Join Date: Mar 2001
Mercedes-Benz SLR McLaren 722 Edition
Mercedes-Benz SLR McLaren 722 Edition
Mercedes-Benz SLR McLaren 722 Edition: Motor-racing blood coursing through its veins
The new Mercedes-Benz SLR McLaren 722 Edition displays thoroughbred motor-racing credentials. Featuring more than 300 modified components, the super sports car serves up a boost in output, more dynamic chassis tuning, improved aerodynamics and distinctly sporty interior appointments to thrill even the most demanding of sports-car enthusiasts.
The flawless roads which today lead through the desert next to Dubai are ideal for demonstrating the pedigree sporting performance that characterises the Mercedes-Benz SLR McLaren 722 Edition. Dubai is the up-and-coming business centre of the United Arab Emirates (UAE). It is the setting for the world's most ambitious construction projects, including the man-made "Palm Jumeirah" island, and over the course of recent decades many wealthy sheikhs have become avid automobile aficionados. It is this flair for the exceptional that links the desert city on the Persian Gulf and its inhabitants with the Mercedes-Benz SLR McLaren 722 Edition premium sports car.
The new SLR 722 Edition model variant from Mercedes-Benz evokes memories of a particularly special victory achieved in 1955 by the British motor-racing legend Stirling Moss and his co-pilot Dennis Jenkinson at Mille Miglia the classic Italian endurance race behind the wheel of a Mercedes Benz 300 SLR with start number 722 (denoting the car's start time of 7.22 a.m.). Boasting an impressive output of 478 kW/650 hp, the new SLR McLaren 722 Edition super sports car not only outperforms its historic forefather, it even outstrips the scintillating peak performance of the current SLR model. The new limited-edition series only 150 models are being produced, for the most part handcrafted, at the McLaren Formula 1 works in Woking is the brand's response to calls from highly discerning SLR customers for even more sportiness combined with the same high level of everyday practicality.
At the heart of the SLR 722 Edition is a 5.5-litre supercharged V8 assembled by hand at the Mercedes-AMG engine workshops in Affalterbach, Germany, based on the "One man, one engine" principle. Among the high-performance powerplant's major strengths are its exceptionally spontaneous response to accelerator pedal movements, high torque and that unmistakable V8 sound.
Crankcase with dry-sump lubrication
The powerplant's entire engine block with its enclosed crankcase sump is made from cast aluminium. Each crankshaft is precision-weighted and revolves in five bearings made from a high-durability material to enable sustained transmission of the tremendous forces emanating from the supercharged engine.
The forged pistons are only manufactured in extremely small numbers. Just like the forged lightweight connecting rods, the pistons are measured and weighed with utmost accuracy before being assigned to individual engines. This keeps any mass balancing tolerances to an absolute minimum. The pistons slide inside extremely durable, wear-resistant, low-friction cylinder barrels made from a special compound which is otherwise only found in race car engines. Twin oil injection is used for effective piston cooling.
The oil cooling technology employed for the power unit as a whole also draws on the brand's racetrack experience: a sophisticated dry-sump lubrication system with a capacity of around eleven litres combines with a five-speed oil suction pump and a two-speed oil pressure pump to guarantee reliable lubrication under all driving conditions. One important knock-on effect of this dry-sump lubrication technology, which is again normally exclusive to race cars, is that the engine height can be kept low, allowing it to be installed deeper down in the engine compartment: the result is a low centre of gravity that fosters dynamic handling.
Screw compressor power
Efficient cylinder charging is the task of a belt-driven compressor with two screw-shaped aluminium rotors that are Teflon-coated in the interests of keeping friction low. In order to keep the engine running as efficiently as possible at all times, the AMG engineers have devised an intelligent engine management system which independently determines when to deploy the screw compressor as the engine's rev speed and load change. Consequently, the supercharger is only called into action when it is really needed. Notwithstanding this, however, maximum power is always available the instant the driver summons it by opening the throttle.
Apart from the compressor, the engine's electronics monitor all of the other variables which are relevant to its operation. At the same time, they ensure optimum operation of the intercoolers' water circuit. After all, efficient cooling of the charge air is a vital ingredient for high performance.
The intercoolers operate based on the extremely efficient air-to-water heat exchanger principle: the air which has been compressed by the compressor, causing it to heat up, is directed through a separate water circuit to cool it down again. This enables the eight-cylinder powerplant to maximise its output and torque delivery.
Manual transmission mode for shift times worthy of a race car
High performance has also been ingrained into the five-speed automatic transmission, which was developed in-house at Mercedes-Benz and has already featured in a number of exceptionally powerful models. It has been optimised to enable it to handle the awesome torque on tap and also offers drivers the possibility of varying the gearshift characteristics. The transmission directs the engine's power to the differential and the rear wheels via a precision balanced drive train made from aluminium and steel.
The interplay of the engine with the gearshift was also subject to modification. For each of the individually selectable transmission modes M (Manual) and S (Sport) on the one hand and C (Comfort) on the other there is now a different accelerator pedal characteristic curve, which has been optimised in line with the varying operating conditions.
