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Enthusiast Groups => B-Class => Topic started by: fasteddy on July 13, 2011, 08:44:03 AM
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A quantum leap in the compact class
Sensational: outstanding aerodynamics set a new benchmark
Efficient: drive system with new engines and dual clutch transmission
Safe: radar-based COLLISION PREVENTION ASSIST with adaptive Brake Assist
Spacious: flexible vehicle concept, also prepared for alternative drives
Substantially more agile and efficient, but as comfortable and spacious as ever – the new B-Class from Mercedes-Benz is a winner on all fronts. The vehicle's lower height and more upright seat position provide for a first impression that hints at the compact sports tourer's dynamic credentials.
With a new four-cylinder petrol engine featuring direct injection and turbocharging, a new diesel engine, a new dual clutch transmission, a new manual transmission and new assistance systems, the front-wheel drive car also rings in a new technological era for compact cars from Mercedes-Benz. "No model change in the history of Mercedes-Benz has ever seen so many new developments introduced in one fell swoop," stresses Dr. Thomas Weber, Member of the Board of Management responsible for Group Research and Head of Development, Mercedes-Benz Cars. "Future B-Class customers will benefit from this quantum leap in terms
of exemplary low fuel consumption and CO2 emissions combined with driving pleasure, plenty of space and the customary high standard of safety from
Mercedes-Benz."
The world premiere of the new B-Class (length/width/height: 4359/1786/ 1557 millimetres) will take place at the Frankfurt International Motor Show (13 to 25 September 2011). It will be making its way to European dealers in November 2011.
Outstanding aerodynamics: astounding cd value despite station wagon rear end
An outstanding drag coefficient of cd = 0.26 places the new B-Class at the forefront of its market segment. Apart from the aerodynamic exterior design, numerous optimisation measures on points of detail such as the air flow around the front wheels, the underbody design and the cooling air flow are also crucial contributory factors to this excellent aerodynamic performance. Patents are pending for innovative details such as the serrated wheel arch spoiler. With the optional ECO Technology package, which will be available at a later date, the B-Class even achieves the world-class aerodynamic credentials of the E-Class Coupé, attaining a drag coefficient of cd = 0.24 which is nothing short of sensational for a vehicle with a station wagon rear end.
New engines, new transmissions: designed for maximum efficiency
The new B-Class features new petrol and diesel engines as well as new manual and automatic transmissions. All transmissions and engines have been developed in-house, with production taking place at the plants in Stuttgart-Untertürkheim and -Hedelfingen, Rastatt/Baden, Gaggenau/Baden and Kölleda/Thuringia. The simultaneous development process enabled perfect coordination of engines and transmissions, e.g. with regard to implementation of the ECO start/stop function which features as standard on all B-Class models.
Common features of the new drive systems are the use of state-of-the-art technologies for maximum efficiency, very smooth running, high tractive power right from low revs, sustainability in terms of compliance with forthcoming emissions standards and low weight. For the purposes of transverse installation the engines, all of which are turbocharged, and the two transmissions are very compactly designed, providing the
B-Class with an exemplary small turning circle for a front-wheel drive vehicle of under eleven metres. The engine and transmission suspension disposes of a four-point mounting system comprising engine mount, transmission mount and two self-aligning supports. This suspension system has been designed specifically to meet the requirements of the high-torque engines with regard to minimum noise levels. The hydraulic damping integrated in the transmission mount is a key contributory factor to the exceptionally high ride comfort.
The new four-cylinder petrol engines (internal designation M270) mark the launch of a completely new engine series. The combustion process is based on the third-generation Mercedes-Benz direct injection system which was introduced last year with the BlueDIRECT V6 and V8 engines. Its use in the B-Class marks this technology's debut in the compact segment. The new four-cylinder engines have been designed for both transverse and longitudinal installation. In the new B-Class they are initially available with a displacement of 1.6 litres, as the B 180 rated at 90 kW (122 hp) and the B 200 with an output of 115 kW (156 hp). Their maximum torque of 200 and 250 Nm respectively is available from an engine speed of 1250 rpm.
