After about four years of development and a total investment of more than 1.36 billion Euro, the Mercedes-Benz C-Class was revealed in 2000. The sedan was available at European branches and dealers of the Stuttgart-based auto maker from May that year and continued the success of its predecessor, which has enjoyed a production run of 1.6 million units and was the market leader among comparable premium sedans in many countries.
With the C-Class, an extensive package of technical innovations was phased in, on an unprecedented level for this market segment. Never before has so much attention been paid in this vehicle class to the aspects of safety and comfort as in the development of the Mercedes-Benz C-Class, which with this top-class technology guarantees a maximum of both dynamism and driving pleasure.
Even at first glance the attractive design, with its modern interpretation of the twin headlamp face, expresses two of the key features of the C-Class, namely dynamism and elegance. The sedan is a youthful, progressive car that is characterized by newly developed chassis technology, powerful engines, the latest technical innovations and, in particular, sporty agility. These dynamic features are combined in the C-Class with traditional Mercedes qualities such as the maximum possible safety, top quality, exemplary comfort and superb reliability.
The standard equipment of the sedan includes pioneering technical innovations that were previously only available in the flagship models bearing the Mercedes 3-pointed star: windowbags, adaptive airbags for driver and front passenger, Headlamp Assist, the multifunction steering wheel and fiber optics are only a few examples of a whole host of new developments that make the C-Class a technological trailblazer in its market segment. Overall, more than 20 technical innovations from the Mercedes flagship models were included as standard in the C-Class.
In addition, maximum safety is ensured by standard-fitted systems such as the Electronic Stability Program (ESP), Brake Assist, automatic child safety seat recognition, seat belt tensioners and belt force limiters for the front seats and rear outer seats, head restraints for all seats and side impact airbags in the front doors. The SPEEDTRONIC electronic speed limiter and the 6-speed manual gearbox are also fitted as standard.
Compared to the outgoing model, Mercedes-Benz has upgraded the value of the standard equipment of the C-Class by about 3700 DM.
Character formation - this was the designers’ brief. They were tasked with giving the Mercedes-Benz C-Class a dynamic character which both instills affection and from the very first glance leaves no doubt about its pedigree. In short, the resulting sedan had to visually reflect Mercedes -Benz’s new, progressive brand image. But, in addition to sporty dynamics and youthful attractiveness, the remit also specified embodying the typical elegance of a Mercedes sedan. The design of the C-Class was a study in integration. It unites different worlds and spontaneously grabs the attention of people with completely different aspirations and interests. Three design and equipment lines simplify the realization of individual wishes in terms of form, colors and materials.
Dynamism and elegance, that was the aim. Some two dozen designers set to work, committed their visions and ideas to paper, discussed many hundreds of sketches and transferred the best of them to the virtual world of the computer so that they could experience them in three dimensions on special-surfaced screens. The choice finally fell on a draft design which unites all the objectives in optimum fashion: dynamism, emotional appeal, elegance, solidity and continuity - in other words, the typical Mercedes language of form.
Twin headlamps merge into harmonious units
The headlamps are again character-shaping features. While the famous twin-headlamp face of the E-Class in 1995 was the visible signal of a new departure for the Mercedes-Benz brand, the C-Class re-interprets this symbolism, thereby marking the launch of the next stage in Mercedes-Benz’s product offensive. Although the sedan’s four “eyes” are still identifiable , the design of the C-Class has seen the oval headlamps merge into harmonious units in line with the basic brief of integration. The hood and fenders pick up this rounded finish and continue it backwards in sweeping curves, forming elegant sheet-steel sculptures. Associations with the human anatomy are inescapable, as the shape of the fenders is reminiscent of the muscles of trained athletes.
Seen through the eyes of the designers, these athletic forms enhance the width of the car’s body, giving a powerful appearance particularly when viewed from the front. This effect is reinforced by the bumper which is perfectly integrated in the bodywork with the discreetly molded spoiler edges in the lower section and the front fog lamps, especially as all the components use the same paintwork - in body color - and therefore present a unified whole in color terms too.
The interplay of dynamism and elegance is also seen in the radiator grille and headlamps. The designers have skillfully worked with different rake angles here to draw attention to the C-Class’s two features: while the slightly raked headlamps are reminiscent of a sports car, the fins and webs of the radiator grille are decidedly more upright. The effect of optically stretching the hood in this way is to give the car power and elegance.
Seen from the side: pronounced wedge-shaped body and powerful shoulders
Seen from the side too, the dynamic character of the C-Class is the dominant first impression. This is ensured primarily by the pronounced wedge-shaped body which is particularly defined by the curve along the waistline. The conscious emphasis on what is generally known as the waistline actually calls to mind the broad shoulders of a well-built athlete, topped by the side windows, roof pillars and roof. This line runs continuously from the front to the rear end, giving form to the power of the body - particularly at the rear where the striking C-pillars meet it and jointly define the form of the rear end.
But the powerfully raked windshield, the coupé-like roof, and the flat backlight are unmistakable signals of a spirited use of forms with stylish emphases from the world of luxury sedans.
Like the headlamps, the rear lamps are now also regarded as typical stylistic elements of Mercedes models with a sporty yet elegant character. The tail lamp covers extend in a wedge shape into the flanks of the body, underlining the car’s sporty lines. This overlapping lamp design was first used on a standard-production car in the SLK roadster and then also caught the eye in the S-Class and the top-of-the-range CL coupé - not just because of its striking shape but also as an integrating style element for formally linking the side and tail sections.
Further similarities with other Mercedes models are seen in the V-shaped cut-out in the tail of the C-Class, which is also formed by the tail lamps. They ensure the formal integration of the entire rear end – creating the visual links between the fenders, trunk lid and bumper. At the same time, the trapezoidal tail lamp design and the large-format bumper emphasize the width of the sedan, which therefore also makes a particularly powerful impression from the rear. The bumper merges almost seamlessly into the body and also forms a unified entity in color terms with the elegant metal skirt.
- A successful balance of dynamism and elegance
- Updated interpretation of twin-headlamp face
- Distinctive waistline as a symbol of power
The term C-Class has long meant more to Mercedes-Benz than just a successful sedan. The C-Class has developed into a complete model family and also provides other Mercedes cars with a solid technical foundation. The same will hold true for the new model range.
In the core disciplines of body technology, the new C-Class sets trailblazing trends, as the results of various tests on the test stand confirm:
- The static torsional resistance of the body structure (without windows) attains a new top result for this vehicle class, with 3.57 millimeters per meter. This value surpasses the good result of the outgoing C-Class model by more than 26%.
- The solidity of different body parts such as the center tunnel and side members – measured in terms of static flexing – is up to 50% higher than for the outgoing C-Class.
- The dynamic resonant frequencies for torsion and bending of the new sedan are up to 12% better than for the outgoing model.
The occupants of the new C-Class will feel the benefits of these advances especially in the improved acoustic and vibration comfort and in enhanced crash protection.
Recycled materials and natural materials are part of the materials concept
In addition to aluminum and plastic, the material composition of the C-Class is still dominated by steel, as the proven material, but the proportion of high-strength panels, which combine minimal panel thickness and weight with a maximum of strength, has been more than doubled compared to the outgoing model. One feature in this field of material technology is the “dual phase” steel. Its high strength conferred by its two-phase microstructure withstands high crash stresses and therefore plays an essential part in the high solidity of the front end and occupant cell.
Recycled materials and natural materials are all part of the materials concept for the C-Class. Mercedes-Benz have approved a total of 38 plastic components with an overall weight of some 30 kilograms for the use of recycled materials; this represents about 13 percent of all plastics used. A further 33 components in the sedan are made of natural materials such as wool, cotton, coconut, wood and other cellulose fibers. They weigh just under 23 kilograms in total – some 27 percent more than in the outgoing model. Thanks to its environmentally acceptable materials mix, the Mercedes-Benz C-Class achieves a recycling potential of over 85 percent by weight and therefore already meets the provisions of Germany’s Scrap Car Decree which will not come into force until 2002.
New firewall concept for even better occupant safety
The new firewall is assembled out of six different individual components of differing panel thickness. In this way, Mercedes engineers adapt the material to the relevant load and obtain an ideal compromise between lightweight construction and crash safety. The special forward-arcing curve of this innovative part also gives it its name: the “ellipsoid firewall”. As in the Mercedes-Benz S-Class, this large part plays an important role in the safety concept of the C-Class, since it is not only able to withstand extreme loads but can also distribute crash impact forces evenly over a wide area, thereby preventing dangerous intrusions into the occupant cell. In the outgoing C-Class, this function was performed by the forked side members, which are now no longer required.
