedes unveiled a Roadster version at the Frankfurt Motor Show in September 2011.

Just over a year later, this trio were joined by a more driver-focused limited edition SLS inspired by the success of the GT3 race version: the SLS AMG GT.

Unveiled at the Paris Motor Show in September 2012, the SLS GT was offered in both Gullwing and Roadster body styles but with a total production run limited to 350 units. It offered enhanced performance thanks to a combination of suspension, engine and transmission upgrades along with some subtle cosmetic tweaks, an array of sporty cockpit additions and several normally optional pieces of equipment thrown in as standard.

ENGINE / TRANSMISSION

Arguably the most significant aspect of the GT package concerned its engine and transmission.

Thanks to what Mercedes dubbed “internal de-throttling measures and an increase in peak combustion pressure”, throttle response was improved and the power output of AMG’s Type M159 naturally aspirated 90° V8 went from 563bhp to 583bhp at unchanged 6800rpm. The torque rating was an unchanged 479lb-ft at 4750rpm.

Like the M156 motor from which it had been derived, the M159 engine created for the SLS featured an alloy block and heads with continuously variable dual overhead camshafts per bank, four valves per cylinder, dry-sump lubrication, a custom intake system with magnesium intake manifold, sophisticated valve drive, racing-style tubular exhaust headers, light weight forged pistons, a reinforced crankshaft bearing, an aluminium crankcase and Bosch ME 9.7 engine management.

As per the base SLS, compression was kept at 11.3:1 and a 6208cc displacement was carried over by way of 102.2mm cylinder bores and a 94.6mm stroke.

The GT’s more powerful engine was hooked up to a re-calibrated version of the AMG Speedshift DCT dual-clutch seven-speed transaxle which offered even quicker shift times in Manual mode thanks to re-mapped gearbox software. The automatic double-declutching function when downshifting was also more pronounced.

As usual, the driver could select from four different gearbox modes: ‘C’ (Controlled Efficiency), ‘S’ (Sport), ‘S+’ (Sport Plus) and ‘M’ (Manual). In the ‘M’ setting, shifts had to be executed manually by way of two F1-style paddles mounted to the steering column.

There was also a Race Start launch control function as per the regular SLS.

CHASSIS

Each GT was based around a standard SLS aluminium spaceframe, the thickness of which varied according to load-bearing requirements. Steel (which made up just 4% of the bodyshell) was added only where necessary to enhance protection.

All told, in Gullwing Coupe trim the spaceframe, which utilised a front-mid-engined layout and 2680mm wheelbase, weighed 241kg.

As for the Roadster, to compensate for the lack of a roof Mercedes reinforced the sills, fitted a beefed up central tunnel, a supplementary dash cross-member and a curved strut between the soft top and fuel tank (to reinforce the rear axle). There was also an additional cross-member behind the seats to support the rollover protection system.

The net result was a spaceframe that was almost as stiff as the Coupe and weighed just 2kg more (243kg).

Like every SLS, suspension was via double wishbones with Sachs coil springs and Bilstein dampers. Anti-roll bars were fitted at either end. The wishbones, steering knuckles and hub carriers were made entirely from forged aluminium.

For this latest GT variant, Mercedes introduced a newly developed AMG Adaptive Performance Suspension with stiffer, more aggressively tuned electronically controlled spring / damper units that adjusted in real time to reduce body roll. One of two alternative modes (‘Sport’ and ‘Sport Plus’) could be selected via the AMG Drive Unit.

Imported without change was the standard SLS brake system which comprised cast-iron vented discs brakes all round. These had a 390mm diameter with six-piston aluminium calipers up front and a 360mm diameter with four-piston iron calipers out back. The one change saw red-painted calipers fitted as standard.

Also automatically fitted to the GT were the normally optional lightweight ten-spoke forged alloy wheels complete with machine polished faces and matt black inlays. As usual, these measured 19 x 9.5-inches at the front (with 265/35 R 19 tyres) and 20 x 11-inches at the rear (with 295/30 R 20 tyres).

ABS was standard along with power steering, electronic tyre pressure monitoring and a three-stage Electronic Stability Programme.

An 85-litre fuel tank was installed over the rear axle.

BODYWORK

Externally, Mercedes made a handful of subtle cosmetic alterations that stood the GT apart from a regular SLS.

The head and tail light assemblies were both given a darker finish.

In a similar vein, the recesses of the three-pointed star and the wing-shaped cross fins mounted alongside, the exterior mirrors and the fins on the front hood and fenders were all now given a high gloss black finish.

On the trunk lid, a special GT script was added to the AMG badge.

Otherwise, the regular SLS and GT were identical to one another.

The Coupe’s manually-operated gas strut Gullwing doors opened to an angle of 70° and a height of 1.5m which enabled the SLS to fit in any normal height garage. The exterior handles lay flush with body until being unlocked at which point they popped out to enable access.

