Automotive fascination combined with spectacular racing car design – the new Mercedes-Benz SLS AMG GT3. This racing version of the gullwing model was designed as customer sports car for competing in race series according to the near-series FIA GT3 rulebook. Outstanding handling dynamics are ensured by uncompromising lightweight construction and specific modifications to the suspension, brakes and aerodynamics. This very special gullwing model will deliver its debut performance on the racetrack in 2011.
The purist design and breathtaking contours of this gullwing model are effectively emphasised by specific modifications to the bodywork. The new components made mainly from carbon-fibre are an unmistakable testimony to the outstanding racetrack performance and extensive aerodynamic development work.
At the front the GT3 racing car has a new front apron with larger air intakes: the wide aperture below the characteristic radiator grille with a large Mercedes star and a wing-shaped transverse fin supplies the engine oil cooler and brake discs with cooling air. The two air intakes below the vertically arranged bi-xenon headlamps have the same function. Downforce at the front axle is provided by four externally mounted "flics" and the carbon-fibre front splitter: this blends into the smooth underbody cladding which ends with the rear diffuser.
The bonnet has a central aperture to dissipate the engine heat. The hot air is vented in the wheel arches from side vents in the front wings. Particularly lightweight polycarbonate is used to glaze the side and rear windows, and this is also available for the windscreen.
The front and rear wings have been widened to make space for the large racing tyres. With a width of 1990 millimetres, the body of the GT3 is a good 50 millimetres wider than that of the standard SLS AMG. The new side skirts have apertures for cooling the rear brakes. The smooth underbody is visible at the lower edges of the side skirts. The standardised filler pipe for the fast-refuel system is accommodated in the B-pillar. The 120-litre fuel tank is centrally located behind the driver.
Viewed from the rear, the SLS AMG GT3 impresses with its sheer width. The boot lid is surmounted by a wide carbon-fibre rear aerofoil, which has multiple adjustments and allows a perfect setup for the type of racetrack concerned. The new rear apron features two apertures designed to vent the rear wheel arches. The carbon-fibre rear diffuser is another eye-catching feature: as an extension to the smooth underbody, it gradually rises in the rear axle area and generates a downforce thanks to its shape. The overall aerodynamic concept of the SLS AMG GT3 was refined and finalised in extensive wind tunnel and racetrack tests.
The black exhaust tailpipes emit a thrilling and very characteristic AMG eight-cylinder sound. The rain light prescribed by the rulebook is integrated into the boot lid – it must remain permanently switched on if the weather conditions are poor.
As prescribed by the FIA GT3 rules, the AMG 6.3-litre V8 engine is practically identical to that in the standard model. Thanks to its lower weight, the GT3 will easily better the already outstanding acceleration of the standard model – 3.8 seconds from zero to 100 km/h; depending on the final drive ratio, the top speed will exceed 300 km/h.
The AMG 6.3-litre V8 engine also has a dry sump lubrication system in the racing model. Using vacuum and pressure pumps, as well as an external oil tank, makes it possible to dispense with a conventional sump. This technology ensures reliable engine lubrication even under the high lateral acceleration forces encountered on the racetrack.
Dry sump lubrication also allows a low installed position for the V8 engine – one of the key technological highlights of the SLS AMG. Installing the eight-cylinder engine in the lowest possible position behind the front axle as a front-mid engine, and combining it with the transmission in a transaxle arrangement, produces a very favourable weight distribution.
Unlike in the standard model, power in the SLS AMG GT3 is transferred by a six-speed racing transmission with sequential gear-changes. Thanks to its compact construction, this race-tested transmission has advantages in terms of packaging – after all, the GT3 version has a smaller ground clearance than the standard model. The driver shifts the gears using two shift paddles on the steering wheel. The transmission is mounted directly on the rear axle, and connected to the V8 engine via a flexurally and torsionally rigid torque tube. This has decisive advantages with respect to handling dynamics, as this sophisticated solution enables the entire powertrain to be configured with far less free play. In conjunction with the traction control sysem, a multi-disc locking differential integrated into the transmission ensures outstanding acceleration. A drive shaft rotates at the engine speed within this torque tube. As in the standard model, and also the Mercedes-Benz C-Class DTM racing cars, the shaft is made from carbon-fibre.
