Guide: Mercedes-Benz C197 SLS AMG Gullwing & Roadster
Background
When the C199 SLR McLaren made its debut in late 2003, the long overdue absence of a super high performance Mercedes-Benz that you could actually buy came to an end.
Aficionados of the marque had waited 40 years for such a machine, during which time they had been teased with the occasional concepts and prototypes that, for one reason or another, never made it to production.
Prior to the SLR McLaren’s arrival, the last production supercar to wear the three-pointed start had been the W198 300 SL. Originally produced in Gullwing trim between 1954 and 1957 and then as a Roadster from ‘57 to ‘63, the W198 was subsequently replaced by a less expensive type of SL with broader market appeal.
When the Gullwing-doored C111 broke cover at the Frankfurt Motor Show in late 1969, it seemed that Mercedes would imminently return to the top tier of performance cars. However, the firm remained true to their word and the C111 served exclusively as an R&D platform for new technologies.
22 years later, the C112 concept of 1991 was ultimately abandoned owing to production and economic issues.
It was those production issues (Mercedes were not geared up for hand-built assembly) that ultimately led the firm to approach their Formula 1 partner of the period, McLaren, to finally build a W198 successor. As the AMG plant was not capable of churning out the number of cars that would be required, it fell to McLaren to produce the all-new SLR in England.
Although the SLR was well received, it proved very expensive and fell well short of the 3500 units that Mercedes had originally hoped to sell. Nevertheless, the SLR programme proved a worthwhile image-building exercise and mid-way through production, plans were afoot for a successor.
For this next car, Mercedes wanted the project handled almost entirely in-house. The SLR’s replacement would also have to be offered at a more reasonable price in the hope of achieving a circa 500% uptick in sales. Such a figure would enable the car to be built on a dedicated line at Mercedes’ Sindelfingen plant alongside other AMG models.
The resultant C197 SLS AMG was unveiled at the Frankfurt Motor Show in September 2009.
It was the first Mercedes road car developed exclusively by AMG who had been given the green light to start work back in March 2006. This new Super Leicht Sport was also the first Mercedes to feature an aluminium chassis and body. Most excitingly though, it marked a return for the Gullwing doors that had made the original 300 SL of 1954 to ‘57 such a design icon.
To manufacture the SLS bodyshell, Mercedes turned to Magna Steyr in Graz, Austria. Born out of the old Steyr-Daimler-Puch conglomerate, at the time, Magna Steyr had an annual production capacity in excess of 200,000 vehicles which made it the largest contract manufacturer for automobiles worldwide.
From Graz, the bare bodyshells were transferred to Sindelfingen where they were united with hand-built-engines shipped in from AMG’s Affalterbach facility.
Deliveries began in September 2010.
One year later, an SLS Roadster was unveiled at the 2011 Frankfurt Motor Show.
Chassis
Each SLS was based around an extremely rigid aluminium spaceframe with a front-mid-engined layout and 2680mm wheelbase.
In order to reduce weight and maximise stability, the thickness of the spaceframe’s cast aluminium was varied according to its load-bearing requirements. Steel (which made up just 4% of the bodyshell) was added only where necessary to enhance protection.
All told, the completed spaceframe weighed just 241kg.
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.
Cast-iron vented discs brakes were fitted all round. Those at the front had a 390mm diameter with six-piston aluminium calipers while the back end ran 360mm diameter discs with four-piston iron calipers.
Mercedes offered a choice of three wheel designs for the SLS. The standard set up comprised seven-spoke light alloy rims with a burnished Titanium Grey finish (19 x 9.5-inches front and 20 x 11-inches rear).
Track was 29mm wider at the front of the car.
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.
Engine / Gearbox
In the engine bay was a Type M159 naturally aspirated 90° V8 derived from AMG’s M156 power unit that had been around in one shape or another since late 2006.
Like the M156 motor, the M159 engine created for the SLS incorporated an alloy block and heads with dual overhead camshafts per bank and four valves per cylinder. Similarly, an 11.3:1 compression ratio was retained and displacement was kept at 6208cc thanks to a bore and stroke of 102.2mm and 94.6mm respectively.
Mercedes stated that 120 updates were made in the transition to M159 trim. The most important concerned the oil supply, intake and exhaust systems, the valvetrain, camshafts and crankshaft drive.
Unlike the base unit, the M159 engine ran a dry-sump lubrication system that allowed the engine to sit lower in the chassis. It also helped avoid oil starvation under hard acceleration and cornering.
An all-new intake system incorporated a more efficient magnesium intake manifold with precisely matched resonance tube lengths for optimised cylinder charging.
There was a more sophisticated valve drive with space-saving bucket tappets that allowed for a rigid set-up and therefore higher engine speeds. The enlarged intake valves had a 40mm diameter while on the exhaust side they measured 34mm.
All four camshafts were now continuously variable over a range of 42°. Both the intake and exhaust camshafts were adjusted electro-hydraulically by the ECU according to engine load and speed.
Other new equipment included racing-style tubular exhaust headers, light weight forged pistons, a reinforced crankshaft bearing and a wholly aluminium crankcase.
Engine management was courtesy of a re-mapped Bosch ME 9.7 control unit.
Peak output was 563bhp at 6800rpm and 479lb-ft at 4750rpm. This was sufficient for Mercedes to proclaim the M159 engine as the most powerfully normally aspirated motor in production.
Transmission was through an AMG Speedshift DCT seven-speed automatic transaxle connected via a lightweight carbonfibre driveshaft. The dual clutch arrangement saw one clutch close while the other opened to ensure minimal loss of torque transmission. Shift times took less than a hundred milliseconds.
