Mercedes-Benz's C-Class sedan is the winner of european car's Grand Prix trophy for 2001, but we could very well have cited the German car maker's entire lineup as recipient of the award. From the top of its model range to the bottom (if such a prosaic term can be applied to so distinguished an array of automobiles), Mercedes-Benz offers a stunning combination of substance and style. Each new release seems to do the impossible by outshining its forerunners with a brilliant mix of technology and luxury, at prices which insert value into the Mercedes-Benz purchase equation. In fact, when the math is analyzed, it reveals a company which has shown record overall growth over the last decade, fueled in great part by "impact" models in market segments not generally associated with Mercedes-Benz--and this includes the entry-luxury group--Audi, BMW, Volvo, Lexus and now Jaguar are potent players in a segment which accounts for more than 70 percent of the entire luxury car market in the U.S. Obviously there's a big pile of money to be made, but, to continue in that same metaphorical vein, Mercedes-Benz has raised the stakes considerably higher with the C-Class model range, and the competition will have play a strong hand to counter Stuttgart's powerful cards. Mercedes-Benz's first foray into the entry-luxury market was with the 190 for the 1984 model year, and that car's success, both in sales and on the racetrack, continued unabated until it was replaced by the C-Class in 1993. That predecessor to our award winner racked up over 1.6 million worldwide sales and helped Mercedes-Benz attain the rank of #1 luxury brand in America in 1999. And the bottom line from these numbers? In these unfortunate bearish times, the outlook for Mercedes-Benz is decidedly bullish. Consider: Since 1995, Mercedes-Benz has introduced over 20 new models to the U.S. market--from the 1995 C36 through the M-Class in late 1997 to the 2001 C-Class--yet the company plans to launch more models over the next three years than it has in the previous five years. It doesn't take a trophy to tell Mercedes-Benz it has been doing extremely well, but we're more than happy to reinforce the good news with european car's 2001 Grand Prix award. Congratulations.
While European buyers of the Mercedes-Benz C-Class are offered a choice of four gasoline engines and three turbocharged diesels, American customers receive only the two upper gasoline options, large and small V6s embodying all of Mercedes-Benz's latest technology. The goal of these technologies, applied to all six-, eight-, and twelve-cylinder engines in Mercedes-Benz's U.S. lineup, is to achieve maximum efficiency and minimum emissions while at the same time increasing performance levels--a tough call, indeed, but one that Mercedes-Benz engineers were able to answer.
Three is Better Than Four
While four valves per cylinder has become an industry standard, and a few manufacturers think five valves are even better than four, Mercedes-Benz has designed an all-new engine lineup around three. The reason for this is a 40-percent reduction in cold-start emissions, required to meet tightening standards both in the U.S. and in Europe. Most engines of the last few years take nearly two minutes to raise the catalytic converter's temperature to the point at which it becomes effective, but any new engines must cut that in half. Having a single exhaust valve reduces exhaust port area and thus heat transfer into the head, increasing exhaust temperature in the cold engine by about 125 degrees F, thus heating the catalytic converter faster. Reliability of the single, large exhaust valves is ensured by the cooling of sodium-filled stems. The exhaust manifolds are also double-walled to retain heat all the way to the cat.
The three-valve chamber does not sacrifice performance versus a four-valve chamber, at least at factory levels of tune. The single, large exhaust valve is heavier, but Mercedes-Benzes are not Hondas and don't need to rev to 8000 rpm to satisfy their drivers. A single valve can breathe on par with multiple valves, because two valves side by side will partially shroud each other in the area where they are closest. When an engine is leaned on with turbo boost, valve cooling becomes important, and the adjacent portions of the exhaust valve seats cool poorly, again causing problems with a four-valve head.
Until the latest round of engine designs, Mercedes had built all its six-cylinders in an inline configuration. The V6 engine is more compact, lighter and, being shorter, is easier to integrate into a vehicle that must pass a frontal impact test. Vee-type engines have the advantage that a short, square box is inherently more rigid than a long, skinny one, so they can take the forces of a given output with less material. The new V6 weighs just under 330 lb, roughly 100 lb less than the inline six it replaces. Once the decision to use the V6 configuration was made, it was advantageous to make it a 90-degree vee, allowing the engines to be built in the same factory as Mercedes-Benz's V8s, sharing parts for reduced costs.
While a 90-degree V6 is imperfectly balanced, engineering compensated by using an offset-throw, "even-fire" crankshaft and a balance shaft nestled in the vee where a domestic, pushrod, vee-type engine carries its camshaft. The balance shaft counter-rotates at crankshaft speed, which company literature says exactly cancels the 90-degree V6's first-order vibrations.