Within 15 milliseconds of a rollover having been detected, explosive bolts located at the tops of the doors fired to separate them from the rest of the body.

By contrast, the SLS Roadster had conventional doors and a fabric soft-top that took eleven seconds to raise or lower and could be operated at speeds of up to 50kmh / 30mph.

Aside from the polyurethane bumpers and sill covers, body panels were aluminium.

INTERIOR

Inside, GT-specific equipment fitted as standard included alcantara for the seat and door inlays along with the steering wheel side sections, an AMG logo embossed onto the seat headrests, red contrast stitching for the seats, centre console, dash and door panels, red seatbelts, red door panel lining, a red 12 o’clock marker on the steering wheel and red-trimmed floor mat edging.

There was also new high gloss black trim for the centre console, door panels, air vent rings and the steering wheel’s vertical spoke plus black dial faces for the speedometer and rev counter and a black shroud for the LED shift lights.

The rest of the cockpit architecture was unchanged.

A full width dash incorporated a small instrument binnacle that housed analogue gauges for road and engine speed. In between was a digital read out, above which was the aforementioned bank of seven LED upshift indicators.

Electric memory seats came with magnesium backrests. They were timmed in Nappa leather with contrast top-stitching to match the dash and door panels (the latter of which featured an embossed AMG insignia).

Anthracite alcantara was used to upholster the headliner along with the A and C-pillars. The footwells and rear bulkhead were carpeted.

The list of standard equipment included electric windows, electric mirrors, parking sensors, eight airbags, central locking with keyless-go and automatic climate control. There was also the aforementioned multimedia system with seven-inch TFT colour display, satellite navigation, six speakers, CD / DVD drive, six-disc shuttle, 4GB of storage space and Linguatronic voice control.

OPTIONS

A new option available exclusively on the SLS GT was the AMG Designo Style package

This expensive upgrade comprised full Designo leather (to include the entire dashboard, the beltlines, door armrests and the centre console handrest), diamond quilting for the seat and door panel inserts, contrast stitching, black floor mats with porcelain leather edging and the option of contrast seat piping. Porcelain alcantara was used for the roof lining and parcel shelf (Coupe) or roll-over bar (Roadster). Customers could choose from three alternative colour combinations which were offered in both mono and duo-tone finishes: Mocha Brown with Porcelain, Titanium Grey with Porcelain or Mystic Red with Porcelain.

Other optional extras included carbon ceramic brake discs (402mm front and 360mm rear) which resulted in a 40% weight saving and gave increased stopping power, exposed carbonfibere for the exterior mirrors, engine compartment covers, seat backrests and sides, door sill panels and centre console, a Bang & Olufsen BeoSound surround sound system, lightweight AMG sports bucket seats (manually adjustable and with no heat or memory option), a reversing camera, telephone pre-wiring, a garage door opener and blind spot assist and the AMG Performance Media system which provided torque, output and accelerator position data, an internet function and lap data analysis facility.

WEIGHT / PERFORMANCE

In its transition to GT trim, weight of both the Gullwing Coupe and Roadster variants remained unchanged at 1620kg and 1735kg respectively.

Both variants had an identical 197mph top speed as per the regular SLS but as a consequence of the re-mapped gearbox software 0-62mph times were a tenth quicker at 3.7 seconds.

SLS AMG GT FINAL EDITION

Although Mercedes had originally stated that only 350 examples of the GT would be built, the German firm subsequently went on to announce a further run of 350 cars dubbed the GT Final Edition.

Unveiled at the Los Angeles and Tokyo Motor Shows which both opened on November 20th 2013, the GT Final Edition comprised 200 Gullwing Coupes and 150 Roadsters, all of which came with several new features.

A high downforce kit comprised the vented hood and fixed rear spoiler from the SLS Black Series (covered separately) along with a custom chin spoiler. All three of these components were finished in exposed carbonfibre. As well as helping to dissipate heat from the engine, the vented hood further increase downforce over the front axle and improved the car’s drag coefficient.

Designo Magno Graphite matt paint was standard issue for the Final Edition.

Additionally, the rear apron’s vent struts now came finished in high-gloss black as opposed to body colour.

Another unique aspect of the Final Edition was its set of forged light-alloy wheels which Mercedes supplied in matt black with either a high sheen rim or high sheen rim and matching spokes.

Dunlop Sport Maxx Race Cup tyres were a no-cost option.

Inside, the Final Edition came with the normally optional AMG Designo Style package and high gloss carbonfibre trim as standard along with black leather upholstery, silver stitching, silver seat belts, a silver 12 o’clock marker for the steering wheel and black floor mats edged in silver leather. There was also a unique alcantara inlay set into the upper dash and an ‘AMG Final Edition 1 of 350’ commemorative plaque mounted on the centre console.