Mercedes W176 A-Class 2012 –
The model range
‘A’ is for all-inclusive
With air conditioning, Audio 5 USB, electric windows all round, Headlamp Assist, 12-button multifunction steering wheel and the comprehensive safety package including COLLISION PREVENTION ASSIST, the A-Class is already fully equipped even in its base configuration.
With “Urban”, “Style” and “AMG Sport” appointment lines, three Design packages as well as further optional extras, the model can be customised to suit every individual taste.
Available appointments, many familiar from higher vehicle classes, also include the Intelligent Light System, electrically adjustable front seats with memory function or dashboard finished in ARTICO man-made leather.
Further sporty details designed to appeal to the vehicle’s young target group include designo seat belts in red or the sporty instrument cluster featuring a “chequered flag” design.
All three design and equipment lines can basically be combined with all engine variants. The “Style” line has a radiator grille with two slats in the vehicle colour and chrome inserts, and the waistline trim strip is finished in a chrome look.
The stylish appearance is enhanced further with light-alloy wheels featuring a 10-spoke design and measuring either 16 inches (all models except for the A 250 BlueEFFICIENCY) or 17 inches (A 250 BlueEFFICIENCY).
Highlights in the interior include matrix-look trim elements as well as front sports seats in ARTICO man-made leather/Messancy fabric with contrasting stitching.
Contrasting stitching is also to be found on the armrests on the centre console and the doors.
The gear lever has a silver chrome surround. The ring around the headlamp switch and the nozzle crosses on the air vents in the dashboard are also finished in silver chrome.
Practical details of the “Style” line include the Seat Comfort package (with height adjustment for the front passenger seat and seat cushion angle adjustment for driver and front passenger), multifunction holder in the centre console and 12 V socket in the rear.
A particular feature of the “Urban” line is the sporty instrument cluster with silver-coloured circular instruments, “chequered flag” design and red dial pointers.
This is matched by the checked pattern of the trim elements. The dynamic impression continues with the sports seats with upholstery in ARTICO man-made leather/Larochette fabric.
Contrasting stitching is used on the seats, armrests, multifunction steering wheel and the gear lever in nappa leather. The 3-spoke steering wheel also has a perforated grip area.
The Seat Comfort package, multifunction holder in the centre console and 12 V socket in the rear again come as standard, as does the chrome finish on the headlamp switch and nozzle crosses.
Distinctive characteristics of the exterior include the twin-pipe exhaust system with oval tailpipe trim in polished stainless steel and the radiator grille with silver-coloured twin slats with chrome highlights.
The “Urban” line also features a chrome-look waistline trim strip and 17-inch 5-twin-spoke light-alloy wheels.
“AMG Sport” is the name of the third equipment line, which again is available for all engine variants.
This is the line in which the colour red comes into play: it features in the contrasting stitching on the sports seats (with upholstery in ARTICO man-made leather/DINAMICA microfibre), the nappa leather multifunction steering wheel with flattened bottom section, and the armrests.
This is matched with the sporty instrument cluster with silver-coloured circular instruments, “chequered flag” design and red dial pointers as well as sports pedals in brushed stainless steel with rubber studs.
Trim elements feature a chrome-look finish, and the front and rear door sill panels are made of aluminium.
The sporty theme is continued with the exterior: as standard the “AMG Sport” model boasts a twin-pipe exhaust system with oval tailpipe trim in polished stainless steel, silver-painted radiator grille with chrome inserts, 18-inch AMG multi-spoke light-alloy wheels and AMG bodystyling (front and rear aprons and side sill panels).
Those opting for the “AMG Sport” model will also get an A-Class with a sports suspension, lowered body and Direct-Steer system. The front brake discs are also perforated.
Even more dynamic: the A 250 Sport
In the case of the A 250 Sport, the “AMG Sport” appointment line is available as standard. The visual affinity to the Concept A-CLASS is especially evident with these models – particularly due to the new diamond grille.
The A-Class Sport features exclusive 18-inch AMG light-alloy wheels in a 5-spoke design with 235/40 R 18 tyres all round and painted in high-gloss black with a high-sheen finish, together with red-painted brake callipers.
These give an indication of the vehicle’s particularly dynamic driving qualities which are characterised, amongst other features, by a special AMG-developed front axle and a suspension that has been configured to match.
With its special engine and transmission configuration, the A 250 Sport also provides a very special driving experience which is enhanced further by the emotionally appealing sound of the modified exhaust system.
Hints of red on the AMG front and rear aprons also serve to emphasise the expressive positioning of the new model. In conjunction with Intelligent Light System or bi-xenon lights, the headlamps also have red highlight rings.
