- Mercedes-Benz A-Class, 2013
The new Mercedes-Benz A-Class is opening up a new chapter in the compact segment: markedly emotive in design, with powerful engines ranging from 80 kW (109 hp) to 155 kW (211 hp), extremely efficient with emissions from just 98 g of CO2/km and a best-in-class drag coefficient of 0.27. At the same time the new model underlines that for Mercedes-Benz, safety is not a question of price - the standard specification includes, amongst other things, the radar-based COLLISION PREVENTION ASSIST system. Prices in Germany start at €23,978.50 (incl. 19% VAT) for the A 180 BlueEFFICIENCY.
Exterior design: The most progressive design in the compact class
Standing as much as 18 centimetres lower on the road than the preceding model, the new A-Class communicates design and dynamism at the very first glance. This radical form language, presented and enthusiastically acclaimed around the world with the A-Class Concept, was consistently implemented in the series production car. The appearance of the new Mercedes-Benz A-Class reflects this new Mercedes-Benz design strategy. The result is what is known as a two-box design with a distinct character of its own, a sportily emotive exterior and an exceptionally high-quality feel to the interior.
Defined edges and tautly drawn surfaces mark out the exterior design of the new A-Class. The constant interplay between concave and convex surfaces creates a characteristic play of light, particularly along the sides of the car, which contributes to its unique appearance.
Typical features of the long, sporty front are its pronounced V-shape, the separate headlamps, the radiator grille with central Mercedes star and double slats to either side of the star, as well as the additional air intakes on the sides. The "dropping line" apparent in the side profile dissipates towards the vehicle's front end. The design of the headlamps, together with the configuration of the light functions within them, are a key element of the design concept.
The light modules and LEDs behind the headlamp cover glass have been arranged in such a way as to create the characteristic "flare effect" for the daytime driving lights and indicators. The so-called "flare" is made up of the feature line within the headlamp, the LED modules for the daytime running lamps and the bulb sets for the indicators. This signature effect gives the car its energetic look and so helps to define a new, youthful face for Mercedes.
The perfect interplay of dynamic design and excellent aerodynamics is nowhere more apparent than in the roof, with its smooth surfaces and taut, arcing curve. The silhouette reveals smooth, flowing lines finishing in a flat edge. The roof spoiler, which conveniently hides all the aerials, provides an extra sporty touch and gives structure to the roof assembly. The beltline rises to the rear to form a pronounced wedge-shape. The side view is distinguished by sensuously moulded sculptural side panels and crisp lines. The front structural edge, above the wing, falls in what is known as a "dropping line" in a gentle arc towards the rear. The powerfully-shaped shoulder muscles above the rear axle serve to emphasise the car's coupé-like character. A further line sweeps up from just in front of the rear wheel arch, then gently fades away. All these lines give depth and dynamism to the car's profile. Dynamic side sill panels provide a final finishing touch towards the bottom of the car, enhancing the appearance of elegant light-footedness.
The broad emphasis of the tail end is revealed in an interplay of convex-concave surfaces and edges. The tail lights continue the line of the muscular shoulders back towards the rear, while their horizontal orientation emphasises the car's powerful breadth. The light functions are provided optionally by fibre-optic cables and LED modules. Here, too, the interaction between design and aerodynamics is very clear: the surface finish of the tail lights is not only an interesting design feature, but also improves the airflow around the vehicle thanks to defined airflow break-away edges in the rear section.
Interior design: Extraordinary perceived value
The starting point for the interior design was the interior sculpture "Mercedes-Benz Aesthetics No. 2" presented at the Detroit Motor Show in 2011 and which directed attention to the new Mercedes-Benz design language in the vehicle interior, too. The first concrete implementation of this was shown in April 2011 with the A-Class Concept.
The process used for the production of this muscle allows diverse soft surface textures. It is thus possible to create different surface appearances with an attractive play of lights thanks to three-dimensional structures embedded in foil.
The instrument panel incorporates five round vents. "Like brilliant jewels they underscore the superior quality of the vehicle interior", explains Kaul. The outer rings of the round vents have a high-quality electroplated finish. The airflow direction is governed by an insert that is reminiscent of an aircraft turbine and reveals a meticulous attention to detail. This too has an electroplated finish in silver-chrome. The free-standing display screen features a black piano-lacquer-look front panel and a flush-fitting silver frame.
