Chassis & Powertrain
The new SL is available with two different suspension systems: the SL features semi-active adjustable damping as standard. The optional active suspension system ABC (Active Body Control) is available as an option. Both suspension variants are combined with a new electromechanical Direct-Steer system featuring speed-sensitive power steering and a ratio that can be varied across the steering wheel angle. Mercedes-Benz says this ensures excellent straight-line stability. It also reduces the amount of steering required when parking and manoeuvring in tight spots.
The new V8 in the SL 500 develops 320 kW (435 hp) from its displacement of 4663 cc and thus around 12 percent more than its predecessor despite some 0.8 litres less displacement. The fuel consumption has been reduced by up to 22 percent. At the same time, the torque has increased from 530 Nm to 700 Nm – a gain of 32 percent.
The SL 350, whose engine capacity remains unaltered, but is a new V6 engine, develops 225 kW (306 hp) and delivers 370 Nm of torque. It uses just 6.8 litres of fuel per 100 kilometres, which is around 14 kpl making it almost 30 percent more economical than its predecessor.
Both engine variants come with a standard-fit ECO start/stop function. The 7G-TRONIC PLUS automatic transmission, which has been optimised in relation to fuel consumption and comfort, also contributes to the exemplary, low fuel consumption. The SL 350 accelerates from 0 to 100 km/h in 5.9 seconds, making it three tenths of a second faster than its predecessor. The SL 500 takes just 4.6 seconds – eight tenths less than the previous SL 500. All this performance improvement without sacrificing frugality.
All Aluminium Bodyshell: In Detail
We’ve seen journos abroad bemoan the fact that cars are getting heavier the last two decades than those before thanks to the additional safety features on board cars. Mercedes-Benz, who has for long been lauded for the leap in safety features made with each generation of the S class, then should be making cars heavier each year. Fortunately, when you have a badge the says SL, there is no option but to make it lighter, and lighter.
A weight loss of 140 kgs definitely seems to be the kind of engineering voodoo that only the Germans are capable of. Under the aluminium outer skin there is a bodyshell made almost entirely from aluminium, with only very few components being made from other materials. Magnesium, which is far lighter than aluminium is used in parts for the rear panel. The A-pillars and the roof frame are of steel sheet metal incorporating high-strength steel tubing. These parts have to be steel for the sake of occupant safety, to provide survival space in the event of the vehicle overturning.
Although aluminium is easy to work with, the structure had to be designed to be superior to a steel construction in terms of rigidity and comfort. Engineers at Mercedes-Benz worked on intelligent lightweight construction, optimizing every single component of the aluminium bodyshell for its particular function and expected load. This led to the necessity of more than one process to make different kinds of aluminium depending on the function of the component. Some parts are made by chill casting or vacuum die casting, some worked into extruded aluminium sections or into aluminium plates of thicknesses that vary within one and the same component; these are the so-called tailored welded blanks.
Chill casting is a term we aren’t yet familiar with and seems to be a method where an object ( the chill ) in introduced to promote solidification in a particular portion of the mold.
The bodyshell weight is made up of: 44 percent cast aluminium, 17 percent aluminium sections, 28 percent aluminium sheet metal, 8 percent steel and 3 percent of other materials.
Mercedes also lists the methods used to join these aluminium bits together.MIG welding, hemming, bonding, self-piercing rivets, flow hole bolting, or friction stir welding ( FSW ). FSW is a joining method by which a highly resistant weld seam is produced by means of friction heat, a method particularly well-suited for aluminium on account of its low melting point. In this method, the metal bits are joined without actually melting, which ensures the metallurgical properties of the bits to be welded are unchanged even after the process.
If you are still with us, read on. Mercedes-Benz helpfully has put out a bulletin list of the highlights of this feat of engineering.
- The Front Wall is at present the largest aluminium cast component made in large series for vehicle bodywork
- Many sheet metal parts are designed in such a way that for the first time they can be made from 100 percent recycled aluminium, saving 80 percent of the energy used in their production.
- The main floorpan is a 3-layer shaped panel made from thin, extrusion-moulded hollow sections, welded together by friction stir welding.
- The longitudinal members in the vehicle front end are made using high-pressure hydroforming (IHU) technology, which enables the creation of highly complex and robust components, permitting optimum use of reduced installation spaces.
- The door sills (longitudinal members) consist of 1.7-metre long, 7-chamber extrusion-moulded aluminium sections; these provide rigidity in the lateral sectors and safety in the event of a collision. Flexible chamber distribution makes possible a minimum component weight coupled with optimum characteristics.
- The tunnel is made of aluminium sheet metal with a reinforcement of varying thickness (3 different thicknesses depending on sector, a so-called tailored welded blank TWB).
- The rear sector floor is a MIG welded frame with a hollow chilled cast longitudinal member as its central element. This technique is employed in the SL for the very first time in automotive bodyshell construction.
- The rear sector floor frame structure is closed by floor sheet metal panels and the boot tub made by vacuum die-casting.
- The boot recess is made from recycled sheet metal.
- The central member connects the front end with the rear sector floor. The mounting points for the drive shaft, the transmission cross beam, the transmission tunnel braces and the seat bolting points on the tunnel side are all integrated into a single element. The wall thicknesses and rib distribution are oriented bionically towards the requirements and loads.
- Many other components were optimised bionically, i.e. based on examples from nature. These structures reduce the vehicle weight compared to a classic design even further. Hence the weird shapes all over the aluminium structure.
All the efforts of the engineers at Merc paid off in with a lightweight, torsionally and flexurally rigid bodyshell with an optimum rigidity/weight ratio. It was possible to increase the bodywork’s torsional rigidity by more than 20 percent over the previous generation.