Front module and crash boxes reduce repair costs
The Mercedes-Benz S-Class and flagship CL Coupe also provided the inspiration for the development of other front end components. For example, the front module consists of an independent unit that provides the same advantages in each body version. Bolts reliably connect the module to the remainder of the body. Even the individual sheet metal parts inside the module are bolted together, so that accident damage can be remedied faster and at lower cost. Welding is no longer required when replacing individual components or the entire front module. The key components of the front module are two steel crash boxes that absorb the impact energy of minor frontal collisions, thereby preventing damage to the load-bearing structure behind. The advantage of this system is that the crash boxes and load-bearing members are fastened together by bolts and can be replaced without problem after an accident. This cost-cutting crash concept is operative for crash speeds of up to 15 km/h against a rigid obstacle.
High-strength crossmembers and robust doors for side impact protection
In a side impact crash, three crossmembers in the floor area and a solid square profiled section under the instrument panel enter into action to strengthen the passenger compartment. The single-piece outer panel of the side wall conceals individually welded inner shells that confer even greater strength to the roof pillars, roof frame and outer side members. The doors too consist of an outer and an inner shell and of several inner sectional reinforcements. In addition, a flexible tubular member is fitted in the lower part of each door to reduce the deformations in a side impact crash.
Soundproofing foam elements in cavities
Strength and safety were not the only goals in the design of the occupant cell: the question of noise comfort was also on the agenda from the start. In this field, body engineers have made a major contribution by filling certain cavities of the bodyshell with foam or fiber materials. These elements are first mounted on special support plates and firmly fastened to the body – then, in the drying zones of the paint shop, these soundproofing materials expand automatically and completely fill the cavities. Overall, 42 of these foam or fiber elements are concealed beneath the metal skin of the C-Class. Each of the two side walls alone contains 11 foam absorbers.
Steel panels with double corrosion protection ensure longevity
In many European countries, Mercedes-Benz gives its car buyers a cost-free long-term warranty for mobility and sustained value. “mobilo-life” is valid for 30 years and also includes comprehensive warranty services in the event of rust perforation of the body and underbody, provided that the car has been regularly serviced and maintained by an authorized Mercedes workshop.
This warranty promise is based on comprehensive corrosion protection. For the C-Class, the engineers in Sindelfingen have again enhanced the rust protection measures. Three main aims were pursued: economical use of materials, avoidance of waste and the rejection of environmentally critical materials. The result is a bodyshell that has 85% of its total surface protected against corrosion by zinc coating. By comparison, in the outgoing model, the share of zinc-coated panels was “only” 65%.
Instead of an all-round fully galvanized body, Mercedes-Benz relies on steel with dual corrosion protection: electrolytically zinc-plated panels are additionally coated with an organic paint that also contains rust-inhibiting zinc pigments. Although this paint is only two to four micrometers thin, it withstands the stresses generated by pressing and spot-welding the panels, thereby ensuring lasting protection. Almost half of the galvanized body parts of the C-Class are made of this innovative steel sheeting. For the front end, side members, A-pillars and the inner shells of the doors, hood and trunk lid, Mercedes-Benz uses sheeting with organic coating on both sides. This coating therefore also replaces conventional cavity sealing in many areas.
Mercedes engineers have also been able to dispense with the conventional PVC underseal in the C-Class, whilst nevertheless still guaranteeing long-term corrosion protection in this area. The solution to the problem is an underbody encapsulation made of glass-fiber reinforced plastic, which also offers aerodynamic advantages.
Exemplary Cd value of 0.26 means best-in-class aerodynamics
When driving on the motorway, more than half the fuel consumption of a passenger car can be attributed to wind drag. That fact alone explains one of the reasons why Mercedes engineers have committed themselves so intensively to the subject of aerodynamics for many years. In the C-Class, this commitment is crowned with particular success: with a Cd value of only 0.26, the C 180 is the most aerodynamic notchback sedan of its market segment in the world.
Compared to the outgoing model, the aerodynamics engineers at Mercedes have been able to reduce drag by a full 13%, thereby bettering even the exemplary Cd value of the E-Class and S-Class (0.27), previously the best attained in this aspect of body development. The product of frontal area (A) and drag which crucially affects fuel consumption is about 13 per cent lower than the comparable figure for the outgoing C-Class,
The exemplary Cd value of 0.26 is essentially due to the following body details:
- Front air dam and rear skirt: Their function is to control the slipstream, diverting it to the sides at the front, so that it flows back smoothly and finally parts from the body at the rear with little turbulence.
- Spoiler lip on the trunk lid: this elegant detail improves the escape of the slipstream, reducing lift and preventing the formation of turbulence behind the body.
- Wheel spoilers at the front and rear wheels: these small plastic elements reduce the back pressure of the air in front of the tires, thereby reducing the Cd value. At the same time they reduce lift.
- Underbody encapsulation: The large, smooth plastic panels that reach back to just in front of the rear axle allow the slipstream to flow back underneath the body without turbulence.
- Engine compartment encapsulation: Complete encapsulation of the engine compartment not only improves acoustic comfort but also guides the slipstream accurately downwards and prevents the air swirling in the engine area.
Superlative aerodynamics provide excellent directional stability
A minimal coefficient of drag is not the only thing that counts for Mercedes-Benz aerodynamics engineers. They are only happy if their work also serves the interests of road safety. The keyword here is lift: the sedan is characterized by exemplary stability, as is proved by the measurements for front and rear body lift, which are up to 57% lower than the equivalent values for the predecessor model. This is due to the encapsulation concept for the underbody, the wheel spoilers for the front and rear wheels, the elegant spoiler lip on the trunk lid and the newly developed flare elements in front of the front wheel arches.
New lighting functions for greater safety and comfort
In the C-Class, the driver no longer has to worry about switching the headlights on and off, because this task has been taken over by electronics with the aid of a light sensor mounted on the windshield. This “Headlamp Assist” system, as it is called, which until recently was only available for luxury sedans and top sports cars, is now included as standard in the Mercedes-Benz C-Class. This comfort function is programmed by the multifunction steering wheel on the central display in the instrument cluster and is activated by the light switch on the instrument panel (“Auto” position). In addition, electronic data bus networking on board the sedan permits a wide range of additional lighting functions and switching facilities that enhance both safety and comfort:
- Emergency light: If a data line or electronic control unit is defective, a preprogrammed circuit prevents failure of the entire vehicle lighting system.
- Failsafe lighting: If bulbs important to vehicle safety go out, the electronic system automatically switches on other lights that can provisionally replace the defective light.
- Daytime driving lights: The driver can program the light system of the C-Class to switch on the low beam headlights, parking lights, rear lights and license plate light automatically after switching on the engine.
- Headlight switch-off delay: Optionally, the headlights remain switched on even after the occupants have left the car in order to help them find their way around in the dark.
Four lighting functions in a single headlight housing
The headlights are not only important design features of the C-Class but also set an example by their modern technology. The large rounded plastic lenses cover a two-chamber reflector that combines four lighting functions: the outer zone is used for low beam and, above it, the turn signal light, whilst the inner reflector surface is reserved for the high beam headlight and sidelight. In other words, in the interests of increased light output, the low beam and high beam are housed separately. The fog lamps are housed in the front bumper trim.
Also new are the exterior mirror housings with integral turn signal repeater lights. In this high position they attract particular attention and therefore offer clear safety benefits.
Xenon light and high-pressure headlight cleaning available as an option
Instead of the standard H7 bulbs for the low beam headlights, Xenon headlights with gas discharge lamps are optionally available to provide an illumination similar to daylight. These headlights are characterized by twice the light intensity, longer service life and a lower power consumption of only 35 Watts. Dazzling of oncoming traffic is prevented by a dynamic headlight range adjustment system. With the aid of inclination sensors on the front and rear axles, this system detects brief movements of the car body when starting from rest, braking or accelerating. Consequently, the reflectors always follow the current body position and adapt the angle of the beam accordingly. The newly developed headlight cleaning system uses water-jet technology. A telescopic nozzle unit is mounted under each headlight, behind the bumper trim. This telescopic unit is extended at the touch of a button and in response to the water pressure to reveal two cleaning nozzles that spray a precisely metered quantity of water against the lens.
The rear lamp units of the C-Class are recessed deep into the vehicle sides and contain the brake light, turn signal light, rear light and reversing light, together with the rear fog lamp on the left-hand side. The brake lights in the rear lamp units are coupled to the third raised brake light in the trunk lid. This third brake light consists of 20 LEDs that light up about 50 milliseconds faster than conventional bulbs in response to the brake pedal. The LEDs therefore make a major contribution to the prevention of rear end accidents.
You feel it immediately on the first encounter: the Mercedes-Benz C-Class has matured even further and is even more comfortable than before. The design of the interior, its materials, equipment and classy appeal emphasize the premium character of the sedan even more strongly than in the outgoing model. Anyone who sits in one of the two newly developed front seats will feel immediately at ease and will have no trouble finding exactly the desired position. All the most important driving controls – the gear lever, ventilation outlets, pushbuttons and adjusters – are arranged within easy reach of the driver, and their functions are instantly recognizable. Everything is literally to hand and in view.