The instrument cluster comprises two large round instruments, each with a small dial set within it. When at rest, the dial needles stand at 6 o'clock. The pointer inlays are in white, although with the sportier design and equipment lines such as Urban and AMG Sport they are in red. The dials on the sporty equipment lines and packages are coloured silver with a chequered flag effect. The 3-spoke steering wheel comes with 12 function buttons and an electroplated bezel.
The centre dome and console, as well as the positioning of the various elements such as the head unit, lower control panel, air conditioning operating unit, stowage compartments, rotary pushbutton and armrest, reflect the findings of the ergonomics experts at Mercedes-Benz.
An extensive range of seat coverings, in terms of material (e.g. leather, fabric, ARTICO/fabric), colour combination and also geometry, provides scope for a broad range of individualisation options. Sports seats with integrated head restraints are available with all optional design and equipment lines. The sporty nature of the seats is emphasised by the opening between the upper edge of the seat backrest and the head restraint. On the back of the front seats this opening is edged with a frame in silver chrome and, in conjunction with the Light and Sight package, can also feature ambient lighting.
Designer Jan Kaul sums up: "If you were to take a seat in the A-Class with your eyes closed - you would never think, upon opening your eyes, that you were sitting in a compact-class vehicle."
The chassis and suspension: Agility and refined sportiness
Refined sportiness means maximum agility combined with the sense of safety, unspoilt driving stability and high levels of ride comfort which are all typical of the brand. The suspension of the new Mercedes-Benz A-Class has a four-link rear axle, electromechanical power steering with assistance functions and ESP® with "Extended Traction Control" (XTC). During development, the suspension experts made intensive use of simulations and the driving simulators at the Mercedes development centre in Sindelfingen as part of the so-called digital ride and handling test.
The preconditions for achieving dynamic handling are excellent in the Mercedes-Benz A-Class. This is because compared with its predecessor the centre of gravity (24 mm lower) and seating position (174 mm lower) has been reduced significantly. A new feature is the four-link rear axle: forces are absorbed by three control arms and one trailing arm per wheel. This means that longitudinal and lateral dynamics are virtually independent of one another. Wheel carriers and spring links are made of aluminium to reduce the unsprung masses. The goal was to achieve high lateral agility with high driving stability thanks to small sideslip angle on the rear axle.
Three chassis and suspension set-ups are available: the comfort suspension and optional sports suspension for sporty yet comfortable handling (in conjunction with the Dynamic Handling package or the AMG Sport equipment line). In addition, the A 250 Sport has a sporty, "engineered by AMG" high-performance suspension. Altogether this results in low dynamic rolling behaviour and low start-off pitch angle. Furthermore, the vehicle also has a reduced tendency to understeer in the higher lateral acceleration range: the driver is therefore able to control changes in direction with low steering input but high steering precision. When accelerating out of bends taken at speed, the tendency to understeer is reduced even further by "Extended Traction Control" (XTC): with this function, ESP®provides support in the form of directional stability by generating a yaw moment on the front and rear wheels located on the inside of the bend.
Steering: mechanical with electric assistance
The electromechanical steering of the A-Class has been redesigned. The electric motor of the servo assistance system is now located directly on the steering gear as a dual pinion EPS system. The steering system makes an important contribution to the vehicle's overall efficiency, as the steering assist function only requires energy when steering actually takes place. A Direct-Steer system is available in combination with the Dynamic Handling package or AMG Sport equipment line. This provides a noticeably more direct steering ratio over the turning angle thanks to the variable ratio, and enhances the vehicle's handling and agility substantially. The steering conveys a high sense of safety, as the driver experiences a consistent and precise response to all steering movements.
The electric power steering also enables various steering assistance functions which are activated by the ESP® control unit
Countersteering in case of oversteering
Corrective steering when braking on road surfaces offering different levels of grip (split-fraction braking)
Mitigating the extent to which the front-wheel drive influences the steering
Compensating crosswind and road gradients
The electric power steering also makes Active Park Assist possible.