The vehicle concept of the SLS AMG is predestined for top-class racetrack performance, with a long wheelbase, a low centre of gravity and a wide track. Its strengths include precise over/understeer characteristics, first-class agility, low inertia during fast changes of direction and high physical limits when cornering.
Very few modifications were required for perfect racetrack performance: the lowered, lightweight aluminium suspension with double wishbones all-round has the ideal kinematics. Multiple adjustments allow the best possible adaptation to the relevant racetrack characteristics and prevailing weather conditions. Not only the spring and damper setups, but also the track width and camber, the suspension height and the stabilisers at the front and rear axles can be adjusted.
The rack-and-pinion steering system with speed-sensitive servo assistance is basically the same as in the standard SLS AMG. The more direct steering ratio makes for even more agile handling on the racetrack.
The AMG motor sports braking system ensures extremely short braking distances, outstanding fade-resistance and great sensitivity: race-tested composite technology is used for all the brake discs. In this system, the grey cast-iron discs are mounted on an aluminium bowl via stainless steel connections in a radially and axially floating arrangement. This sopisticated technology allows perfect heat conduction, and therefore reliable fade-resistance. The SLS AMG GT3 also features precisely configured cooling ducts: apertures in the front apron and in front of the rear wheels supply the brake discs with cool air when on the move. All four brake discs are ventilated, grooved and perforated. Six-piston fixed calipers at the front and four-piston fixed calipers at the rear in anthracite with a white AMG logo allow generous brake lining surfaces. An anti-lock braking system with a special racing configuration is standard. For space reasons, the AMG high-performance ceramic composite braking system optionally available for the standard model is not compatible with the 18-inch wheels prescribed by the FIA rulebook.
The size 12 x 18-inch (front) and 13 x 18-inch (rear) AMG light-alloy wheels with central locking are shod with racing tyres in size 287 x 682 mm (front) and 315 x 708 mm (rear). Depending on the conditions, untreaded slicks, intermediates or rain tyres are used. The classic multi-spoke design assists ventilation of the braking system. Rapid pitstops and wheel-changes are assured by the pneumatic jacking system integrated into the underbody: four pneumatic jacks lift the GT3 racing car by around 190 millimetres to allow very rapid wheel-changes by the pit crew.
Opening the gullwing doors of the SLS AMG GT3 reveals a functional interior with a racing car atmosphere. The driver is seated in a racing bucket seat, his safety assured by a six-point seat belt and the HANS system (Head and Neck Support), which fixes his helmet in a defined position during an accident to minimise the risk of injury. Additional safety is provided by the steel rollover cage, which also serves to reinforce the aluminium spaceframe.
A racing steering wheel with a diameter of 330 millimetres allows perfect vehicle control. Thanks to the open upper section of the rim, the driver always has a clear view of the central display. This keeps him informed about all the relevant parameters such as speed, engine rpm, operating temperatures, lap times and the selected gear. The steering wheel also has a quick-locking feature which allows much easier access and egress. Switches on the steering wheel boss enable the driver to activate additional functions such as the radio link to the pits, headlamp flasher or the drink function. Further controls are mounted on the centre console, for example the start/stop function for the AMG V8 engine, the traction control system, reverse gear and – if the worst should happen – the integrated fire extinguisher system. The brake balance adjustment control is mounted on the tunnel of the torque tube.
The near-series specification of the GT3 version is reflected in the dashboard, whose powerfully arching wing section gives an impression of width. Strikingly integrated into the dashboard, the air vents galvanised in "Silver Shadow" have adjustable, cruciform nozzles reminiscent of an aircraft's jet engines.
The new SLS AMG GT3 was developed to comply with the international FIA GT3 race rules, and is entitled to take part in all GT3 race series – which of course includes the popular 24-hour race in Spa-Francorchamps (Belgium) or the Nürburgring. Interested customers are able to order the GT3 from autumn 2010, and delivery will take place in time for the start of the 2011 racing season. Homologation will be completed in March 2011.