The new four-cylinder diesel engine is a further development of the OM651 deployed in the C- to the S-Class, a common rail direct-injection engine of the third generation. With its displacement scaled down to 1.8 litres and numerous optimised points of detail, this is the first time that the compression-ignition engine has been mounted transversely in a Mercedes-Benz car. The B 180 CDI generates 80 kW (109 hp) of power, while the B 200 CDI has an output of 100 kW (136 hp). The maximum torque stands at 250 Nm from 1400 rpm for the 80 kW variant and 300 Nm from 1600 rpm for the 100 kW variant.
Another Mercedes-Benz premiere is the new 7G-DCT dual clutch transmission in the
B-Class. This transmission is extremely compact, extremely variable with regard to adaptation of the engine speed thanks to seven gears, incorporates an electric oil pump for start/stop capability, shifts gear without any interruptions in tractive power and combines the comfort of an automatic with the efficiency of a manual transmission.
The new 6-speed manual transmission designed along similarly compact lines as a three-shaft transmission is a close relative of the DCT. Extremely easy gear shifting, low shift forces, low internal friction and a low weight are among its most important characteristics.
Chassis and suspension: refined sportiness now for the sports tourer, too
"Fascinatingly agile" is the assessment of all test drivers who have put the new
B-Class through its paces to date. Three factors are instrumental to the substantially enhanced dynamic performance in comparison to its predecessor, which does not come at the cost of any compromises on comfort: the lowered centre of gravity, the new four-link rear axle and the upgraded ESP® Electronic Stability Programme. A sports suspension is optionally available for further enhanced agility. This suspension is lowered by 20 mm for an even lower centre of gravity and features sports dampers with amplitude-selective damping and a Direct-Steer system to emphasise the car's sporty character.
Steering: mechanical with electric assistance
The electromechanical steering of the B-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, thereby optimising the package as a whole. A Direct-Steer system is available in combination with the sports package. Locating the EPS system here results in a noticeably more direct steering ratio over the turning angle with the aid of the variable ratio. This enhances the vehicle's handling and agility substantially.
The electromechanical 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.
New assistance and braking system reduces the risk of rear-end collisions
As a world first in the compact segment, the B-Class features a radar-based collision warning system with adaptive Brake Assist as standard, which lowers the risk of rear-end collisions. The COLLISION PREVENTION ASSIST system gives a visual and acoustic warning to alert a possibly distracted driver to identified obstacles, and prepares Brake Assist for the most precise possible braking response. This is initiated as soon as the driver emphatically operates the brake pedal.
In contrast to other systems available on the market for the compact class, the new COLLISION PREVENTION ASSIST feature is not merely an urban driving system designed to minimise the effects of minor collisions. Rather, this innovative solution aims to provide protection against typical rear-end collisions in all dangerous driving situations at speeds of over 30 km/h. Mercedes-Benz expects the new safety system to have a significant, positive effect on accident statistics.
The democratisation of safety also encompasses an array of other assistance systems which have been adopted into the B-Class from the larger model series. These include:
Adaptive Headlamp Assist
Blind Spot Assist and Lane Keeping Assist
ATTENTION ASSIST (standard)
Speed Limit Assist (speed limit sign recognition)
Active Parking Assist
Brake HOLD function (standard with 7G-DCT)
Hill Hold function
Linguatronic
Reversing camera
DISTRONIC PLUS with BAS
PRE-SAFE® (featuring for the first time in this class of vehicle).
Driving simulator: performance capabilities unsurpassed in the car industry
Fine-tuning of the safety systems prior to deployment in real test-drive conditions took place in the new driving simulator at the company's Technology Centre in Sindelfingen. With its 360° screen, fast electric power system and the twelve metre-long rail for transverse or longitudinal movements, the dynamic driving simulator is the most powerful in the entire car industry. It went into operation at the end of 2010.
