New Engines for the New Mercedes-Benz S-Class

Press Release

Two-stage intake module and tumble flaps for better combustion

In addition, the new V8 features the same technical innovations for situation-related control 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 cylinders 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 engineers 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 up, optimising the airflow and increasing the speed of combustion; under higher engine loads the tumble flaps are not required, and can be completely recessed into the intake manifold so as not to impede the intake process. The use of these tumble flaps has two positive effects in practical operation, namely smoother running and a reduction in fuel consumption 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 information with the other onboard control units in the new S-Class via a databus. In the interests of the shortest possible electrical paths the engine control unit is centrally 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 situation-related 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. Coolant circulation is interrupted during the warm-up phase, for example, so that the engine reaches its normal operating temperature more rapidly. This in turn improves the oil flow and considerably reduces friction in the engine. When the engine 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 situations 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 measures such as continuous camshaft adjustment, need-related combustion control by tumble flaps, internal exhaust gas recirculation and secondary air injection, which ensure low untreated 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 between 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 controlling 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.

Powerful 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 standard ensures the best possible use of the outstanding output and torque potential in any driving situation.

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.

Key data for the V6 diesel engine in the new S-Class:

*Available from first quarter of 2006; ** provisional figures

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 changes within milliseconds under an electric voltage. This lifts the needle jet 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 considerably 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 engine func-tions ??????????????????????????????????????? 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 particulate emissions of the V6 engine are within the strict limits of the EU4 standard. Two oxidising catalytic converters are responsible for conversion of the carbon monoxide and hydrocarbons: a so-called starting converter located near the engine and a main converter in an underfloor location. To reduce soot emissions even further, Mercedes-Benz offers a maintenance-free particulate filter system which is standard equipment in the new S 320 CDI in various markets. The filter regenerates without the use of additives by selective adjustment of different engine functions.

Depending on the operating parameters and filter condition, the variable third-generation common-rail technology allows up to two precisely coordinated post-injections with the aim of specifically increasing the exhaust temperature. This means that the particles trapped in the filter are burned off in a controlled manner.