Mercedes-Benz SLR McLaren (2004)

460-kW/626-hp V8 powerplant with cutting-edge compressor technology

In the interests of optimum dynamic handling and high stability on braking, the new Mercedes-Benz SLR McLaren has a front mid-engined design. The high-performance V8 engine, mounted on a robust aluminium frame, is installed at a low level which allows a low centre of gravity for agile handling.

With its 5.5-litre displacement, the supercharged engine develops a peak output of 460 kW/626 hp and delivers its maximum torque of 780 Newtonmetres from 3250 rpm - a figure which remains constant across a broad engine speed range of up to 5000 rpm. This means that the SLR 8-cylinder is among the most powerful engines currently available in a series-produced roadgoing sports car. This high-performance car takes just 3.8 seconds to sprint from 0 to 100 km/h, it passes the 200 km/h mark after 10.6 seconds, and from a standing start it takes just 28.8 seconds to reach 300 km/h. The top speed is 334 km/h.

Water-type charge-air cooling, dry sump lubrication and four metal catalytic converters are further special features of this powerful engine - an engine which already meets stringent EU 4 exhaust gas regulations which are not due to come into force until 2005.

The 5-speed automatic transmission, fitted as standard, is also designed for high performance. It allows the driver to choose between three programs with different shift characteristics. When "Manual" is selected, the five gears can either be shifted using buttons on the steering wheel or using the selector lever's Touchshift function. In this mode the driver can also select between three shift stages - "Sport", "SuperSport" and "Race" - significantly shortening the shift times still further for an even sportier drive.

Aerodynamic concept uses expertise from the world of Formula 1

The body design of the Gran Turismo with the Mercedes star takes classical styling elements from the legendary SLR race cars of the 1950s and blends them masterfully with the sophisticated, avantgarde design language of both the latest Mercedes passenger car models and of the modern-day Silver Arrow race cars which took the McLaren Mercedes team to Formula 1 World Championship glory in 1998 and 1999. The design's concept, in other words, thrillingly spans the divide between past and present, whilst at the same time showing the way forward for the sports car designs of tomorrow.

In order to meet the highest of standards in terms of handling at top speed, directional stability and the cooling air requirements necessary for high-performance cars of this kind, Mercedes-Benz worked with McLaren on developing this model's superlative aerodynamics, ensuring exemplary roadholding plus the on-road safety standards typical of Mercedes. Following extensive wind-tunnel tests, the Mercedes-Benz SLR McLaren was given a virtually smooth underbody with a special six-channel diffusor under the rear. Both features are familiar design principles from Formula 1. They ensure that the airflow beneath the vehicle is virtually unimpeded and that negative lift, or downforce, is produced at higher speeds. The distinctive sidepipes on each side of the vehicle are also the result of this high-performance sports car's aerodynamic underbody concept: a conventional exhaust gas system would have disrupted the smooth line of the underbody.

At the rear of the Mercedes-Benz SLR McLaren an adaptive spoiler provides additional downforce. From a speed of 95 km/h, it automatically adopts a 10-degree position, increasing the contact pressure at the rear axle. The spoiler also doubles as an airbrake: when the driver brakes heavily, it rises to an angle of 65 degrees, not only ensuring increased aerodynamic drag but also shifting the aerodynamic centre further towards the rear. This lends the Mercedes-Benz SLR McLaren excellent stability when braking from high speeds.

Functionality and luxury stylishly combined

It is the very high levels of practicality and luxury that truly make the interior of the Mercedes-Benz SLR McLaren stand out. Individually padded carbon-frame seats, a multifunction steering wheel with race-car-type buttons for manual gear selection, clearly arranged chronometer-style instruments and high-grade materials define the atmosphere inside the high-performance sports car.

Alongside carbon and aluminium, the Mercedes designers have used "Silver Arrow" leather, specially developed for the Mercedes-Benz SLR McLaren, which is available in the distinctive red of the legendary 1950s SLR race car.

