The new CLK Coupé is a unique model series within the Mercedes-Benz passenger car portfolio. A fact emphasised by a two-door design – newly developed right down to the finest detail – which exudes both elegance and dynamic progression. Prominent styling elements – such as frameless, fully-lowering side windows that form a continuous band, a classic Mercedes radiator grille with central three-pointed star, the new reinterpretation of the twin-headlamp face and the sweeping curve of the coupé roof – highlight the confident character of the new CLK-Class.
Seven engines with power outputs ranging from 163 hp to 367 hp
Complete with its newly developed chassis, more powerful engines and the ultimate in Mercedes-Benz equipment and technology, the new Mercedes Coupé serves up a driving experience that is unique in this vehicle class. Mercedes customers can choose from seven engines, three types of transmission, two design and trim lines and numerous attractive colour combinations. Six of the seven engines on offer are new developments or further improved models, providing up to 20 kW/27 hp more power and 15 percent more torque than their predecessors. Yet, on average, the new CLK models consume six percent less fuel.
Topping the new CLK range are two V8 models that deliver performance on a par with a typical sports car: the CLK 500 (225 kW/306 hp) and the CLK 55 AMG with a further developed powerplant that now produces an impressive 270 kW/367 hp. The high-power engines propel these CLK Coupé models from 0 to 100 km/h in just 6.0 or 5.2 seconds respectively.
Direct-injection petrol engine consuming 16 percent less fuel
A new generation of four-cylinder engines will also celebrate its debut. In terms of power delivery, torque characteristics, refinement and fuel consumption, these powerplants set new standards in this displacement class, thanks mainly to their unique TWINPULSE system. There are two four-cylinder models available: the CLK 200 KOMPRESSOR (120 kW/163 hp) with conventional fuel injection and the CLK 200 CGI (125 kW/170 hp) with direct petrol injection. The TWINPULSE system combines numerous technologies – including balancer shafts, compressor, intercooler, variable valve timing and four valves per cylinder – to ensure low fuel consumption, sheer driving pleasure and a level of refinement similar to that of a six-cylinder model.
To complement the TWINPULSE system, Mercedes-Benz equips the new CGI petrol engine with leading-edge, direct-injection technology which reduces fuel consumption to a meagre 7.9 litres per 100 kilometres (NEDC combined), a figure which is 16 percent lower than that of the preceding model. Meanwhile the new CLK 200 KOMPRESSOR consumes 8.6 litres per 100 kilometres (NEDC combined), making it around 8.5 percent more economical than its predecessor.
Mercedes-Benz has added a second six-cylinder engine to the new CLK-Class line-up, in the form of the tried-and-tested 2.6-litre model with an output of 125 kW/170 hp. The powerful 3.2-litre V6 version (160 kW/218 hp) remains part of the engine range. A new innovation in this coupé class, the high-powered CLK 270 CDI diesel model has a sophisticated five-cylinder engine with common-rail injection beneath its bonnet. It develops 125 kW/170 hp and, with a fuel consumption of just 6.7 litres per 100 kilometres (NEDC combined), it is one of the most economical engines in its class.
Increased body rigidity, leading cd figure and exemplary safety
The Mercedes engineers have made further advances in the field of body technology, particularly with respect to safety and aerodynamics. Torsional stiffness has been improved by 40 percent whilst the percentage of high-strength steel alloys used for the bodyshell – to create a lightweight yet extremely strong design – has almost doubled. A cd figure of just 0.28 makes the new CLK Coupé the new leader in this vehicle class. In addition, substantially reduced body lift on the front and rear axles means the new model has what it takes to provide an extremely high level of active safety and directional stability.
Standard equipment in the new Mercedes Coupé includes a range of state-of-the-art occupant protection systems: adaptive front airbags, sidebags and windowbags as well as belt tensioners and belt force limiters for all seats. For the first time, passenger weight is one of the factors taken into account before the two-stage front-passenger airbag is deployed, to ensure an optimum level of protection every time. The CLK-Class therefore displays the practical features of the Mercedes safety concept and, at the same time, meets the strict requirements of the latest crash tests.
Compared to its predecessor, the new CLK Coupé is 71 mm longer, 18 mm wider and 42 mm higher. The wheelbase has been extended by 25 mm and now stands at 2715 mm. These enhanced dimensions afford the occupants even more space and comfort: in terms of the space between seats, headroom, rear knee room, elbow room and shoulder room, the interior of the new CLK-Class has really grown in stature.
Interior featuring sublime forms, the finest materials and exclusivity in abundance
Smooth forms, high-grade materials, attractive colours and a design displaying superb attention to detail combine to create an interior ambience that arouses an immediate feeling of contentment. New interior developments such as the instrument panel, centre console, door panelling and seats further emphasise the unique character of the CLK-Class. All the controls are within easy reach whilst the main dial instruments – speedometer, rev counter and clock – feature a classic round design and deliver crystal-clear information. Exquisite details such as the chrome surrounds on the dial instruments and the generous fine-wood or aluminium trim on the centre console enhance the high-quality feel of the interior. There is also a range of automatic systems, to help relieve driver stress and ensure optimum ease of use.
In the rear of the Coupé, the asymmetrically split-folding seat backrests and cushions – fitted as standard – fold forward individually or together, enabling variation of the luggage space. The rear loading area is virtually flat when the seats are folded down.
Standard equipment for an exceptionally high level of safety and comfort
The standard equipment package for the new CLK-Class is even more extensive than that for the previous model and is worth an extra € 2800. Alongside windowbags, automatic belt feeders, power-operated rear windows, Headlamp Assist, rain sensor, mixed-profile tyres and an adjustable steering column, the package also includes a highly effective automatic climate control system. This system works based on up-to-the-second information it receives from sensors regarding inside temperature, outside temperature and humidity. Options include the added luxury of the THERMOTRONIC system with additional solar sensor, pollutant sensor, rear blower and activated charcoal filter. This system is fitted as standard in the CLK 500 and CLK 55 AMG models with V8 engine.
Debut for DISTRONIC and other innovations in this vehicle class
Another first for the CLK-Class is a range of options which includes some of the best leading-edge, high-tech systems Mercedes has to offer: DISTRONIC autonomous intelligent cruise control, KEYLESS-GO access and drive authorisation system, bi-xenon headlamps and LINGUATRONIC voice-operated control for telephone and car radio.
