Engines and transmission: Strong performance

Sep 12, 2005
  • New V8 engine with 285 kW/388 hp and high-tech features
  • Up to 26 percent more output and 15 percent more torque
  • Six-cylinder diesel with latest-generation common-rail technology
  • Standard-fitted automatic transmission with three different modes
The engine is the heart of a car. And to make sure that this heart beats strongly over a long working life, the engineers at Mercedes gave it their particular atten-tion during the development of the new S-Class: all the engines in the Mercedes flagship series are new or further developments. They develop more output and torque than the engines in the preceding series, operate even more smoothly and meet the most stringent worldwide exhaust emission standards.
In other words: whatever the choice of engine to power the new S-Class, its heart will certainly be strong and healthy.
The range of petrol engines comprises three power units with six, eight and twel-ve cylinders. At the lower end of this range is the new V6 engine with 200 kW/272 hp, which Mercedes-Benz has also offered in other car model series for a number of months. The message of this up-to-date six-cylinder unit is: more power, yet lower fuel consumption. Compared to the previous V6 in the S-Class, the new engine develops around eleven percent more output (up 20 kW/27 hp) and consumes nine percent less fuel in the NEDC test (= 1.0 l/100 km).
In addition to the latest 24-valve technology and four variable camshafts, this is considerably aided by the unique 7G-TRONIC seven-speed automatic transmis-sion, which is standard equipment in the V6 and V8 models.
From the first quarter of 2006 the top-of-the-range model will enter the lists with an improved twelve-cylinder bi-turbo engine. Its output has increased by 12 kW/17 hp to 380 kW/517 hp, while the maximum torque has improved further from 800 to 830 Newton metres. The engine already makes this high torque avai-lable from 1900 rpm and maintains this level to 3500 rpm. Despite the increase in power, the fuel consumption of the V12 has been reduced by 0.5 litres/100 km compared with the previous S 600.
The eight-cylinder engine in the S 500 is a new development which will celebrate its world premiere in autumn 2005, together with the new S-Class. This power unit develops 285 kW/388 hp from a displacement of 5.5 litres, an increase of more than 26 percent versus the previous V8. At 530 Newton metres the torque also comfortably exceeds the maximum for the preceding engine by around 15 percent. This high level of torque is available from 2800 rpm and remains con-stant throughout a wide engine speed range up to 4800 rpm, providing ideal con-ditions for powerful acceleration and fast intermediate sprints:
  • The new S 500 accelerates from zero to 100 km/h in 5.4 seconds, and is therefore one second faster than the previous eight-cylinder Saloon.
  • In third gear, the V8 Saloon sprints from 60 to 120 km/h in just 5.6 seconds.
The fact that the combined NEDC fuel consumption of 11.7 to 11.9 litres per 100 kilometres has remained at the level of the preceding model despite a higher out-put and more torque clearly demonstrates the efficiency of the up-to-date concept and high-tech features of the new Mercedes eight-cylinder unit.
With a specific fuel consumption of 233 grams per Kilowatt hour (g/kWh) when operating at peak efficiency, and 345 g/kWh at part-throttle (2000 rpm, 2 bar), the engine has easily the lowest fuel consumption in this displacement and output class.
Key data for the petrol engines in the new S-Class at a glance:
S 350

S 500

S 600*

Cylinder arrangement/
valves per cylinder




Displacement cc




Bore/stroke mm




Compression ratio

10.7 : 1

10.7 : 1

9.0 : 1

Output kW/hp




Max. torque
Nm at rpm

2400 - 5000

2800 - 4800

1900 - 3500

Fuel consumption
Combined     l/100 km

10.0 - 10.3

11.7 - 11.9


0 - 100 km/h       s
60 - 120 km/h     s




Top speed.