Design: Spanning the divide between the past, the present and the future

Legend and innovation - this is the precept underpinning the body design of the new Mercedes-Benz SLR McLaren, as it takes the classical styling elements from the legendary SLR racing cars of the 1950s and blends them masterfully with the sophisticated, avant-garde design language of both the latest Mercedes passenger car models and of the modern-day Silver Arrows race cars with which the McLaren Mercedes team competes in the Formula 1 World Championship.

The design's concept therefore spans the divide between past and present and cre-ates a car with a unique charisma - a Mercedes synthesis of legend and innovation which is impressive in every respect.

It is the front end in particular which singles out the new Mercedes-Benz SLR McLaren as a direct descendent of the racing cars which have been so successful in recent times: the centre is dominated by the distinguishing, arrow-shaped nose of the Formula 1 Silver Arrow, encompassing the Mercedes star at the front, an unmistakable hallmark of manufacturing origins that are steeped in tradition.

Underneath the nose can be found a further typical styling element taken from the Formula 1 race cars which took McLaren Mercedes to the World Championship crown in 1998 and 1999: the twin-fin front spoiler with the distinctively curved struts. As on the Silver Arrows, these aerofoil fins are more than just a stylish identifying feature, they are actually crucial to the car's aerodynamics. The high contact pres-sure they produce at the front axle plays a key role in the Mercedes-Benz SLR McLaren's sure-footed, race-car-like roadholding.

The fin design was adopted as a recurring feature of the Mercedes-Benz SLR McLaren's exterior, thereby main-taining a high level of design consistency: finned sections also separate the head-lamps from the nose, form the base for the two exterior mirrors and adorn the tail lights on each side of the car, where the indicators' LEDs are housed in two self-supporting fins positioned one above the other.

Mercedes design breeding: twin-headlamp face forms identifying feature

Above the generously proportioned air intake for the engine cooling is the wide, flat bonnet, whose rear edge lies below the starting point of the A-pillars, permitting the deep-set design of the front windscreen. This is another typical element taken from the world of motorsport which gives drivers the good level of visibility needed for high-speed motoring.

The headlamp arrangement is a refreshingly new version of the highly familiar and equally successful twin-headlamp face, which has been the calling card of Mercedes-Benz passenger cars since 1995. In this SLR-style reinterpretation, al-though the dipped-beam and main-beam headlamps form a single unit, they never-theless succeed in emphasising their basic, pronouncedly oval form. The design team has reinforced the powerful visual effect by sheathing the powerful projection head-lamps in casings which resemble high-quality camera lenses, all housed behind clear glass.

As with all current Mercedes passenger cars, the oval lines of the twin-headlamp face form the starting points for modelling the bonnet and the wings. The rounded contours of the headlamps develop into powerful domed curves which quite deliberately evoke associations with the human anatomy: the curves extend back over the wings like the sinewy muscles of a trained athlete, leaving no doubt in anyone's mind that this car bristles with the pure power of a sporting superstar.

These contours - soft yet brimming with power and dynamism - combine with taut lines to produce a fascinating, sculpted exterior form, a clear expression of the uncompromising manner in which this car's high-performance credentials have been honed. The car flexes its muscles visibly but without any hint of aggression, with each fibre of its lithe body trimmed and tensed, ready to launch forward at any time.

The domed curves leading off from the inner pair of headlamps sweep seamlessly all the way back to the A-pillars, forming a smooth visual link between the front end and the passenger compartment. As they run up the long bonnet, the softly rounded domes again transform into taut, clean-cut lines, which in turn mould the appearance of the A-pillars and the side profile. This is also one of the elements underpinning the characteristic, powerful proportioning of the SLR silhouette: the long bonnet, taut midriff, compact passenger compartment and short tail create a deliberate association between the flow of the SLR's lines and the styling elements of Mercedes sports cars from years gone by, and symbolise the sense of forwards surge that courses through the Mercedes-Benz SLR McLaren.

The high-performance sports car exudes the same powerful, yet harmonious impression when seen from the rear too. This is down to the elegant way in which the lines flow from the passenger compartment into the lid of the boot, helped by the slender roof pillars which taper towards the bottom. Unlike the SLR Silver Arrows of the 1950s, whose tail curved gently downwards, the boot of the Mercedes-Benz SLR McLaren continues at the same high level in order to enhance the aerodynamic qualities.