To enable individualisation of the CLK Coupé, Mercedes-Benz has developed two lines: ELEGANCE and AVANTGARDE. Each makes a different statement through its unique design and equipment features.
Sporting emotive lines, equipped to an exceptionally high standard and incorporating leading-edge technology, Mercedes-Benz Coupé models have always been that little bit extra-special. They are cars that simply ooze passion and excitement; objects of sheer desire.
The new CLK-Class follows in the tracks of previous Coupé models; however, its markedly unique style gives it a special place in what is a long and illustrious model history.
The two-door newcomer delivers a clear message: gone are the days when a coupé was little more than a derivative of an existing saloon, when developers interpreted the term "coupé" all too literally and simply chopped off the rear end.
The new CLK-Class is a unique model series and, as such, features an entirely new interior and exterior design. All of which emphasises the exclusive character of the new Mercedes model, establishing a clear distinction between itself and other coupés in this vehicle class.
Many of the traits at the heart of the new Coupé – notably its unique character, confidence and excellence – are immediately apparent and can be felt as soon as the doors are opened. They help bring a totally new, unmistakable style to the automotive experience, creating a new "drivestyle".
Front end with new yet familiar distinguishing features
One of the main features of this unique style is the front end. Inspiration was drawn from the Mercedes-Benz CL-Class – the elder brother of the CLK Coupé – and the SL Roadster, both of which acted as templates for the classic coupé radiator grille with distinctive vanes and a large, central Mercedes star. In this position, the three-pointed emblem has become the mark of all sporty models produced by the Stuttgart manufacturer. A discreet chrome trim enhances the appearance of the four vanes which, depending on the line, are finished in high-sheen black (AVANTGARDE) or atlas grey (ELEGANCE).
The new yet familiar twin-headlamp face of the CLK-Class is a stunning achievement, comprising two ellipses which merge effortlessly to form a single headlamp unit. This impression is maintained until the "eyes" light up and it becomes clear that there are actually four separate lighting systems concealed beneath the lenses: main beam, dipped beam, parking lights and indicators. A sophisticated clear-glass look adds to the appeal of these headlamps and affords a deep insight into the supremely styled inner workings – high-tech design in an extremely attractive form.
As a prominent design feature, the headlamp ellipses largely set the formal tone at the front end: the bonnet and the front wings follow the rounded contours of the headlamps and continue these rearwards along the body. The muscular, tapering domes of the front wings evoke the image of a superbly-conditioned athlete and are symbolic of the sheer power that lies within. The appearance is sleek and athletic, an impressive blend of tight lines and soft, naturally rounded surfaces.
Sweeping coupé roof on powerful, muscular shoulders
The A-pillars pick up on the dynamic interplay between the front wings and the bonnet, extending it into the sweeping coupé roof which gives a surprising impression of lightness by virtue of its flush, slim pillars. This almost gives the impression that the coupé roof is floating. However, the filigree roof structure is well supported: the continuous waistline extends from the vehicle front to the tail lights with a pronounced, taut curve, the precise lines creating superb definition. Thus the side design also evokes anatomical images: the coupé waistline is reminiscent of a strong, tensed muscle.
The roof line flows effortlessly into an elegant C-pillar configuration, sloping gently downwards towards the Coupé rear, rounding off the side view in harmonious style: the rear light clusters, drawn deep into the vehicle flanks, pick up the side lines and draw them smoothly downwards. At the same time, the sweeping parallel lines of the bumper, boot lid and rear windscreen produce an unusually rounded and sculpted appearance. In a gentle curve, the highly aerodynamic spoiler lip on the boot lid joins the rear lamp clusters which, in turn, appear in a new and totally unique light.
Attractive insight afforded by fully-lowering, frameless side windows
There is little doubting that the CLK-Class is at its best when viewed from the side. Especially when the side windows are rolled down to give a perfect view of the Coupé interior. What is more, there are no window frames or upper B-pillars to obscure the view, just one continuous opening. This is the feature that perhaps best captures the appeal of the Coupé, accentuating the manner in which the exterior seems to merge effortlessly into the interior.
When the side windows are down, the eyes are naturally drawn to the elegantly formed dashboard. Here the visual link with the dynamic exterior is immediately apparent: once more, a combination of straight lines and smoothly rounded contours conveys lightness, dynamism and elegance.
The sporty, round air outlets in the dashboard also form a perfect link with the exterior design. Echoing the front-headlamp concept, the contours of the air outlets are extended rearwards and also take in the perforated indirect ventilation outlet. In addition, the circular air outlets for the rear passengers – located at the tail-end of the centre console and armrest – mirror the design of the outlets in the dashboard, proving that even the smallest of details contributes to the overall design concept.
Interior design displaying superb attention to detail
As one would expect, many other features also highlight a meticulous attention to detail on the part of the Mercedes designers. By way of example, the extended ellipsoid trim strip on the glove compartment lid illustrates form and function in perfect harmony: its shape emphasises the width of the dashboard whilst the perfectly integrated chrome strip accentuates the elegant character of the CLK Coupé. Even the simplest of functions – such as the button for opening the glove compartment – are elegantly incorporated with an unwavering attention to detail.
A further detail discreetly yet effectively enhances the visual impact of the CLK interior: a slender, chrome strip defines the lower edge of the long and exquisitely formed trim – in fine wood (ELEGANCE) or aluminium (AVANTGARDE) – which extends along the length of the door panel. This is the first time that the Mercedes designers have combined wood and chrome or aluminium and chrome in this elegant manner — the result of a new and complex process.
Precise design and ergonomic features
The completely new-look dashboard has several horizontal divisions; the upper section provides a visual contrast by virtue of its shape and a prominent overhang. This is accentuated by a colour contrast if a light interior colour is chosen. Moving downwards, the centre dome and centre console merge to form a sweeping S-shape, a further eye-catching feature in the CLK interior. This same dynamism is apparent in the interior panels on the wide coupé doors. If leather upholstery is specified, the door centre panels also get the full treatment: the elegant and sophisticated ruffled-leather lining is a mark of true craftsmanship.
Those lucky enough to sit behind the sporty four-spoke wheel will instantly notice another quality of the new CLK-Class: superb ergonomic design — or, to put it another way, precision in every respect. And all the controls are within easy reach. Furthermore, the main instrument dials – speedometer, rev counter and clock – feature a classic round design and provide crystal-clear information.
