Mercedes-Benz introduces a 'horizontal' A-Class

  • 01-Aug-2012 04:03 EDT
Merc7-12 A Class 1.jpg

There are virtually no links between the old and new A-Class models except the name. The new car is 160 mm lower. It will be produced in Germany and Hungary, and by Valmet in Finland.

The original Mercedes-Benz A-Class (1.1 million produced) became famous—or infamous —for its dramatic behavior when undergoing a “moose test” slalom, calling for significant electronic chassis applications. The new, low-slung generation A-Class could almost be driven underneath the animal.

Mercedes has decided that its latest B-Class (introduced late last year) fulfills the role of a “vertical” people and load carrier, and that the A-Class nomenclature should now be applied to a low, distinctively styled “horizontal” range of cars that will appeal to younger buyers and that have a clear element of sportiness about them. The new A-Class is 160 mm (6.3 in) lower than the original.

An interesting design detail is that Mercedes used clay in preference to a computer to achieve the car’s final shaping and low height. British designer Mark Fetherstone said: “You really couldn’t get the lines we wanted on the computer.”

Overall packaging is no longer the same major design criterion although the car does pack a lot of technology.

So confident is Daimler of the success of the two-box, cab-rearward, long-hood A-Class that Finnish contract assembler Valmet will help out with the production. Starting in 2013, it is expected to build 100,000 units through 2016. The A-Class is being built initially by Daimler at Rastatt, Germany and Kecskemét, Hungary, alongside the B-Class with which it shares chassis, powertrain, and other elements.

There will be at least five distinctly different versions of the A-Class: a five-door hatch, the CLS-like CLA four-door "coupe;" a compact SUV, and probably a shooting brake, although Mercedes has not confirmed the last. Rival models, the BMW 1 Series and Audi A3, are offered as convertibles, but Mercedes has not confirmed a cabriolet or roadster A-Class. Despite its different name, the B-Class rather confusingly is regarded as a member of the A-Class range, therefore making it the fifth member.

There will also be a high-performance 2.0-L AMG variant, the A45, for 2013 and based on the five-door hatch. It is scheduled to have the highest power-to-displacement ratio of any standard production engine in its class, plus the lowest fuel consumption.

Prof. Dr. Hans-Georg Engel, Development Director of the A-Class and Strategic Project Manager, Compact Cars, says that the over-arching design and technology aspects of creating the A-Class family was achieving an architecture that would meet the requirements of such a wide spectrum of applications. It also needed to have a character of “refined sportiness.”

Although an engineer, Engel makes use of the word “emotional” when describing the model definition: “I would say that means dynamic, sporty, efficient, comfortable, safe—and not at all bad looking!”

The A-Class represents a significant expansion of Mercedes’ car lineup, so the company has taken time to get it as right as possible: “At the beginning of the project, we did not know exactly what would be needed to be based on the architecture (designated MFA: Mercedes front- and all-wheel-drive architecture) much later on," said Engel. "We had to develop an architecture that was not too heavy, not too expensive, and would meet those future needs incorporating every possible version. By architecture I mean every aspect of the bodyshell, chassis, and powertrain.”

The origins of this architecture for the A- and B- models can be traced back to 2006, but it was 2008-2009 before development of the A-Class started.

Just about everything of the A-Class (and B-Class) is new, stated Engel. The big difference between them is that the B-Class has what he describes as a “half sandwich” floor—the half referring to an energy storage area (batteries or high-pressure liquid hydrogen tanks) to facilitate the use of alternative powertrains. A fuel-cell version of the B-Class will be available.

Despite the very obvious aesthetic differences between the two models (vertical and horizontal), cross-linking aspects also include powertrain, underbody, electrics, kinematics, intelligence, and ECUs plus many components, even including steering wheels.

Aerodynamics was a central issue. The B-Class achieves a best Cd of 0.23 and the A-class 0.26. The same team worked on both cars. Said Engel: “We have achieved these figures through very detailed work. The key is not to say it has to be achieved in 12 months and that’s that; it means 3 to 3.5 years of work, work, work—and to spend much time with engineers and stylists highly focused in the wind tunnel.”

