by Adrian-Liviu Dorofte

The new Mercedes-Benz GL-Class: Drive and efficiency - More driving pleasure, lower consumption

Both the GL 350 BlueTEC 4MATIC's BlueTEC diesel engine as well as the GL 500 4MATIC BlueEFFICIENCY's turbocharged BlueDIRECT V8 petrol engine offer exhilarating performance combine with high efficiency. On average, the new range's models consume 18 or, respectively, 20 percent less than their predecessors – while output has been substantially increased.

The GL 350 BlueTEC 4MATIC with SCR technology and AdBlue® injection today already meets the requirements of the emissions standard EU 6 planned for 2014. At a consumption of 7.4 - 8.0 l/100 km (NEDC combined), the diesel model consumes 20 percent less than its predecessor. CO2 emissions of 192 grammes per kilometre are the best value in this output segment. Despite the significantly reduced energy requirements, performance has been substantially increased. While the first-generation GL 350 BlueTEC's output was 155 kW (211 hp) and its maximum torque was 540 Newton metres, the new model now achieves 190 kW (258 hp) and 620 Newton metres. Together with the output, the capacity for acceleration and the top speed have of course also increased.

An overview of the key data:
*Preliminary data for international model range, country-specific deviations possible.

The GL 350 BlueTEC 4MATIC is among the cleanest diesel-powered SUVs in the world: BlueTEC is a technology developed by Mercedes-Benz that reduces diesel-vehicle emissions, particularly nitrogen oxides. The system injects AdBlue®, an aqueous urea solution, into the exhaust flow. This releases ammonia which then reduces up to eighty percent of the nitrogen oxides to harmless nitrogen and water in the downstream SCR catalytic converter (Selective Catalytic Reduction). The result: the model today already meets the emission values required by the EU 6 standard planned for 2014. The AdBlue® tank is located under the luggage-compartment floor to protect it in the event of a crash, has a capacity of 31.2 litres and is refilled at the regular 25,000-kilometre maintenance intervals. The filler aperture is located behind the fuel filler flap on the side of the vehicle, behind the fuel filler neck, and is easily recognisable by the bright blue cap. GL drivers can thus easily refill the tank themselves if they make intensive use of the GL's off-road capabilities and happen to find themselves beyond the frontiers of civilisation without access to a service station. AdBlue® is available in refill containers at every Mercedes-Benz dealership. The need for a refill is indicated in good time in the instrument cluster.

Superior thrust – the GL 500 4MATIC BlueEFFICIENCY

With NEDC consumption figures of 11.3 - 11.5 l/100 km, the GL 500 4MATIC BlueEFFICIENCY features the most economic V8 petrol engine in its class. The engine is a turbocharged 4.6-litre BlueDIRECT power unit with 320 kW (435 hp). The latest generation consumes an average eighteen percent less fuel and, thanks to EU 5-compliance, offers the best classification presently available.

The new V8 engine produces 320 kW (435 hp) from 15 percent less cubic capacity (4663 compared to 5461 cc), roughly 12 percent more power than its predecessor's 285 kW (388 hp). At the same time, torque has been increased from 530 to 700 newton metres – a 32-percent increase. As the high maximum torque is already available at only 1,800 revs, the new V8 produces superior power even at low engine speeds and provides a smoothness of performance that is exemplary even for an eight-cylinder engine. Mercedes-Benz's engineers achieved the higher output from the lower cubic capacity primarily by means of two exhaust-gas turbochargers – one each per cylinder bank.

The turbochargers are designed to provide high torque even at low engine speeds – compared to the predecessor's engine, they produce above 40 percent more at 2,000 rpm. Outstanding 700 newton metres are available in the range from 1,800 to 3,500 revs. The driver will thus notice no turbo lag, instead perceiving the new V8 as pleasant and powerful. The latest generation of engines also incorporates such innovations as the third-generation direct injection featuring guided-spray combustion and piezo-injectors as well as multi-spark ignition.

