OFFICIAL PRESS RELEASE
Stuttgart, Germany, Mar 03, 2009
Drive system: Less fuel and more driving pleasure: sophisticated engine technology reduces consumption and exhaust gas emissions
* Fuel consumption: 23 percent lower than in the predecessor model
* Torque: 25 percent more in the new E 250 CDI BlueEFFICIENCY model
* Direct injection: eight of nine engines with CGI technology
* Emission control: BlueTEC for the cleanest diesel in this class
* Transmissions: new technology for fuel-efficient motoring
"Less is more". This slogan certainly proves true when looking under the bonnet of the E‑Class. That's because the newly developed and modified four-cylinder powerplants have a higher output than the previous six-cylinder units, despite the reduction in displacement. Plus they return impressive fuel-consumption figures that were previously only achievable in the compact-car class. The Mercedes strategy is to use turbocharged engines with lower displacement in place of high-displacement, non-turbocharged engines. Key benefits of the concept include lighter weight, reduced internal friction and a more economical fuel-consumption map.
The new four-cylinder diesel engine in the E 250 CDI BlueEFFICIENCY model, for example, is proof that the plans have worked out successfully: with an output of 150 kW/204 hp, a peak torque of 500 Nm and a displacement of 2.1 litres, it develops around seven percent more power and delivers 25 percent more torque than the previous V6 diesel engine with a displacement of three litres whilst consuming around 23 percent less fuel: just 5.3 litres per 100 kilometres (NEDC combined figure), making it far more fuel-efficient than comparable saloons in this performance class. The CO2 emissions figure for the new four-cylinder diesel models is 139 grams per kilometre – up to 24 percent lower than the figures achieved by the previous CDI models.
In the case of the petrol models too, "more power and more driving pleasure with even lower fuel consumption" proves to be the perfect formula: the E 200 CGI BlueEFFICIENCYmodel with direct petrol injection has a displacement of 1.8 litres and an output of 135 kW/184 hp yet consumes a mere 6.8 litres of premium unleaded petrol per 100 kilometres (provisional NEDC combined figure). Plus the CO2 emissions figures for the four-cylinder petrol models are more than a fifth lower than those for the outgoing models.
As with carbon dioxide emissions, the engines for the new E-Class have also taken a further major step towards the future when it comes to exhaust gas emissions: all of the powerplants meet the requirements of the EU 5 standard, whose limits are up to 80 percent more stringent than those in previous standards. And with the new E 350 BlueTEC, Mercedes-Benz offers the world's cleanest diesel, undercutting the limits of the EU 6 standard, which is not even due to come into force until 2014.
Diesel engines: newly developed four-cylinder model with a choice of three power outputs
The newly developed diesel engine extends the range of four-cylinder CDI units for the E-Class to three. These engines span the power output range from 100 kW/136 hp to 150 kW/204 hp; fuel consumption and CO2 emissions in all the new four-cylinder diesel engines have been reduced to just 5.3 litres per 100 kilometres and 139 grams per kilometre respectively (NEDC combined fuel consumption).
The technical advances made by the Mercedes-Benz engine designers responsible for this new four-cylinder diesel unit can also be seen in the performance figures: the most powerful variant, with an output of 150 kW/204 hp, outperforms its predecessor by 20 percent yet has the same displacement. Plus the peak torque has been increased by 25 percent from 400 to 500 Nm. When it comes to specific output too, the powerplant posts a new record: 70 kW/95 hp and 233 Nm per litre of displacement.
The new engines are characterised by high output, agile response and exceptional pulling power. Plus they are exceptionally refined for four-cylinder units. Then there is the highly impressive agility, reflected in the performance figures, for example: the E 250 CDI BlueEFFICIENCY accelerates from zero to 100 km/h in just 8.2 seconds, while the sprint from 80 to 120 km/h takes the Saloon a mere 9.7 seconds. The E 220 CDI BlueEFFICIENCY developing 125 kW/170 PS takes 9.1 seconds to reach 100 km/h from a standing start and accelerates from 80 to 120 km/h in 11.3 seconds, while the E 200 CDI BlueEFFICIENCY completes the burst from zero to 100 km/h in 10.7 seconds and from 80 to 120 km/h in 13.2 seconds.
A wealth of innovative technologies has been implemented to enable the four-cylinder diesel engines to achieve their exceptional power and torque characteristics, economy, emissions performance and refinement, including new developments that do not currently feature in any other standard-production diesel engine for passenger cars.