One of the main aims has been “rational automation”, so that the driver can concentrate on the essentials, namely the traffic situation and the driving experience. As a result, certain functions on board the C-Class are automatically controlled and monitored. These functions focus on the routine tasks of drivers, thereby relieving the pressure exactly where most needed. Examples from a wide range of settings:
- Once programmed and set on the light switch, the exterior lights are automatically switched on in dark conditions.
- All open windows and the sunroof can be closed with a single touch of a button on entering a tunnel or underground parking garage.
- Once programmed, on inserting the ignition key, the seats, steering wheel and rear view mirror move to the position desired by the front occupants. The key also stores the settings of the automatic climate control.
- Once programmed, on removing the ignition key, the driver’s seat is always moved back and the steering column automatically raised for a more comfortable exit.
- Once activated, the optionally available luxury automatic climate control switches to air recirculation mode upon detecting increased pollutant levels in the outside air.
- A touch of a button on the steering wheel is sufficient to instruct the car radio, CD or cassette player and car phone to obey the driver’s spoken commands by means of the LINGUATRONIC voice control system.
Individual settings can be stored using the steering wheel
Many of these settings are entered with the aid of the standard-fitted multifunction steering wheel, which is coupled to the central display in the instrument cluster and to the car radio and car phone. The driver simply has to touch the lower left-hand button in the steering wheel briefly in order to display the main “Settings” menu, where more than 50 individual functions can be programmed under five different submenus – from digital speed display to automatic door locking once on the move, from automatic mirror adjustment for parking to the easy exit/entrance feature.
In addition to these individual setting options, the central display unit provides a whole range of information, messages and data: daily and total distance traveled, engine oil level, next service due, coolant temperature, name of radio station when listening to the radio, track number when listening to tapes or CDs, recommended directions of the navigation system, fault messages or remaining distance to empty.
The instrument cluster has been redesigned. Instead of the previous round instruments, three arc-shaped displays indicate the engine revs (left), speed (middle) and fuel level (right). The telltale and warning lights are located under the rev counter, inside the middle speedometer segment and under the fuel gauge. These lights only come on when the ignition is switched on or if there is a fault – otherwise the instrument panel remains dark at these points.
The glovebox is three times the size of the outgoing model
The top section of the dashboard includes the instrument cluster cover and the side and middle ventilation outlets, which have a modern, cylindrical design that integrates perfectly in the rounded front edge. The lower half of the dashboard includes the knee bolster on the driver’s and front passenger’s side, which is made of a special blend of polymers with a soft foamed film, and the center console and two-part glovebox that is part of a comprehensive stowage space concept. With a volume of 8.2 liters and measuring 400 millimeters wide by 162 millimeters deep, the glovebox is almost three times bigger than its equivalent in the outgoing model (3.0 liters). Consequently, a CD changer can now optionally be installed in the upper section of the glovebox. A compartment for sunglasses or spare spectacles is also built into the glovebox. The pockets in the interior linings of the driver’s and front passenger’s doors provide sufficient space to stow an umbrella, road maps, an ice scraper and spectacles cases. The capacity of each of these door pockets is about 3 liters and is therefore double that of the outgoing model. The cover of the two-part stowage box between the front seats also serves as a padded armrest, which in the Elegance and Avantgarde lines as well as in conjunction with THERMATIC or THERMOTRONIC is adjustable in two tilt angles.
Comfortable, improved spaciousness for all occupants
The C-Class has the typical comfortable spaciousness of a Mercedes. The occupants of the front seats have a shoulder room of 1350 millimeters and an elbow width of 1400 millimeters, representing increases of 11 and 8 millimeters respectively on the equivalent dimensions of the outgoing model. The comfort of the rear passengers has been improved by extending the knee-room by 4 millimeters and the elbow room by 12 millimeters. The rear headroom in models with a sliding sunroof is 948 millimeters –10 millimeters more than previously.
Measured by the VDA measuring method, the trunk has a capacity of 455 liters – including a stowage space of 45 liters in the handy recess that Mercedes-Benz provides instead of the traditional spare wheel. This recess holds not only the on-board toolkit but also the TIREFIT tire repair kit and the electric air pump that get the driver back on the road in the event of a flat tire without having to fit a spare wheel
The driver and front passenger of the C-Class can make themselves thoroughly comfortable on the newly developed seats that combine modern design with significant advances, especially in the fields of ergonomics and operation. Whereas the occupants previously had to adjust the seat height and backrest reclining angle manually, each of these functions has now been taken over by two electric motors. All the occupant has to do is to operate a two-part switch on the outer seat trim, and the seat cushions and backrest immediately move to the desired position.
A microchip in the ignition key stores individual seat adjustments
Even greater operating convenience is provided by the complete power adjuster package for all functions of the driver’s and front passenger’s seats, available as an option from Mercedes-Benz. In this case, not only the seat height and backrest angle but also the longitudinal adjustment, seat cushion angle, head restraint, steering column and exterior rear view mirrors are adjusted by electric motors. A microchip stores the individual adjustment data of the driver’s seat and transmits it to the electronic ignition key. Subsequently, as soon as the driver inserts the key in the ignition starter switch, the seat, head restraint, steering wheel and exterior rear view mirror automatically move to the desired position.
Compared to the outgoing model of the C-Class, the engineers at the Mercedes plant in Sindelfingen, Germany, have improved the lateral and thigh support of the seat cushions. The technical basis for the front seats is provided by two suspended aluminum shells that can rotate at the front for the tilt adjustment facility and that rest on two small coil springs at the rear. Consequently, the seat shells rock on the metal frame and can perform additional springing and damping functions to supplement the effect of the foam cushions lodged in the aluminum frames. A comfortable seat climate is ensured by ventilation holes in the foam cushion, an 8-millimeter thick coating of rubberized hair and the fabric seat cover, which, due to its high wool content, has highly active “breathing” properties.
Split-folding rear seat bench available as an option
For drivers who wish to vary the trunk format of their sedan, Mercedes-Benz has developed an asymmetrically split rear seat bench that can be folded down in a few simple steps at a ratio of 1:2. First, the seat cushions are folded forwards individually or together into a vertical position behind the front seats. Then the backrests are folded forwards to produce an almost entirely flat load floor.
Electronically controlled heating system for additional comfort
“Heatmatic” is the name given by Mercedes-Benz engineers to the automatic heating and ventilation system on board its passenger cars. As the name indicates, this is a little more than just an ordinary, conventionally engineered heater: Heatmatic consists of an electronically controlled system that measures the interior temperature by means of sensors and maintains it constant at the level desired by the driver and front passenger. This innovative technology has long been in standard use at Mercedes-Benz and has now been further developed and improved by Mercedes engineers for the C-Class. The control panel for the heating and ventilation system is characterized by a design that provides a clearly organized disposition of all relevant functions, namely the 6-speed fan adjustment (previously 4-speed), air distribution, separate temperature controls for the driver and front passenger, air recirculation mode, defrost mode and heated rear window.
Furthermore, the number and area of the various outlets in the dashboard and rear footwell have been increased to provide comfortable – in other words draft-free – ventilation. This important aspect of draft prevention was also behind the development of an innovative indirect ventilation system that has its debut at Mercedes-Benz. An outlet located in the middle of the dashboard and directed at the windshield distributes cold air over a wide area and therefore without causing a draft.
Electric heater booster for CDI models
In addition to the standard-fitted Heatmatic system, the diesel models of the C-Class are equipped with an additional electrical heating system to ensure pleasant warmth in the interior. This heater booster is necessary because although the CDI engines of the C-Class have the advantage of consuming very little fuel, due to their high thermal efficiency they only transfer little heat to the coolant when running at part-throttle. As a result, the heating effect is less than in a car with a conventional engine. The additional heating requirement of the CDI models is also supplied by a water-cooled alternator (190 Amp) that rotates at up to 18000 rpm when the car is on the move and delivers its waste heat to the coolant.
Humidity sensor and variable compressor for optimum air conditioning
When it comes to air conditioning, Mercedes customers have a choice with the C-Class. Two systems are available: the THERMATIC automatic climate control with automatic fan control and air distribution (standard in the C270 CDI, C240 and C320 models) and the THERMOTRONIC luxury automatic climate control with an activated charcoal filter, a sun and pollutant sensor and many other extra functions. Compared to the outgoing model, the electronic air conditioning control has been further improved: for example, two sensors (previously one) are now used to measure the interior temperature and to supply the system with even more precise data, so that it can respond even more rapidly to temperature fluctuations.
The newly developed automatic climate control of the C-Class operates on the same basic principle as many other air conditioning systems – namely the “reheat” principle. In other words, even at cold outside temperatures, the system is in permanent operation and always first cools the incoming air, thereby drying it so that the windows remain mist-free. The air is then reheated to the desired temperature. The new feature of this intelligent circuit is a 3-stage control system that activates the reheat mode as a function of relative humidity. This feature has been made possible by a newly developed dew point sensor which supplies the air conditioning microcomputer with the data required for need-oriented control of the 3-stage reheat function and ensures that the incoming air is cooled and then reheated as a function of its actual moisture level. As a result, the air conditioner operates much more economically than conventional systems.