The contrast between black trim and additional accents in red continues in the interior: the contrasting decorative topstitching on the steering wheel and seats is in this same bright shade, as are the seat belts.
The highlight rings of the air vents are similarly finished in red.
Even more choice: the three Design packages
Further individualisation options are possible with the three Design packages which are available for all engine variants.
The “Night package” builds on the scope of equipment making up the Style, Urban, and AMG Sport lines as well as the Sport model and supplements them further with a variety of different, additional appointments.
The exterior highlights include:
- gloss black radiator grille with chrome inserts (except the A 250 Sport)
- black-painted exterior mirrors (not in conjunction with magno and black metallic paint finishes as in those cases they are in the vehicle colour)
- beltline trim strip in high-gloss black
- heat-insulating dark-tinted glass as of B-pillar
- 18-inch 5-twin-spoke light-alloy wheels painted in matt black and with a high-sheen finish (in conjunction with AMG Sport: AMG 5-twin-spoke light-alloy wheels)
The Exclusive package, which can be chosen in addition to one of three equipment lines, does full justice to its name, featuring a high-quality interpretation of the compact class with leather sports seats, dashboard and door centre panels in ARTICO man-made leather with contrasting stitching, and also trim elements in the appointments colour.
The scope of equipment includes a 3-spoke leather steering wheel with 12 function buttons, as well as an infrared receiver in the driver’s door (summer opening/closing function), electric 4-way lumbar support on the front seats and heated seats.
The “AMG Exclusive package“, which is only available in conjunction with the “AMG Sport” equipment line and cannot be combined with the Exclusive package, comprises the following details:
- heated front sports seats with black RED CUT leather upholstery with red contrasting stitching as well as 4-way lumbar support
- dashboard in ARTICO man-made leather with red contrasting (upper part) and high-gloss headlamp switch with silver-chrome surround ring and air vents with silver-chrome surrounds and crosses
- cover over the stowage compartment in the centre console
- infrared receiver in the driver’s door (summer opening/closing function)
From ‘A’ for accessories to ‘X’ for xenon: additional optional extras
The A-Class is optionally available with bi-xenon lights instead of halogen lights. The latter are furthermore optionally combinable with the Intelligent Light System (ILS). ILS, which is familiar from other Mercedes model lines, comprises bi-xenon headlamps with variable light distribution and dynamic headlamp range for country roads, motorways and dense fog, Adaptive Highbeam Assist, active light function, LED daytime driving lights and headlamp cleaning system.
The Light and Sight package comprises the following details:
- indirect illumination of front and rear door handles/door openers
- front and rear footwell illumination
- illuminated vanity mirrors for driver and front passenger
- illuminated interior mirror
- illuminated stowage compartment in the centre console
- reading lights and console light in the roof lining in the rear
- illuminated door sill panels
- illuminated openings in the front and rear head restraints (sports seats only)
- courtesy and warning lights for driver and front passenger
- warning and ambient lighting in the boot lid
- windscreen wipers with rain sensor
A reversing camera is optionally available starting with the Audio 20 CD. This is activated automatically when reverse gear is engaged.
It supports the driver during lengthways and crossways parking manoeuvres by means of static and dynamic guide lines indicating the vehicle’s line of travel and clearances.
Active Parking Assist offers even greater comfort here (see section “Driving assistance systems”).
Internet access, the convenient LINGUATRONIC voice control system, two navigation solutions tailored to different budgets, connection for mobile audio devices, iPhone® integration and an intuitive operating concept – the A-Class offers information and communication systems with a superior level of functionality which to date has been the reserve of higher vehicle classes. For details see the section on “Multimedia systems”.
Fitted as standard to each A-Class is the THERMATIC manual air conditioning system. Just like the THERMOTRONIC two-zone automatic air conditioning system (optional extra), it has been enhanced in a number of areas.
The air conditioning systems now feature noticeably quieter and vibration-free operation, since the blower motor has been mechanically isolated from the housing using special rubber elements.
Furthermore, the equipment features optimised air intake in snow and more manual blower settings. An important development goal was also the efficient handling of the drive energy.
The air conditioning compressor is operated based on actual requirements, and in dry weather or at temperatures at which no cooling is necessary, the compressor is automatically and steplessly throttled back.
Other optional extras include front seats with memory function, automatic dimming interior and exterior mirrors, designo seat belts in red (expected to be available from the fourth quarter of 2012) for driver and front passenger and rear outer seats, electrically operated panoramic sliding sunroof, auxiliary heating, folding trailer coupling and a Stowage Space package.
The latter comprises a spectacles compartment in the overhead control panel, stowage boxes beneath the front seats, nets beneath the parcel shelf, in the front passenger footwell, on the front seat backrests and on the left and right of the luggage compartment, as well as a 12 V socket in the luggage compartment.