GL 63 AMG: efficiency and driving dynamics of the highest degree

With the shift to the new model range, the GL is for the first time available as an AMG variant. The high-performance SUV GL 63 AMG features an AMG 5.5-litre V8 Biturbo engine with 410 kW (557 hp) and a maximum torque of 760 newton metres, resulting in superior driving performance: the GL 63 AMG accelerates from zero to 100 km/h in 4.9 seconds; top speed is 250 km/h (electronically governed). NEDC consumption is 12.3 litres per 100 kilometres (288 g of CO2/km).

The AMG eight-cylinder designated M157 features an innovative high-tech package comprising guided-spray petrol direct injection, piezo injectors, biturbo charging, air/water charge air cooling, fully aluminium crankcase, four-valve technology with camshaft adjustment, generator management and ECO start/stop.

Overview of the key data:
Power is transmitted to the four permanently driven wheels by the AMG SPEEDSHIFT PLUS 7G-TRONIC. The seven-speed gearbox impresses with its high variability gained through the three driving programs and the automatic double-clutching function for downshifts. In "Controlled Efficiency" (C) mode, ECO start/stop is active and switches off the eight-cylinder engine whenever the vehicle comes to a standstill. "C" also incorporates a soft accelerator-pedal and gearbox characteristic with early shift points; in this mode, the vehicle generally pulls away in second gear. An "ECO" icon in the AMG instrument cluster tells the driver that ECO start/stop is active.

A further increase in efficiency is provided by the AMG SPEEDSHIFT PLUS 7G-TRONIC automatic gearbox featuring a fuel-economy torque converter with mass-damper pendulum, low-friction bearings and thermal management for the transmission fluid. Additional fuel-consumption reductions are achieved by low-friction axle drives, the electromechanical AMG speed-sensitive sports steering, the optimised belt drive and the adaptive management of all auxiliary units and pumps.

For the 4MATIC permanent four-wheel drive, Mercedes-AMG employs an autonomous transfer case: it distributes drive power between the front and rear axle at a ratio of 40: 60 to achieve a high degree of driving dynamics. And there's more: the AMG RIDE CONTROL sports suspension with AIRMATIC package, comprising air suspension, special spring struts, automatic ride height adjustment and the Adaptive Damper System (ADS), is combined with ACTIVE CURVE SYSTEM anti-roll stabilisation.

Reduced energy requirements thanks to BlueEFFICIENCY

Besides the state-of-the-art engine technology, fuel economy is further aided by a comprehensive package of BlueEFFICIENCY measures. These include, in addition to the standard ECO start/stop, the new 7G‑TRONIC PLUS seven-speed automatic gearbox. Further fuel-consumption reductions are achieved by the low-friction axle drives, electric steering and low-rolling resistance tyres.

The redesigned 7G-TRONIC PLUS comes as standard for the models GL 350 BlueTEC 4MATIC and GL 500 4MATIC BlueEFFICIENCY and is characterised by integrating ECO start/stop, by its reduced torque converter clutch slip and its optimised efficiency. The most important details include the new torsion damper that now attenuates rotational imbalances and vibration in the gearbox even more effectively. Such vibration becomes potentially greater the lower the engine speed and the lower the number of cylinders. This results in a conflict of interests between comfort and economic operation. The conflict is resolved by employing a so-called twin-turbine damper which, in the diesel models, additionally features a mass-damper pendulum. The damper shifts the centre of gravity in accordance with the engine speed and facilitates comfortable vehicle operation even in the economic operating range. Additionally, the optimised damping also allows for a substantial reduction in torque converter clutch slip even at low loads, again contributing to better fuel economy. The optimised attenuation of imbalances and vibration in the gearbox also ensures a faster response to accelerator pedal actuation. Low-friction bearings and a new thermal management for the transmission fluid further reduce fuel consumption.

The energy requirements of the new GL-Class are reduced even more by an optimised belt drive with decoupler and the intelligent, adaptively controlled activation of all auxiliary units and pumps. In the same way as the fuel pump in the vehicle's rear, the engine's oil and water pump are activated only as far as required by the actual loads. The same control logic is also utilised in the standard THERMATIC (GL 350 BlueTEC 4MATIC) and THERMOTRONIC (GL 500 4MATIC BlueEFFICIENCY) climate control systems, which activate the refrigerant compressor only when necessary. In addition, an internal heat exchanger and the sophisticated sensor system including a misting sensor on the windscreen ensure the highest-possible efficiency for passenger-compartment climate control. Also significant in the case of the diesel model is the flow and counter pressure-optimised BlueTEC exhaust system with AdBlue® injection.