A dome measuring 7.5 metres in diameter is mounted on six individually extendable cylinders forming a so-called hexapod and on a linear motion system. A complete vehicle is installed in the dome. The inner surface of the dome serves as a projection panel on which road traffic situations are displayed true-to-life, with moving pedestrians, oncoming traffic and housing. The handling of any current or future Mercedes model can be simulated mathematically and the test driver experiences the calculated vehicle movements realistically and in real time by means of the motion system.
Plenty of space inside, prepared for alternative drives
The new vehicle concept underscores the dynamic aspirations of the new B-Class. The most striking aspect is the reduced height: at 1557 millimetres, the new model crouches almost five centimetres lower on the road than its predecessor. The seat height in relation to the road has also been reduced (minus 86 mm). In response to requests from many customers, the seat position is more upright, however. The headroom has nevertheless been further improved. With 1013 mm of headroom at the front (without sliding roof), the B-Class is among the most spacious cars in its segment in this discipline, too.
The B-Class is optionally available with the so-called EASY-VARIO-PLUS system. This enables simple reorganisation of the interior so as to enable the transportation of bulky items. Features of the EASY-VARIO-PLUS system include fore/aft adjustment of the rear seats by up to 140 millimetres and a front passenger seat whose backrest can be folded forward onto the seat cushion.
The new B-Class features an enhanced variant of the sandwich floor. The modular "Energy Space" concept means that it is already designed to accommodate versions with an alternative drive: appropriate interfaces in the body shell enable the main floor panel to be modified and a step to be produced for the versions with alternative drive. This multifunction well begins under the driver's seat and offers space for the alternative energy accumulators.
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The chassis and suspension: Refined sportiness for the sports tourer
Chassis and suspension: new four-link rear axle, sporty ESP® tuning
Steering: new electric power steering with assistance functions
Brakes: electric parking brake improves overall package
"Fascinatingly agile" is the assessment of all test drivers who have put the new
B-Class through its paces to date. Three factors are instrumental to the substantially enhanced dynamic performance in comparison to its predecessor, which does not come at the cost of any compromises on comfort: the lowered centre of gravity, the new four-link rear axle and the upgraded ESP® Electronic Stability Programme.
On the four-link rear axle, the arising 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 consist of aluminium, in order to reduce the unsprung masses.
Mercedes-Benz is deploying the latest ESP® generation in the B-Class for the first time. Torque Vectoring Brake helps to counter the tendency towards oversteering during fast cornering. Specific steering impulses assist the driver. The engineers' overall aim has been to provide gentle intervention by the ESP® system which will afford the B-Class's occupants protection whenever possible, without detracting from the pleasures of driving: experienced motorists can drive very speedily, while less experienced drivers with a less well-rounded driving style will be reminded of the physical limits involved in driving whenever possible.
Steering: mechanical with electric assistance
The electromechanical steering of the B-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, thereby optimising the package as a whole. 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 sports package. Locating the EPS system here results in a noticeably more direct steering ratio over the turning angle with the aid of the variable ratio. This enhances the vehicle's handling and agility substantially. The electric power steering also enables various steering assistance functions which are activated by the ESP® control unit. These include:
Counter-impulse 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 a turning circle of under eleven metres in diameter, the B-Class is particularly agile.
On all engine variants, the B-Class comes with disc brakes on all wheels. The callipers on the rear axle and the brake boosters are made of aluminium. For the first time in the compact class, the HOLD function which is familiar from the larger model series has been adopted into the B-Class: when stopping, for example at traffic lights, the driver merely has to press the brake pedal slightly more firmly. They can then take their foot off the brake pedal and the brake will remain engaged until they move 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.
Mercedes-Benz is equipping the B-Class for the first time 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 4 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 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.