Under the microscope: CAMTRONIC valve lift adjustment
Using the camshaft to accelerate
Mercedes-Benz is the first automobile manufacturer to equip the 1.6-litre version of the M 270 engine with CAMTRONIC intake valve lift adjustment.
The system operates mechanically, but is served by an electronically controlled actuator. The intake camshaft is made up of several components: two hollow-drilled sub-shafts of equal size are mounted on the carrier shaft.
Mercedes-Benz engineers refer to these as “cam-pieces”, of which the first controls the intake valves of cylinders 1 and 2, and the second those of cylinders 3 and 4.
The cams themselves are masterpieces of the caster’s art: they take the form of a double-cam with two curved surfaces. The surface operating the valves via roller-type rocker arms is only half as wide as on a conventional cam, therefore the space requirement is the same.
When the steeper half of the cam is active, the valve lift is increased and the valves remain open for longer. Switching to the flatter half of the cam shortens the valve lift and the valves close sooner.
“Accelerating” with the camshaft
Load control with the smaller valve lift is realised using various components. At very low engine torque the load control is conventional, using the position of the throttle flap, at medium torque levels using the position of the intake camshaft and at high torque levels using the charging level of the turbocharger.
As the torque increases the valve lift is switched to the larger level, load control once again being conventional via the throttle flap or, in the charged operating range, via the charging level of the turbocharger.
In popular terms one might also say that the new Mercedes-Benz A-Class also accelerates with its camshaft.
Mercedes-Benz development engineers took numerous measures to ensure the most efficient combustion even with the smaller valve lift. Owing to the smaller valve lift and early intake valve closure, the turbulence in the combustion chamber is reduced at the spark plug.
This turbulence decisively influences the combustion speed and full combustion of the fuel/air mixture.
To compensate this apparent disadvantage, the turbulence is increased in the lower partial load range by using a multiple injection strategy with injection ignition, while multi-spark ignition ensures reliable combustion.
The switchover from the smaller to the larger valve lift goes unnoticed by the driver. As cylinders 1 and 2 as well as 3 and 4 are coupled in pairs with one cam-piece each, it is possible to adjust the valve lift of all four cylinders within one camshaft revolution using just one double actuator.
A correspondingly large effort was required to develop the synchronisation for the switching process and ensure the long-term durability of the components.
The variable, hydraulic vane-type camshaft adjusters on the intake and exhaust sides have a wide adjustment range of 40 degrees with reference to the crankshaft.
This new development excels by virtue of its significantly smaller dimensions. The installation space along the engine’s longitudinal and vertical axes can therefore be made very compact.
Under the microscope: engine test benches
Trial by ordeal
Before the new engines were allowed onto the roads for practical endurance trials, they had already absolved a series of tortures on the engine test benches of the test facility in Untertürkheim.
24 of the very latest engine test benches are installed on each floor of this imposing three-storey building. These 72 test benches are in operation by day and night, on 365 days of the year.
The test-benches can be used to simulate a wide variety of road and load cycle situations to reflect every conceivable operating profiles, e.g. hot and cold-starting, stop-and-go traffic and long-distance operation under a wide variety of conditions.
Even steep mountain gradients can be simulated in the laboratory: a pivoting test rig is e.g. used to tilt the engine by up to 40 degrees to examine the effects on the oil circuit.
At various development stages the engines are subjected to accelerated stress tests. “This simulates stresses that no customer can achieve,” says Thomas Uhr, who is responsible for the workshops at the Mercedes-Benz development centre and for powertrain testing.
The test-bench programmes have a duration of 500 to 2400 hours, with large proportions under full load and partial load.
Thermal characteristics and component durability are tested under full load conditions, however particularly low loads can also be a real torture for an engine in the form of e.g. engine oil sludging.
Other tests include heavy stresses such as cooling the coolant from 110° C to approx. 25° C within a max. of 60 seconds, and running the engine up to its rated speed under full load when the coolant is cold. Thomas Uhr: “We test our engines more intensively than any other manufacturer.”
The new OM 607 diesel engine absolved more than 25,000 hours on the test-benches, for example, before it received approval for use in the A-Class.
The energy generated by the test engines is recovered as fully as possible. The engine testing facility in Untertürkheim is certificated as a combined heating and power plant: only active equipment is used to monitor and measure engine power.
This power is not used to propel a vehicle as in normal use, but rather converted into electrical energy and fed into the plant’s power network.
In addition to long-term durability, fuel consumption, emissions and driveability in conjunction with the transmission are the major development goals.
This requires enormously painstaking dynamometer tests followed by practical trials on the roads.