Refined details like the chrome surrounds on the dials and the generous fine-wood or aluminium trim which adorns the centre console enhance the high-quality feel of the CLK interior. In other words, the perfect blend of ergonomics and design, for a feel-good factor that makes motoring an even more pleasurable experience.
Fully personalised colour schemes
In keeping with the Mercedes "maximum individuality" philosophy, the new CLK-Class offers a whole host of personalisation options:
- A choice of four colour shades for the ELEGANCE interior: anthracite, pebble beige (if leather upholstery is specified), alpaca grey and pacific blue. This line comes with "ash brown" fine-wood trim combined with elegant chrome.
- Two standard interior colours for the AVANTGARDE line: anthracite or alpaca grey. If leather upholstery is specified, three further individual combinations are possible: anthracite/alpaca dark grey, anthracite/berry red and anthracite/dark blue. The trim is in "ellypta" aluminium combined with high-sheen chrome.
There is also a choice of 13 colour shades for the CLK exterior, two of which are exclusive to the new Mercedes Coupé. Further exclusive colours, materials and appointments are available as part of the designo range.
Colours that can be specified to individualise the CLK 55 AMG interior include anthracite, merlot red and dark blue. Standard two-tone leather appointments in the flagship sports version are a unique combination of the finest leather grades, namely nubuk leather for the interior door panels and perforated seat cushions – available in three colour shades: anthracite, merlot red and dark blue – and nappa leather in anthracite for all other leather appointments. Further unique touches are provided by the aluminium trim, the leather steering wheel and the instrument cluster, all of which feature a special AMG design.
Engines and transmission
A whole host of new developments lie beneath the bonnet of the new CLK-Class, in particular many innovations that herald major technical advances. For instance, six of the seven powerplants available for the Coupé are new to this Mercedes model series: the powerful five-litre V8 engine from the S-Class, the state-of-the-art V6 powerplant with 2.6-litre displacement, the torquey five-cylinder CDI engine and the powerful eight-cylinder AMG engine. Not to mention the newly developed four-cylinder powerplant that is one of the first direct petrol injection engines in the world to feature the unique TWINPULSE system, including a compressor supercharger and Lanchester balancer among other things. This new engine line-up delivers substantially lower fuel consumption and exemplary emissions performance whilst ensuring vastly enhanced driving pleasure, agility and power delivery — in every displacement class. The numbers back this up:
- Fuel consumption in the CLK models is, on average, six percent lower than in the preceding models.
- All petrol models already comply with the strict EU-4 emission standard due to come into force in the year 2005 and the US-American standards for "Ultralow Emission Vehicles" (ULEV). The CDI engine meets the requirements of the EU-3 standard.
- The seven CLK engines have power outputs ranging from 120 kW/163 hp to 270 kW/367 hp (preceding models: 120 kW/163 hp to 255 kW/347 hp).
- Maximum engine torque ranges from 240 to 510 Newtonmetres (predecessor models: 230 to 510 Newtonmetres).
New V8 CLK 500 model with power to match a thoroughbred sports car
The new eight-cylinder model in the CLK-Class line-up is called the CLK 500. In this guise, the new Coupé delivers driving dynamics and performance on a par with thoroughbred sports cars such as the SL 500 or top-of-the-range Coupés such as the CL 500. One look at the figures confirms this: the CLK 500 takes a mere 6.0 seconds to accelerate from 0 to 100 km/h and, thanks to its exemplary torque characteristics, completes the sprint from 60 to 120 km/h in just 6.2 seconds — class-leading figures in this coupé segment. A quick dab of the accelerator is all it takes to feel the sheer power beneath the bonnet of the new top-of-the-range CLK model: even at a speed just above idle, the V8 powerplant plants 344 Newtonmetres of torque onto the road -– an impressive 75 % of maximum torque. Furthermore, at 2240 rpm, there are a massive 428 Newtonmetres available — 93 percent of the maximum torque of 460 Newtonmetres, which the engine provides from 2700 rpm and maintains until 4250 rpm. At launch, the eight-cylinder engine will be available with five-speed automatic transmission as standard.
Two powerful six-cylinder models with 2.6 and 3.2-litre displacement
Mercedes-Benz has extended the six-cylinder line-up for the new CLK-Class by adding the tried-and-tested 2.6-litre V6 engine which develops 125 kW/170 hp and provides a maximum torque of 240 Newtonmetres at 4500 rpm.
The CLK 320 remains unchanged in the line-up. And with good reason: the powerful V6 powerplant (160 kW/218 hp), which Mercedes-Benz offers with five-speed automatic transmission as standard, is particularly well-suited to the new Mercedes Coupé, since it delivers equally impressive performance during either sporty driving with high power output or more serene and relaxed driving at lower engine speeds. With 310 Newtonmetres of torque on tap from just 3000 rpm, the six-cylinder engine offers the very best of both worlds.
New four-cylinder engine with the option of direct petrol injection
Mercedes-Benz will again show the way forward, this time in the field of four-cylinder technology, when a new generation of engines is launched in mid-2002. The newly developed engines highlight the shape of things to come in all the major areas of development: fuel consumption, torque characteristics, power delivery, lightweight design and refinement.
There is a choice of two versions of this sophisticated engine for the CLK-Class, both featuring the unique TWINPULSE system. This technology package contains a host of innovations, designed to ensure sheer driving pleasure and low fuel consumption: mechanical supercharger, intercooler, four valves per cylinder, double overhead camshafts with variable valve timing, Lanchester balancer shafts, adaptive drive system, aluminium construction and optional direct petrol injection. The options:
Four-cylinder engine developing 120 kW/163 hp with electronically controlled fuel injection in the intake ports for the CLK 200 KOMPRESSOR.
Direct-injection petrol engine developing 125 kW/170 hp — the first latest-generation Mercedes powerplant featuring this new technology and the world’s first engine of its kind, which combines leading-edge, direct-injection technology with a compressor supercharger and counter-balancer. Mercedes models incorporating this sophisticated engine technology will be recognisable by the CGI badge on the rear, which stands for (Stratified) Charged Gasoline Injection.
