The 2009 Mercedes-Benz S-Class - PART VI


Stuttgart, Germany, May 11, 2009

Drive system: Serene and efficient

- Up to seven percent lower fuel consumption and CO2 emissions
- Energy management: on-demand control of the ancillary components
- S 350 CDI BlueEFFICIENCY with up to 7.6 litres of diesel per 100 kilometres

Apart from the trailblazing hybrid of the S 400 HYBRID, the range of engines for the 2009 S-Class comprises eight other units: two diesels and six petrol engines with six, eight and twelve cylinders. Their fuel consumption and CO2 emissions have been reduced by up to seven percent for the same, high output. Mercedes-Benz developers have achieved these advances with aerodynamic fine-tuning, tyres with a lower rolling resistance and a higher air pressure, and modifications to the fuel pump and 7G-TRONIC automatic transmission.

Tyres with a lower rolling resistance

The 2009 S-Class makes use of tyres for which the rolling resistance has been reduced by up to ten percent, thanks to the use of specially specified rubber blends for the tyre tread and sidewall, while retaining good handling and braking characteristics. Rolling resistance is primarily caused by deformation of the tyre on contact with the road surface, known as the working defelection. This causes the vehicle to slow down and also requires it to use more energy in order to overcome this deformation resistance. As a general rule: the greater the rolling resistance, the higher the fuel consumption. As much as 20 percent of the fuel consumption can depend on the tyres.

Lower engine speeds, demand-controlled fuel pump

In addition, the standard 7G-TRONIC transmission has a fuel economy shift program in the comfort ("C") driving mode of the V6 and all V8 petrol models. This is always active when the engine is started. Thanks to earlier upshifts, the engine operates at a lower speed and therefore consumes less fuel.

In order to ensure on-demand energy management, Mercedes-Benz uses demand-controlled fuel pumps in the petrol engines of the S-Class. In this setup, the engine control unit only calls for the maximum pump output during full-load operation. In all other driving situations, the pump adapts the delivery volume and pressure in line with the current driving situation, resulting in a fuel saving of 0.15 litres per 100 kilometres (NEDC).

An additional new development: the V6 models as well as the V8 petrol-engine versions with AIRMATIC air suspension feature an electric power steering pump. The main advantage of this system is that when driving in a straight line, only a small quantity of oil is delivered to the steering gear when needed and as a result the power steering pump requires less energy.

S 350 CDI BlueEFFICIENCY: as economical as a medium-class model

Mercedes-Benz developers have come up with a tailor-made package to realise even greater savings potential in the S 350 CDIBlueEFFICIENCY. In addition to the above measures, these include aerodynamically efficient, enclosed underbody panelling and standstill decoupling of the 7G-TRONIC automatic transmission when the car is at rest. The torque converter interrupts the power flow as soon as the car comes to a stop with the engine running. This eliminates the hydrodynamic resistance of the torque converter, the engine is subjected to less load and the fuel consumption falls. This decoupling function also reduces noise and vibrations when at rest, and improves idling smoothness even further. The slip-controlled clutch is engaged as soon as the drive releases the brake pedal.

With a combined NEDC fuel consumption of up to 7.6 litres of diesel per 100 kilometres, which corresponds to CO2 emissions of 199 - 201 grams per kilometre, the 173 kW/235 hp S 350 CDI BlueEFFICIENCY has the fuel consumption and emissions of a medium-class car. At the same time this V6 CDI engine impresses with superior output and torque figures of 173 kW/235 hp and 540 Nm at 1600 rpm. Accordingly this model accelerates to 100 km/h is 7.8 seconds, with a maximum speed of 250 km/h.
This highly efficient diesel is also available in the S 350 CDI4MATIC with permanent all-wheel drive, where it consumes 7.8–8.0 litres of fuel per 100 kilometres (NEDC), corresponding to CO2 emissions of 207 - 211 grams per kilometre.

Key technical features of the engine include an aluminium crankcase, common-rail injection and piezo-electric injectors in place of solenoid valves. Their crystalline structure changes within milliseconds when subjected to an electric voltage. As a result the needle at the tip of the injector is raised with a precision of only a few thousandths of a millimetre, producing a particularly fine injection of fuel. Up to five fuel injections with a peak pressure of up to 1600 bar are possible for each power stroke.