As many other modern engines do, the C-Class V6s use aluminum for both block and head. However, Mercedes pioneered the production of cast-in-place silicon/aluminum-composite cylinder liners. These sleeves are more than a pound lighter than conventional iron sleeves, and being an integral part of the block helps provide greater stiffness. The bare V6 block weighs just 57 lb, a savings greater than 50 percent versus the old, iron inline six. As well, the silicon provides a low-friction bore surface that essentially doesn't wear at all. Piston-ring tension is reduced, contributing to an internal drag reduction of 50 percent.
Timing is Everything
While a four-valve combustion chamber has one good spark-plug location, at the center of the clover leaf, the three-valve chamber has two, in the corner between each intake valve and the exhaust valve, providing another opportunity to improve performance. The two plugs are fired not simultaneously but in succession, with a "stagger" that varies depending on engine load and speed. This provides a new level of control over the combustion process, for greater efficiency and smoothness. As well, the increased ability to light the mixture allows lean running and late ignition timing on cold-start, again pumping heat out the exhaust to warm the catalyst.
Mercedes-Benz has joined the variable-intake club with lightweight, cast magnesium dual-path intake manifolds on all its vee-type engines. At low- and mid-range speeds, air travels through the longest intake runners in the industry, enhancing dynamic cylinder filling for increased torque. At higher speeds, above about 3700 rpm, individual flaps open, allowing the air to reach each cylinder through a more direct, less restrictive path for maximum power.
Connecting rods are forged as a single piece, then cracked, giving perfectly matched mating surfaces as well as fewer production steps.
Camshafts are of composite construction, for lighter weight, and are driven by double roller chains running on silent, rubber-coated sprockets. Rockers are aluminum, with a roller reducing friction on the camshaft end and a small hydraulic lifter on the end that actuated the valve.
While Mercedes-Benz's new V6 engines are a break with tradition on the surface, the true Mercedes engineering tradition is the technology that lies beneath surface concepts. These engines are poised to carry that flag forward for many years, satisfying the performance requirements of Mercedes customers while meeting the standards of the strictest governments in the world.
Most readers will be aware, by now, that the new C-Class is the sportiest small Mercedes sedan yet. A large measure of that improvement is due to completely new concepts for a Mercedes front suspension and steering. Traditionally double A-arm, each of the lower, front A-arms have been replaced with two individual links. Adding the locating properties of the steering tie rod, Mercedes calls this arrangement a "three-link axle." Mercedes claims that this system provides more precise wheel location, as well as being better able to offset vibrations caused by wheel imbalance or brake torque fluctuations. In addition, they allow the chassis to more effectively absorb energy in a frontal collision. What those links attach to is likewise a significant departure from any previous Mercedes: a MacPherson strut. The damper is a low-pressure gas, twin-tube type, and the anti-roll bar attaches to the strut itself, for more direct action on the wheel.
Perhaps most significant is the first use of rack-and-pinion steering in a road-going Mercedes. Though rack-and-pinion gear has long been recognized by sporting enthusiasts for its ability to provide precise steering response and clear feedback, Mercedes has conservatively adhered to recirculating ball steering until now. Besides more agile, enjoyable handling, the rack-and-pinion unit delivers several other benefits. While the recirculating ball steering box formed a solid block that absorbed no energy in a crash, the steering rack is mounted to a deformable aluminum bracket, allowing the unibody to crush and absorb energy. Additionally, because of its more efficient load paths and hardware, the rack-and-pinion steering arrangement removes approximately ten pounds from the front of the vehicle.
The rear suspension is enhanced as well. First seen on the 190 in 1983, it has been a part of every subsequent Mercedes-Benz passenger car. In the 2001 C-Class, the designs of the track rods, hub carriers, and rear-axle subframes have been thoroughly revised. While the basic geometry has been changed, elastokinematics--what happens when suspension bushings deflect under severe load--has received a great deal of attention. Together, the many updates improve vibration properties and ensure safe handling under autobahn conditions.
A sport suspension package is available, which lowers the vehicle, stiffens spring and damper calibration, and includes wider tires on unique 5-spoke wheels. Unavoidably, suspension travel is slightly reduced.
Braking has always been a Mercedes-Benz strength. The new C-Class' have been fortified, with vented discs measuring 300mm in diameter and 28mm thick. Rather than cooling fins in the ventilation ducts, these new discs use narrow, stud-like structures to link the two friction ring halves. Mercedes says they ensure an optimal flow of cooling air and help retain the cast-iron disks' shape under high thermal load. The single-piston, sliding, front calipers are made of nodular cast iron for strength. Solid rear discs are 290mm in diameter, with a fixed, two-piston caliper. By selectively applying the brakes on one wheel at a time, Electronic Stability Program (ESP) adjusts the vehicle's actual path through a turn to correspond to what it determines is the driver's intent.
It's a trick to introduce a new car with leading-edge looks yet also retain strong elements of its visual lineage--but that's what M-B stylists have pulled off with the C-Class. Its themes reflect the overall styling of the 2000 S-Class, but a coupe-like profile, slim waistline and muscular shoulders add the necessary spice of sportiness and youthful vigor.