The large tail lights are an immediate eye-catcher. The distinctive, triangular form of the transparent lenses, a typical feature of Mercedes passenger cars, has a wrap-around design which extends far into the side panelling to emphasise the width of the body.

Side gills and wide-opening swing-wing doors

It is above all the side profile of the high-performance sports car that identifies it as a car whose maker has a long and illustrious motor-racing tradition, with large, finned air openings breathing new life into the SLR legend. These "gills" are far more than a mere styling touch, serving now as they did back then to ventilate the engine compartment. The designers of the Mercedes-Benz SLR McLaren have lent further emphasis to this particular function by enlarging the surface of the fins towards the rear of the gills, and by placing a clean-cut line at the end of the fins which then sweeps further backwards to add to the styling of the swing-wing doors.

If there is one distinctive feature that the new Gran Turismo has adopted from the Uhlenhaut Coupé, the coupé version of the legendary SLR race car, designed in 1955 by Mercedes' head of testing at that time, Rudolf Uhlenhaut, it is the doors.

In their modern interpretation, however, they are attached to the front roof pillars rather than to the roof itself and swing forwards and upwards in a wide angle. No less sensational than the gullwing design from the 1950s, this new concept also enlarges the entrance to the vehicle to make getting in and out easy for both driver and passenger.

Functionality and an inspiring look define the interior design

Inside, every detail of the interior reflects the high-performance character of the Mercedes-Benz SLR McLaren. Take your place on board, and you'll feel the thrill of sitting in a thoroughbred sports car. The on-board atmosphere, however, is also one of safety and calm - key requirements where concentrated, fast driving is concerned.

The reason behind this is a straightforward yet very emotional design language. It takes up the fin design and continues it consistently in the interior. Here the typical SLR fins are reflected in the ventilation outlets, the airbags and the instruments. The profiles appear light and delicate, deliberately reducing the cockpit to the bare essentials, in keeping with motor racing philosophy. The design deliberately concentrates on the essential factor: the dynamic driving experience.

The focal point of the interior is undoubtedly the centre console with its high-grade aluminium trim. A visual extension of the distinctively shaped Formula 1 domes on the bonnet, the centre console serves as the transition between exterior and interior, whilst also picking up the powerful lines of the front-end design before they flow backwards over the transmission tunnel to the tail of the SLR. In order not to disrupt this clear-cut look, the radio and navigation system are inconspicuously housed below a cover in the centre console which opens in an elegant arc when pressed lightly. The instrument cluster surround also reinforces the impression of power. The two tubes appear to plunge into the bonnet, forming a visual link with the Gran Turismo's power source. Clearly designed, circular instruments are centrally located in these tubes and perfectly positioned in the driver's field of vision.

The design of the instruments is based on the look of a high-quality chronometer. The large dials are inscribed with letters specially developed for the Mercedes-Benz SLR McLaren. The rather stark appearance conceals the latest display technology.

Despite its motor racing character, the interior of the Mercedes-Benz SLR McLaren also has a high-quality, in-viting feel. This is thanks to the stimulating interplay of select materials. Aluminium and carbon contrast with supple "Silver Arrow" leather, which was specially devel-oped for the new high-performance sports car and sets peerless standards in terms of its quality and material thickness. 20 different appointments colours are available to choose from, including the same bold shade of red which set new trends back in the 1950s when it was featured in those legendary, unforgettable sports cars, the SL and the SLR: the result is automotive tradition you can truly feel. A two-tone interior concept ensures both high functionality and an exquisite on-board atmosphere. In many areas the various materials are combined to create visual islands. A fine, haematite-coloured frame, for example, embedded in sumptuous leather, surrounds the aluminium centre console.

Interior: Harmony of forms and materials

The combination of luxurious appointments and a stark sports car-style feel creates a uniquely spellbinding atmosphere on board the Mercedes-Benz SLR McLaren. Exclusive, soft "Silver Arrow" leather, specially developed for the SLR, and select materials such as aluminium and carbon contrast strikingly with the pure functionality of a ve-hicle whose roots lie in the world of motor racing. In the interior, as in the exterior, the motor racing heritage is combined with the clear advantages of a classic Gran Turismo: outstanding ride comfort and a deliberate concentration on the pleasures of refined dynamic driving.