The concept has also been made possible by the use of a new refrigerant compressor with infinitely variable electronic control as a function of the cooling power actually required. Whereas until now the air conditioning compressor was engaged or disengaged with the aid of an electromagnetic clutch, it is now directly connected to the engine by belt drive, so that it is in constant operation. The infinitely variable control function is provided by a solenoid valve.
The system stores the individual driver’s settings and transfers the data to the electronic ignition key. This memory function ensures that the automatic climate control will restart with the desired program on the next journey.
THERMOTRONIC for luxury automatic climate control like in the S-Class
The newly developed luxury automatic climate control lives up to its name: it brings S-Class comfort to the C-Class. Examples of this luxury comfort include:
- Automatic control of temperature and air distribution individually for the driver’s and front passenger’s sides;
- Additional sensor signals for sunlight and pollutant levels in the outside air;
- Standard-fitted activated charcoal filter;
- Clearly organized display for temperature and fan speed;
- Storage of additional individual setting data in the electronic ignition key;
- Ventilation outlets at the rear.
The Mercedes-Benz C-Class is the only car in its market segment to have automatic climate control using sensors for sunlight and pollutant levels as well as an activated charcoal filter.
All the latest-generation telematics systems are being premiered in the Mercedes-Benz C-Class. They not only optimize up-to-the-minute traffic-jam warnings and use all the latest traffic data to guide drivers “dynamically” to their destination, but also for the first time provide a direct link to the team of advisers at the Mercedes-Benz Customer Assistance Center who can give advice in the event of technical queries or organize breakdown assistance.
With dynamic routing, the navigation system uses the connected car phone to contact Tegaron Telematics, a joint venture established in Bonn between DaimlerChrysler and mobile phone company T-Mobil. Tegaron Telematics analyzes the information from Gesellschaft für Verkehrsdaten, a traffic data provider that monitors the traffic situation on German autobahns by means of about 3800 infrared or ultrasonic sensors. Using the Short Message Service (SMS ) of the mobile phone network, Tegaron transmits congestion warnings to the dynamic navigation system of the C-Class, which takes the latest traffic information into account for the individual routing function and recommends an alternative route in the event of a traffic jam. As soon as the system calculates an alternative route, a voice in the loudspeaker announces: “This route has been computed on the basis of traffic news,” and the message “Congestion ahead” appears on the navigation system display.
Radio Data System transmits digital traffic data to the car
A second possible method of receiving digital traffic data and using it for individual routing is provided by the Radio Data System (RDS) over the Traffic Message Channel (TMC). On this channel, radio broadcasters transmit inaudible signals that the navigation system decodes and evaluates. These signals contain traffic jam messages that are put together with the aid of induction loops in the road surface of autobahns or on the basis of information provided by the police. The information contained in these messages corresponds to the traffic news of the normal (audible) radio stations and is free of charge. RDS-TMC is already in operation all over Europe. Dynamic routing with this technology is currently operational in Germany, and preparations are also under way to introduce the system in other European countries.
The system requirement for dynamic routing is the APS navigation system (Auto Pilot System) developed by Mercedes-Benz. This system guides drivers automatically to their destination with the aid of GPS (Global Positioning System) satellites, wheel sensors and digital road maps.
Car radio comprises navigation system and dynamic routing
A choice of two combination units incorporating navigation systems with the capacity for the modern “dynamic routing” telematics service is available for the C-Class. The Audio 30 APS combines an FM/MW/SW/LW tuner, CD player and navigation system inside a single housing that is the size of a conventional car radio. The unit also includes a built-in 4-channel amplifier (4x20 watts), LCD display, GPS tuner and antenna diversity system, which evaluates the signals from four radio antennas. Radio reception is based on the two-tuner principle: while one tuner tunes into the radio station selected by the driver, a second tuner in the background constantly monitors the reception quality of all receivable transmitters. As a result, the radio can immediately switch over to another frequency of the desired station.
In order to reach the desired destination under the guidance of the APS navigation system, the driver must insert the CD-ROM containing the digital map in the combination unit when specifying the destination. The car radio then stores the necessary data of the CD-ROM and starts calculating the route. At this point, the CD player can again be used to play music CDs.
COMAND integrates all communications control features
The other system integrating the navigation system and dynamic routing is the Cockpit Management and Data System – or COMAND for short. This system was first introduced in late 1998 in the Mercedes S-Class and acts as a control center for all audio, telematics and telecommunications functions, namely car radio, CD player, navigation with dynamic routing, CD changer, sound system, car phone, voice control and TV receiver.
The driver can either operate these functions directly on the COMAND unit in the center console and read the necessary user messages on the large color display or else can transmit instructions with the buttons of the standard-fitted multifunction steering wheel. These buttons can be used to control the volume, car radio, CD player, phone and navigation system display. The central display in the instrument cluster and the information on the COMAND display in the center console are coupled together but can also be operated separately. For example, the cockpit display can show the graphical routing instructions (arrows) of the navigation system while the front passenger is browsing through the electronic phonebook on the COMAND screen.
The technology of the integrated navigation system is based on the same principle as the Audio 30 APS unit. Here too, the CD player can be used both as a data storage medium for the CD-ROM map and also for playing audio CDs. However, COMAND provides even more functions and above all is unique in having a color LCD display. On this display, an additional easy-to-read map of the area and selected route can be called up by pushbutton. With the aid of this map and a crosshair cursor, the driver can pinpoint and program the destination. A TV tuner can be optionally connected.
TELE-AID automatically alerts the emergency services in an accident
The TELE-AID automatic emergency call system is one of the additional telematics services provided for Mercedes customers. “Automatic” means that the system itself emits an SOS call following an accident without human intervention, to alert the rescue services and guide them to the accident site. The SOS signal from the car is transmitted by mobile phone to an emergency call center. The message consists of the following information: time, vehicle license plate number, vehicle model and precise location. On the basis of this information, the call center operators immediately determine the closest emergency service center and forward the call.
Like the navigation system, TELE-AID works with GPS (Global Positioning System), a system of satellites that send digital direction-finding signals to the vehicle from their orbit around the earth. Depending on the accident type, the emergency call system is triggered automatically either by the standard-fitted crash sensor that is also responsible for activating the airbags and seat belt emergency tensioning retractors, or by the rollover sensor. The occupants of the C-Class can also send out the emergency call message manually by means of a button in the interior of the C-Class. After the emergency call, TELE-AID automatically permits a connection to the operations control center of the police.
TeleDiagnosis provides a direct connection to the customer adviser
TeleDiagnosis is the latest telematics service for Mercedes customers and is making its debut together with the C-Class. As a basic system requirement, the sedan must be equipped with TELE-AID. In the event of a breakdown, the TeleDiagnosis system establishes contact with the central Customer Assistance Center (CAC) at the touch of a button. The customer advisers then speak with the driver by mobile phone and provide advice and practical support. At the same time, the system automatically sends all necessary data to the Center: vehicle and engine model, year of construction, engine temperature, battery voltage, mileage and any stored fault and warning messages. In addition, the telephone automatically transmits the car’s exact position, so that the service engineers of the closest Mercedes branch or workshop can be directed as rapidly and accurately as possible to the breakdown site. In order to establish the voice and data link to the CAC, all that is required is to press the blue button with the screwdriver signal on the fixed receiver of the TELE-AID system.
“MB Info” provides information about Mercedes-Benz
By mobile phone and with the aid of the TELE-AID system, Mercedes customers can also ask the customer advisers general questions and obtain advice and information on all subjects relating to the car. This service is entitled “MB Info”. The phone number is stored in the electronic phone book of the car phone and appears on the display with the label “Info” after a short initial period in the operating menu. Subsequently a single press on the call button is enough to establish the toll-free voice connection.
With LINGUATRONIC the car radio does what it is told
The innovative LINGUATRONIC voice operation system that Mercedes-Benz was the first car manufacturer in the world to develop for the operation of the car telephone does even more in the C-Class. Available as an option, it now not only controls the most important telephone functions but is also, for the first time, connected to the audio systems. As a result, a couple of words from the driver are sufficient for the radio to seek another station automatically, change to the next CD track or switch over to navigation mode.
With this technology, Mercedes-Benz is providing a further major contribution to traffic safety, because drivers no longer have to take their hands off the steering wheel to operate the car phone or audio systems. LINGUATRONIC therefore relieves the burden on drivers, who can now concentrate fully on the road, and also considerably improves driver comfort. Only the tone and volume controls cannot be voice-operated. The heart of the LINGUATRONIC system is a software package that is programmed with algorithms for voice recognition and for peculiarities of the human voice. Consequently, the system can even adjust to the individual speaking style of the relevant user. For instance, in Germany, it can understand both high German and local dialects. The system also operates in English, French, Spanish and Italian.
