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Mercedes-Benz M-Class

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The new Mercedes-Benz M-Class will have 25 per cent better fuel economy, with the ML 250 BlueTEC 4MATIC averaging 47.0 mpg, or 158 g/km CO2.

It looks like Mercedes has made a huge effort to improve efficiency in the new M-Class, due next year. The company says that state-of-the-art engines, a policy of engine downsizing, a best-in-class Cd value of 0.32 and a comprehensive range of BlueEFFICIENCY measures all contribute to delivering improved energy efficiency.

The third-generation M-Class has BlueTEC diesel engines and the new generation of BlueDIRECT petrol engines. Diesel models are now only available as BlueTEC units with SCR emissions technology.

In the ML 250 BlueTEC, the 3.0-litre V6 of the previous model is replaced by the four-cylinder EU6-standard unit which also appears in the S-Class. With an NEDC consumption of 47.0 mpg, the ML 250 BlueTEC 4MATIC with its standard 70-litre tank can cover around 720 miles before needing to stop for fuel. If the vehicle is fitted with the optional 93-litre tank, a distance of up to 930 miles is possible between refuelling stops.

The ML 350 BlueTEC uses a completely reworked 3.0-litre V6 engine, which also more than meets the EU6 emissions standard and delivers far better performance, yet with considerably reduced fuel consumption. The efficiency improvements have been achieved through the use of the TWAS (twin-wire-arc spraying) cylinder wall coating technology already used since 2005 in AMG’s high-performance engines; the process reduces internal friction in the engine significantly.

The weight of the engine has also been reduced by 4.3 kg, as there is no longer any need for the cast iron cylinder liners that previously had to be pressed into the engine block. Mercedes claims that these measures alone could reduce fuel consumption by around three percent.

The cars come with a package of BlueEFFICIENCY measures; in addition to the ECO start/stop function that comes as standard, there is a new seven-speed 7G-TRONIC PLUS automatic transmission with a new fuel-economy converter, friction-optimised bearings and a transmission oil thermal management system. Low-friction axle drives, electric steering and tyres with low rolling resistance also play their part in reducing fuel consumption.

The optimised belt drive system with decoupler, together with on-demand control of all ancillary components and pumps, also helps to reduce the energy requirements of the new M-Class. The oil and water pumps in the engine, as well as the fuel pump, are only activated according to actual need. The same control logic is used in the THERMATIC and THERMOTRONIC air conditioning systems. In these, the coolant compressor only runs when necessary.

A key factor in the diesel engines is also the optimisation that has been undertaken of the flow and counterpressure in the exhaust system with its SCR (Selective Catalytic Reduction) emission control technology.

The use of lightweight construction techniques has enabled the weight of the M-Class to be kept similar with that of its predecessor, despite more equipment. The control arms of the front and rear axles, for example, and also the bonnet and wings, are made out of light and yet very strong aluminium alloys, while the cross member for the instrument panel is made of magnesium.

The development tool “energy-transparent vehicle”, created in-house by Mercedes-Benz, was used for the first time as part of the M-Class development process. This detects the possibilities for optimisation, right down to the smallest component, and will be exploited on all new model series in the future. An examination of the flow of energy throughout the vehicle (tank-to-wheel) helps to optimise every single assembly that has an impact on fuel consumption, right down to individual wheel bearings.

With a drag coefficient of 0.32, the new M-Class (ML 250 BlueTEC) also sets a new best figure for this vehicle class (total aerodynamic drag Cd x A = 0.92 m 2 ; predecessor 0.94 m 2 ). Simulations undertaken with the digital prototype, along with final touches added in the wind tunnel, ensure the best flow of air around the vehicle. The key factor determining the low wind resistance is the aerodynamic efficiency of the basic body shell, including the optimised design of the front bumper with its integrated spoiler, of the A-pillars and of the roof spoiler, plus numerous other detailed improvements. These include:

? Sealing around the radiator section with adjustable fan shutter

? Sealed joints between the bonnet and the headlamps

? Front wheel spoilers

? Air outlets in the front wheel well liners

? Redesigned exterior mirror housings

? Optimised roof spoiler

? Side spoilers on the rear window (ML 250 BlueTEC 4MATIC)

? Underfloor and engine compartment panelling

? Aerodynamically optimised light-alloy wheels

Mercedes claims that all these efficiency measures have no adverse impact on the new car’s off-road ability. The ML 350 BlueTEC 4MATIC and ML 350 4MATIC BlueEFFICIENCY models feature the permanent all-wheel drive system 4MATIC and the electronic traction control system ETS, as well as an off-road button that activates a special off-road transmission mode.

To improve traction, the slip thresholds and shift points of the 7G-TRONIC PLUS system have been raised; a flatter accelerator pedal curve improves the sensitivity with which the driver can accelerate; and off-road ABS ensures optimum braking on a loose surface.

Start-off Assist and the HOLD function are further features helping the driver to pull away on a slope. Downhill Speed Regulation, or DSR, enables the M-Class to maintain automatically the speed set via the cruise control lever.

There’s also an optional ON&OFFROAD package; this uses a range of six transmission modes to optimise driving dynamics and handling safety, by ensuring that the necessary drive control is there to cope with the very different operating conditions encountered on and off-road. One automatic mode, two specifically off-road modes and three on-road modes are available.

The system is controlled via a rotary actuator on the centre console. The settings for AIRMATIC, and the driveline, are adapted to accommodate these specific requirements. The six transmission modes are:

? Automatic – covers most everyday driving operations

? Offroad 1 – light terrain, dirt roads and tracks

? Offroad 2 – challenging off-road terrain with hilly stretches

? Winter – for driving in wintry conditions on slippery roads, on snow, ice or with snow chains

? Sport – more adventurous, dynamic driving on winding roads

? Trailer – optimises moving off, manoeuvring and braking with a trailer

The gear reduction, lock, DSR or the self-levelling suspension of the AIRMATIC system can always be adjusted individually.

In terms of hardware, the ON&OFFROAD package comprises an under-ride guard, a two-stage transfer case with reduction gear, a longitudinal differential lock and enhanced AIRMATIC functionality that allows a maximum ground clearance of 285 millimetres and a fording depth of 600 millimetres.

Active roll stabilisation in the form of the ACTIVE CURVE SYSTEM can be combined as on option with AIRMATIC air suspension with Adaptive Damping System (ADS) as well as with the ON&OFFROAD package. This system uses active anti-roll bars on the front and rear axles, which it controls automatically, irrespective of lateral acceleration, speed or the switch setting of the ADS Comfort/Sport switch. ACTIVE CURVE SYSTEM compensates for the roll angle of the body through bends. At the same time the system increases driving stability and safety, especially at high speeds. Improved ride comfort together with enhanced options for off-road driving are also among the benefits of the ACTIVE CURVE SYSTEM.

At market launch of the new M-Class, there are three models available: the ML 250 BlueTEC 4MATIC, with fuel consumption according to NEDC of 47.0 mpg (158 g/km CO2), and delivers an output of 204 hp along with 500 Nm of torque. It can accelerate from a standing start to 62 mph in 9.0 seconds, while its top speed is 130 mph.

The ML 350 BlueTEC 4MATIC returns 41.5 mpg. With a maximum output of 258 hp and torque of 620 Nm, the V6 diesel can accelerate to 62 mph in 7.4 seconds and reach a top speed of 139 mph.

With 306 hp, the petrol-engined ML 350 4MATIC BlueEFFICIENCY has an average consumption, according to NEDC, of 33.2 mpg, with a top speed of 146 mph.

UK pricing and specification are still to be confirmed. The M-Class will go on sale in spring 2012.