Despite its focus on luxury and comfort, the Mercedes-Benz SLR McLaren's interior dimensions are clearly those of a high-performance sports car. In keeping with extraordinarily high demands in terms of dynamic handling, the passenger cell is com-pact, creating a tailored feel. Nevertheless, there is a generous sense of space inside the two-seater, thanks, in part, to the deep seat position, which allows a low roof line, at the same time lowering the centre of gravity, which benefits dynamic handling. The backrest of the carbon fibre seat is set at an angle of 28 degrees to the seat cushion, rather than 25 degrees, in order to allow a sporty seating position.

Generous dimensions ensure an attractive interior. The SLR exceeds the shoulder and elbow width dimensions of many luxury and mid-class saloons, providing its occupants with plenty of personal space. The key interior dimensions of the Mercedes-Benz SLR McLaren:

• Interior length: 1006 mm
• Headroom: 919 mm
• Shoulder-height width: 1371 mm
• Elbow width: 1443 mm
• Seat cushion height: 565 mm

Interchangeable seat cushions for an individual fit

Having entered through the wide-opening swing-wing doors, the driver and passenger take their places on light, single-piece carbon fibre seats, the basic design features of which have proven their benefits in the world of motor racing. Thanks to the multi-layer carbon fibre composite structure, they are not only 25 percent lighter than con-ventional car seats but also offer ergonomic advantages: a set of two upholstery modules, in three different sizes, allows the seat contour to be adapted individually to the anatomy of the driver. Three sets of these side upholstery modules are available, ensuring that the seats can be adapted to the optimum upper body and hip width for the driver, providing made-to-measure lateral support. The individual modules, upholstered in semi-aniline leather, are bolted onto the carbon frame.

The single-piece carbon fibre composite frame is connected at four points to an electric seat adjustment mechanism, which is used to adjust the seat's fore-and-aft position (by 130 millimetres), height (by 41 millimetres) and angle (up to 9.6 degrees) according to personal requirements. As a result of the single-piece design of the carbon fibre composite seat frame, the angle of both the seat cushion and the backrest are adjusted simultaneously.

High-class chronometer look for cockpit

Even the process of inserting the electronic ignition key has been imbued with an enthralling, uniquely SLR feel: a starter button on the solid metal shift knob at the top of the gearshift lever on the centre tunnel instantly begins to glow red. Apply slight pressure with your thumb, and the grid-style flap opens to provide access to the illuminated button. One press with your thumb brings the tremendous power of the V8 supercharged engine to life.

The interaction of various well-designed details in the interior underlines the thoroughbred character of the SLR at all times. Nevertheless, the cockpit design deliberately focuses on the essentials, in keeping with motor racing philosophy. Easily readable characters on a dark background, which were specially created for the SLR, define the instruments' attractive, classic chronometer design - a design which, even at first glance, signals outstanding precision. They are enclosed by a matt chrome surface and are flanked by further displays, indicating the coolant temperature (left) and tank capacity (right), plus pilot lights and warning lights which only light up when the ignition is started or if there is a fault.

The brightness of the backlit dials automatically adapts to the prevailing light conditions in the interior of the swing-wing-door vehicle. A further unusual detail: when the engine is started, the needles spring back to their home position.

Cutting-edge displays in the lower section of the speedometer and the rev counter serve as an information centre for a number of functions. The aim of this control and display concept is to inform the driver of the operating status of the car without diverting his or her attention from the road. The two central displays are coupled both with the multifunction steering wheel and with the car radio, the telephone and the navigation system - which means that, at the touch of a button, the driver's personal list of stations, the selected CD, the telephone directory or navigation information appears directly in the driver's field of vision.

Multifunction steering wheel with buttons for quick gear changes

Eight illuminated buttons on the multifunction steering wheel allow the driver to specify his or her requirements - a light tap with the thumb is all it takes. They provide a simple means of regulating the volume and of accepting or terminating phone calls.