Data transfer at the speed of light
The transmission of sensor signals, measurement data, information, music and TV pictures at lightning speed is ensured by three high-capacity databus systems on board the C-Class. These systems divide the transmission functions into three sections – interior, drive train/chassis and audio/communication/navigation – and are interconnected by means of interfaces ("gateways"). The “Class C” CAN network for the drive train/chassis section integrates seven control units. In the “Class B” network, up to 20 nodes exchange their data. For the first time, the control unit for the airbags and TELE-AID emergency call system are also integrated in the network. In total, the on-board electronic system of the C-Class controls more than 130 functions by databus and processes more than 850 different items of information for this purpose.
In addition to the proven CAN systems, the C-Class also has an optical system that uses pulses of light to transmit signals. The name of this system is the “Domestic Digital Bus”, or “D2B” for short. Instead of copper cables, this system uses fiber optic cables made of plastic. In these cables, measurement data and switching signals can travel at the speed of light. Consequently, nodes connected to the “D2B” ring network can transfer much larger amounts of data in a shorter time than in the CAN bus: up to 5.6 million bits are transmitted per second in the fiber optic cable, representing a transmission rate some 60 times faster than CAN transmission in the interior by copper cable. The fiber optic cable therefore carries many more information units in a comparable time, so that even the data of a music CD can be transferred with perfect sound quality.
Engines and transmissions: More power under the hood
- State-of-the-art four-cylinder and V6 engines with increased output
- Torque increased by up to 43 per cent
- Exhaust emissions of all gasoline engines comply with EU-4 standard
- Output of direct-injection diesel engines boosted by up to 14 per cent
- Six-speed manual transmission for greater driving dynamics and enhanced comfort
More power, greater torque, lower pollutant emissions – these were the objectives when it came to developing the engines for the C-Class. These objectives have been achieved: The model range kicks off with seven high-torque power plants which, compared with the corresponding predecessor models, provide up to 20 per cent more output, with pulling power boosted by up to 43 per cent.
By increasing engine displacement, Mercedes engineers have obtained extra torque for the entry-level C 180 and the six-cylinder C 240 model to make this sedan even more nimble and flexible than the predecessor model, particularly in the lower engine speed range. High levels of driving enjoyment and sporty dynamics are also provided by the engine powering the C 200 KOMPRESSOR, which replaces the previous 2.0 liter engine. Superior performance and a high level of comfort are among the special features of the C 320 range-topper which replaces the previous C 280.
The two four-cylinder models are powered by the proven Mercedes engine which, in different displacement sizes, is also used in the C-, E-, M- and V-Classes as well as in CLK models. Engineers at Stuttgart have, however, refined major engine components and modified them to suit the installation conditions in the sedan. In addition, the 2.0 liter engine of the C 180 was provided with a secondary air-injection system which significantly boosts the effectiveness of the emission control during the engine‘s cold-start phase. All in all, more than 150 components of the Mercedes four-cylinder engine were optimized. For example:
- The cylinder head is characterized by airflow-optimized intake and exhaust ports with an oval cross-section for greater volumetric efficiency. A new, more compact combustion chamber design serves the same purpose.
- The inlet camshaft on both four-cylinder engines now features a special Hall sensor which during cold starting senses the position of the piston in the first cylinder. As a result a significant improvement in the starting characteristics of the cold engine is achieved.
- The timing gears now have a special rubber coating which helps reduce engine running noise.
- A newly developed electric suction-type fan provides the engine compartment with cold air. It allows the amount of engine cooling to be fine-tuned in the interests of fuel economy and noise reduction.
- The air ducts and the intake manifold were also modified with a view to noise reduction. The newly developed broadband resonator reduces intake noise.
- Modern single spark ignition coils integrated right behind the cylinder head increase the efficiency of the ignition system. Other features include the modern platinum spark plugs which only need to be replaced every 100,000 kilometers.
- Using a torque interface, a new electronic engine management system perfects the interaction of engine, transmission and standard-fitted Electronic Stability Program (ESP).
The C 180 offers greater flexibility and greater performance
With the further developed 2.0 liter naturally aspirated engine which develops 95 kW/129 hp at 5300 rpm, the C 180 typifies the dynamic and agile character of the C-Class. The increased displacement and refined engineering of the four-cylinder unit provide extra flexibility and greater performance compared with the previous entry-level model. 185 Nm of torque is available from just 3500 rpm, cutting the time for the sprint from 60 to 120 km/h in fifth gear to 20.2 seconds or by around six seconds compared with the predecessor model. Despite the increase in power output and the approximately 100 kg higher vehicle weight, fuel consumption of the C 180 rises by just 0.1 to 9.3 liters per 100 kilometers (NEDC overall consumption, provisional figure).
C 200 KOMPRESSOR for dynamic driving enjoyment in the two-liter class
The two-liter compressor engine with 120 kW/163 hp provides a dynamic driving experience which is pretty rare in this displacement class. In conjunction with its excellent value for money, the C 200 KOMPRESSOR has all the right ingredients to assume an outstanding position within its market segment. Fitted with a belt-driven supercharger, this power plant matches the performance and torque characteristics of a larger six-cylinder engine. With a hefty 230 Nm, the C 200 KOMPRESSOR races from 60 to 120 km/h in just 15.1 seconds (in fifth gear). This sedan requires a mere 9.3 seconds for the sprint from rest to 100 km/h. These remarkable performance and torque values do not conflict with the engine designers’ commitment to reduce fuel consumption further. On the contrary: compared with the outgoing C 200, which developed about 20 per cent less output and torque, the C 200 KOMPRESSOR uses only 9.5 liters of gasoline per 100 kilometers, or a mere 0.1 liters more (NEDC overall consumption). Together with specialists from the Eaton company, Stuttgart engineers developed the compressor further and optimized countless features which translate into audible progress. The power plant under the hood of the C 200 KOMPRESSOR features new engine mounts which make the use of an electro-magnetic coupling between the engine and the charger superfluous. Thanks to this new mounting technology, the compressor is much quieter in operation.
C 240 with increased engine displacement for improved dynamism
Mercedes engineers have increased the cylinder diameter of the V6 engine inside the C 240 from 83.2 to 89.9 millimeters, ensuring that a total displacement of 2597 cubic centimeters is now available. While power output remains unchanged (125 kW/170 hp), this measure actually provides a torque increase of almost seven per cent: the six-cylinder unit now develops 240 Nm at 4500 rpm. It is remarkable how these improved engine characteristics in conjunction with the good aerodynamics of the C-Class affect driving performance: the C 240 requires exactly 16.4 seconds for the sprint from 60 to 120 km/h and is thus 5.7 seconds quicker than the predecessor model with the same number of horses under the hood.
C-Class with 3.2 liter V6 power plant for the first time
The C-Class offers even greater driving fun when equipped with the powerful 3.2 liter engine, which is regarded as one of the most torquey power plants in its displacement class. In the C 320, Mercedes -Benz for the first time combines the visual and technical dynamics of the model with a performance potential matched by few other automobiles in this market segment. Its 160 kW/218 hp and 310 Nm propel the C 320 from rest to 100 km/h in just 7.8 seconds.
All gasoline engines comply with the strict EU-4 exhaust limits
Mercedes-Benz has developed a sophisticated emission control system to meet the strict exhaust limits of the European EU-4 Directive and the American ULEV (Ultra Low Emission Vehicles) regulations. This consists mainly of an air-gap-insulated exhaust manifold, bulkhead and underbody catalytic converters as well as an onboard diagnostics system comprising four oxygen sensors. Exhaust emissions measured in accordance with the EU-4 Directive are 1.0 g/km of carbon monoxide, 0.1 g/km of hydrocarbons and a mere 0.08 g/km of nitrogen oxides – i.e. they are up to 56 per cent lower than under the EU-3 Directive which is currently in force. Moreover, the high quality of these systems ensures that these low emissions remain constant over a covered distance of at least 80,000 kilometers. German buyers of a gasoline model from the C-Class by Mercedes-Benz benefit from these exemplary exhaust values in that they receive a one-off tax credit of 600 marks (if first registration occurs before December 31st 2004), with subsequent motor vehicle tax charged at the reduced rate of ten marks per 100 cc engine displacement.
New CDI engines develop up to 43 per cent more torque
The acronym CDI now adorns the trunk lid on all diesel sedans of the Mercedes-Benz C-Class. It is synonymous with the most advanced technology: fuel injection which employs the common-rail principle plus pilot injection plus four-valves-per-cylinder technology plus turbocharger plus intercooling. The result of this diesel formula guarantees high torque, exemplary agility and low fuel consumption – the ideal prerequisites for unspoiled driving enjoyment.
Compared with the predecessor models, the three diesel engines for the C-Class offer up to 14 per cent more power output and up to 43 per cent more torque. This is mainly due to the use of the VNT charger (Variable Nozzle Turbine). The adjustable position of the guide vanes inside the turbocharger ensures optimum exhaust gas energy at any engine speed. In the lower rev range in particular the effect is that of a quicker build-up of charge pressure, improved volumetric efficiency and hence greater torque.