When judged against its forebear, the presence of the wind tunnel becomes immediately apparent, the car's 0.27 Cd (reduced 16% from the earlier C) a testament to the designer's art of wrapping nuts and bolts in a beguiling skin. The integrated front bumper, laid-back grille and twin headlamps evoke the tension of a sprinter's stance, which is carried through the sculpted hood, its character lines continuing the shape of the headlamps rearward to the A-pillar. Lending support to the "of-a-piece" styling are the body-colored door handles, integrated trunklid spoiler and ribbed rear lamps.
The C's wedge-shaped design helps it stay stable while forcing a way through the atmosphere, keeping it firmly planted. Aided by underbody encapsulation to further manage airflow, the new design boasts 70/38% less lift front/back than last season's C-Class.
A good portion of a car's "luxury" element is in the area of noise suppression, and the C-Class fulfills that brief through a plenitude of tweaks to the outside shape. The configurations of the A-pillars, door seals, sideview mirrors, sunroof air deflector and windshield wipers contribute to the noise-cheating design, and even the auxiliary turn signals were integrated into the outside rearview mirrors to minimize drag. Standard running gear--the car's jewelry--is a set of nicely styled 7-spoke alloys. Buyers of the Sport package get handsome 5-spoke alloys with a high-luster machined finish.
Mercedes-Benz patented its energy-absorbing car body with front and rear crumple zones in 1951, cementing a tradition of safety that remains unabated. Mercedes expresses its safety program as a five-element strategy. First, as any enthusiast will point out, is actively avoiding an accident. Effective suspension and braking systems are the means by which a driver maintains control of a vehicle. Mercedes also provides active electronic assistance, with anti-lock braking systems, Electronic Stability Program, and Brake Assist, which increases the force of brake application if it is determined that an emergency stopping situation exists.
The third element of safety is impact absorption. As required, the C-Class' bumpers will absorb collisions up to 2.5 mph with no damage, while damage from impacts up to 9.3 mph is limited to easily replaced, energy-absorbing crash boxes, minimizing repair costs. Impacts at greater speeds are transferred to the front module's aluminum crossmember, the longitudinal chassis members that extend to the front, the section panels above the wheel wells and finally to the front wheels themselves, which transfer the forces to the passenger cell's side structure.
The C-Class has strong rocker panel sections, which transfer the forces of side impacts to side structures under the front seats and a full-width rear crossmember. Another crossmember is found in the dashboard. Doors are built with sectional reinforcements and hinges sufficient to support the door of a smallish vault. A-, B- and C-pillars are constructed of three concentric shells, a technique that is repeated in the roof frame.
Limiting passenger movement in an accident begins with properly fastened three-point seatbelts, which are provided for all five seating positions in the C-Class. The four outer positions employ electronically controlled belt tensioners, while front-seat occupants benefit from seatbelt force limiters, further reducing the risk of injuries. Airbags are in good supply, with nine-chamber side-curtain bags spanning the distance from A-pillar to C-pillar augmented by door-mounted air bags. Two-stage front airbags are deployed according the the severity of a frontal impact, while BabySmart ensures the safety of children using compatible child or booster seats.
The TeleAid system is activated if any airbag is deployed. The TeleAid operator has instant access to vehicle location, and can direct emergecy resonse services with information to help identify the vehicle.
This is the area where the "luxury" label needs to be immediately apparent--and the C-Class delivers both in content and quality of materials. Notable improvements from the previous C-Class include more legroom and interior space and additional SmartKey functions.
Every C-Class dashboard has its upper part finished in charcoal to minimize interior glare, while the lower section mirrors the dominant interior color. The newly designed instrument cluster and center console offer all the requisite readouts, switches and controls without clutter, the graphics clean and readable. The large center speedometer is flanked by tachometer and fuel gauge, and within the radius of the speedo is the central display, which indicates time, temperature and all settings controlled by the multifunction steering wheel (more than 50 separate functions, including trip computer, audio system and lighting controls). The wheel also adjusts for both rake and reach (manual in C230; electric in C320). An overhead console houses controls for the interior lights, sunroof and TeleAid (standard across the line). This electronic lifeline provides live responses to emergencies and also provides informative, non-emergency services.
Deeply sculpted seating provides support in all the right areas, and adjustments are either semi-electrical (C240) for backrest angle and cushion height or fully electrical (C320). Leather seating surfaces are standard across the line, as is a dual-zone climate control system with rear-cabin outlets and activated charcoal filtration. Cruise control and automatic headlamps, which can be set to turn on at dusk, are also standard on both models.
Options are numerous: A GPS nav system that features an integrated console-mounted screen; the COMAND system, which integrates navigation, telephone and audio controls in one control center; Xenon headlamps; heated front seats; 10-speaker Bose premium sound system (engineered specifically for theC's interior layout); split fold-down rear seats; 6-disc CD changer; and a fully integrated digital and portable cellular phone.