The combination of a modified V6 petrol engine and a compact hybrid module makes the Mercedes-Benz S400 BlueHYBRID the world's most economical luxury saloon with a spark-ignition engine. The NEDC combined fuel consumption is a mere 7.9 litres per 100 kilometres. This makes for the world's lowest CO2 emissions in this vehicle and performance class - just 190 grams per kilometre. These exemplary figures go hand in hand with assured performance. The 3.5-litre petrol engine develops an output of 205 kW/279 hp, the electric motor generates 15 kW/20 hp and a starting torque of 160 Nm. The result is a combined output of 220 kW/299 hp and a combined maximum torque of 385 newton metres. Moreover, the new Mercedes-Benz S400 BlueHYBRID is the first series-production model to be equipped with a particularly efficient lithium-ion battery specially developed for automotive use. This is another major contribution by Mercedes-Benz to the electrification of the car.
The new Mercedes-Benz S400 BlueHYBRID is based on the S350, and features an extensively modified drive train. This encompasses a further development of the 3.5-litre V6 petrol engine, an additional magneto-electric motor, the 7G-TRONIC seven-speed automatic transmission specially configured for the hybrid module, the necessary operating and control electronics, the transformer and a high-voltage lithium-ion battery.
The compact hybrid module is a disc-shaped electric motor that also acts as a starter and generator. The system offers a double benefit, as it both helps to save fuel and increases driving enjoyment. This is partly due to the booster effect of the electric motor, as it powerfully backs up the petrol engine with a maximum additional torque of 160 newton metres during the high-consumption acceleration phase. The driver benefits from the combined action of these two units in the form of even more impressive torque characteristics and smooth, effortlessly superior acceleration.
The hybrid module also has a comfortable start/stop function, which switches the engine off when the vehicle is at a standstill - for example at traffic lights. When it's time to move off again, the electric motor almost imperceptibly restarts the main power unit. This likewise makes a contribution to fuel economy and environmental protection: because the engine restarts first time, and practically instantly, emissions are also minimised during the starting phase.
When the vehicle is braked the electric motor acts as a generator, and is able to recover braking energy by a process known as recuperation. Working in finely tuned partnership, the electric motor supplements the braking effect of the petrol engine and the wheel brakes to deliver a smoothly progressive braking action. The recuperated energy is stored in a compact yet highly efficient lithium-ion battery in the engine compartment, and made available when required. This complex system is managed by a high-performance control unit, which is likewise located in the engine compartment. 
Mercedes-Benz S400 BlueHYBRID
The centrepiece of the modular, very compact and highly efficient hybrid drive system is the new high-voltage lithium-ion battery, which was specially developed for automotive use and is the first such unit worldwide to be introduced in a series-production vehicle. In this way Mercedes-Benz is making a trailblazing contribution to the electrification of the car, with the Mercedes-Benz S-Class once again playing the role of the technological trendsetter.
Major advantages over conventional nickel/metal hydride batteries include a higher energy density and better electrical efficiency, together with more compact dimensions and a lower weight. Thanks to space-saving installation in the engine compartment, where it replaces the conventional starter battery, the generous interior space and boot capacity of the S400 remain unchanged. The lithium-ion battery not only stores energy for the electric motor, but is also connected to the 12-Volt onboard network via the transformer to supply power to other standard consumers such as the headlamps and comfort features. The completely newly designed battery system consists of the cell block with its lithium-ion cells and the cell monitoring system, the battery management function, the high-strength housing, the cooling gel, the cooling plate, the coolant feed and the high-voltage connector.
The 3.5-litre V6 petrol engine with variable valve control has been throughly re-engineered and improved. In the process the development engineers made use of the advantages offered by the Atkinson principle,where the expansion phase is longer than the compression phase. The intake valve is kept open slightly longer between the intake and compression phases, which improves the engine's thermal efficiency while reducing the specific fuel consumption and untreated emissions. A new cylinder head, different pistons and a modified camshaft with different camshaft control increase the output by 5 kW/7 hp to 205 kW/279 hp - while reducing fuel consumption at the same time.
The compact, disc-shaped electric motor, which is space-savingly installed in the torque converter housing between the engine and the 7G-TRONIC seven-speed automatic transmission, improves efficiency even further. This is a 3-phase AC external rotor magneto motor, which develops a peak output of 15 kW/20 hp and a starting torque of 160 newton metres with an operating voltage of 120 Volts.
The Mercedes-Benz S400 BlueHYBRID accelerates from zero to 100 km/h in 7.2 seconds, and reaches an electronically governed top speed of 250 km/h. The Mercedes-Benz S400 BlueHYBRID betters the already very favourable NEDC fuel consumption of the conventionally powered S350 by up to 2.2 litres per 100 kilometres. CO2 emissions are reduced by 21 percent.
In addition the hybrid module features an extremely comfortable and efficient start/stop function, which already switches the engine off when the vehicle is rolling to a stop at less than 15 km/h, for example before stopping at traffic lights. When it's time to move off again, the electric motor immediately and imperceptibly restarts the main engine as soon as the driver releases the brake pedal or operates the accelerator. This likewise contributes to fuel economy and environmental conservation: as the engine restarts practically instantly, emissions are also minimised during the starting phase. The vibrations and jolts that are unavoidable when starting with a conventional starter are also reduced to a minimum.
The new S400 BlueHYBRID exemplifies the strategy of Mercedes-Benz, whose declared aim is to offer the brand's customers economical and environmentally compatible premium cars - without compromising in terms of typical brand attributes such as safety, comfort and a superior driving experience.
Major areas of development focus include modular drive technologies, which are used on a stand-alone basis or in combination depending on the vehicle class, operating profile and customer requirements - Mercedes-Benz has already described how this applies to the product portfolio in its "Road to the Future". In this context Mercedes-Benz also provides an outlook on the future of the internal combustion engine, with the innovative DIESOTTO engine in the Mercedes-Benz F700 research car.