The three-spoke steering wheel, which has a diameter of 380 millimetres, was specially designed for the Mercedes-Benz SLR McLaren. It can be adjusted for reach by 60 millimetres and its height can be varied by 2.7 degrees. On the back of the spokes are buttons which the driver can use to change gears in Manual mode without having to take his or her hands from the wheel - a familiar feature in Formula 1.

Aluminium console with buttons for airbrake and shift program

The centre console, made from high-grade aluminium, is a further eye-catching feature on board the high-performance sports car. It houses not only the car radio with its navigation system, but the climate control unit and several new switches too, which activate and control various innovative technological features on board the SLR.

One of these switches operates the airbrake on the boot lid. From a speed of 95 km/h this automatically extends to provide more downforce, and when slowing down it rises to a steep angle to ensure optimum deceleration. The SLR driver can also use the switch here to position the airbrake as required.

The two rotary switches on the centre console are a further unusual feature. They can be used by the driver to select between the automatic transmission's three different shift programs: "Manual", "Comfort" and "Sport". The driver can also use the right-hand rotary switch to determine the speed of the gearshifts.

The radio and navigation unit are also accommodated in the centre console, concealed by an aluminium flap so as not to distract the driver. Beneath the radio/navigation unit are two ergonomically placed aluminium rotary switches for controlling the air conditioning system.

Material concept underlines elegance and sportiness

In the two-tone interior, which uses only select materials such as high-quality leather, fine Alcantara for the entire roof trim and elegant pearl velour for the carpets, the dashboard is dark in order to prevent irritating reflections while the seats, door panels, tunnel trim, rear wall console and the rear shelf panel come in a contrasting colour.

There are plenty of inspired details: the high-quality integral loudspeakers in the door panels, for example, have a grid-form cover which echoes the styling of the air outlets on the sides of the vehicle. The rear of the grid surround forms the door handle, while a simple leather loop in the upper area of the door serves as a separate door pull - a traditional feature derived from the legendary Mercedes-Benz motor racing vehicles. The uncompromising, clean-cut interior of the Mercedes-Benz SLR McLaren also features aluminium pedals with rubber studs.

Large boot and roomy stowage compartments

An exceptionally large, saloon-style boot underlines the fact that this is a thorough-bred Gran Turismo, designed for long-distance travel. According to the VDA measur-ing method, it has a capacity of 272 litres. Even when the luggage compartment is fully laden, the occupants are still assured unimpeded access to the CD changer, which is housed in the boot.

In addition to the spacious boot, there is plenty of stowage space in the interior - a total of 46.1 litres, including a 42.5-litre compartment below the rear shelf. Further stowage compartments can be found in the rear wall and console of the centre tunnel.

The switches for adjusting the seats, the power window buttons and the door release are positioned within easy reach between the door sill and the seat, providing a further example of the sports car's consistent use of space and ergonomic design. The handbrake is located in a moulded recess to the right of the centre tunnel.

Automatic climate control with sensors which register the position of the sun, the air quality and humidity

Despite its uncompromising motor-racing character, the Mercedes-Benz SLR McLaren is fitted with a state-of-the-art climate control system, which offers the ulti-mate in power, functionality and controllability. The two easy-grip aluminium dials on the air conditioning control unit in the centre console allow separate temperatures to be selected for the driver and passenger side - the set value is illuminated on the aluminium dial.

In automatic mode, a microcomputer monitors the functions of the automatic climate control system, receiving and processing a whole range of data. This includes information on the battery voltage, coolant temperature, engine speed and road speed plus the position of the doors and the side windows. Sensors supply further key readings:

• Two sensors continuously record the temperature in the interior.
• A solar sensor on the dashboard measures the angle of incidence and intensity of the sun's rays so that the temperature, quantity and distribution of the air blown into the interior can be regulated appropriately.
• A dew point sensor in the air conditioning system's intake duct registers humidity and allows economic regulation of the refrigerant compressor.
• A pollutant sensor in the automatic climate control system's intake channel detects any increase in the concentration of carbon monoxide and nitrous oxides in the incoming air. If an increase is detected, the system automatically switches to recirculation mode.