With its common rail direct injection Mercedes-Benz has achieved considerable advances compared with the earlier pre-chamber engines – not least in the areas of driving and noise comfort. Further engineering features particular to the CDI engines in the Mercedes-Benz C-Class include:
- The aluminum cylinder head with two spiral induction ports, one of which has been optimized for swirl and the other for volumetric flow. This leads to an optimum fuel and intake air mixture particularly under part-throttle conditions.
- The intake system with a hot film air mass sensor which permits an exact analysis of the air mass taken in. This provides the micro computer which is responsible for engine management with precise data. It is thus capable of controlling exhaust gas recirculation in accordance with engine load and speed.
- The mixing chamber with an integrated exhaust gas recirculation valve where fresh and exhaust air combine in a computer-calculated ratio. The valve is vacuum-operated via an electro-pneumatic converter.
- The intake module, which upstream of each cylinder at first features just one port before developing into a two-port system that takes on specific functions. While one of them is used for swirling the fuel-air mixture, the second one ensures adequate cylinder charging when the air flow is high. Under part-throttle this port is, however, closed by electrically operated flaps. This ensures that swirl inside the cylinders is increased further, producing more complete combustion.
- Pilot injection, which helps significantly to reduce the noise level of direct-injection diesel engines. A few milliseconds before the actual fuel injection occurs, a small amount of diesel is pre-injected into the cylinder. This ignites immediately, thereby preheating the combustion chamber. As a result, the fuel ignites more rapidly, while pressure and temperature do not rise so abruptly.
The C 220 CDI offers a powerful 315 Newton meters of torque
Thanks to the power output hike from 75 kW/102 hp to 85 kW/115 hp and the extra torque of around 6.4 per cent, the C 200 CDI offers even greater diesel driving pleasure. Particularly remarkable is the engine’s enhanced flexibility which propels the sedan in 18.0 seconds from 60 to 120 km/h (in fifth gear) – taking 7.2 seconds less than the outgoing model. With its 105 kW/143 hp and the powerful torque of 315 Nm, the C 220 CDI even matches the more powerful C 200 KOMPRESSOR in terms of pulling power. The diesel sedan sprints from 60 to 120 km/h in just 15.0 seconds and achieves a maximum speed of 220 km/h. The fuel consumption of the C 220 CDI, is only 6.2 liters per 100 kilometers (NEDC overall consumption).
The C 270 CDI uses 14 per cent less fuel
The C 270 CDI is a particularly agile and dynamic automobile which is superior to its predecessor model in every respect. With a power output up more than 13 per cent the model uses almost 14 per cent less fuel than the outgoing C 250 TURBODIESEL: a mere 6.9 liters per 100 kilometers (NEDC overall consumption, provisional figure).
The modern diesel engines of the C-Class comply with the emission limits of the EU 3 Directive.
Electronic monitoring of engine oil level
The Active Service System ASSYST is part of the standard equipment of all engines of the C-Class. On the basis of sensor-derived data, ASSYST calculates the actual load on the engine oil and works out a need-oriented servicing schedule for the engine. This means that oil change intervals can be increased, depending on the driving style and engine load, to up to 30,000 kilometers on gasoline models and up to 40,000 kilometers on the C-Class diesel sedans.
The advanced electronics that provide ASSYST with the necessary sensor data also make life easier for the driver: on the Mercedes-Benz C-Class it is no longer necessary to check the oil level manually using a dipstick. Instead it is sufficient to press a button on the multi-function steering wheel for the requested information to be shown on the central display of the instrument cluster. While the car is on the move, the system works automatically and only informs the driver if the oil has reached a critical level. Only on the four-cylinder models C 180 and C 200 KOMPRESSOR is it possible to manually check the oil level.
Six speeds as standard
With the exception of the C 320 all models of the Mercedes-Benz C-Class are equipped as standard with the newly developed six-speed manual transmission. The six-cylinder range-topper features the five-speed automatic transmission as standard. The six-speed manual gearbox was developed to offer drivers even greater comfort while at the same time further reducing fuel consumption. The C-Class reaches its top speed in sixth gear.
The gear-changing effort is greatly reduced thanks to the use of sophisticated multiple-cone synchromesh. Engineers have paid particular attention to easy diagonal gear changes, i.e. when changing up from second into third. Compared with the previous five-speed gearbox, shift effort has been reduced by about 25 per cent. At the same time, shorter shift travel has reduced gear-changing time by an average of 0.3 seconds – all in the interests of an agile and dynamic driving style which is made possible by the torquey engines of the C-Class.
Automatic transmission offers even more convenience thanks to one-touch gearshift
Life is made even easier for drivers who opt for the modern five-speed automatic transmission, particularly as this component now offers even greater convenience. This is ensured by the one-touch gearshift which Mercedes-Benz first introduced in 1998 on the S-Class. Thanks to this technology, the individual driving ranges can be selected in position D by a slight movement of the selector lever to the left or right. Moving it to the left means changing down; moving the lever to the right engages a higher driving range. If the driver moves the selector lever to the left for longer, the driving range changes to the gear selected by the automatic transmission.
Transmission: five speed automatic one-touch gear shift
With the exception of the C 320 all engine variants of the C-class estate are fitted with a standard five-speed manual transmission. The six-cylinder range-topper features the five-speed automatic transmission as standard from the assembly line. The one-touch gearshift is also standard here: the individual driving ranges can be selected in position D by a slight movement of the selector lever to the left or right. Moving it to the left means changing down; moving the lever to the right engages a higher driving range. Overrevving is ruled out in this because the electronic control system only permits a downshift to be made when the engine speed is not too high. Each gear change is shown in a display on the instrument cluster.
SEQUENTRONIC: fast no-clutch gear changing
The SEQUENTRONIC transmission (optional equipment) offers a particularly dynamic driving experience. This is supplied as an option by Mercedes -Benz for the models C 180, C 200 KOMPRESSOR, C 240, C 200 CDI, C 220 CDI and C 270 CDI. Just a light nudge of the lever and the transmission changes gear automatically, quickly and precisely, without the need for a clutch pedal. Electrical impulses relay the driver’s desired gear change to a microcomputer, which in turn controls a special hydraulic unit. The previously standard mechanical linkages between the gear lever and transmission also no longer exist with SEQUENTRONIC. This fast and easy automatic gear changing reduces fuel consumption in the NEDC cycle compared with the standard six-speed manual transmission by two to three percent.
The driver uses SEQUENTRONIC by lightly nudging the gear lever forwards or backwards: push it towards the "+" symbol on top of the gear lever and the hydraulics will open the clutch via the central release bearing and shift to a higher gear at lightning speed. During this process, the electronic unit takes into account the engine speed, engine torque, wheel speeds and a whole series of other parameters that are important for a precise gearshift. This is how the system puts the driver’s gear change wishes into effect, always in the right order, and changes the gears one after the other. This also applies to changing down through the gears, which is done by moving the SEQUENTRONIC lever towards the "—" symbol.
Compared to a standard six-speed manual transmission SEQUENTRONIC is distinguished by an add-on unit on the transmission casing that contains all the extra components with the exception of the control unit and the gear lever:
- The hydraulic unit is coupled to the central shift shaft and carries out the gear changes.
- The central release bearing operates the clutch: an integral sensor monitors this component’s movements.
- Energy supply comes from an electric motor and a hydraulic pump. A special oil reservoir supplies the system with hydraulic oil.
- The reservoir module uses sensors to keep the required pressure constant, so that the hydraulics are operational in an instant.
- The sensor system monitors the movements of the shift shaft and determines which gear is currently selected. Another sensor relays data on the transmission speed.
All the SEQUENTRONIC sensor signals are transmitted to the microcomputer. The control module also processes information on the current engine speed, engine torque, wheel speed and on the different brake system functions. The electronic unit of the automated manual transmission is activated as soon as the driver’s door is opened. When the ignition is switched on, the hydraulic unit builds up the necessary pressure in the system, allowing the driver to move the gear lever from neutral, "N", to "+" as soon as the engine has started. In the interests of safety, SEQUENTRONIC will only do this if the brake pedal is depressed. Then, the driver just has to release the brake pedal, the clutch engages and the car slowly rolls forwards and picks up speed as soon as the accelerator pedal is pressed.
Out on the road, the system carries out the driver’s requested gearshifts almost instantly. The automated shift means that drivers no longer have to worry about the revs, this is all done for them by SEQUENTRONIC, which automatically intervenes if the engine speed exceeds or falls below certain rev ranges. For example, if the driver forgets to change down in time when slowing down for a traffic light, the system automatically selects the correct gear and disengages the clutch as the car draws to a halt so that the engine cannot stall. The transmission’s gear changes can be checked at any time with the display in the instrument cluster, which indicates the gear that is currently selected.