Fourth-generation common-rail technology with piezo injectors
This series of four-cylinder engines sees Mercedes-Benz introducing fourth-generation common-rail direct injection into series production. One of its hallmarks is a 400-bar increase in the maximum rail pressure, which now stands at 2000 bar for the E 220 CDI BlueEFFICIENCY and the E 250 CDIBlueEFFICIENCY models. This increased pressure potential was a key factor in raising the engine output to up to 150 kW/204 hp and the peak torque to 500 Nm whilst also achieving a significant cut in untreated emissions.
Newly developed piezo injectors are key components in the latest CDIgeneration. They use their piezoceramic properties to change their crystal structure – and therefore their thickness – in a matter of nanoseconds when electrical voltage is applied. The injectors are equipped with a stack of thin piezoceramic layers (called the "piezo stack") to enable them to achieve a sufficient overall lift from the very small lift per layer. In contrast to the systems commonly used to date, this lift activates the nozzle needle directly, so that the fuel injection can be adjusted more precisely in line with the current load and engine-speed situation – for example by means of precise multiple injections, which have a favourable effect on emissions, fuel consumption and combustion noise. What's more, the engine is far quieter when idling than its predecessor.
Another key factor behind the impressive output and fuel consumption at full load with respect to emissions is the maximum ignition pressure. And, with 200 bar, the new four-cylinder diesel unit from Mercedes-Benz is among the leading contenders in the field of passenger-car diesel engines.
Impressive torque yield thanks to two-stage turbocharging
The new diesel engine in the E 220 CDI BlueEFFICIENCY and E 250 CDI BlueEFFICIENCY models marks the debut of two-stage turbocharging in a standard-production diesel engine for passenger cars at Mercedes-Benz. The aim is to achieve further advantages compared to a single-stage turbocharger, for example a further improvement in start-up performance and peak output. A single-stage turbocharger with variable nozzle turbines is used in the E 200 CDIBlueEFFICIENCY model. The lower engine power allows a smaller turbocharger to be used and, therefore, ensures likewise excellent start-up performance.
The compact module for the new two-stage turbocharger consists of a small high-pressure (HP) turbocharger and a large low-pressure (LP) turbocharger. These are connected in series, and each has a turbine and a compressor driven by this turbine. The HP turbine is located directly at the exhaust manifold and initially allows exhaust gas to flow through it; it then rotates at up to 215,000 revolutions per minute. The HP turbine housing features an integral bypass duct, which can be opened or closed by means of a charge-pressure control flap triggered by a vacuum cell. If the flap is closed, the whole exhaust stream flows through the HP turbine, meaning that the exhaust-gas energy is available solely for the HP turbine drive. This means that the optimum charge pressure can be built up at low engine revs.
As the engine speed increases, the charge-pressure control flap opens, primarily to prevent the HP turbocharger from becoming overloaded. A portion of the exhaust stream then flows through the bypass duct to relieve the HP section. Downstream of the HP turbine, the two exhaust gas streams join up again, and any remaining exhaust gas energy drives the HP turbine at a maximum speed of up to 185,000 revolutions per minute.To protect against overloading, the LP turbine is also equipped with a bypass, which is opened or closed by means of a wastegate. Once the engine reaches medium revs, the HP turbine's charge-pressure control flap is opened so wide that the HP turbine ceases to perform any appreciable work. This allows the full exhaust gas energy to be directed with low losses into the LP turbine, which then does all of the turbine work.
The two compressors are likewise connected in series and are in addition connected to a bypass duct. The combustion air from the air cleaner first flows through the low-pressure compressor, where it is compressed as a function of the LP turbine's operating energy input. This pre-compressed air then passes into the high-pressure compressor, which is coupled to the HP turbine, where it undergoes further compression – the result is a genuine two-stage turbocharging process.
The key benefit of this sophisticated, on-demand control of the combustion air supply by means of two turbochargers is the improved cylinder charging and, consequently, a high torque even at low revs. What's more, fuel consumption is reduced. During normal operation, the advantages of this concept can be seen in the harmonious driving characteristics without turbo lag, a good torque curve across the entire engine speed range, spontaneous throttle response and noticeably improved performance.
As a logical addition to the turbocharger system, Mercedes-Benz installs a larger intercooler than the one seen in the previous models, which reduces the temperature of the compressed and heated air by around 140 degrees Celsius so that a larger volume of air can enter the combustion chambers.