*Available from first quarter of 2006; **electronically limited
Eight-cylinder unit: pinnacle of a new engine generation
With the eight-cylinder unit for the S 500, Mercedes-Benz is presenting the top power unit in its new generation of V-engines, which was successfully introduced in mid-2004. This engine is produced in tandem with the six-cylinder engine of the S 350, at the DaimlerChrysler location in Stuttgart-Bad Cannstatt. This means that both engines belong to a single family and therefore share the attributes that make them prime examples of modern engine technology:
  • High output
  • Powerful torque
  • Exemplary comfort
  • Favourable fuel consumption
  • Low exhaust emissions
In order to achieve these five development goals and exceed the previous stan-dards, the engineers in Stuttgart developed an extensive technological package. Its components interact perfectly, complement each other in their effects and thereby achieve remarkable progress in every aspect.
Lightweight construction for smooth running and dynamic agility
A crankcase of diecast aluminium with low-friction aluminium/silicon cylinder liners is the solid and durable basis of the new Mercedes eight-cylinder engine. It houses a five-bearing, forged steel crankshaft with induction-hardened main and big-end bearings. The connecting rods are also of forged steel, with specific areas milled away to make them around one fifth lighter than those of the previous V8 engine for the S-Class.
Saving weight was not the only important aspect during the design work on the new engine, however. The engineers were just as determined to achieve the best possible results where smooth running and flexibility are concerned. Lightweight construction principles were helpful in this respect, for the lower the moving masses in the crankcase, the lower the vibrations and the more responsive the engine is to movements of the accelerator pedal.
The new eight-cylinder unit does not require a balancer shaft to improve its smoothness. Unlike in a V6 engine, its cylinder angle of 90 degrees is ideal for the vibration characteristics of the eight-cylinder powerplant.
Shifting camshafts for a perfect gas cycle and higher torque
Mercedes engineers have already used an intelligent valve control system in the new V6 engine, achieving remarkable progress and a major contribution to the good performance characteristics and low fuel consumption of the unit. In addition to four-valve technology, continuously adjustable intake and exhaust camshafts en-sure that the cylinders are optimally supplied with fresh mixture. The valves are opened at precisely the right moment in any driving situation, significantly improv-ing the gas cycle in the combustion chambers and reducing energy losses.
The camshafts are controlled by electro-hydraulically operated vane-type adjust-ers, which are located at the forward ends of the camshafts and are controlled by four integral hydraulic valves. The intake camshafts are driven by a duplex chain, while the exhaust camshafts are directly driven by the intake camshafts via a braced pair of gears.
In the new eight-cylinder engine the engineers at Mercedes-Benz have optimised the effect of this four-fold, continuous camshaft adjustment by using what are known as shifting camshafts. These control the opening of the exhaust valves and improve the engine’s gas cycle even further. Depending on the ignition sequence, the exhaust cams are designed in such a way that the valves open at different ti-mes during the exhaust cycle. This reduces the pressure fluctuations in the ex-haust tract which are inherent to a V8 engine, and which lead to fluctuations in the residual gas content in the cylinders.
The valve lift interval on the exhaust sides of the new Mercedes eight-cylinder engine is as follows:
  • Cylinders 3, 4, 5, 7: 180 degrees crankshaft with 2 mm valve lift
  • Cylinders 1, 2, 6, 8: 190 degrees crankshaft with 2 mm valve lift
The newly developed shifting camshafts improve the torque and smoothness of the V8 engine by ensuring a more uniform residual gas content, a higher knock limit and better cylinder charging in the lower to medium engine speed range. At 2000 rpm, for example, the effective mean pressure is around six percent (10.3 : 11.0 bar) higher than in a comparable engine without shifting camshafts.
Two-stage intake module and tumble flaps for better combustion
In addition, the new V8 features the same technical innovations for adaptive con-trol of the combustion processes that have already proved successful in the six-cylinder engine:
  • Two-stage intake module for a controlled air supply depending on the engine load and engine speed: the length of the intake ducts leading to the cyl-inders is varied by flaps. At high engine speeds – from approx. 3500 rpm -- the flaps are open and the air flows directly to the combustion chambers. This allows high outputs to be achieved. At low engine speeds the flaps are closed to increase the length of the intake ducts. This creates pressure waves which support the intake process and improve the torque yield in the lower engine speed range. As a result 435 Newton metres of torque, and therefore more than 82 percent of the maximum torque, are already available from 1500 rpm.