Reverse gear can be selected just as easily: briefly move the gear lever backwards from the "N" position to "R" and the C-class estate will start to move slowly backwards as soon as the brake pedal is released. The system will accept the "R" shift request provided the vehicle is either stationary or moving at a speed below five km/h.
For getting around town, in stop-and-go traffic, or at any other time if needs be, the sophisticated transmission also offers a further plus, the auto-shift mode. By pressing the gear lever fully to the left towards the "A" symbol, the SEQUENTRONIC operates fully independently and uses the numerous sensor signals to change automatically through the six gears.
Dynamic handling as standard
- Further advances in handling, safety and comfort
- New three-link system at the front, proven multi-link independent suspension axle at the rear
- New disk brakes with large performance reserves
- Latest driving safety systems fitted as standard
Mercedes-Benz engineers have spared no effort in upgrading existing or designing new axles, steering and brakes in order to surpass the high standards of the outgoing model yet again. The advances made are immediately noticeable: exemplary agility, precise straight-line stability, extremely accurate steering, excellent rolling comfort, effective braking performance and safe handling even when pushed to the limit.
The agile handling of the C-class is attributable to a substantial degree to the new front-axle design. Wheel location, comfort and steering response are enhanced by a design which Mercedes-Benz are using for the first time in this form: a three-link axle with McPherson struts and rack-and-pinion steering. In the interests of even better suspension kinematics the engineers have replaced the lower wishbones used to date by two individual link elements which function as torque struts and transverse links. In addition to more precise wheel location, the main benefit of this design is that it is better able to compensate for vibrations resulting from tire imbalance or brake force fluctuations than rigid wishbones. The third element in the front-axle suspension is the track rod, which connects the transverse steering gear to the wheels. The spring struts also have a multiple role since they not only spring and damp the axle, but also actively assist with locating the front wheels. The spring struts consist of cylindrical coil springs, twin-tube dampers and large head bearings. The standard-fitted torsion bar stabilizer is connected to the spring struts by a linkage.
The wheelbase has been extended by 25 millimeters
The wheelbase of the C-Class is 2715 millimeters, and therefore 25 millimeters longer than its predecessor. The track widths of the front and rear axles have also increased - at the front by six millimeters and at the rear by twelve millimeters. However, the sedan’s turning circle, at 10.76 meters, has remained almost unchanged.
High-precision steering with modern rack-and-pinion principle
There are several reasons for using rack-and-pinion steering instead of the recirculating ball steering system used before. The most important was undoubtedly the more immediate response, which is more in line with the dynamic character of the C-Class. Furthermore, locating the steering gear in front of the wheel center plane results in safe understeering performance when cornering. However, the system also offers benefits in certain aspects of passenger protection and lightweight construction: whereas the recirculating ball steering gear forms a solid block which absorbs no energy in the event of a front impact, the rack-and-pinion steering can be transversely mounted on the deformable aluminum bracket and, therefore, does not impede the energy absorption process. And because this system has no need of supplementary components such as a Pitman arm, steering rod, idler arm and reinforcing plate, it is some 4.5 kilograms lighter than the recirculating ball steering gear of the outgoing model.
As previously, a standard-fitted servo-system reduces the steering effort. A new feature, however, is the easy-operation, speed-sensitive steering, which Mercedes-Benz are also offering as an option for the first time in the C-Class. Its effect is particularly noticeable at speeds below 100 km/h and reduces the steering moment as a function of speed. Thanks to an electronically controlled rotary slide valve which regulates the power assistance, the steering effort in urban traffic is reduced by up to 50 percent compared with conventional power steering, with the result that parking is particularly easy with speed-sensitive steering.
Proven multi-link independent-suspension system has been retuned
The multi-link independent-suspension axle, which is still unsurpassed in many respects, made its first appearance when the Mercedes-Benz 190 went into production in 1983. This patented axle design therefore also remains in use in the C-Class where, in conjunction with the new front axle, the extended wheelbase and the standard-fitted Electronic Stability Program (ESP®), it ensures a level of safety, handling and comfort which has never been available before in this vehicle class. The Mercedes engineers have thoroughly revamped the design of the track rods, hub carriers and rear-axle subframe. New kinematics and elastokinematics, based mainly on the use of optimized bearings, ensure even better vibration properties and reinforce the sedan’s understeering self-steer effect, which also guarantees a high level of handling safety. All the engine versions of the C-Class, with the exception of the C 180, have a torsion bar stabilizer on the rear axle. It is directly attached to the vehicle body. Springing and damping of the rear axle are provided by coil springs and single-tube gas dampers with enlarged rubber mountings.
Drivers who prefer a particularly sporty driving style can order their C-Class with sports suspension, in which the vehicle body is lowered by 15 millimeters at the front and rear axles, as an optional extra for all lines and engine versions. The overall travel is 20 millimeters shorter on the front axle and ten millimeters shorter on the rear axle with the sports suspension tuning than in sedans with standard suspension. The spring rates are up to 21 percent higher. Furthermore, the “Sports Suspension” option also contains 16-inch light alloy wheels and 225/50 R 16 wide tires for all models.
High-performance braking system can cope with any situation
Mercedes engineers have again made significant advances in the field of brake systems too – particularly in terms of braking performance and braking comfort. Thus, all engine versions are now manufactured with ventilated front disk brakes whose diameter has been increased to 288 millimeters and thickness to 25 millimeters on the four-cylinder gasoline and diesel engines. In the C 240, C 320 and C 270 CDI sedans the diameter of the front disk brakes is 300 millimeters, while the disk thickness measures 28 millimeters. Thanks to their large size and the newly developed brake calipers made of high-strength nodular cast iron the sliding-caliper disk brakes on the front axle of the C-Class feature above-average performance reserves even under heavy loads.
Another new feature is the narrow stud-like castings in the ventilation ducts of the brake disks, where they replace the cooling fins used previously. The special design of these components, which link the two friction ring halves of a brake disk, ensures an optimal flow of cooling air and therefore increases the gray cast iron disks’ shape retention under thermal load. In concrete terms this means the annoyance of brake judder, which frequently occurs because of deformed brake disks, is effectively prevented by this modern system. The rear axle of the C-Class is fitted with solid disk brakes with a diameter of 278 millimeters (C 240 and C 320: 290 millimeters) to ensure safe deceleration. Here the Mercedes engineers use fixed-caliper brakes with a twin-piston system. The new aluminum brake booster for the C-Class is a uniform 7/8 inch for all engine variants – which means that it is approx. 15 percent more powerful than in the outgoing model.
Advanced control systems for optimum safety
Like all the latest Mercedes passenger cars, the C-Class, too, is fitted with the world’s best and most efficient handling safety systems – as standard. They reduce the risk of skidding when cornering, keep the sedan safely on course when braking, ensure improved accelerating from rest on slippery surfaces and shorten stopping distances in emergencies. This efficient technology is an important element of the safety concept of the Mercedes-Benz brand (see also on page 36) and actively helps to prevent road accidents:
Electronic Stability Program (ESP): Thanks to a variety of sensor signals, the Electronic Stability Program detects hazards far sooner and faster than even the most experienced driver. The system can therefore intervene in a highly controlled fashion to stabilize the vehicle. While the car is in motion, the ESP computer constantly compares the car’s actual handling with the calculated set points. If the car diverges from the safe “ideal line”, ESP intervenes extremely rapidly and returns the car to the right line in two ways: by delivering precisely gauged braking pulses to one or more wheels and by reducing the engine torque. ESP will also stabilize the C-Class in the event of skidding caused by extreme driving maneuvers, ice, wet, gravel or other unfavorable road conditions. The latest ESP generation is particularly impressive: it works extremely smoothly because of its almost imperceptible responsiveness. It is this fine tuning in particular that demonstrates the great experience which Mercedes’ engineers have as inventors of this innovative system.
- Anti-lock braking system: ABS prevents the wheels from locking when braking in an emergency and works just as reliably on dry asphalt as on wet or icy roads.
- Acceleration skid control: The sensor signals provided by the anti-lock braking system are also available to the acceleration skid control system (ASR), which is also part of the Electronic Stability Program (ESP). ASR helps to prevent wheel spin at the drive wheels when accelerating from rest or in motion or for general driving – in the event of ice, for example.
- Brake Assist: This system, which Mercedes-Benz developed to reduce stopping distances in emergencies, is also one of the functions included in ESP in the C-Class. Brake Assist (BAS) springs into action if the driver brakes too hesitantly or gently in critical situations. In such cases the system automatically generates the maximum brake boost within fractions of a second, thereby substantially shortening the car’s stopping distance quite considerably by up to 45 per cent.
The range of wheels also meets the wishes of sporty drivers
The C 180, C 200 KOMPRESSOR, C 200 CDI and C 220 CDI in the Classic and Elegance lines are shod as standard with 195/65 R 15 wide tires on 6 J x 15 wheels. The Avantgarde line stands out with its standard-fitted 16-inch wheels and 205/55 R 16 tires. This combination is also the standard equipment for the five- and six-cylinder models (C 240, C 320 and C 270 CDI) in all the lines.