Engel is totally convinced of the payback for this type of investment: “I feel that some other OEMs might be under-estimating this, and I wonder why. In the official test cycles, aerodynamics may not play a big role at low speeds, but in real-life driving they certainly do, becoming particularly significant from 90-100 km/h upwards. At 140 km/h, the difference between a Cd of 0.26-27 and 0.30 is 10 g/km of CO2—and that is a lot. In powertrain development, you would have to spend very large sums of money to achieve that. Of course in aerodynamics, money must be spent but very often gains can be achieved via details that cost little.”

The A-Class CLA is expected to better the B-Class’s 0.23 Cd, which may make it the world’s most aerodynamic series production car. Until recently, a Cd of around 0.25 was regarded as a practical limit for appropriate aesthetics.

Creating “polyglot” architecture usually demands some compromise, and Engel confirms that the A-, B-, and C-pillars of the core A-Class will be in the same position (essentially hard-points) despite the model range overall length—cars varying by about 0.30 m (1 ft): “So entry and egress is the same for all.”

Measuring 4292 mm (169.0 in) long, 1780 mm (70.1 in) wide, and 1433 mm (56.4 in) tall, the A-Class is a five-seater. Trunk space is a fairly modest 341 L (12.0 ft³) by the VDA method and 1157 L (40.9 ft³) with the rear-seat backrests folded. Interior quality is to a high standard and includes a fixed 5.8-in color display. Sports seats are available or fitted as standard on some versions. An opening panoramic glass roof is optional.

With Mercedes very firmly focused on providing end-users with environmentally responsible vehicles that are still enjoyable to drive, it is able to offer a 1.5-L A180CDI (diesel) with a CO2 figure of 98 g/km. Power output is 80 kW (107 hp) and maximum torque 260 N·m (192 lb·ft) from 1750 to 2500 rpm. The car uses a variable turbine geometry (VTG) turbocharger. Combined fuel consumption is 3.6 L/100 km. Performance figures include a top speed of 190 km/h (118 mph) and 0-100 km/h (0-62 mph) time of 11.3 s. Curb mass is 1395 kg (3075 lb).

Two other diesels are available at launch, both with 1.8-L capacity, the more powerful (A200CDI) producing 100 kW (134 hp) and 300 N·m (221 lb·ft), the latter from 1600 to 3000 rpm.

The most powerful gasoline version of the car is the 2.0-L A250 Sport with 155 kW (208 hp) and 350 N·m (258 lb·ft) from 1200 to 4000 rpm. Performance includes 0-100 km/h in 6.6 s and a 240-km/h (149-mph) top speed. Emissions are 148 g/km, curb mass 1445 kg (3186 lb).

Transmission choice across the A-Class range is six-speed manual or seven-speed twin-clutch automatic.

Chassis details include a new four-link layout at the rear (three control arms and one trailing arm). Wheel carriers and spring links are of aluminum. Three suspension setups are offered: normal, sports, and “extremely sporty," which is engineered by AMG for range topping gasoline and diesel versions of the car.

Steering is electromechanical positioned on the rack-and-pinion steering gear as a dual-pinion EPS (electric power steering). A variable ratio system is an option. The A250 CDI’s braking system comprises ventilated discs at the front, solid rears, electric park brake, adaptive brake assist, ABS, and ESP.

Safety priorities see a radar-based collision warning system as standard. It gives visual and audible warnings and prepares Brake Assist, which is triggered when the driver brakes “decisively.” The car is offered with a plethora of electronic safety systems including the company’s established Pre-Safe.

Infotainment is to a high level, and an Apple iPhone can be integrated into the system.

The compact SUV A-Class will be the third (including the B-Class) version of the A-Class. The first production A-Class left the Rastatt plant in mid-July. Dr. Wolfgang Bernhard, responsible for Mercedes’ manufacturing and procurement, said: “Thanks to the use of joint architecture, we can flexibly produce all models of our new compacts on the same production line at the respective site.”

Daimler is spending €1.2 billion on the Rastatt plant. B-Class production started there in September 2011. The CLA will be built at Kecskemét. Investment in German powertrain plants by Daimler for A- and B-Class supply will total almost €400 million.

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