Less drag through sophisticated aerodynamics

With a drag coefficient of cd = 0.35 (GL 350 BlueTEC), the new GL-Class improves upon its predecessor and takes a peak position in its market segment (overall drag cd x A = 1.05, predecessor 1.07). Intense simulations as part of the digital prototyping process as well as fine-tuning in the wind tunnel have provided for perfect airflow around the vehicle. An overview of the most important aerodynamic improvements:

- Adjustable radiator shutter facilitating adaptive limitation of the cooling air intake which otherwise results in substantial pressure losses when travelling through the engine compartment, thus increasing drag.

- Aerodynamically optimised 18 and 19-inch alloy wheels that reduce flow separation and airflow losses around the wheels.

- Sealed panel gaps between bonnet and headlamps for further optimisation of the front-end airflow.

- Wheel spoilers on the front wheels to improve airflow around the tyres while simultaneously reducing lift.

- Engine compartment and underbody panelling that optimise outflow of the cooling air from the engine compartment and prevent flow losses caused by accumulation and turbulence in the underbody area.

Findings from the "energy-transparent vehicle" put to good use

The GL-Class's energy efficiency has also been improved by applying experiences gained from the energy-transparent vehicle (ETV), a process first employed during the development of the M-Class. Through high-precision, in-depth examination of the energy flows within the entire vehicle (tank-to-wheel), engineers are capable of optimising all consumption-related assemblies – right down to individual components such as the wheel bearings. The notion of the ETV arose from the fact that, in the past, many consumption effects and correlations between economy measures could not be conclusively verified or validated. Thanks to the ETV, developers can now identify in detail the optimisation potential by breaking down the energy-related causal loops and by analysing the correlations within the overall vehicle.

The process utilises extremely complex high-precision measurement technology capable of recording up to 1,000 measurement values per second at around 300 energy-related measurement points. Thus, approximately 2.4 million values are obtained per minute. Their analysis provides reliable indication of optimisation potential. The process is supplemented by energy simulation models that are validated by means of measurement values. In combination, these procedures facilitate analysis and quantification of the energy efficiency of individual units and components as well as of the entire vehicle.

Where the specialists identify a vehicle component with dissatisfactory energy efficiency, solutions are developed in collaboration with the technical departments. These solutions can focus, on the one hand, on design or material properties of individual vehicle components such as wheel or axle bearings but may also be achieved by modifying control strategies.

Dietary measures for improved agility and efficiency

Thanks to extensive lightweight design measures, a reduction of the new GL's weight by 90 kilogrammes compared to the predecessor model (GL 350 BlueTEC 4MATIC) has been achieved – in spite of additional equipment such as the standard sliding sunroof, the significantly improved second row of seats with easy-entry on both sides of the vehicle, the optimised crash characteristics and the noise-reduction measures. The front and rear-axle links as well as the bonnet and the wings, for instance, are made of light but strong aluminium alloys. The further weight reduction was achieved through the new high-insulation windscreen, the dashboard's magnesium cross beam, the BlueTEC system with SCR technology or components such as the new electromechanical steering, the electric parking brake, the plastic engine bracket or the new aluminium brake booster.

Long-distance travel with less refuelling stops

Particularly impressive is the range of the new GL-Class on just a single tank. This parameter is especially important in a terrain-going vehicle that is able to get almost anywhere. At an NEDC consumption of 7.4 l/100 km, the particularly economic compression-ignition engine of the GL 350 BlueTEC 4MATIC with the standard 100-litre fuel tank can cover around 1,350 kilometres without a refill. The GL 500 4MATIC BlueEFFICIENCY's V8 petrol engine achieves a range of up to 890 kilometres before requiring refuelling.

Credits: Daimler AG

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