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Aerodynamics: Taking the drag out of aerodynamics
New benchmark for cars with station wagon rear end: cd = 0.26
An outstanding drag coefficient of cd = 0.26 places the new B-Class at the forefront of its market segment. With the optional ECO Technology package, which will be available at a later date, the five-door B-Class even achieves the world-class aerodynamic credentials of the E-Class Coupé, attaining a drag coefficient of cd = 0.24 which is nothing short of sensational for a vehicle with a station wagon rear end. In practical driving, aerodynamics have a crucial influence on fuel consumption: an improvement in the cd value of just 0.01 results in fuel savings of up to 0.4 litres per 100 kilometres at a speed of 130 km/h.
"A whole range of measures were necessary in order to attain the excellent drag coefficient of cd = 0.26," explains Dr. Teddy Woll, Head of Aerodynamics at Daimler AG. "Apart from an aerodynamically efficient basic design, these include numerous optimisation measures on points of detail, such as the air flow around the front wheels, the underbody design and the flow of cooling air."
Designers and aerodynamicists worked closely together. Aerodynamically efficient lines are demonstrated by the exterior mirrors with braces, for example. The low height of the shoulder on the A-pillar accompanied by optimised A-pillar geometry also contributes to the good aerodynamics. The entire front apron is sealed, including special seals fitted on the headlamps, for example. The large roof spoiler at the rear provides for defined flow separation.
Flow losses at the front wheel arches have been reduced substantially with the aid of innovative serrated wheel spoilers at front and rear - patent pending -, slots in the wheel arches and optimised hub caps. These measures result in improved wind flow around the wheel arches.
Equally comprehensive measures have been undertaken to design the underbody along aerodynamic lines. 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 improved cooling air flow by means of an adjustable radiator shutter which is familiar from other Mercedes models now features on the basic petrol-engine model in the B-Class. This feature enables infinite adjustment of the air flow through the engine's cooling module and the engine compartment by means of a circular louvred shutter installed in parallel with the fan. When there is no special need for cooling air, the shutter is closed. This improves the aerodynamics and reduces fuel consumption.
The ECO Technology package, which will be optionally available for all versions of the B-Class, incorporates additional optimisation measures designed to further reduce drag. These include lowering of the body, the sealing of joints at the rear window and the cladding of chassis components at the rear axle.
The aerodynamics of the new B-Class were optimised at an early stage in the development process by means of complex computer calculations and flow simulations. Over 275,000 CPU hours were required for the purposes of digital flow simulation. Models and prototypes spent around 1100 hours in the wind tunnel for measurement purposes.
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The drive: High tech under the bonnet
New petrol engine series M270: displacement of 1.6 and 2.0 litres
New diesel engine OM651/D18: maximum efficiency
New 7G-DCT dual clutch transmission: a new quality of automatic gear shifting
New manual transmission F-SG 310: 6 gears in compact design
ECO start/stop function: standard on all models
A model change that takes place under the bonnet, too: the new B-Class features new petrol and diesel engines as well as new manual and automatic transmissions. All transmissions and engines have been developed in-house, with production taking place at the plants in Stuttgart-Untertürkheim, Stuttgart-Hedelfingen, Rastatt/Baden, Gaggenau/Baden and Kölleda/Thuringia. The simultaneous development process enabled perfect coordination of engines and transmissions, e.g. with regard to implementation of the ECO start/stop function which features as standard on all B-Class models.
Common features of the new drive systems are the use of state-of-the-art technologies for maximum efficiency, very smooth running, high tractive power right from low revs, sustainability in terms of impending emissions standards and low weight. For the purposes of transverse installation the engines, all of which are turbocharged, and the two transmissions are very compactly designed, providing the B-Class with an exemplary small turning circle for a front-wheel drive vehicle of under eleven metres. The engine and transmission suspension disposes of a four-point mounting system comprising engine mount, transmission mount and two self-aligning supports. This suspension system has been designed specifically to meet the requirements of the high-torque engines with regard to minimum noise levels. The hydraulic damping integrated in the transmission mount is a key contributory factor to the exceptionally high ride comfort.