Like the automatic climate control system in the Mercedes-Benz SL-Class sports car, the system on board the SLR operates according to the reheat principle: depending on its humidity, the incoming air is first cooled and in the process dried so as to ensure mist-free windows. Only then is it passed through the heating element and heated to the desired temperature.

Sophisticated lighting concept for the interior

One of the air conditioning system's sensors, which records the interior temperature, is accommodated in the overhead control panel. The panel also houses the switches for several of the lights which make up the sophisticated interior lighting concept.

Special features include lights below the sun visors which automatically switch on as soon as the visor is folded down and the vanity mirror opened. There is also a reading light which is installed in the interior mirror, and the doors each feature a round lens-shaped light which illuminates the door sill area when the doors are opened. The intensity of most of these lights is automatically regulated according to the ambient light conditions.

Specially adapted audio and navigation system

The Mercedes-Benz SLR McLaren is equipped with a top-class communication system which has been adapted to the requirements of a high-performance sports car. The Audio 30 APS car radio combines a radio and a cassette player plus the controls for the CD changer and the dynamic-route-guidance navigation system in a single unit. It has a clear design, is easy to operate and its functions are displayed in the speedometer and the rev counter - which means that the driver can concentrate on the driving rather than searching for information in excessive detailed displays.

The optimum sound quality comes courtesy of the Bose sound system, which has been specially attuned to the SLR. It uses a total of seven loudspeakers and sophisticated electronics, and not only compensates for interference but also has a microphone which constantly registers driving noise and adjusts the volume accordingly, without the driver having to intervene.

Other integral features include the permanently installed mobile phone system and all of the aerials which are required for radio and telephone reception and for operating the satellite navigation system.

Telematic functions for accidents or breakdowns

SLR drivers also benefit from new traffic services with this cutting-edge communication system. The following highly effective telematic functions are available:

• TELEAID is an automatic emergency call system which, in the event of an accident, sends out an SOS signal to alert the emergency services and lead them to the scene of the accident. The emergency call is either triggered via a crash sensor or by pressing a button in the overhead control panel. At present TELEAID functions in Germany and the USA.
• TELEDIAGNOSIS makes contact with Mercedes-Benz's central Customer Assistance Centre (CAC) at the touch of a button on the car phone headset, at the same time informing the centre of all necessary vehicle data and the precise position of the car. This means that service personnel can be directed to the vehicle quickly and precisely. TELEDIAGNOSIS is available in Germany.
• MB Info is a service which offers Mercedes customers the opportunity, using the TELEAID technology, to direct general questions to the customer advisors at the Customer Assistance Centre. One touch of the "Info" button is all it takes to establish a free call. This service is currently offered in Germany and will be ex-tended to other countries in the future.

Engine and transmission: V8 powerplant with motor racing in its genes

An abundance of power and high-tech features from the world of motorsport - these are the defining characteristics of the V8 engine in the Mercedes-Benz SLR McLaren. Which means that the first 8-cylinder to be completely developed by Mercedes-AMG fits perfectly into the high-performance concept of the new Gran Turismo.

When developing the powerplant, the AMG engineers applied both the expertise they had acquired during their three-decade involvement in motorsport and the stringent standards of the Mercedes-Benz brand. After an extensive concept phase, they decided in favour of an 8-cylinder design with a 5.5-litre displacement, a cylinder angle of 90 degrees, a screw-type compressor and a crankshaft supported by five bearings.

The result is impressive: from a mere 1500 rpm, the SLR powerplant delivers torque of over 600 Newtonmetres, rising to 700 Newtonmetres at 2000 rpm. The maximum of 780 Newtonmetres is available from 3250 rpm and remains constant in a broad engine speed range up to 5000 rpm. The supreme torque curve, coupled with the agile response of a sporty engine which never denies its high-performance character (it offers a peak output of 460 kW/626 hp at 6500 rpm - an extraordinarily high engine speed for this displacement size) speak a powerful language. As the figures indicate, the Mercedes-Benz SLR McLaren is endowed with what is currently one of the most powerful engines to be found in a series-produced roadgoing sports car. An overview of the key data:

• Cylinder arrangement: V8
• Cylinder angle: 90
• Valves per cylinder: 3
• Displacement: 5439 cc
• Bore/stroke: 97.0/92.0 mm
• Cylinder spacing: 106 mm
• Compression ratio: 8.8 : 1
• Output: 626 hp (460 kW) at 6500 rpm
• Max. torque: 780 Nm at 3250-5000 rpm
• Engine weight: 232 kg
• Power/weight ratio: 1.9 kW/kg

With this much power under the bonnet, the Mercedes-Benz SLR McLaren's performance figures are among the best in its class:

• 0-100 km/h: 3.8 s
• 0-200 km/h: 10.6 s
• 0-300 km/h: 28.8 s
• Top speed: 334 km/h
• Fuel consumption: 14.8 litres per 100 kilometres (NEDC combined consump-tion, provisional figure)

Power from screw-type compressor

To ensure good cylinder charging, the engine has a mechanical compressor with two screw-type aluminium rotors which, in the interests of low friction losses, are Teflon-coated. The charger is so compact that the engine specialists were able to install it between the two cylinder banks of the V8 powerplant. Despite the space-saving design, its innovative technology allows a significantly higher charge pressure than conventional mechanical chargers because the two rotors achieve a top speed of around 23,000 revs per minute, forcing air into the air inlet of the 5.5-litre powerplant at a maximum pressure of 0.9 bar. This means that they compress around 1850 kilograms of air into the eight combustion chambers per hour - which is up to 30 percent more than the figure achieved by rival charging systems.

In order to ensure the greatest possible efficiency, the AMG engineers created an intelligent engine management system which regulates the operation of the screw-type compressor according to the engine speed and load. This means that the charger is only active when it is needed. Nevertheless, the system ensures that the maximum output is available as soon as the driver calls it up by stepping on the accelerator. When this occurs, the electronics of the engine management system trigger an electromagnetic coupling which immediately activates the compressor, which is powered by a separate poly-V-belt. Because the charger de-livers its output in fractions of a second, even the most perceptive driver will not notice the phases without charger support. The charger system's air recirculation flap, opened under partial load, helps reduce fuel consumption.

Two charge-air coolers with separate water circuit

In addition to the compressor, the electronics also monitor all other variables relevant to the engine - both the powertrain management for the pedal-dependent drive characteristics and the implementation of spontaneous transmission or ESP® interventions. They also ensure optimum control of the water circuit for the charge-air cooling system, as efficient charge-air cooling is essential where high output is concerned. This is because cold air is denser than warm and also con-tains significantly more oxygen for combustion. In the Mercedes-Benz SLR McLaren's V8 engine, two separate charge-air coolers are responsible for this key task - one per cylinder. This ensures that loss of pressure is very low.

The highly effective engine-based charge-air coolers operate along the lines of an air/water heat exchanger: the air, compressed and hence warmed by the compressor, is cooled via a separate water circuit - making the process independent of the temperature outside. This means that the 8-cylinder can deliver its maxi-mum output and torque spontaneously at any time. The high performance figures of the 8-cylinder engine in the Mercedes-Benz SLR McLaren, however, not only demand good cooling of the combustion air but also result in an overall increase in engine cooling requirements. The engineers met this need by incorporating generous cooling air inlets and outlets and a powerful 850-Watt suction-type fan.

Crankcase with dry sump lubrication

The Mercedes-AMG GmbH engineers also applied their extensive experience in the world of motorsport and in the design of high-performance engines to other details of the SLR powerplant. The entire engine housing, for example, and the lower section of the closed crankcase are cast in aluminium. Each crankshaft is finely balanced and is supported by five bearings made from durable plastic, allowing long-term transfer of the impressive forces from the compressor engine.

The pistons are forged and are therefore only manufactured in minimal numbers. Like the forged lightweight conrods, they are precisely measured and weighed and allocated to the individual engines in such a way as to produce minimal balancing tolerances. The pistons move in highly robust, wear-resistant and friction-optimised walls made from a special compound which is otherwise only used in motor racing. Dual oil injection effectively cools the pistons.