One look at the performance and fuel consumption figures reveals that both four-cylinder engines have everything it takes to deliver superb economy and a dynamic driving experience:
The new CLK 200 KOMPRESSOR accelerates from 0 to 100 km/h in 9.3 seconds, going on to reach a top speed of 230 km/h, making it 7 km/h faster than the equally powerful predecessor model. Fuel consumption has been reduced to 8.6 litres per 100 kilometres (NEDC combined), 0.8 litres less than in the previous CLK 200 KOMPRESSOR.
The four-cylinder newcomer also delivers when it comes to pulling power and flexibility: the maximum torque of 240 Newtonmetres is available from 3500 rpm. And accelerating from 60 to 120 km/h (in fifth gear) takes the new CLK 200 KOMPRESSOR a mere 15.8 seconds.
To put it another way, mechanical supercharging and sophisticated engine technology enable the newly developed engine to combine the pulling power and refinement of a six-cylinder engine with the economy of a four-cylinder engine.
Direct injection petrol engine consuming 16 percent less fuel
The CLK 200 CGI is even more impressive at underlining the qualities of the new generation of Mercedes engines. Offering similar levels of performance — 0 to 100 km/h in 9.2 seconds and a top speed of 231 km/h — fuel consumption in the direct petrol injection engine is around eight percent lower than in its counterpart with port injection. In concrete terms: the new CLK 200 CGI consumes a mere 7.9 litres of sulphur-free Super Plus per 100 kilometres (NEDC combined). This represents a fuel saving of around 16 percent, compared to the predecessor model, despite the higher engine output.
Over 75 percent of the torque is available from just 1500 rpm. And the four-cylinder engine develops its maximum torque of 250 Newtonmetres from 3000 rpm. What is more, it maintains this impressive level up to 4500 rpm.
Lean-burn operation under partial load and emission control with storage catalytic converter
Mercedes-Benz has a long tradition in the field of direct petrol injection. As early as the mid-fifties, the Stuttgart manufacturer unveiled this technology in the 300 SL, the legendary "Gullwing". This classic sports car was the first series-produced automobile to receive a four-stroke engine with direct injection — a sensational development that significantly boosted the six-cylinder powerplant’s output.
Nowadays further development of this particular injection technology focuses on two different aspects: fuel consumption and exhaust emissions. Major advances in the fields of emission control and engine management have resulted in a solution to a familiar technical problem: producing an engine that is sufficiently lean-burning to provide the desired fuel consumption whilst using catalytic converters that usually require a "stoichiometric" air/fuel mixture (14.6 : 1). The solution in question is a newly developed NOx storage catalytic converter which absorbs the nitrogen oxides during the lean-burn cycle and then re-releases them in brief regeneration phases, so that they react with other constituents of the exhaust gas to form harmless nitrogen.
Thanks to this technology, which Mercedes-Benz combines with exhaust gas recirculation and secondary air injection in the new direct-injection petrol engine, the CLK 200 CGI is able to comfortably comply with the future EU-4 emissions standard. Up to 35 percent of the exhaust gases can be recirculated, depending on the engine operating characteristics, thus bringing about a substantial reduction in nitrogen oxide emissions. Another new innovation comes in the form of the "linear" oxygen sensor which becomes active immediately when the engine is started from cold and supplies information about the exhaust gas composition. This information is then processed by the engine computer, for the purpose of warm-up control among other things. It enables the catalytic converter to reach operating temperature in considerably less time. In addition, a newly developed, electronically networked NOx sensor with digital control is used, to ensure optimum control of the NOx storage catalytic converter.
Direct injection at a pressure of up to 120 bar
In the direct-injection system, the air and fuel are not mixed until they reach the combustion chambers. With the help of an injector, the fuel is injected into the cylinders at an angle of 42 degrees and, depending on the engine operating characteristics, at a pressure of between 50 and 120 bar. Here the fuel droplets and the air particles form a mixture which flows to the spark plugs via specially shaped recesses in the pistons. By way of comparison, the fuel pressure in a four-cylinder engine incorporating conventional injection technology is approximately 3.8 bar.
The CGI engine has two separate intake ports with flow characteristics that have been developed using sophisticated processes. These ports ensure optimum swirl in the mixture, thus making combustion fast and as complete as possible. In each case, one of these intake ports also has an adjustable swirl flap. The high-pressure fuel pump is driven by the intake camshaft. A pressure regulator controlled by the engine computer regulates the pressure in the fuel line (rail) which is directly connected to the injectors. The regulator receives signals from a pressure sensor.
Under partial load, at a mean pressure of four to five bar and at low engine speeds, the four-cylinder engine is "lean-burning". In other words, with the throttle wider open and with a high level of excess air. Engineers talk about "stratified charging": the fuel is injected into the air compressed by the piston at a relatively late stage. Outside of this range, the direct-injection engine is operated with the usual air/fuel mixture for engines with catalytic converters (lambda 1).
Aluminium cylinder head with variable valve timing
Made from high-strength aluminium alloy, the cylinder head in both versions of the new Mercedes engine has 16 valves and double overhead camshafts. Unlike in the previous four-cylinder engine in the CLK-Class, both camshafts are adjustable and have variable valve timing. A newly developed vane-type adjuster with integrated control valve ensures optimum valve timing at all times. This has a positive effect on torque characteristics under full load as well as on fuel consumption and exhaust emissions. The valves are controlled by means of cam followers with roller mechanism and have hydraulic valve lifters.
Highly efficient, low-noise compressor
The Mercedes developers have reengineered the compressor – which ensures exemplary bottom-end torque characteristics in both engine versions – by reducing the clearance between the rotors and the supercharger housing and by using a new coating for the rotors. The result is an even higher rate of air flow and even better efficiency than in the mechanical supercharger used in previous Mercedes four-cylinder engines. Special wide-band silencers are installed on the intake side and pressure side.
After being compressed, the air exits the compressor and flows through an intercooler, thus reaching the optimum temperature and density for the combustion process. The standard version and the CGI version of the new engine have different plastic intake pipe arrangements: in the direct-injection version, they separate into two lines per cylinder before actually entering the cylinder head. In each case, one of these pipes has an electrically adjustable swirl flap which further promotes air swirl
Electronic control unit on the air cleaner housing
The round air cleaner attached to the intake pipe has the advantage of being able to provide a relatively large filter area in the smallest of spaces. In addition, the electronic control unit – equipped with two powerful processors – is located on the side of the air cleaner housing. The two processors share the complex tasks: one is responsible for the real-time processes, such as calculation of the ignition and injection pulses, whilst the other deals with time-synchronised tasks, such as lambda control or determining the ignition timing and the injection quantity. The control unit is integrated in the electronic network of the new CLK-Class via CAN databus (Controller Area Network) and swaps data with other microcomputers. The hot-film air flow sensor, incorporating reengineered functions, is positioned directly behind the air cleaner housing.
