Mercedes-Benz is opening a new chapter in its brand's core segment and at the same time setting new standards for luxury-class business vehicles: the E 300 BlueTEC HYBRID, available as a Saloon and Estate, impresses with new record values when it comes to efficiency. It boasts exemplary consumption levels (4.2 l/100 km[1]) as well as impressive performance: the 4-cylinder diesel engine of the E 300 BlueTEC HYBRID has 150 kW (204 hp) and 500 Nm. Combined with an electric motor producing 20 kW and 250 Nm, this results in a coherent overall concept. The E 300 BlueTEC HYBRID is the most economical luxury-class vehicle in the world.
The V6 petrol engine in the E 400 HYBRID produces 225 kW (306 hp) and 370 Nm, and is also supplemented by a further 20 kW and 250 Nm from the electric motor. The consumption figures based on the American CAFE standard are: City 24 mpg, Highway 31 mpg, Combined 27 mpg.
"With these two E-Class models we are now continuing our comprehensive hybrid offensive. The modular technology opens up a quick way for us to complement other model series with hybrid models", explains Professor Dr. Thomas Weber, Daimler Board Member for Group Research and Head of Mercedes-Benz Cars Development. "With a clear focus on the different requirements of the global markets, we are able to offer precisely the models which our customers want. The E-Class hybrids provide a clear reduction in consumption as well as a very impressive driving experience: they represent hybrid motoring at the premium level."
The new models do not require their passengers to have to compromise when it comes to space, however, whether in terms of the interior or the luggage compartment. And there are also additional benefits to the intelligent modular hybrid concept, which represents a comprehensive enhancement of the Mercedes-Benz S 400 HYBRID which has advanced to the position of clear market leader since 2009: no changes to the vehicle body are required, the hybrid module is both flexible and modular, thus allowing its use in other model series, and in addition to diesel and petrol variants there will also be right-hand drive variants. Meanwhile, the extra cost involved here is only moderate. The new hybrid models will be celebrating their world premiere at the Detroit Motor Show (14 to 22 January 2012) and will appear on the market over the course of the year. The E 300 BlueTEC HYBRID is initially planned to be launched on the European market, while the E 400 HYBRID will be made available on the American market first, followed by other countries such as Japan and China later.
The philosophy: increase efficiency without compromising comfort or use
The new hybrid models from Mercedes-Benz are part of the company's intelligent downsizing strategy which aims to make conventional models perform significantly more efficiently than ever before – without compromising when it comes to driveability or comfort. As part of this move, rather than focusing primarily on regular consumption, the engineers at the company have been examining exemplary consumption levels in everyday traffic. The notorious safety philosophy known as "Real Life Safety", which similarly highlights gains in safety under practical conditions rather than standard crash test results, is now being paired with "Real Life Efficiency".
Take the E 300 BlueTEC HYBRID by way of example: the hybrid model is based on the notoriously economical E 250 CDI, but exceeds it in terms of performance and undercuts in terms of fuel consumption by around 15 percent. The details are as follows:
- E 250 CDI: output of 150 kW, max. torque of 500 Nm, top speed of 242 km/h, acceleration from 0 to 100 km/h in 7.5 seconds, consumption of 4.9 litres of diesel/100 km, CO2 emissions of 129 g/km
- E 350 BlueTEC: output of 155 kW, max. torque of 540 Nm, top speed of 239 km/h, acceleration from 0 to 100 km/h in 7.8 seconds, consumption of 6.8 litres of diesel/100 km, CO2 emissions of 180 g/km
- E 300 BlueTEC HYBRID: output of 150 kW + 20 kW electric motor, max. torque of 500 Nm + 250 Nm, top speed of 242 km/h, acceleration from 0 to 100 km/h in 7.5 seconds, consumption of 4.2 litres of diesel/100 km, CO2 emissions of 109 g/km (values for Saloon)
As a result, the E 300 BlueTEC HYBRID is on a par with the E 300 CDI (170 kW/540 Nm) in practical use. However, it undercuts this model in terms of consumption and CO2 emissions by around 35 percent. The E 300 BlueTEC HYBRID also matches the E 300 CDI when it comes to vehicle weight too.