Lower NOx emissions thanks to cooled exhaust gas recirculation
The newly developed EGRvalve works like a rotary disc valve and ensures precise control of the fresh air and recirculated exhaust gas. So as to optimise the quantity of exhaust gas recirculated and thereby achieve high recirculation rates, the exhaust gases are cooled down as required in a highly efficient heat exchanger with a large cross-sectional area. Together with the HFM (hot-film air-mass sensor) module integrated in the fresh-air ducting, which provides the engine control unit with precise information about the current fresh-air mass, this setup brings about a significant reduction in nitrogen oxide emissions.
The combustion air subsequently flows into the charge-air distributor module, which supplies air to each cylinder in a uniform manner. Built into the distributor module is an electrically controlled intake port shutoff, which allows the cross-sectional area of each cylinder's intake port to be smoothly reduced in size. This alters the swirl of the combustion air in such a way as to ensure that the charge movement in the cylinders is set for optimum combustion and exhaust emissions across the full range of engine loads and speeds.
The advantages of a rear-mounted camshaft drive
Another of the highlights of the new four-cylinder diesel engine is the rear-mounted camshaft drive, which allows statutory pedestrian protection requirements to be met when the engine is installed longitudinally and the bonnet rises from front to rear. The valve timing mechanism is another new development and reduces friction at the 16 intake and exhaust valves, which are controlled by one overhead intake camshaft and one overhead exhaust camshaft acting via cam followers featuring hydraulic valve clearance compensation. The camshaft, Lanchester balancer and the ancillary assemblies are driven by a combination of gearwheels and just a short drive chain.
The switchable water pump, another highlight of the new Mercedes diesel engine, helps to quickly heat up the combustion chambers and the friction partners as well as reducing fuel consumption and untreated emissions. The pistons are cooled by an oil pump with a central control valve for all four piston-cooling sprayer units with large oil-spray nozzles. It creates identical, thermal boundary conditions for all cylinders. The generous dimensions ensure optimum piston cooling, even at full load, and make for a long service life. What's more, the controlled oil pump reduces the oil flow rate and, therefore, consumption.
Six-cylinder CDI engine: higher output and torque but lower fuel consumption
In a similar vein, the V6 diesel engine for the new E-Class is one of the most sophisticated compression-ignition units on the world market. It offers substantially greater output, comfort and driving enjoyment than other engines thanks to the immense torque of 540 Nm alone, which is available between 1600 and 2400 rpm, ensuring outstanding agility when accelerating from rest and exemplary flexibility when accelerating in any gear. To put this into figures, the E 350 CDI BlueEFFICIENCY model (170 kW/231 hp) accelerates from 0 to 100 km/h in 6.9 seconds and from 80 to 120 km/h in 5.1 seconds.
Despite the higher output and torque, fuel consumption has been reduced by 0.5 litres to 6.8 litres per 100 kilometres (NEDC combined figure), equivalent to 179 grams of CO2 per kilometre. The 7G-TRONIC seven-speed automatic transmission is specified as standard for the E 350 CDI BlueEFFICIENCY model.
The Mercedes engineers have gone to great lengths to optimise the technology at the heart of the V6 diesel engine, reducing the compression from 17.7 to 15.5, enhancing the turbocharger with a more efficient EGR cooling zone, switchable bypass duct, ceramic glow system, modified injection nozzles and optimised air ducting.
E 350 BlueTEC meets the requirements of the EU6 emission standard
BlueTEC is a key concept for the future of the diesel engine. Thanks to the highly efficient emission control system developed by Mercedes-Benz, the compression-ignition models meet the strictest of emission requirements, making them the world's cleanest diesel cars. This technology will be available for the E-Class in the new E 350 BlueTEC model with V6 diesel engine from autumn 2009 onwards. In this model variant, the powerplant has an output of 155 kW/211 hp and provides its maximum torque of 540 Nm from 1600 rpm. Fuel consumption in the E 350 BlueTEC model with seven-speed automatic transmission is 7.0 litres per 100 kilometres (provisional NEDC combined figure), while the CO2 emissions figure is 183 grams per kilometre.
For its installation in the BlueTEC model, the V6 engine has been modified in detail, among other things to further reduce in-engine untreated emissions and to meet the statutory requirements with respect to on-board diagnostics (OBD). The emission control system features a close-coupled oxidation catalytic converter and a diesel particulate filter which is located in the firewall area. Regeneration times are reduced as a result.