As is the case in all state-of-the-art petrol engines from Mercedes-Benz, the new four-cylinder generation uses electronic monitoring for components that simply have to function correctly in order to ensure low emissions. By way of example, this on-board diagnostic system permanently monitors catalytic converter efficiency and the ignition system as well as checking the purge valve electrics and the oxygen sensor. The "Check Engine" display on the CLK-Class instrument cluster lights up if a fault occurs in one of these systems. Meanwhile, details of any malfunctions are stored so that service engineers can detect the problem immediately and remedy the fault.
Refinement similar to a six-cylinder engine thanks to newly developed counter-balancer
Alongside exemplary power delivery, low fuel consumption and low exhaust emissions, the new Mercedes four-cylinder engine has a further advantage, namely refinement and acoustics similar to a six-cylinder engine. This is primarily down to the newly developed Lanchester balancer which consists of two forged shafts supported in multiple bearings. The shafts rotate in opposite directions at twice the crankshaft speed and, in so doing, counter-balance the inertia forces caused by the motion of the pistons, for example, which tend to cause irritating vibration.
The size, weight and arrangement of the counter-balance shafts have been perfectly harmonised to neutralise the vibratory forces in the four-cylinder engine. This technology thus substantially reduces noise emissions and vibrations and vastly enhances ride comfort.
The aluminium housing that contains the bearing-mounted balancer shafts is located in the oil sump and bolted to the crankcase from below. The drive is provided by a newly developed silent chain with low masses. The crankcase also contains the engine oil pump which is driven by one of the two shafts by means of a gear pair.
The crankcase is made from diecast aluminium (previous engine: cast iron) and is a major component in the lightweight design concept at the heart of the new four-cylinder engine. To put this into figures, the engine only weighs around 167 kilograms, making it some 18 kilograms or almost ten percent lighter than the preceding model.
Driving dynamics tailored to driver requirements
Mercedes-Benz also offers a newly developed system in the four, six and eight-cylinder CLK-Class models, which recognises individual driving styles and adapts the drive characteristics of the engine accordingly, thus further adding to the scintillating, dynamic driving experience. For those that fancy themselves as racing drivers, the ECU does its best to please, providing superlative accelerator response. If, on the other hand, the computer detects a driver looking for comfort rather than speed, it adapts the ECU control characteristics, harmonising the engine settings to suit this particular style of driving.
To ensure there is no doubt when detecting the driving style or the driver’s requirements, the system monitors the pedal movements extremely closely and records every instance of acceleration before adapting the pedal characteristics. This is a continual step-by-step process which ensures that the driving characteristics never contradict the driver’s expectations. In the case of a sporty driving style, the pedal characteristics change so that, although pedal travel may remain the same, the throttle valve is opened further than would usually be the case. The engine therefore reacts more instantaneously to driver input and is quicker to provide maximum acceleration. If a more comfort-oriented driving style is detected, the ECU sets flatter pedal characteristics. In this instance, although the pedal travel remains the same, the throttle valve opens more slowly than usual and acceleration is smoother.
Assuming the CLK 500 is being driven at 120 km/h in third gear, for example, and the ECU has detected a sporty driving style, the accelerator pedal only needs to be pressed halfway to the floor to obtain an effective acceleration of over 80 percent. If the driving style is more comfort-oriented, this degree of acceleration potential is not obtained until the accelerator has been pressed approximately 75 percent to the floor.
CDI diesel engine with fuel consumption of just 6.7 litres per 100 km
The CLK 270 CDI is the first state-of-the-art direct diesel injection engine Mercedes-Benz has offered its customers in the coupé segment. What really makes it stand out, alongside the high torque, is the extremely low fuel consumption. In terms of acceleration and top speed, the new CDI Coupé is therefore on a par with the V6 CLK 240 model.
The superb torque characteristics ensure that the five-cylinder engine always reacts instantaneously to driver input, accelerating immediately. For instance, the maximum torque of 400 Newtonmetres is available from just 1800 rpm and is kept constant until 2600 rpm. With so much bottom-end torque, the CLK 270 CDI accelerates from 0 to 100 km/h in just 9.2 seconds and from 60 to 120 km/h (in fifth gear) in a mere 12.6 seconds. The direct injection diesel engine’s power curve reaches its summit – 125 kW/170 hp – at 4200 rpm.
However, the five-cylinder model delivers low fuel consumption of just 6.7 litres per 100 kilometres (NEDC combined), an astonishing figure given the impressive performance figures.
As is the case with all diesel engines in the Mercedes-Benz passenger car line-up, the new five-cylinder version is crammed with technical refinements:
- The common-rail injection system keeps the injection pressure of up to 1350 bar constant in the common fuel rail, upstream of the cylinders, at all times. And it meters the injection quantity according to requirements, depending on the engine load and speed.
- The intake system operates using a hot-film air flow sensor that enables accurate analysis of the air intake. This is important for ensuring precise control of the exhaust gas recirculation and, therefore, a reduction in nitrogen oxide emissions.
- The engine ECU controls all the processes within the sophisticated CDI engine and, thanks to a databus network, also uses information provided by other control units.
- The intercooler cools the intake air, thus enabling the engine to deal with greater quantities of air, for high torque and power output.
- The four valves per cylinder allow the injector nozzles to be positioned centrally so that the fuel can be evenly dispersed in all directions within the combustion chamber. This makes combustion more complete than is the case in engines with two valves per cylinder, leading to lower exhaust emissions.
- The VNT turbocharger ensures a fast build-up of charge pressure at low revs thanks to variable turbine geometry. This noticeable benefits of this are improved cylinder charging and, consequently, higher torque.
Facts and figures: engine and performance data for the new CLK-Class
The new CLK-Class will be available with a choice of seven engines with power outputs ranging from 120 kW/163 hp to 270 kW/367 hp. Six of these powerplants have been newly developed or further improved.