The new four-cylinder petrol engines (internal designation M270) mark the launch of a completely new engine series. The combustion process is based on the third-generation Mercedes-Benz direct injection system which was introduced last year with the BlueDIRECT V6 and V8 engines. Its use in the B-Class marks this technology's debut in the compact segment. The new four-cylinder engines have been designed for both transverse and longitudinal installation. In the new B-Class they are initially available with a displacement of 1.6 litres, as the B 180 rated at 90 kW (122 hp) and the B 200 with an output of 115 kW (156 hp). Their maximum torque of 200 and 250 Nm respectively is available from an engine speed of 1250 rpm.
The new four-cylinder diesel engine is a further development of the OM651 deployed in the C- to the S-Class, a common rail direct-injection engine of the third generation. With its displacement scaled down to 1.8 litres and numerous optimised points of detail, this is the first time that the compression-ignition engine has been mounted transversely in a Mercedes-Benz car. The B 180 CDI generates 80 kW (109 hp) of power, while the B 200 CDI has an output of 100 kW (136 hp). The maximum torque stands at 250 Nm from 1400 rpm for the 80 kW variant and 300 Nm from 1600 rpm for the 100 kW variant.
Another Mercedes-Benz premiere is the new 7G-DCT dual clutch transmission in the B-Class. This transmission is extremely compact, extremely variable with regard to adaptation of the engine speed thanks to seven gears, features an electric oil pump for start/stop capability, shifts gear without any interruptions in tractive power and combines the comfort of an automatic with the efficiency of a manual transmission.
The new 6-speed manual transmission designed along similarly compact lines as a three-shaft transmission is a close relative of the DCT. Extremely easy gear shifting, low shift forces, low internal friction and a low weight are among its most important characteristics.
The new petrol engines: high tech in the compact class
Direct injection with fast-acting piezo injectors for multiple injection, controlled oil pump, switchable water pump, high compression (10.3:1) despite turbocharging, fast and convenient start/stop system – the technical details of the new generation of four-cylinder petrol engines read like a catalogue illustrating the fine art of high tech engine construction.
With regard to the combustion process, the new all-aluminium engines with two overhead, chain-driven camshafts are closely related to the BlueDIRECT V-engines which were originally introduced in the S-Class in mid-2010 and have since been setting new benchmarks worldwide in terms of performance and fuel consumption under everyday conditions in the luxury and top-range models from Mercedes-Benz. Direct petrol injection with spray-guided combustion, which Mercedes-Benz was the first car manufacturer to introduce in series production, has been developed further by the engineers into third-generation direct petrol injection with spray-guided combustion. The system pressure is up to 200 bar and is variably optimised according to the engine's characteristic map. Completely newly developed piezo-electric injectors allow up to five injections per power stroke for the best possible mixture formation, while multi-spark ignition helps to ensure reliable combustion of the mixture.
The end result is excellent fuel efficiency combined with minimal emissions and agile response. The new four-cylinder engine in the B-Class supplies its maximum torque right from an engine speed of 1250 rpm, for example, maintaining this maximum level up to 4000 rpm. In conjunction with the new 7G-DCT transmission, whose control system communicates with the engine control unit, the new four-cylinder engine responds highly spontaneously to movements of the accelerator pedal, while during cruising higher gearing can be selected, thereby further reducing fuel consumption and noise.