The end result is an extremely impressive set of performance figures, even by high-end super sports car standards: the SLR 722 Edition completes the sprint from 0 to 100 km/h in a breathtaking 3.6 seconds (SLR 3.8 seconds), with the speedometer needle proceeding to pass the 200 km/h mark in a mere 10.2 seconds (SLR 10.6 seconds) and the 300 km/h mark in just 28.0 seconds (SLR 28.8 seconds). Plus, the top speed of 337 km/h is even higher than that of the current SLR (334 km/h).
New chassis set-up for further enhanced handling dynamics
One of the main driving forces behind the enhanced performance of the SLR 722 Edition is the retuned chassis. Development work at McLaren's Formula 1 headquarters was based on the set-up of the SLR's proven aluminium chassis, that is itself the handiwork of experienced race car developers: wheel guidance is the task of double wishbones at both the front and rear. The bottom links are arranged in such a way that the wheels receive a negative camber when the springs compress or when cornering at speed. This guarantees optimum contact with the road in any situation. Meanwhile, the axle technology also minimises the degree of diving and squatting while braking heavily and accelerating respectively.
The axle's wishbones are made from forged aluminium, while cast aluminium is used for the wheel carriers. This lightweight material boasts a host of advantages compared to conventional steel constructions, including the far superior response of the suspension and damping that results from the reduced weight.
The relatively long wheelbase of 2700 millimetres likewise contributes to the exemplary handling characteristics, with the most notable benefit being the outstanding straight-line stability, while the wide track combines with the low centre of gravity to enable high cornering speeds.
The chassis construction has the anti-roll bar positioned above the front axle where it is controlled via rocker arms, just like on a Formula 1 car. With this set-up, the anti-roll bar does not take up any additional installation space. In this way, the smooth lines of the underside of the vehicle are not disrupted, which is vital for the sports car's outstanding aerodynamic characteristics.
In the first phase of chassis development for the Mercedes-Benz McLaren 722 Edition, various combinations of chassis parameters, such as springing and damping, underwent a series of tests on the Formula 1 dynamometer in Woking. Then the Mercedes-Benz and McLaren engineers made further refinements and finalised the new set-up by performing an extensive series of tests on the road and, above all, on the race track.
The stiffer spring rates and shock absorber characteristics of the chassis as well as the lowering of the body by 10 mm at both the front and rear are what gives the SLR 722 Edition its increased directional stability and noticeably further enhanced handling dynamics. Body roll on bends has been reduced by over 20 percent, allowing the new SLR 722 Edition to corner at even greater speeds.
New 19-inch forged aluminium wheels also help to improve the handling dynamics of the special-edition model, their unique, palladium grey design highlighting the car's motor-racing heritage. Their lower weight compared to conventional wheels reduces the unsprung masses, making the responsiveness of the SLR 722 Edition all the sharper. Plus, the 19-inch wheels allow larger brake discs with a diameter of 390 mm to be fitted on the front axle. Hailing from the Italian manufacturer "Brembo", the new braking system combines with the carbon-fibre-reinforced ceramic discs to provide formidable decelerating power which is fully in keeping with the SLR 722 Edition's scintillating all-round performance. Exhaustive testing was carried out to develop a new ESP® control system for this new brake configuration.
High-tech material for exemplary safety and maximum strength
The high-performance sports car's bodyshell bristles with high tech. The entire bodyshell, including the crash structures at the front and rear, the occupant cell, the swing-wing doors and the bonnet, is made from carbon-fibre-reinforced plastic (CRP). This lightweight yet, at the same time, extremely rigid material is a technology borrowed from the aviation and space travel industry and has already proven its worth in ultra-sophisticated Formula 1 race cars. Despite the weight-saving of 50 percent that this high-tech material represents compared to steel, it is just as strong, which allowed the engineers to focus on achieving the body's enormous strength.
Plus, in the event of an impact, carbon fibres have a specific energy absorption that is some four to five time higher than steel or aluminium. Mercedes-Benz has capitalised on this material property by also fitting two 620-millimetre-long side member elements made from carbon fibre in the front structure of the SLR 722 Edition; these are capable of absorbing all of the impact energy in a head-on collision without exceeding the maximum levels of deceleration that the occupants are able to withstand. In the event of an impact, the fibres of these two elements tear from front to rear to crumple in a carefully predetermined manner and thereby produce a constant rate of deceleration.
The super sports car's occupant cell is likewise made from this high-tech material, offering passengers a very rigid and therefore safe survival space in an accident. At the rear of the car, the task of absorbing energy in a crash falls to two internal side members made from laminated carbon fibre and a sturdy cross member, which together ensure that the occupant cell remains virtually intact. The occupant protection system also encompasses adaptive front airbags, which are deployed in two stages depending on the severity of the impact, head/thorax bags and knee bags, as well as seat belt tensioners and belt force limiters.