Automotive Intelligence - the web for automotive professionals and car enthusiasts
September 17, 2008
Moreover, the new S 400 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 S 400 BlueHYBRID is based on the S 350, 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.
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 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 S 400 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.
Especially on rural journeys and on motorways, the S 400 BlueHYBRID achieves a further efficiency improvement by moving the so-called operating point of the petrol engine to produce a lower specific fuel consumption. The extremely high start-off torque made possible by the boost effect of the electric motor gives the driver a particularly exhilarating feeling of powerful acceleration, while fuel consumption and emissions are reduced.
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.
This compact motor also acts as a starter and generator, adopting the functions of both these conventional ancillary units. Sophisticated interaction with the internal combustion engine makes numerous additional functions possible that positively influence the emissions and agility of the S 400 BlueHYBRID in equal measure. Moreover, this disc-shaped motor effectively dampens torsional vibrations in the drive train, thereby further reducing noise and vibrations in the interior. The result is even more ride comfort for both driver and passengers.
The overall system offers extensive benefits: firstly by helping to save fuel, and secondly by increasing driving pleasure with the help of the "boost" effect, where the electric motor gives powerful assistance to the petrol engine with its maximum torque of 160 newton metres right from the beginning of the fuel-intensive acceleration phase. This means that the hybrid drive system of the S 400 BlueHYBRID moves off powerfully even from very low engine speeds, as the torque curve impressively confirms. The additional torque of the hybrid module also has a consistently positive effect during subsequent acceleration phases. In all driving situations, the driver therefore benefits from the interaction between the two units in the form of powerful responsiveness and muscular torque - but without an increased fuel consumption.
The S 400 BlueHYBRID accelerates from zero to 100 km/h in 7.2 seconds, and reaches an electronically governed top speed of 250 km/h. The S 400 BlueHYBRID betters the already very favourable NEDC fuel consumption of the conventionally powered S 350 by up to 2.2 litres per 100 kilometres. CO2 emissions are reduced by 21 percent.
Locally emission-free driving with fuel-cell and battery-powered vehicles
The company is also actively involved in the development of clean and alternative fuels that do not compete with the production of foodstuffs - particularly in SunDiesel, which is obtained from plant waste.
An intelligent mix of drive systems as a solution for the mobility of the future
Mercedes-Benz has already brought numerous answers to the challenges of tomorrow to market. The most recent examples are the BlueEFFICIENCY models in the A-Class, B-Class and C-Class, the natural-gas-powered B 170 NGT and the powerful yet economical and clean BlueTEC SUVs, which were first introduced into the US market this year. A mix of modular drive systems, from the latest internal combustion engines with BlueTEC or direct injection, with or without hybridisation, right up to locally emission-free battery and fuel-cell-powered vehicles, provides all the conditions that will enable Mercedes-Benz to offer its customers need-related mobility to the brand's customary high standard into the long-term future.
(Sept. 17, 2008)