At the same time, hybridisation also represents an increase in ride comfort: starting up and moving off are practically silent, and the hybrid module also dampens any vibrations from the combustion engine. Furthermore, the vehicle's full range of climate control functions remain available even in start/stop mode.
The E 300 BlueTEC HYBRID and E 400 HYBRID at a glance:
The hybrid technology from Mercedes-Benz provides a whole host of additional functions which enhance comfort and efficiency at the same time, while making an overall contribution to creating a special driving experience with a sense of refined sportiness:
- Stationary vehicle/ECO start/stop function: the combustion engine can already be switched into deceleration mode at speeds below 160 km/h, since ancillary components such as the steering, brakes and air conditioning compressor operate electrically. The combustion engine is restarted quickly, conveniently and almost silently. A special Mercedes feature is the way in which the practical HOLD function interacts with the start/stop system: as soon the HOLD function is enabled (by fully depressing the brake pedal when stationary), the combustion engine also remains switched off when the driver then takes their foot off the brake pedal. Alternatively, when waiting for longer periods, the gear selector lever can be put into position "P" or the parking brake enabled, thus allowing the driver to remove their foot from the brake pedal.
Manoeuvring: parking or turning are for the most part carried out in electric mode
Accelerating: moving off and driving at low loads are carried out in purely electric mode. Accelerating from a standstill is particularly powerful, since the full torque of up to 250 Nm is available from the electric motor
Boost function: the electric motor supports the combustion engine when accelerating, such as when executing an overtaking manoeuvre, by providing additional drive torque
Cruising: at constant speeds, the engine control unit shifts the operating range towards lower specific fuel consumption levels
- "Sailing": the so-called "sailing" function can be used at speeds below 160 km/h. With this function, the combustion engine switches off and the desired speed is maintained primarily by using the electric motor, until the batteries need to be recharged
- Recuperation of kinetic energy (regenerative braking)in deceleration mode or when braking: during deceleration (reduction in speed by snapping off the throttle), the electric motor works as a generator and stores the converted kinetic energy back in the high-voltage battery. If the brake pedal is pressed, the generator output is initially increased proportionally for greater deceleration. Only when increased brake pressure is applied are the wheel brakes additionally called upon. To implement these functions, the new hybrid models have brakes which have been specially adapted for recuperation ("energy recuperation")
Comprehensive road tests using different test subjects have shown that it only takes a relatively short time for additional savings to be achieved as drivers learn to make increasingly deliberate and effective use of such functions. They are supported in their use of the features by the display concept of the hybrid models. The central display provides information on the current energy flow and the charge status of the batteries, as well as a top view of the vehicle, depicting the drivetrain and coloured energy flow. The driver is able to monitor fuel consumption via energy/time graphs.
Consumption: benefits in actual traffic, not just on paper
In urban traffic, with its frequent stationary, deceleration and short acceleration phases, the hybrid drive is able to play to its strengths in particular. This is thanks, on the one hand, to the frequent regenerative braking phases when decelerating and, on the other, to the capability to offer purely electric motoring when approaching traffic lights. The purely electric driving mode can also be used in stop-and-go traffic up to a speed of around 35 km/h and on journeys of up to a kilometre. When stationary, the combustion engine is switched off in most cases.
When it comes to inter-urban motoring, the boost, "sailing" and regenerative braking phases alternate in conjunction with an intelligent displacement of the combustion engine's load point. The actual effect depends on both the route profile as well as the behaviour of the driver.
On the motorway, the boost function takes a back seat in the higher engine speed range. Savings are achieved by the "sailing" function at speeds up to 160 km/h, for example on slight downhill gradients, by displacement of the combustion engine's operating point, electric operation of accessories, and regenerative braking when decelerating.
Extensive road tests on a wide variety of different routes have shown that compared with the notoriously economical E 250 CDI, it is possible to achieve additional significant increases in efficiency with the E 300 BlueTEC HYBRID.
The increased fuel efficiency is even more pronounced when the E 300 CDI is used as the comparison vehicle.