New CLK 55 AMG: 0 to100 km/h in 5.2 seconds
At the heart of the new high-performance CLK 55 AMG Coupé is a further improved V8 powerplant with 5439-cc displacement, developing 15 kW/20 hp more than its successful predecessor model. The eight-cylinder engine provides 510 Newtonmetres of pulling power from just 4000 rpm, impressive figures for a naturally aspirated engine. This enables the two-door model to accelerate from 0 to 100 km/h in just 5.2 seconds, making it exactly 0.2 seconds faster than the previous CLK 55 AMG. The top speed is electronically limited to 250 km/h — although the speedometer dial in the flagship sports model goes up to 320 km/h, giving an indication of the potential power harnessed beneath the bonnet.
Prominent features of the V8 engine from Mercedes-AMG include the use of forged-aluminium pistons and specially developed oil jets for cooling the pistons. Optimum cylinder charging is assured thanks to a twin-pipe intake train, specially formed camshafts and a sports-tuned variable intake manifold, which provide the eight-cylinder engine with all it needs to deliver exemplary torque characteristics. The exhaust system consists of two firewall and four underfloor catalytic converters as well as specially designed silencer systems which minimise exhaust gas backpressure.
Three transmission versions available
Standard equipment in the CLK 200 KOMPRESSOR, CLK 200 CGI, CLK 240 and CLK 270 CDI models includes the sophisticated six-speed manual transmission which is ideally suited to the car’s agile character thanks to its short shift travel. The Mercedes engineers have configured 6th gear as a real "driver’s gear" in which the Coupé reaches its top speed.
For an especially dynamic driving experience, these models are also available with the option of SEQUENTRONIC. Here the driver merely has to nudge the shift lever, without pressing the clutch pedal, to change gear automatically and with the utmost speed and precision. Electric pulses transfer the driver input to a microcomputer which, in turn, controls a special hydraulic system for engaging the desired gear.
Components that do not feature on the SEQUENTRONIC spec list include the mechanical connections that usually link the shift lever to the six-speed transmission. In contrast to the previous six-speed manual transmission, the new system has an "add-on" unit attached to the transmission housing, containing all the auxiliary components with the exception of the control unit: the hydraulic unit connected with the main shift rail, the central release mechanism required for clutch operation, the power supply comprising electric motor and hydraulic pump, a special oil tank, the accumulator module required in order to maintain the constant system pressure and the sensors which check all movements of the shifter shaft and ascertain which gear is engaged.
To operate the SEQUENTRONIC, the driver simply has to nudge the shift lever forwards or backwards: nudging the lever towards the "+" symbol causes the hydraulic system to disengage the clutch and, via the main shift rail, engage a higher gear. During this process, the ECU takes into account the engine speed, engine torque, wheel speeds and a series of further parameters that are necessary in order to ensure precise gear changing. The system then engages the next-highest gear with lightning speed. The SEQUENTRONIC therefore fulfils the driver’s shift requests in the correct order every time. In other words, the system is sequential, shifting and engaging the gears one after the other, be it for upshifts or downshifts.
Moving the shift lever in "+" or "—" direction and holding it there causes the SEQUENTRONIC to automatically shift up or down one or several gears, in order to select the optimum ratio for the current situation.
On the road, the system is quick to translate driver input into action. Furthermore, the driver no longer needs to monitor the engine speeds during automated gear changes as this is done by the SEQUENTRONIC which automatically kicks in if the engine speed exceeds or falls below certain limits. What is more, the transmission status can be checked at any time, since a display in the instrument cluster always indicates the currently engaged gear.
The new transmission has a further function that is of benefit when driving in town, in stop-and-go traffic and for many other situations encountered on the road: Autoshift mode. If the driver nudges the shift lever fully to the left – towards the "A" symbol – the SEQUENTRONIC assumes control, relying on numerous sensor signals to automatically change up and down through the six gears. By using intelligent technology, the new SEQUENTRONIC combines the benefits of a six-speed manual transmission with those of an automatic transmission. In addition, the innovative system increases driving pleasure as it is so easy to use and offers a choice of either fast and precise manual shifts or automatic gear changes
Five-speed automatic transmission with new converter lockup mechanism
For drivers who demand even greater comfort and convenience, Mercedes-Benz offers the option of an electronically controlled five-speed automatic transmission with Touchshift for the CLK-Class. This is fitted as standard in the CLK 320 and CLK 500 models.
With its modified control set-up, the Touchshift feature gives the driver even more options for engaging the ideal gear for the situation in hand. Holding the selector lever in the "—" position tells the transmission to keep moving down the ratios until the one that can best slow or accelerate the Coupé is found. When driving downhill, the driver thus has the convenient option of shifting down to obtain the best possible engine braking effect. The same is true when accelerating, since the ratio from which the vehicle derives optimum performance can be engaged. Manual shifts down into the optimum gear are monitored by the transmission ECU so as to prevent the permitted engine speed limits from being exceeded. The Mercedes engineers have extended the operating time during which the torque converter lockup clutch is engaged, both to further improve vehicle agility when moving off and to reduce fuel consumption. Torque converter lockup is now possible in any gear – even first gear – whereas, before, it could only be engaged in third, fourth and fifth. Torque converter lockup reduces the slip that usually occurs between the pump and the turbine wheel. This increases efficiency and reduces fuel consumption.
Formula 1-style gearshift on the steering wheel
Another special technical feature enhances the sporty driving experience in the new CLK 55 AMG: a five-speed automatic transmission with steering wheel gearshift and SPEEDSHIFT function. This means that – as in the top-of-the-range SL 55 AMG sports car – the driver can opt for a Formula-1-style gearshift with two selector switches located behind the top two steering wheel spokes. To enable the system, the driver must first activate manual transmission mode by pressing the program select button on the automatic selector lever. The selector switch on the right of the steering wheel is used for upshifts whilst the one on the left is for downshifts. The transmission only intervenes of its own accord and changes gear if the maximum permitted engine speed is exceeded. A display in the instrument cluster tells the driver f which transmission mode is active and which gear is selected.