An electrically controlled intake port shut-off modifies the swirl characteristics of the air flowing into the cylinders, which also optimises the combustion process with the aim of reducing the fuel consumption and exhaust emissions even further. The VNT turbocharger (Variable Nozzle Turbine) with electrically adjustable turbine blades, the exhaust gas recirculation with a control valve and the intake air throttling are also regulated as the situation requires on the basis of measured data.

S 450 CDI: plenty of torque with a moderate fuel consumption

The second diesel variant for the S-Class is the eight-cylinder S 450 CDI, which has the same output (235 kW/320 hp) as in the preceding model but consumes three percent less fuel (NEDC combined) at 9.1-9.3 litres per 100 kilometres. CO2 emissions are reduced to 240 - 245 grams per kilometre.

The S 450 CDI accelerates to 100 km/h in 6.6 seconds, and has a top speed of 250 km/h (electronically limited). The 4-valve CDI engine develops a maximum torque of 730 newton metres from 2200 rpm and has a displacement of 3996 cubic centimetres. High-pressure common-rail injection with a maximum injection pressure of 1600 bar ensures highly efficient combustion. Optimised flow characteristics for the best possible gas cycle, plus two turbochargers with variable turbine geometry, guarantee a high output and torque yield. Up to five diesel injections per injection cycle, special multi-hole nozzles, piezo-electric injectors and effective exhaust gas recirculation help to reduce emissions substantially. To minimise emissions still further, this V8 engine is equipped with a maintenance-free diesel particulate filter as standard.

S 350: performance, smoothness and economy

Compared to the preceding model, the V6 petrol engine in the 2009 S-Class consumes around one percent less fuel. The combined NEDC consumption is 10.0-10.2 litres of premium petrol per 100 kilometres, while CO2 emissions have been reduced to 234 - 237 grams per kilometre. In the S 350 4MATIC the reduction in fuel consumption is even more dramatic at four percent, to 10.2 - 10.5 litres per 100 kilometres(CO2: 240 - 245 g/km).

The six-cylinder powerplant develops 200 kW/272 hp at 6000 rpm from a displacement of 3498 cc, as well as 350 newton metres of torque which is available from as low as 2400 rpm and remains constant up to 5000 rpm. That guarantees exceptional pulling power and rapid mid-range acceleration, but also relaxed driving in high gears. The S 350 sprints from standstill to 100 km/h in 7.3 seconds, and reaches a top speed of 250 km/h.

With four-valve technology and four overhead camshafts, Mercedes engineers created major conditions for an exemplary performance curve, but this was not all. In addition they developed a system by which the interaction of the 24 valves can be controlled as required – depending on the engine load – while ensuring an extremely rapid gas cycle in the cylinders: continuously variable adjustment of all four camshafts. This means that the angles of both the intake and exhaust camshafts can be continuously varied by 40 degrees, ensuring that the valves open or close at the best possible moment in any driving situation.

Tumble flaps in the intake ducts, a two-stage intake manifold and intelligent thermal management to keep the engine oil and coolant at the best possible temperature round off this high-tech package. The cylinder head and crankcase of the V6 engine are of aluminium. A balancer shaft between the two banks of cylinders ensures exemplary smoothness. This counter-rotates with the crankshaft and at the same speed.

S 450 and S 500: eight cylinder models with effortless power delivery

In the S 450 V8 petrol model, Mercedes-Benz developers have reduced the combined NEDC fuel consumption by five percent to 10.6 - 10.9 litres per 100 kilometres. CO2 emissions have fallen to 249 - 255 grams per km.

The combined NEDC fuel consumption of the S 450 4MATIC is 11.0 - 11.1 litres per 100 kilometres (256–258 g CO2/km). This is likewise five percent less than for the preceding model.

The ultra-modern 4.7-litre eight-cylinder engine generates 250 kW/340 hp and a torque of 460 newton metres at 2700 to 5000 rpm, providing the basis for outstanding performance: the S 450 accelerates to 100 km/h in 5.9 seconds, with a top speed of 250 km/h (electronically limited).

The difference is even more pronounced for the S 500: while the rear-wheel drive variant requires six percent less fuel at 11.0 - 11.2 litres per 100 kilometres (NEDC combined), the 4MATIC models are happy with seven percent less premium petrol (11.3 - 11.4 l/100 km). CO2 emissions are correspondingly lower too (S 500: 258–262 g/km; S 500 4MATIC: 264-266 g/km).