The hybrid module: compact, intelligently integrated powerhouse
The hybrid drive unit is an enhancement of the module used in the S 400 HYBRID and is based on the 7G-TRONIC PLUS automatic transmission.
A new element is the lack of hydraulic torque converter. Instead a wet clutch has been added, as also found in a number of powerful AMG models. As a result, the electric motor can be integrated into the transmission unit in such a way that it only requires marginally more installation space than the 7G-TRONIC (+65 mm). The lack of converter allows for a purely electric driving mode as well as the "sailing" function, and also therefore significantly increases the potential for reducing consumption.
The compact electric motor, which is installed in the clutch housing between the engine and the transmission to save space, is a 3-phase AC internal rotor magneto motor, which develops a peak output of 20 kW and a peak torque of 250 Nm at an operating voltage of 120 Volts.
The components: perfectly integrated into the vehicle
The electric energy of the hybrid drive comes courtesy of the high-voltage lithium-ion battery which has been specially developed for automotive use. Its characteristics include an output of 19 kW and an energy content of 0.8 kWh, enabling the E-Class to achieve a speed of up to 35 km/h and a range of up to one kilometre in purely electric mode.
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 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 DC transformer to supply power to other standard consumers such as the headlamps and comfort features. The 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.
To support cold starting and act as a buffer store for the on-board electrical system, a regular 12 Volt battery is located beneath the luggage compartment, and an additional small backup battery prevents unpleasant flickering of the vehicle lighting and dropouts in the infotainment system in start/stop mode.
By using sophisticated packaging it has been possible to integrate numerous hybrid-specific components, such as the high-power electronics, directly into the engine compartment along with the combustion engine, thus perfectly rounding off the modular principle: the hybrid models can be produced together with the regular versions on the same assembly line, without any specific issues. Another plus point of the overall concept is the scalability and compatibility with other vehicles and engines.
Safety: on a par with previous models
The intelligent integration of hybrid systems without having to make any changes to the vehicle body not only has the practical benefit of enabling full use of the available space. At the same time it also helps to ensure that the same high level of safety can be offered as in their counterparts fitted with combustion engines – something which is particularly important to Mercedes-Benz. The crash behaviour of the vehicles has also been safeguarded accordingly by means of crash simulations and tests.
When it came to the hybrid-specific properties which were relevant to aspects of safety, the development engineers were able to call on the extensive experience gained with the S 400 HYBRID introduced in 2009. The challenge in this area lay in ensuring the greatest possible safety for the electrical components. This safety system already applies in production, includes workshop personnel during servicing and maintenance, and also takes the emergency services into account when passengers need to be recovered following an accident.
Accordingly the hybrid technology of Mercedes-Benz is equipped with an extensive 7-stage safety concept.
1. In the first stage, all of the high-voltage wiring is colour-coded to eliminate confusion, and marked with safety instructions. This prevents assembly errors in production, and makes the regular quality checks easier to carry out.
2. The second stage comprises comprehensive contact protection for the entire system by means of generous insulation and newly-developed, dedicated connectors.
3. As part of the third stage, the lithium-ion battery has been given a whole package of carefully coordinated safety measures. This innovative battery is accommodated in a high-strength steel housing, and also secured in place. Bedding the battery cells in a special gel effectively dampens any jolts and knocks. There is also a blow-off vent with a rupture disc and a separate cooling circuit. An internal electronic controller continuously monitors the safety requirements and immediately signals any malfunctions.
4. The fourth stage of the safety concept includes separation of the battery terminals, individual safety wiring for all high-voltage components and continuous monitoring by multiple interlock switches. This means that all high-voltage components are connected by an electric loop. In the event of a malfunction, the high-voltage system is automatically switched off.
5. Active discharging of the high-voltage system as soon as the ignition is switched to "Off", or in the event of a malfunction, is part of the fifth stage.
6. During an accident, the high-voltage system is completely switched off within fractions of a second (stage six).
7. As the seventh and last stage, the system is continuously monitored for short circuits.
[1] All consumption and performance figures are preliminary figures based on the Saloon model, as at December 2011
Credits: Daimler AG
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