With all engine variants, the Mercedes-Benz A-Class comes with disc brakes on all wheels. The callipers on the rear axle and the brake boosters are made of aluminium. A particularly convenient feature is the HOLD function, which is familiar from the larger model series: when stopping, for example at traffic lights, the driver merely has to press the brake pedal slightly more firmly and the brake will remain engaged until he moves off again. The brake is released automatically when the driver steps on the accelerator. On versions with manual transmission, the Hill Hold function automatically prevents the vehicle from rolling back unintentionally when starting on a slope.
The Mercedes-Benz A-Class is equipped with an electric parking brake, which operates by means of actuator motors acting on the callipers of the rear axle. The parking brake is activated via a button under the light switch on the left of the dashboard. This creates additional space in the centre console, as the handbrake lever is no longer required. When the button is pressed at speeds of over four km/h, the parking brake acts as an emergency brake, activating all four wheel brakes via the ESP®'s hydraulic unit.
In conjunction with the 7G-DCT automatic transmission, the parking brake offers a particularly convenient mode of functioning: when the driver accelerates sufficiently after fastening their seat belt, the parking brake is released automatically.
Aerodynamics: Saving fuel the aerodynamic way
With a drag coefficient (Cd) value of 0.27, the aerodynamic experts at Mercedes-Benz succeeded in creating another masterpiece with the Mercedes-Benz A-Class. And the A 180 BlueEFFICIENCY Edition due to follow later is even able to exceed this record for hatchback vehicles: thanks to a number of aerodynamic enhancements, this beacon of efficiency achieves a Cd value of 0.26.
Countless flow simulation studies on the computer and a great deal of fine tuning in the wind tunnel resulted in a clear goal: to enhance the basic shape of the A-Class design further, with a view to achieving an exceptional drag coefficient. This is no easy task, particularly for a hatchback model with a short rear overhang. But an improvement in the Cd value of just one hundredth will reduce fuel consumption by one tenth of a litre per 100 km when driving on the motorway at approx. 120 km/h. Based on NEDC figures, this corresponds to a CO2 reduction of one gram per kilometre.
With a Cd value of 0.27 and a frontal area of 2.20 m2, the drag area (CdA) is less than 0.6 m2 - a benchmark figure for hatchback vehicles in this segment.
The detailed work behind this development is highlighted by the following examples:
- The distinctive side spoilers next to the rear window ("finlets") help to create a run-on design which significantly reduces the disruptive longitudinal vortices generated at the D-pillars.
- Flow losses at the front wheel arches have been reduced substantially with the aid of patented serrated wheel spoilers at front and rear, slots in the wheel arches and optimised hub caps. These measures result in improved wind flow around the wheel arches.
- The Mercedes-Benz A-Class has an adjustable radiator shutter, already familiar in larger model series. The louvres behind the radiator grille are for the most part closed when there is no specific need for cooling air.
- The underbody has also been aerodynamically enhanced: the main floor panel features extensive cladding up to the rear wheel arch, followed by additional cladding of the rear axle. The rear silencer has also undergone aerodynamic optimisation.
- The new A-Class features exterior mirrors which have been optimised in terms of a number of details and already proven their excellent aerodynamic properties in large model series such as the S, E and C-Class, and also the B-Class. The position of the exterior mirror is adjusted in respect of the A-pillar in such a way that the airflow is directed along the side window without any significant interference or disruption.
The exterior mirrors and the low stepped height of the A-pillars reflect the fact that the work conducted in the wind tunnel was not just about optimising the flow conditions, but also about minimising wind noise. And in addition to aerodynamics and aeroacoustics, there is often another discipline to consider: in terms of water management too, the flow around the exterior mirrors and the A-pillars also has to be optimised in the wind tunnel in order to guarantee good visibility is maintained towards the rear and at the sides during wet weather.
More than with previous model series, in the case of the Mercedes-Benz A-Class the aerodynamics experts at Mercedes-Benz made particular use of flow simulation (CFD, Computational Fluid Dynamics): each component was first improved over several cycles using flow simulation before having its aerodynamic properties put to the test in the wind tunnel.
Digital flow simulation is based on so-called finite volumes as a mathematical model. A volume net is formed from around 60 million hexahedrons, or cubes, and is based around the CAD data of the new A-Class. This enables the driving cycle to be simulated over a free area in a large virtual wind tunnel. The Mercedes engineers generate the airflow using a predetermined turbulence level.