The turbo engines also retain their exemplary fuel efficiency at high load levels, as the mixture does not require enriching to cool the cylinder head up to a speed of 200 km/h (full-load enrichment). A two-piece water jacket with optimum cross-flow cooling and fine cooling ducts measuring only three millimetres between spark plugs and injectors convey the cooling fluid to the critical points. A new thermal management system has also been developed: in cold state, a switchable water pump with flow-optimised ball valve ensures that no coolant flows through the engine, providing for swift heating-up of the combustion chambers after starting up the engine. The thermostat is electronically controlled and the coolant temperatures are adjusted according to driving style and ambient conditions. The thermostat itself is also a flow-optimised ball valve. In the interest of high efficiency, the volumetric flow of the oil pump is also controlled, as in the V-engines.
The new four-cylinder generation features cylinder spacing of 90 millimetres and is highly compact in design, thanks to the expedient arrangement of the power take-off units. The variant to be unveiled at the premiere with a displacement of 1.6 litres features a short stroke of 73.7 mm with a bore of 83.0 mm. The hollow crankshaft is a further factor contributing to the low weight of 137 kg.
The new diesel engines: direct-injection models with displacement of
1.8 litres
Since its world premiere in 2008 the direct-injection diesel engine known as the OM651 has been setting standards in terms of performance and torque characteristics, economy, emissions and smooth running. It is in more widespread use than any other Mercedes-Benz diesel engine and serves as a model of efficiency and power right up to the S-Class.
A new variant with a displacement of 1.8 litres is now being introduced into the compact car segment for the first time on board the B-Class. The belt drive for the power take-off units, the turbocharger mounting position and the air ducting have been modified for the purposes of transverse mounting. With a cylinder spacing of 94 millimetres and camshafts driven via spur gears, transverse mounting and the appurtenant short design formed part of the specification for the engine from the outset.
The displacement was reduced by shortening the stroke (83 mm instead of 99 mm). The markedly longer connecting rods provide for lower lateral forces, thereby reducing friction loss. The bearings of the two Lanchester balancer shafts have also been optimised for reduced friction. The efficiency of the new, single-stage turbocharger has been optimised. It possesses adjustable guide blades. Combining the engine control unit with the control system of the 7G-DCT involved a great deal of coordination work. Similarly to its big brothers in their latest version, the engine incorporates vibration isolation between belt drive and crankshaft to enable implementation of the start/stop function. Other common features are:
Common rail technology with a rail pressure increased to 1800 bar.
The maximum ignition pressure of 180 bar also contributes to the high power output.
The oil injection nozzles and the water pump are activated only when required, in order to save energy and fuel. The controlled oil pump additionally reduces oil flow and thus fuel consumption.
The engine block is made of cast iron, the cylinder head of aluminium.
A two-piece water jacket in the cylinder head provides for optimum cooling in the area of the combustion chamber plate. This enables high ignition pressures and a high specific power output.
The cast iron barrels have undergone considerably finer honing than on the predecessor, also contributing to the reduction in fuel consumption.
To compensate for the second-order forces which are inherent to four-cylinder in-line engines there are two Lanchester balancer shafts at the bottom of the engine block running in low-friction roller bearings rather than conventional plain bearings.
The two-mass flywheel has been specifically designed for high engine torque at low engine speeds in order to isolate the crankshaft's vibration stimuli, thereby contributing to the engine's excellent smooth running.
The 7G-DCT dual clutch transmission: convenient and efficient
Drawing on over 50 years of experience in the development and production of automatic transmissions, Mercedes-Benz is venturing 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 enables 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. This transmission is nine percent more efficient than the CVT employed in the B-Class to date and attains the efficiency of a manual transmission for the first time.
At a length of 367 millimetres and a weight of 86 kilograms, the 7G-DCT is more compact and lighter than the transmissions which have been available on the market to date. The clutches take the form of "wet" multi-disc clutches running in an oil bath. 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.
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 electrical 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 B-Class. In combination with the electric parking brake, additional space has thus been created in the centre console for additional stowage facilities.
Three gearshift programmes are available to the driver:
ECONOMY: In this mode, the transmission performs gear shifting fully automatically and particularly conveniently. The gears are selected with due regard to a particularly economical style of driving at low revs.