The additional SPEEDSHIFT function combines the advantages of a five-speed automatic transmission with the dynamism of a manual transmission. Notable technical features include active downshifting: once deceleration reaches a certain level, the transmission automatically shifts down and engages the correct gear, for example if a sporty driver brakes before entering a bend. Similarly, when cornering at speed, the transmission reliably retains the engaged gear once lateral acceleration reaches a certain level, thus ensuring unbridled driving pleasure whilst preventing any power-off effects.
Furthermore, to shift down before overtaking, the driver of the new CLK 55 AMG merely has to move the Touchshift lever to the left and briefly hold it there. The transmission control unit then selects the optimum gear for powerful acceleration, depending on the road speed and the engine map.
In terms of agility, straight-line stability, steering precision, road roar, tyre vibration and braking power – in short, practically all areas of chassis technology – the new CLK-Class achieves peak-performance figures which add up to ensure one thing above all: an even more dynamic driving experience.
The Mercedes engineers spared no expense in newly developing or further improving the axles, steering and brakes, to exceed the already high standards set by the predecessor model. In doing this, they were able to call upon tried-and-tested systems from the Stuttgart manufacturer’s passenger car line-up and adapt these systems for use in the new Coupé. This involved the following:
- Replacing the previously installed double-wishbone design with state-of-the-art three-link front suspension with McPherson struts, thus enabling major advances, particularly with respect to wheel location, comfort and steering precision. Furthermore, this design provides greater deformation paths in the area of the lower links, enabling the front end of the CLK Coupé to absorb more impact energy than previously. The forwards-slanting tension struts on the front axle and the integral support – to which front axle components, the steering gear and the engine mounts are attached – are made of aluminium.
- The Mercedes engineers have replaced the previously fitted recirculating ball-type steering with power-assisted rack-and-pinion steering which is even more responsive and thus better suits the dynamic character of the new Coupé. What is more, this system is lighter and offers added safety benefits in the event of a frontal collision.
Mercedes-Benz offers the option of speed-sensitive parameter steering for the CLK-Class (standard in the CLK 500). This makes manoeuvring or parking practically child’s play. At 380 mm, the steering wheel diameter is 10 mm smaller than in the preceding model. The steering wheel rim is made from an combination of steel and magnesium, which deforms in a predetermined manner in the event of a collision, thus reducing the risk of injury to the driver.
- In conjunction with the newly developed front axle, the longer wheelbase and the standard-fitted Electronic Stability Program (ESP®), the tried-and-tested multi-link independent rear suspension ensures a high degree of active safety, dynamism and comfort. The track rods, hub carriers and subframe for the rear axle have also been radically reengineered by the Mercedes engineers. New kinematics and elasto-kinematics, largely due to the use of optimised bearings and mounts, ensure even better vibration response and reinforce the understeer characteristics of the Coupé. All engine versions available with the new CLK-Class are equipped with anti-roll bars.
Facts and figures: the main chassis data for the new CLK-Class
Whilst the front and rear track width remain almost the same as for the predecessor model, the wheelbase has been extended by 25 mm. The new CLK-Class has mixed-profile tyres as standard – these are in 17-inch format for the new top-of-the-range V8 CLK 500 model.
Factory-fitted sports suspension for further enhanced driving dynamics
Motorists who fancy themselves as racing drivers can order the CLK Coupé chassis with tauter suspension and damper settings. Mercedes-Benz supplies this sports suspension set-up, in which the body is 15 mm lower at the front and rear axle, as an option for all lines and model versions. Spring rates for the sports suspension are five percent higher.
The CLK 55 AMG is to be launched with high-performance AMG sports suspension. Enlarged anti-roll bars on the front and rear axles, coupled with specially tuned springs and gas-filled shock absorbers, ensure supreme roadholding and incorporate the technical advances necessary for sporty handling.
Brake technology for the ultimate in performance
In terms of size, technology and equipment, the Mercedes engineers have tuned the brakes to each of the different engines and the wide range of outputs available with the new CLK-Class. For instance, the flagship CLK 500 has 4-piston fixed-caliper disc brakes on the front axle, of the kind used for the SL 500 Roadster. The eight-cylinder model has 2-piston fixed-caliper disc brakes on the rear axle. The diameters of the internally ventilated front and rear brake discs are 345 and 300 mm respectively.
The technology used for the tandem brake booster (7/8-inch) made of aluminium is lifted from the S-Class. It is equipped with an electronically controlled solenoid valve that enables particularly precise application of the brake pressure. The main brake cylinder – also made of aluminium — is fitted with a pretensioned compression spring between the primary and secondary pistons. In contrast to conventional systems, in which the secondary piston only moves due to the pressure in the primary circuit, both brake circuits are activated simultaneously in the new CLK-Class. Substantially shorter pedal travel is just one of the benefits of this immediately obvious to the driver.
The development team drew on its experience in motorsport when designing the brakes for the high-performance CLK 55 AMG Coupé. And the upshot: four-piston fixed-caliper disc brakes on the front axle, with internally ventilated and perforated brake discs measuring 345 mm in diameter, and two-piston fixed-caliper disc brakes at the rear, also with internally ventilated disc brakes (diameter 300 mm). This means the brake system on the AMG Coupé can rise to almost any challenge with an impressive maximum deceleration of 10.5 metres/second².
Electronic control systems for superlative active safety
As is the case with all state-of-the-art Mercedes passenger cars, the new CLK-Class is equipped with the best and most highly effective active safety systems available – as standard. They reduce the risk of skidding when cornering, hold the Coupé safely on track when braking, improve starting on slippery surfaces and reduce the emergency-stopping distance. This high-performance technology is an important part of the Mercedes-Benz safety concept and actively helps to prevent road accidents.
- The Electronic Stability Program (ESP®) uses various sensor signals to detect dangerous situations even earlier and faster than the most experienced of drivers can, intervening automatically with the utmost precision to stabilise the vehicle. It does this through precisely modulated brake pulses on one or more wheels and by reducing the engine torque. The new CLK Coupé is equipped with latest-generation ESP® which operates extremely harmoniously thanks to its supremely smooth response.
- The Anti-lock Brake System (ABS) prevents the wheels from locking up during emergency braking and works as reliably on dry tarmac as it does on wet surfaces or black ice. As a result, the Coupé retains directional stability at all times — even under maximum deceleration.
- Acceleration Skid Control is part of the Electronic Stability Program and prevents the driven wheels from spinning when starting off or accelerating. If the driver accelerates too abruptly and one of the driven wheels starts to spin, this wheel is braked by ASR until sufficient traction is re-obtained. In addition, the engine torque is also reduced, depending on the situation on the road.