Setting new standards in terms of Cd value and consumption: BlueEFFICIENCY Edition
Due to follow later is the A 180 CDI BlueEFFICIENCY Edition boasting even better consumption levels. It is among the most efficient vehicles of its class: thanks to a series of additional aerodynamic optimisation measures, it has been possible to reduce its Cd value from 0.27 (standard model) to 0.26.
These measures:
partially covering the upper part of the radiator grille
aerodynamically shaped spring link coverings to improve the underbody airflow at the rear axle
lowering of the suspension by 15 mm
Diesel engines: three efficient power bands
The new basic engine in the OM 607 series develops 80 kW (109 hp), delivers 260 Nm to the crankshaft and with a manual transmission consumes 3.8 litres per 100 km, corresponding to 98 g of CO2/km. This is a 22-percent improvement over the only 60 kW (82 hp) preceding model, the A 160 CDI, which consumed 4.9 litres. The new top diesel, the A 220 CDI, is no less than 25 percent better than its predecessor: it develops an output of 125 kW (170 hp) and 350 Nm of torque, and in combination with the 7G-DCT automatic dual clutch transmission it consumes only 4.3 litres/100 km (provisional figure). The figures for the preceding A 200 CDI were 103 kW(140 hp), 5.7 litres, and 149 g of CO2/km.
Petrol engines: turbocharging and direct injection for all
A comparison between the new and previous A 200 demonstrates what has been achieved with the petrol engines: with 115 kW(156 hp) and 250 Nm of torque, the new engine delivers superior performance but consumes only 5.4 litres/100 km (127g CO2/km - figures for the 7G-DCT), which is 26 percent less than its predecessor (100 kW, 185 Nm, 7.4 l/100 km, 174 g CO2/km). Even the new top model with the 7G-DCT and producing 155 kW(211 hp) and 350 Nm is considerably more efficient with a consumption of 6.1 litres and CO2 emissions of 143 g.
The completely new engines and transmissions are not the only decisive factors in this exemplary efficiency. Thanks to the modular system it has been possible to select the optimally designed transmission for each diesel and petrol engine. The overall package is rounded off perfectly with progressive aerodynamics with a Cd figure of only 0.27, as well as a number of other improvements.
The 7G-DCT dual clutch transmission: Dynamic and efficient
Drawing on over 50 years of experience in the development and production of automatic transmissions, Mercedes-Benz ventured into new technical territory with the 7G-DCT dual clutch transmission: the new system is an automated three-shaft manual transmission consisting of two subtransmissions, each with its own clutch. Both actuation of the clutches and gear shifting take place fully automatically and without any interruption in tractive power. This allows a particularly comfortable but nevertheless dynamic mode of driving.
Thanks to its seven gears it offers an exceptionally large spread of up to 7.99. This means that a very short transmission ratio is available when moving off on an uphill slope with a high payload, for example, while during cruising the engine speed can be lowered considerably. The efficiency of this transmission leads to a nine percent improvement in fuel consumption compared to the CVT employed in the Mercedes-Benz A-Class to date, and betters the consumption with a manual transmission.
At a length of 367 millimetres and a weight of 86 kilograms, the 7G-DCT is more compact and lighter than the transmissions in this torque class which have been available on the market to date. The clutches take the form of oil-cooled multi-disc clutches. The specially developed hydraulic fluid is actively cooled, thus ensuring correct functioning of the transmission even under extreme conditions, despite the comparatively low filling level of six litres. Excess engine heat can also be transferred to the transmission, which improves its efficiency.
For the first time on this type of unit, the transmission is supplied with oil by two oil pumps - one mechanical and one electric. The electric pump maintains the oil pressure when the engine is switched off via the start/stop function. This means that the transmission is immediately operational when the engine is restarted and the vehicle can move off again without any delay. In addition, the electric pump is able to support the mechanical pump when peak loads apply, enabling a more compact and efficient design for the mechanical pump.
Another new feature is electric activation of the hydraulics for the parking lock, which is locked by mechanical means. This "park by wire" function enables the transmission selector lever to be positioned as desired: it is located in the form of a steering column lever on the right behind the steering wheel in the A-Class. In combination with the electric parking brake, additional space has thus been created in the centre console for additional stowage facilities.