SPORT: The transmission performs gear shifting fully automatically in this mode, too. The shift and response times are shorter, however.
MANUAL: In this mode, the driver operates the transmission manually via shift paddles behind the steering wheel (standard with 7G-DCT). Shift and response times are shorter still.
In ECO or Sport mode, the driver is still able to intervene manually in the gear-shifting process via the shift paddles. The transmission reverts to the selected automatic mode after the paddles have remained inactive for ten seconds, or after a longer delay when driving downhill or on winding roads.
A key factor contributing to the overall efficiency of the B-Class is the closely coordinated operation of the transmissions and engines. A continuous exchange of data between the control units ensures that the engines run at the ideal operating point at all times. The 7G-DCT is manufactured at Daimler's Stuttgart-Hedelfingen plant.
The six-speed manual transmission: convenient manual gear-shifting
The new six-speed manual transmission has been developed alongside the 7G-DCT. The two transmissions share a large number of components and are both produced in Stuttgart-Hedelfingen. This three-shaft transmission is also very compact (length 345 mm) and light (dry weight 46 kg) and incorporates a number of special features for particularly pleasant gear shifting. An integrated magnet on the gearshift shaft is detected by a Hall sensor. The idle position is identified in this way, enabling the start/stop function. The signal for reverse gear activates the reversing lights.
The large spread of 6.7 allows a reduction in engine speed while at the same time ensuring that sufficient tractive power is available when moving off with a fully laden B-Class and trailer up to a gross weight of 3.4 tonnes. The clutch is operated hydraulically and the gears are actuated via cables.
The overhead camshaft with third and fourth gears and the reverse gear do not run in the oil bath. This reduces drag torque, thus facilitating gear shifting at low temperatures in particular. The three-cone synchronisation of the first two gears serves the same purpose, while the following gears are provided with two-cone synchronisation. The weight-optimised cast aluminium shift forks are installed on anti-friction bearings on the shift rods, in order to reduce the shift forces.
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Radar-based collision warning system: A new milestone in safety technology
Detailed analysis by Mercedes-Benz's in-house accident research department indicates that almost half of all rear-end collisions could be avoided or the severity of such accidents reduced with the aid of radar-based safety systems such as COLLISION PREVENTION ASSIST and adaptive Brake Assist. This analysis drew on the experience acquired with the Mercedes innovations DISTRONIC PLUS and BAS PLUS. The company is now claiming the role of innovation leader in the compact segment, too, and will be introducing a radar-based collision warning system with adaptive Brake Assist in the new B-Class in the course of this year. In contrast to systems currently on the market in this class, the new Brake Assist feature is not merely a system intended to minimise minor damage in urban traffic. Rather, this innovative solution is aimed at protecting motorists from typical rear-end collisions in all traffic situations.
New Brake Assist system: world premiere in the compact class
This year will witness the next milestone in the democratisation of automotive safety technology: the new B-Class from Mercedes-Benz will be the first car worldwide in the compact segment to offer radar-based collision warning with adaptive Brake Assist as standard. The company expects the introduction of this technology to have a significant positive effect on accident statistics.
This expectation is backed up by test results: during tests with 110 car drivers in the driving simulator, the accident rate in three typical situations fell from 44 to eleven percent thanks to a combination of COLLISION PREVENTION ASSIST and adaptive Brake Assist.
The new assistance system fits the bill perfectly here: it gives a visual and acoustic warning to alert a possibly distracted driver and prepares Brake Assist for the most precise possible braking response. This is initiated as soon as the driver emphatically operates the brake pedal.