  • Optimised airflow for the best possible engine aspiration. Mercedes engi-neers used highly sophisticated flow calculations to optimise the airflows in the new eight-cylinder power unit. Particular attention was for instance paid to the airflow from the twin-chamber air filter, the housing of the hot film air mass sensor and the intake manifold.
  • Tumble flaps for more complete combustion: electro-pneumatically driven flaps at the end of each intake duct increase the turbulence of the air flow, which is thus more uniformly distributed in the combustion chambers. At part-throttle the tumble flaps pivot up, optimising the airflow and increasing the speed of combustion; under higher engine loads the tumble flaps are not re-quired, and can be completely recessed into the intake manifold so as not to im-pede the intake process. The use of these tumble flaps has two positive effects in practical operation, namely smoother running and a reduction in fuel con-sumption by up to 0.2 litres per 100 kilometres, depending on engine speed.
The tumble flaps, fuel injection, ignition and numerous other engine functions are managed by a powerful control unit, which also communicates and exchanges in-formation with the other onboard control units in the new S-Class via a databus. To reduce communication distances to a minimum, the engine control unit is cen-trally located above the intake manifold and is integrated into the engine design. Combustion of the fuel/air mixture is by means of a direct coil ignition system. The spark plugs project into the centre of each cylinder between the four valves, with the ignition coils located directly above them.
Electronically controlled thermostat for adaptive heat management
The developers of the new Mercedes eight-cylinder engine have also made a major contribution to fuel economy with a sophisticated heat management system. Cool-ant circulation is interrupted during the warm-up phase, for example, so that the engine reaches its normal operating temperature more rapidly. This in turn im-proves the oil flow and considerably reduces friction in the engine. When the en-gine is warm and under full load, the heat flows are directed in such a way that the engine oil and coolant are always at an optimal temperature. This is ensured by an innovative, logic-controlled thermostat which is active in all operating situa-tions and adjusts the coolant temperature according to the style of driving and the prevailing conditions. This also enables the heat supply to the heater core to be controlled as needed.
Twin catalytic converters und linear oxygen sensors for low exhaust emissions
The emission control system of the new Mercedes eight-cylinder engine follows a two-stage concept and is therefore highly effective. In addition to in-engine meas-ures such as continuous camshaft adjustment, adaptive combustion control by tumble flaps, internal exhaust gas recirculation and secondary air injection, which ensure low engine-out emissions, the new S 500 is equipped with two close-coupled catalytic converters as standard. These consist of two individual monoliths or bricks, each of which is monitored by two oxygen sensors: a control sensor and a diagnostic sensor which analyses the exhaust flow in the gap be-tween the two bricks.
This oxygen sensing is linear, which means that the oxygen sensors are already active immediately after a cold start, supplying information about the exhaust gas constituents for the electronic control unit of the V8 engine to process when con-trolling the warm-up phase. This enables the catalytic converters to reach their normal operating temperature more rapidly.
Thanks to its ultra-modern technology and efficient emission control system, the new eight-cylinder engine complies with the most stringent exhaust emission standards currently in force; it also has the potential to meet limits which are planned for the future.
Six-cylinder diesel with latest-generation CDI technology
From the beginning of 2006 the newly developed CDI six-cylinder engine will join the range of engines for the S-Class. It has an output of 173 kW/235 hp, topping the figure for the engine in the preceding S 320 CDI by 15 percent. Maximum torque has increased by eight percent, from 500 to 540 Newton metres which are available between 1600 and 2800 rpm. These remarkable values make the direct-injection diesel unit one of the most powerful in its displacement class.
Combining this with the 7G-TRONIC seven-speed automatic transmission as stan-dard ensures the best possible use of the outstanding output and torque potential in any driving situation.
Key data for the V6 diesel engine in the new S-Class:

Displacement cc



Bore/stroke mm


Compression ratio


Output kW/hp


Max. torque
Nm at rpm

540 at 1600 - 2800 rpm

Fuel consumption
Combined                   l/100 km

8.3 - 8.5

0 - 100 km/h             s
60 - 120 km/h           s


Top speed km/h** 


*Available from first quarter of 2006; ** electronically limited
Lightweight construction as a factor in exemplary diesel driving pleasure
The choice of materials, technical design, fuel injection and engine management system of the V6 diesel engine reflect the state of the art. For the first time with a diesel engine in this displacement and output class, Mercedes-Benz has developed an aluminium crankcase with cast-in grey iron cylinder liners for this unit, which makes a major contribution to weight reduction. As a result, the new six-cylinder engine weighs a total of only around 208 kilograms (acc. to DIN) and achieves a remarkable power-to-weight ratio of 0.83 kW/kg -- a major contribution to the outstanding diesel agility offered by the new engine.
Piezo-injectors for finely metered fuel injection
Third-generation common-rail direct injection is a further technical highlight of this engine. It produces significant improvements in terms of fuel consumption, exhaust emissions and combustion noise. Instead of the previous solenoid valves, the injectors are equipped with piezo-ceramics whose crystalline structure chan-ges within milliseconds under an electric voltage. This lifts the nozzle needle at the tip of the injector with a precision of only thousandths of a millimetre and thereby achieves an extremely fine jet of fuel. Moreover, piezo injectors are con-siderably lighter and operate at twice the speed of conventional solenoid valves. With a response time of only 0.1 milliseconds, the fuel injection process can be even more precisely suited to the current load and engine speed situation, with favourable effects on emissions, fuel consumption and combustion noise. Five fuel injections per power stroke at a peak pressure of up to 1600 bar are possible thanks to this piezo technology.
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 likewise newly developed electronic control unit manages all the en-gine functions – from the quick-start glow system and automatic start function to control of the high-pressure pump. The VNT turbocharger (Variable Nozzle Turbine) with electrically adjustable turbine blades, exhaust gas recirculation with a control valve and intake air throttling are also regulated as the situation requires on the basis of measured data.
Catalytic converters and a particulate filter for emission values below the EU-4 limits
Thanks to this precise engine management system, the nitrogen oxide and par-ticulate emissions of the V6 engine are within the strict limits of the EU4 stan-dard. A close-coupled oxidation catalyst is responsible for conversion of the car-bon monoxide and hydrocarbons. To reduce particulate emissions even further, Mercedes-Benz offers a maintenance-free particulate filter system which is stan-dard equipment in the new S 320 CDI. The filter regenerates without the use of additives by selective adjustment of different engine functions.
Depending on the operating parameters and filter condition, the adaptive third-generation common-rail technology allows up to two precisely coordinated post-injections to increase the exhaust temperature. This means that the particles trapped in the filter are burned off in a controlled manner.
Automatic transmission: seven ratios, three different modes
The new S-Class V6 and V8 saloons are specified as standard with the 7G-TRONIC seven-speed automatic transmission, the only passenger car transmission of this type in the world. 7G-TRONIC incorporates numerous engineering innovations which, in conjunction with the state-of-the-art engines, provide enhanced accel-eration and mid-range power, reduced fuel consumption and greater shifting com-fort. 7G-TRONIC is combined with the DIRECT SELECT gearshift, which replaces the conventional centre console-mounted automatic selector lever. A brief press of the DIRECT SELECT steering-column selector lever allows the driver to select the "P", "N", "R" and "D" positions. The commands are transmitted electronically, although the actual gear changes are actuated by cable.
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 ac-celerator pedal and the suspension (springing and damping) settings to be varied. In Manual mode, the driver changes gear using the steering-wheel gearshift buttons.
The special characteristics of the seven-speed automatic transmission are attrib-utable to various different design features, the most important of which is the in-crease in the number of forward speeds from five to seven. This results in a wider overall ratio spread, while at the same time the ratios are also closer together than on the five-speed transmission. An optimal ratio can therefore be selected for vir-tually all driving situations. The fact that the electronic control unit has a greater number of ratios to choose from also reduces fuel consumption and increases smoothness. Depending on driving situation, average engine speeds at 100 km/h are approximately twelve percent lower than with a five-speed automatic trans-mission. The optimal matching of engine speed to driving conditions means that the engine is more economical on fuel and is also quieter in operation.
The Mercedes engineers have also made important advances in terms of the transmission's control logic: if the 7G-TRONIC transmission needs to shift down quickly through several gears, for example under kickdown, a multiple downshift function comes into operation. Instead of changing gear sequentially, one gear at a time, the transmission shifts down by up to four gears at a time, depending on the driving situation, resulting in significantly faster shift times.
The new seven-speed automatic transmission is fitted with a hydrodynamic torque converter with lockup clutch. Whenever possible, the lockup clutch creates a virtually rigid connection between the engine and the transmission shaft, thus preventing slip between the pump and turbine, and thus power losses, in a wide range of operating situations. On the Mercedes-Benz seven-speed automatic transmission, the lockup clutch engages even in first gear, rather than only in the higher gears as on conventional automatic transmissions. On comfort grounds, the torque converter lock-up clutch is slip-controlled and therefore engages very smoothly.
Cylinder angle
  S 320 CDI*
Cylinder arrangement/valves per cylinder