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.
Bodywork
Visually it was the C197’s Gullwing doors that stole the headlines and guaranteed the SLS a massive amount or press exposure. While other manufacturers had adopted scissor and butterfly doors over the years, the Gullwing approach remained unique to Mercedes.
Instead of heavy electric door mechanisms, Mercedes opted for manual operation with simple gas struts which saved a reputed 40kg.
The 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.
The front of the SLS was dominated by a quintet of intakes above which elegant headlight clusters were mounted underneath clear glass covers. As per the original W198, a large nose-mounted three-pointed star was accessorised with distinctive horizontal whiskers.
Down each flank, scalloped engine cooling vents were carved out from each front fender to break up what would otherwise have been a rather slab-sided profile.
The cropped and rounded tail was home to an electric rear spoiler that deployed into the airflow at 120kmh / 75mph. It also acted as an airbrake. Underneath was a massive black diffuser.
Aside from the polyurethane bumpers and sill covers, body panels were aluminium.
Interior
The SLS cockpit was dominated by a wide transmission tunnel trimmed with an enormous natural alloy fascia that extended most of the way up the central console. It housed an array of switchgear and topped out just below the TFT colour display screen.
More switches were located on the leather-rimmed three-spoke steering wheel, behind which were the steering column-mounted natural aluminium shift paddles.
The 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 a 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
Mercedes offered an extensive list of optional upgrades for the SLS.
Perhaps the most desirable was carbon ceramic brake discs (402mm front and 360mm rear) which resulted in a 40% weight saving and gave increased stopping power.
Instead of dark grey, customers could specify brake calipers in either red or bronze.
The two wheel upgrades comprised a five twin-spoke design (with burnished Titanium Grey finish) or lightweight ten-spoke forged alloy wheels. The forged rims could be specified with either a burnished Titanium Grey finish or with Matt Black centres and a burnished Titanium Grey edge.
AMG Ride Control automatically adjusted the damping level to suit driving style and road surface. It also enabled the driver to manually select one of three different modes: ‘C’ (Comfort), ‘S’ (Sport) and ‘S+’ (Sport Plus).
The AMG Performance Suspension pack came with firmer springs and dampers.
In addition to carbonfibre exterior mirrors and a carbonfibre engine compartment cover, buyers could select from two levels of carbonfibre interior equipment: the AMG Carbonfibre Interior Trim option included a carbonfibre centre console and door trim while the AMG Interior Carbonfibre Package added carbonfibre door sill panels and seat trim.
In terms of paint, there was a range of gloss or matte shades to include the extremely expensive AMG Alu-Beam Silver option.
Further cockpit personalisation was offered in the shape of lightweight AMG sports bucket seats (manually adjustable and with no heat or memory option), an AMG Performance steering wheel with alcantara inserts and seats in single or two-tone Designo Exclusive leather or with a combination of natural and woven hide.
Electronic devices available included an eleven-speaker 1000-watt Bang & Olufson audio system, a reversing camera, telephone pre-wiring, a garage door opener and blind spot assist. The multimedia system could be enhanced with torque, output and accelerator position data, an internet function and lap data analysis facility.
Weight / Performance
The SLS weighed in at 1620kg and had a 47-53 front-rear distribution.
0-62mph took 3.8 seconds and top speed was 197mph.
SLS AMG Roadster
Having planned to produced an open-top variant from the outset, Mercedes unveiled an SLS Roadster at the Frankfurt Motor Show in September 2011.
To compensate for the lack of a roof, the Roadster’s aluminium spaceframe featured reinforced sills, 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 as opposed to 241kg).
Moreover, as a consequence of Mercedes’ decision to fit a fabric soft-top with a steel, magnesium and aluminium construction (instead of a complex and heavy metal roof), the Roadster ultimately tipped the scales at only 40kg more than the Coupe (1660kg as opposed to 1640kg).
The SLS Roadster had conventional instead of Gullwing doors and a roof that could be specified on one of three colours (black, beige or red).
The roof itself took eleven seconds to raise or lower and could be operated at speeds of up to 50kmh / 30mph.
Performance figures were identical to the Coupe.
The Roadster could not be configured with the optional AMG Performance Suspension with its stiffer springs and dampers.
SLS AMG Matte Edition
In June 2012, Mercedes announced a batch of 25 special edition cars for the Japanaese market. They were produced in four different variations, all of which came with Matte paint, ten-spoke forged alloys with matt black centres, red brake calipers, matt black exhaust tips, high gloss black interior trim, AMG Ride Control adjustable suspension and the AMG Performance steering wheel with alcantara inserts.
The Matte Black variants were painted Designo Magno Night Black with contrasting red accents applied to the nose-mounted three-pointed star and whiskers, the wheel rims, front fender vent blades, the hood vent blades, the fuel filler cap plus all badges / emblems. Interiors were equipped with two-tone black and red upholstery. Five Coupes and five Roadsters were produced.
The Matte White variants were painted Designo Magno Cashmere White with contrasting black accents and two-tone porcelain and black upholstery. Five Roadsters and ten Coupes were built.
Deliveries began in September 2012.
End of Production
SLS production ended in late 2014 and Mercedes have been highly secretive about the number built.
Our best guess is that somewhere in the region of 8000 Coupes and 4000 Roadsters left the Sindelfingen production line.
Text copyright: Supercar Nostalgia
Photo copyright: Mercedes-Benz - https://www.mercedes-benz.com