The C-Class looks even more dynamic with the sports suspension in conjunction with the “Light alloy wheels in 5-double-spoke design” option. 225/50 R 16 tires are fitted to 7 J x 16 wheels on the front axle and to even wider 8 J x 16 light alloy wheels on the rear axle – which perfectly underlines the car’s sporty handling. It is also possible to have mixed 17-inch tires on attractive AMG light alloy wheels in conjunction with the sports suspension: 225/45 R 17 (7.5 J x 17) at the front and 245/40 R 17 (8.5 J x 17) at the rear.
Real-life safety in six stages
- Sophisticated front-end structure with crash boxes and new firewall
- Airbags with two-stage gas generators for driver and front passenger
- Windowbags as standard for excellent side impact protection
- Belt tensioners and belt-force limiters even at rear
When Mercedes engineers consider concepts for the further improvement of vehicle safety, only one standard counts: real life. All new developments or enhancements that provide car occupants with greater safety are invariably based on careful analysis of actual traffic conditions and accident processes. The upshot is that today’s C-Class benefits from more than six decades of experience of Mercedes safety development rooted in practical observation.
he technical safety concept of Mercedes passenger cars is largely defined not only by the various test specifications laid down by different international bodies but also by the findings of in-house accident research. Consequently, the term safety will in future mean more than just crash safety: more than ever before, the theme of safety is governed by an integrated approach that covers the whole ground, starting with questions of accident prevention by means of electronic assistance systems and ending with the fastest possible rescue of the vehicle occupants after a crash. The C-Class is an outcome of this pioneering “Real-Life Safety Concept”, which essentially consists of six stages:
Sensors on the axles and bodywork monitor the car’s handling characteristics. On reaching the limits of driving dynamics, a yellow warning symbol lights up in the cockpit.
Standard-fitted assistance systems such as ABS, Brake Assist and ESP® automatically enter into action in critical situations, thereby helping the driver to keep everything under control.
The impact energy of minor bumps at speeds of up to 15 km/h is absorbed by the bumpers and crash boxes in the front-end module. The inertia reels on the seat belts are locked. Sensors monitor the severity of the accident and prevent the airbags being inflated until their supplementary protective effect is actually needed.
In a severe collision, robust members in the front, side and rear structures absorb energy and distribute the impact forces over a wide area. The belt tensioners are activated. Depending on the severity of impact, the front airbags initially inflate less than fully, in line with actual need, so that the optimal protective effect is assured. In a side-on crash, the occupants are protected by sidebags in the front doors, combined with windowbags. For the front passenger seat, the automatic seat occupancy and child seat recognition system prevents the passenger-side front airbag, belt tensioner and sidebag being activated if not actually needed. The fuel supply to the engine is cut off.
In the event of even greater danger to the vehicle occupants, a second inflation stage for the front airbags is triggered. At the same time, the belt force limiters are also activated.
After an accident, the doors are automatically unlocked. The TELEAID emergency call system (optional) alerts the rescue service and guides it to the accident site. The hazard warning lights are switched on.
Front-end impact: occupant protection in three stages
In order to take into account all possible accident conditions, an integrated approach to body design is required. The C-Class is proof of this fact: in a front-end crash, depending on the severity of impact, a three-stage protection system enters into action, with due attention to both the aspect of cost-savings in accident repair and the typically high Mercedes requirements for occupant protection:
- Up to a collision speed of 4 km/h, the foam elements in the bumpers absorb the impact energy, so that the metal panels behind remain undamaged.
- Up to a collision speed of about 15 km/h, the impact energy is absorbed by the newly developed front module and the two crash boxes made of an innovative, high-strength dual-phase steel.
- At a collision speed of more than 15 km/h the robust side members in the front-end structure come into their own and absorb the impact energy. The load is distributed to four mutually independent zones, as follows: via the aluminum crossmember of the front module, which transfers the impact forces of the offset crash to the side not directly involved; via the side members, which extend far to the front (behind the crash boxes); via the robust sectional panels above the wheel arches and via the front wheels, which are supported on special impact-absorbing elements in front of the side members (rocker panels), thereby transferring impact forces to the body’s side structure. Another important feature is the newly developed ellipsoid firewall, which is joined to the front side members and spreads the impact forces over a wide area.
Front airbags: two-stage inflation dependent on severity of impact
The front airbags of the C-Class also adapt to the specific accident situation and thereby provide even more effective occupant protection. The era of these innovative adaptive restraint systems began in 1998 in the Mercedes-Benz S-Class: the Stuttgart-based auto manufacturer has now further developed this technology and for the first time is providing the C-Class with two airbags that inflate in two stages as a function of the severity of impact. In other words, like the body structure of the sedan, the restraint system is not solely designed to respond to high-speed collisions but also for the first time takes into account the special protective functions required for low to medium impact forces.
The technical explanation behind this system is that both the driver’s and front passenger’s airbags are fitted with two-stage gas generators. If the sensor system detects a minor front-end impact, it fires only one chamber of these inflator units, so that the airbags are only partially filled. Consequently, the airbags catch the occupants “softly”. According to accident research, this feature is especially advantageous in collisions in the speed range between 20 and 35 km/h. If the airbag sensors register a higher accident load, the electronic control unit also activates the second chamber of the inflators, and the airbags are fully inflated. Depending on the severity of impact, this second airbag stage is triggered within only 5 to 15 milliseconds of the first.
The adaptive airbag system of the Mercedes sedan includes a sensor system that decides whether or not to activate the protection system. For example, the airbag, belt tensioner and the sidebag on the front passenger’s side are deactivated if the front passenger seat is unoccupied. A sensor mat in the seat cushion provides the necessary information to the electronic control unit. If the car owner installs a “reboard” child safety seat from the Mercedes-Benz accessories range, special antennas in the front passenger seat exchange data with a transponder in the base of the child seat. The airbag electronic system therefore recognizes that a reboard child seat has been fitted and immediately deactivates the airbag on the front passenger’s side, since it is not required in these cases. On the other hand, the belt tensioner, sidebag and windowbag remain activated.
Highly robust protective zone for the occupants in a side-impact crash
The importance of side impact protection for the safety concept of modern passenger cars is continuing to increase. According to accident research, the proportion of side impact collisions in traffic accidents involving injuries to car occupants has more than doubled since 1985 – just under 44% of all car accidents with fatal consequences are now in the side impact category. Mercedes engineers have responded to these practical findings with a comprehensive package of measures, which, like the front occupant protection system, is primarily geared to actual accident situations. It is effective at three levels:
- In the floor area, reinforced side rocker panels transfer the impact forces to two robust side members on each side under the front seats and to a full-width crossmember underneath the rear seat. The center tunnel reinforcements also improve the transfer of forces between the front seats.
- At medium height, the occupants are protected by laterally stiffened doors integrated in the side panels and with several sectional reinforce-ments, robust door hinges, and also by the extra-strong frames of the seats and backrests. A square-section member under the dashboard also improves lateral support.
- In the roof area, intrusions are kept to a minimum by the A, B and C-pillars with their full-height 3-shell construction and by a reinforced roof frame, which is again of 3-shell construction.
The highly robust occupant cell, which provides optimal protection in front-end and side impact collisions, is also highly effective even in the event of an offset rear-end impact at high collision speeds. The secondary load-bearing member structure and the newly developed rear end module perform similar functions to the comparable components at the front and are geared to actual accident processes.
Sidebags and windowbags as standard
Another important example of the Real-Life Safety Concept of the C-Class is provided by the standard-fitted windowbags that have already proved their protective effect in the Mercedes S-Class, E-Class and flagship CL Coupe models. The development of these special airbags is based on the results of updated accident analyses on the risks of injury in side impact collisions. Scientists found that these accidents involved a broad range of angles of impact, so that the movements forced upon the car occupants could differ vastly, thereby limiting the protective effect of more simple solutions.
Consequently, in the opinion of experts, an airbag covering as wide an area of the side of the car as possible is necessary in order to provide optimal protection to the heads of the occupants in particular – both at front and rear – in the many conceivable crash configurations. The result is the windowbag. This special airbag meets the requirements of accident researchers and provides excellent results even in the side impact crashes that deviate from the standard right-angled configuration used in most crash tests conducted by international test institutes. The airbag consists of 9 chambers with a total volume of 12 liters. After a crash, it inflates to span like a curtain from the front to the rear roof pillar of the interior.
Whereas the sidebags particularly protect the chest area, the windowbags prevent the occupant’s head striking the side window, roof pillars or roof frame. In other words, sidebags and windowbags belong together. Consequently, Mercedes-Benz fits sidebags as standard to the front doors of the C-Class and offers them as options for the rear.
Front airbags for the driver and passenger, door-mounted sidebags and standard-fitted windowbags are all part of the comprehensive restraint system which ensures maximum occupant protection at all levels.