Key functions of the coming generation
Radar-based COLLISION PREVENTION ASSIST with adaptive Brake Assist
recognises an inadequate distance from a vehicle ahead in the speed range between 30 and 250 km/h,
recognises when the gap is decreasing. In case of an imminent danger of collision, the driver is provided with a visual and acoustic warning,
is able to recognise stationary objects ahead of the vehicle and output corresponding warnings,
recognises specific driving situations such as bumper-to-bumper traffic and adapts the activation threshold for the warning and adaptive Brake Assist accordingly,
calculates the precise braking force ideally needed to avoid an accident when a danger of a collision is detected and makes best possible use of any distance remaining. This means that the driver behind also has better chances of preventing a rear-end collision.
The brake pressure is adjusted if the situation changes – if the vehicle ahead accelerates, it is decreased to the level the driver requires; if the distance to moving and stopping vehicles decreases, the brake pressure is increased further.
Preventive safety systems (PRE-SAFE®) can be activated as necessary (e.g. belt tensioners).
The new system meets the key "Forward Collision Warning" requirements of the NHTSA, the American road and vehicle safety authority.
In Germany rear-end collisions are still responsible for 22 percent of accidents involving injury or fatalities, and in the USA the figure is as high as 31 percent. Mercedes-Benz has been working on methods to prevent such accidents for many decades now. Milestones of the company's safety developments include ABS (1978), Brake Assist BAS (1996), DISTRONIC proximity control (1998) and the further development stage DISTRONIC PLUS with BAS PLUS (2005). These new systems were always premiered in the luxury class models, but in the interests of traffic safety it has always been a principle of Mercedes-Benz to make innovative technology available on a broad basis as rapidly as possible – also outside its own model range. As a result ABS and BAS, and incidentally also the Mercedes development ESP®, are nowadays standard equipment in practically all automobiles.
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The new driving simulator: Fast response and a photorealistic environment
With its 360° screen, fast electric power system and the twelve metre-long rail for transverse or longitudinal movements, the new dynamic driving simulator from Mercedes-Benz is the most powerful in the entire car industry. It went into operation at the end of 2010.
"With the new simulator, we are able to reproduce highly dynamic driving manoeuvres such as lane-changing even more realistically and to research the behaviour of the driver and the vehicle in road traffic in even greater depth," explains Dr. Thomas Weber, Member of the Board of Management responsible for Group Research and Head of Development, Mercedes-Benz Cars. The system is not intended to replace real test drives entirely. The simulator will enable systems and components for future Mercedes models to be tested throughout all development phases, however. The new Mercedes B‑Class was one of the first models to receive its final fine-tuning in the new driving simulator prior to the real test drives.
The driving simulator is additionally used to conduct tests with test subjects. During these, normal car drivers are able to approach the physical limits with no danger, providing the Mercedes engineers with findings concerning the acceptance and operation of new safety systems, such as radar-based COLLISION PREVENTION ASSIST with adaptive Brake Assist in the new B-Class.
How the simulator works
The simulator cell is a hexapod mounted on six moveable supports. Inside there is a complete Mercedes model in which the test driver is seated, as well as the 360° projection screen showing a realistic image of the traffic scenario, with moving pedestrians, oncoming traffic and houses.
The vehicle controls are linked to the computerised control system of the driving simulator by data lines. When the test driver turns the steering wheel, accelerates or operates the brakes, these reactions are registered by the computer control system and have the same effects as in real traffic situations. The scenery on the screen changes constantly, and the moving cell simulates the vehicle's attitude on the road, for example front-end dive when braking or body roll during fast cornering. The computer calculates the driving behaviour of the car more than 1000 times per second, issuing the relevant commands to the electrics. It is able to move the cell transversely by up to twelve metres at a maximum speed of ten metres per second (36 km/h), so that double lane-changes can also be simulated, for example.
Equally high-tech: part of the energy required to operate the simulator is obtained by means of energy recuperation during braking and fed into the power network of the Sindelfingen plant.
Mercedes-Benz has been playing a pioneering role in the use of simulators for a long time. The first driving simulator, an in-house development, was commissioned at the Daimler-Benz research centre in Berlin-Marienfelde over 25 years ago.