The design of the powerplant's oil cooling system is also based on experience gathered in the world of motor racing: a sophisticated dry sump lubrication system with an oil capacity of around eleven litres, combined with a five-stage oil suction pump and a two-stage oil pressure pump, ensures reliable lubrication under all on-road conditions. An important side effect of this technology is that, because of the dry sump lubrication, usually only used in motor racing vehicles, the engine is less tall and can therefore be installed at a lower level, allowing a low centre of gravity which benefits dynamic handling.

Following the usual practice at Mercedes-AMG, each SLR engine is manufactured by hand. In order to achieve the highest quality, the principle of 'one man, one engine' is applied. This means that each powerplant is the responsibility of one AMG engineer, who carries out the entire engine assembly process - from installing the crankshaft in the engine block and assembling the camshafts and the compressor to cabling.

Powerful high-pressure pumps in the tanks

The Mercedes-Benz SLR McLaren's high-performance engine draws its fuel from two interconnected aluminium tanks. They are installed at a relatively low level to the left and right of the rear axle in order to keep the centre of gravity as low as possible to further en-hance dynamic handling. The tanks, which have an overall capacity of 97.6 litres - of which twelve litres form the reserve - are equipped with two integral high-pressure fuel pumps. These are controlled by the engine management system and ensure that the fuel supply matches the engine speed and load. Here too a highly effective, SLR-specific solution was developed: one pump operates constantly while the second is only activated as required.

Four metal catalytic converters for efficient emission control

Where the engine is concerned, secondary air injection and dual ignition create the criteria required for low exhaust gas emissions. A sophisticated exhaust gas system complements these measures: the cascade-design twin-pipe system consists on both sides of a bulkhead-mounted catalytic converter and a main catalytic converter with a special noble metal coating, accommodated in the same housing. The state-of-the-art metal design allows extremely thin wall thicknesses and therefore a very low exhaust gas backpressure. Thanks to its cutting-edge technology of its engine management and emission control systems, the new SLR's 8-cylinder engine already meets the stringent exhaust gas limits stipulated by EU 4 plus the current US limits.

On each side of the vehicle the catalytic converter housing opens into a rear silencer which, just behind the front wheels, flows into two stainless steel pipes with a diameter of 60 millimetres. These sidepipes - a further reminder of the 1950s SLR racers - allow the smooth-surfaced underbody, which plays a crucial role in producing the new Mercedes-Benz SLR McLaren's first-class aerodynamic properties. The silencers are folded several times in precisely calculated acoustic sections which produce the thrilling characteristic engine sound of the Mercedes-Benz SLR McLaren. The capacity of each silencer is 19.6 litres.

Manual transmission program for racing car-style shift times

The five-speed automatic transmission, developed by Mercedes-Benz and already successfully used in several exceptionally powerful models, is also designed for high performance. It has been specially optimised for very high torque and also offers the driver the option of choosing between different shift characteristics. The transmission transmits the engine power via a finely balanced aluminium and steel powertrain to the differential and the rear axle.

The Speedshift system, developed by Mercedes-AMG for particularly sporty driving, offers even more functions in the Mercedes-Benz SLR McLaren. The driver can decide, for example, whether to leave the shift work to the automatic transmission or to shift gears manually. He or she can also select the shift speed, determining how sporty the gearshifts are. A rotary switch in the centre console offers a choice of three settings: "Manual", "Comfort" and "Sport". The activated programme is indicated in the instrument cluster display by the letters "M", "C" or "S".

"Comfort" and "Sport" are automatic shift programs which, as the names indicate, place the emphasis either on comfort or on a more sporty drive. In "Manual" mode, on the other hand, the driver can select the five gears either using the but-tons on the steering wheel or using the Touchshift function on the selector lever. When "Manual" is selected, he or she also has the option of choosing between three shift stages for a sportier driving style:

• Stage I = "Sport"
• Stage II = "SuperSport"
• Stage III = "Race"

In the sequence indicated here, the response, reaction and closing times of the couplings in the automatic transmission, and hence the shift processes themselves, become increasingly shorter.