The 5.5-litre engine develops 285 kW/388 hp, with a torque of 530 newton metres. Maximum torque is available from 2800 rpm, remaining constant over a wide engine speed range up to 4800 rpm. An ideal basis for powerful acceleration and fast mid-range sprints:

- The S 500 accelerates from zero to 100 km/h in 5.4 seconds.
- In manually selected third gear, the V8 Saloon sprints from 60 to 120 km/h in just 5.6 seconds.

The maximum speed of the S 500 is likewise an electronically limited 250 km/h.
Both V8 engines are produced together with the six-cylinder unit of the S 350 in Stuttgart Bad Cannstatt. This means that all four engines come from the same family, and share the same characteristics: lightweight alloys for the blocks and cylinder heads, four overhead camshafts, four-valve technology and variable camshaft adjustment on the intake and exhaust sides for an optimal supply of fresh mixture to the cylinders.

The "quadruple", continuously variable camshaft adjustment process is further enhanced by shifting camshafts, which are used to enable opening of the exhaust valves and, therefore further improve the engine's gas cycle. The exhaust cams are designed so that the valves open at different times during the exhaust process. As a consequence, the pressure fluctuations inherent to a V8 engine's exhaust train are reduced. Thanks to a more constant residual gas content, a higher knock limit and improved bottom-end and mid-range cylinder charging, the shifting camshafts increase the engine's torque and refinement.

Moreover, the V8 engines have the same technical innovations for the demand-related control of the combustion processes with which the six-cylinder engines excel: a two-stage intake module for a controlled air intake depending on the engine load and engine speed, flow-optimised air ducting for the best possible air supply to the engine and tumble flaps at the end of each intake duct for more complete combustion. As a further feature shared with the V6 units, a characteristic map controlled thermostat ensures that the engine oil and coolant are always at the optimal temperatures.

Other characteristics of the V8 engines in the S 450 and S 500 include low-friction cylinder liners made from an aluminium/silicon alloy and the forged steel crankshaft with five bearings, whose main and connecting rod bearings are induction hardened. The connecting rods are likewise of forged steel, are are weight-optimised by precision milling.

S 600: twelve-cylinder engine with twin turbochargers

The flagship model remains the S 600 with a 380 kW/517 hp twelve-cylinder biturbo engine, which accelerates the luxury saloon from zero to 100 km/h in just 4.6 seconds. Maximum torque is 830 newton metres at 1800 rpm, which makes the 5.5-litre engine one of the world's most powerful series-production car engines. The V12 combines its impressive performance potential with exemplary smoothness and outstanding noise comfort – the best possible preconditions for refined and highly enjoyable travel.

The crankcase of the twelve-cylinder engine is made from diecast aluminium, while diecast magnesium is used for the cylinder-head covers. Fracture-split or "cracked" conrods made from high-strength forged-steel alloy, pistons made from a high-quality aluminium alloy, hollow camshafts of induction-hardened forged steel, a weight-optimised forged-steel crankshaft and a diecast aluminium sump feature among the other lightweight components of the engine.

On both sides, the turbines of the two turbochargers are integrated into the exhaust manifolds to save space, and are therefore in the best position for high efficiency. The compressed air flows through two close-coupled water intercoolers on the cylinder head covers. Depending on the engine load the air is cooled by up to 100 degrees Celsius, achieving just the right temperature and density for the combustion process.

The Mercedes-AMGhigh-performance contributions to the range are the S 63 AMG with its 386 kW/525 hp V8 engine (displacement 6.2 litres) and the S 65 AMG with a 450 kW/612 hp twelve-cylinder engine (displacement 6 litres).

Transmission: seven ratios and three driving modes

The six and eight-cylinder engines are combined with the 7G-TRONIC seven-speed automatic transmission as standard, while Mercedes-Benz combines the V12 engine of the S 600 with a five-speed automatic transmission. The DIRECT-SELECT lever on the steering column enables the driver to select "P", "N", "R" and "D" by nudging the selector. The operating commands are transferred purely electronically, by wire.

The S/C/M/ mode selector switch on the centre console allows the driver to choose between three different modes: Sport, Comfort and Manual. As well as the transmission characteristics, these modes also allow the characteristics of the accelerator pedal and the suspension (springing and damping) settings to be varied. In Manual mode, the driver changes gear using the steering-wheel gearshift buttons.

Copyright © 2009, Mercedes-Benz-Blog. All rights reserved.

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