- Brake Assist (BAS) is activated if a critical situation arises and the driver is too slow or not hard enough on the brake pedal. In such instances, the system automatically provides maximum-power braking within a fraction of a second, thus substantially reducing the car’s stopping distance.
Light-alloy wheels and wide-base tyres for a distinctly sporty appearance
Further special features of the new CLK-Class designed to further enhance the sporty nature of the Coupé include different-sized tyres on the front and rear axles. The standard equipment package includes 205/55 R 16 tyres on the front axle and 225/50 R 16 tyres at the rear. The top-of-the-range V8 CLK 500 model has 17-inch tyres, namely size 225/45 R 17 at the front and 245/40 R 17 at the rear. The Mercedes engineers have adapted the design of the standard-fitted light-alloy wheels to suit the individual character of each line: they fit the ELEGANCE model with smart seven-hole rims, whilst the AVANTGARDE line comes with a distinctly sporty five-spoke-rim look that makes it really stand out.
Optional equipment for all model versions includes special 17-inch light-alloy wheels or 18-inch AMG light-alloy wheels. The CLK 55 AMG catches the eye with its 18-inch light-alloy wheels, with new twin-spoke design as standard or classic five-spoke design as an option. This high-performance Coupé has size 255/40 R 18 tyres on the front axle and size 255/35 R 18 on the rear axle.
Further standard equipment for the new CLK-Class includes the innovative TIREFIT repair kit in place of the conventional spare wheel. The spare wheel recess in the boot can therefore be used as a stowage compartment. Mercedes-Benz still supplies the spare wheel as a no-cost option.
Practical, multi-level occupant protection system
In addition, the new CLK-Class incorporates the pioneering, practical Mercedes safety concept. This concept also takes into account occupant protection in the frequent collisions that occur at mid-range speeds. For instance, in the event of a frontal impact, a three-stage protection system is activated, based on the severity of the collision:
- At impact speeds of up to 4 km/h, the foam elements in the bumper absorb the crash energy, thus ensuring that the panels behind remain undamaged. The plastic bumpers even revert to their original shape after the accident.
- At impact speeds of around 15 km/h, the energy is absorbed within the newly developed front module and its integrated crash boxes made of highly-resistant steel.
- At impact speeds in excess of 15 km/h, the impact forces are channelled into four independent zones:
- 1. Via the aluminium crossmember in the front module, which channels the impact force to the side of the vehicle unaffected by the collision;
- 2. Via the substantially forwards-extended side members (behind the crash boxes);
- 3. Via robust sectional panels above the wheel housings, which provide an additional path for channelling the impact forces;
- 4. Via the front wheels which are supported by special crash elements in front of the side members (doorsills), enabling them to channel the impact forces into the body side structure.
Ellipsoid bulkhead for effective energy absorption during a frontal crash
The front end is connected to the passenger cell by means of an ellipsoid bulkhead comprising several panels of differing thickness. This set-up enables the material to be adapted according to the severity of the impact and represents an ideal compromise between lightweight design and crash safety. The thickness of the high-strength steel varies by up to 150 percent, meaning that the bulkhead is not only capable of withstanding extreme loads, it can also evenly disperse the forces generated by a frontal collision over a wide area. This prevents dangerous intrusions into the passenger cell. Consequently the previously installed front side member extensions are no longer required.
2-stage airbag deployment, based on impact severity and passenger weight
Adaptive front airbags – airbags that adapt according to the type of collision and deploy in two stages depending on the severity of the collision – prove the perfect complement to the practical protection concept in the new CLK-Class:
- Stage 1: in the event of a minor frontal collision, the ECU only fires one chamber of the two-stage airbag gas generators. The airbags are therefore inflated to a lower pressure.
- Stage 2: if the ECU detects a severe frontal collision, it also activates the second chamber of the gas generator after a delay of between 5 and 15 milliseconds. The airbags are thus inflated to a higher pressure, offering the occupants a level of protection in line with the severity of the accident.
Mercedes-Benz has further developed this adaptive airbag technology for the new CLK-Class: when calculating the required degree of airbag deployment, the airbag ECU does not just take the severity of the collision into account, it also considers the front passenger’s bodyweight. This means that the protection systems are able to adapt with even more precision in the event of a frontal collision. By way of example, the microcomputer may even fire both generator chambers in the event of a minor collision, depending on the severity of the accident and the passenger’s weight, so as to provide a heavy front passenger with the best possible level of protection. Conversely, if the front passenger is very light, the second chamber may only inflate in the case of more severe collisions. The ECU assigns the front passenger to one of four weight categories using data it receives from a special measuring membrane in the seat: 1 to 30 kg; 31 to 50 kg; 51 to 70 kg; over 71 kg. At the same time, the newly developed measuring membrane acts as a seat occupancy sensor and ensures that the passenger airbag, belt tensioner and sidebag are automatically deactivated if the seat is unoccupied.
The automatic child seat recognition system, which is fitted as standard, deactivates the passenger airbag when it detects that a Reboard child seat from the Mercedes range of accessories is fitted on the front passenger seat. This child seat uses a special transponder system that receives and responds to signals from two antennae inside the seat upholstery. This exchange of data tells the ECU whether a Reboard seat has been installed and, if this is the case, the ECU deactivates the airbag on the passenger side. The belt tensioner, sidebag and windowbag remain activated and offer the smaller passenger in the child seat additional protection in the event of an accident.
Windowbags and sidebags for optimum side-impact protection
Fitted as standard, the windowbags are a further example of the real-life safety concept at the heart of the new CLK-Class. They were also developed based on the findings of the latest accident research. During the course of this research, which took into account a wide range of impact angles, scientists established that an airbag in the side wall area needs to be as large as possible to ensure the best possible protection for all occupants, given the wide range of possible impact constellations. The windowbag meets the requirements stipulated by the accident researchers. It consists of several chambers which, in the event of a crash, are drawn like a curtain across the interior area between the front and rear roof pillars, all within the space of 25 milliseconds.
And whilst the windowbag prevents a person’s head from colliding with the side window or roof frame, as well as catching glass splinters or other objects that can be propelled into the interior following a crash or subsequent rollover, the sidebags offer additional protection for the thorax area.