At the heart of the BlueTEC system are two SCR catalytic converters (SCR= Selective Catalytic Reduction) and an upstream "AdBlue®" injector. "AdBlue®" is an aqueous urea solution which converts the nitrogen oxides (NOx) in the SCRcatalytic converters into harmless nitrogen through a process of reduction. The complex exhaust gas aftertreatment process is monitored and diagnosed by several sensors, including a differential pressure sensor and an oxygen sensor as well as NOX and temperature sensors.
For the "AdBlue®" additive, the E 350 BlueTEC is installed with an additional 25‑litre tank equipped with a diaphragm pump, valve, pressure and temperature sensor, and an electric heater. The latter prevents the 33-percent urea solution from freezing at low temperatures. The tank is refilled as part of the scheduled maintenance programme.
The range of diesel engines for the new E-Class at a glance:
Petrol engines: new four-cylinder units with direct injection
CGI appears at the end of the model designation of the four- and six-cylinder engines for the new E-Class, signifying that Mercedes-Benz uses direct petrol injection for these powerplants - a technology which allows further advances when it comes to reducing petrol consumption.
Compared to conventional port injection, direct fuel injection allows higher compression and, therefore, improved thermodynamic efficiency, saving motorists money at the pump: the new four-cylinder direct-injection powerplants for the E‑Class consume up to 21 percent less fuel than the comparable engines installed in the outgoing model. In the E 250 CGI BlueEFFICIENCY model (150 kW/ 204 hp), Mercedes-Benz has replaced the previous V6 2.5-litre engine with a four-cylinder 1.8-litre unit yet still manages to increase torque by over 26 percent. This result reveals a further Mercedes strategy for the future: the use of turbochargers in small-displacement engines.
The new four-cylinder petrol engines combine excellent economy with outstanding power delivery and agility, as highlighted by the performance figures for the E 200 CGI BlueEFFICIENCY and E 250 CGI BlueEFFICIENCY models:
E 200 CGI BlueEFFICIENCY:
0 to 100 km/h: 8.7 seconds
80 to 120 km/h: 13.9 seconds
E 250 CGI BlueEFFICIENCY:
0 to 100 km/h: 7.7 seconds
80 to 120 km/h: 6.0 seconds (in 3rd gear)
Mercedes-Benz equips the E 250 CGI BlueEFFICIENCY model with a five-speed automatic transmission, while the E 200 CGI BlueEFFICIENCY model features a six-speed manual transmission and the ECO start/stop function (also see page 90), which shuts off the engine automatically when it is idling, thus making a significant contribution towards saving fuel.
Variable camshaft adjustment and intelligent thermal management
The four-cylinder engines are made almost entirely of aluminium: the crankcase is made of cast aluminium, while a special, high-strength aluminium alloy is used for the cylinder head. Two forged overhead camshafts with variable adjustment are used to control the 16 valves. A vane-type adjuster with integrated control valve allows fast and smooth adjustment of the timing, ensuring that it is always at the optimum setting. This setup has two advantages: firstly, the variable camshaft adjustment enables a high torque yield even at low revs; secondly, this technology allows high specific outputs. The valves are controlled by means of cam followers and feature maintenance-free, hydraulic valve clearance compensation.
The Mercedes engineers have paid special attention to the engine's warm-up governor because it affects fuel consumption. This is why the new direct-injection petrol model features an electronically controlled thermostat to ensure that circulation of the coolant is stopped when the engine is cold. This setup allows the engine oil to heat up quickly and, therefore, minimises in-engine friction. This intelligent thermal management system is logic-controlled. In other words, it is based on driving style, ambient temperatures and other parameters.
The turbocharger module is welded to the exhaust manifold on the engine's exhaust side and features a wastegate valve and a deceleration air function for controlling the pressure characteristics. There were very good reasons for using a turbocharger in place of the previously installed mechanical supercharger – not least the higher efficiency as the engine does not need to provide the extra drive power required for the mechanical supercharger. What's more, the turbocharger takes up far less space than the supercharger, weighs around four kilograms lighter and, in addition, also offers better noise and vibration characteristics. The Mercedes engineers brought about a noticeable improvement in the turbocharger's bottom-end response by incorporating newly developed turbine geometry and a cylinder-flushing process.
Injection pressure of up to 140 bar and new multi-hole injectors
Mercedes-Benz has a long tradition in the field of direct petrol injection. As early as the mid-1950s, the Stuttgartmanufacturer unveiled this technology in the 300 SL, the legendary "Gullwing" model. This classic sports car was the first series-produced automobile to feature a four-stroke engine with direct injection - a sensational development that boosted the six-cylinder powerpack's output significantly.
In the direct-injection system, the air and fuel are not mixed until they reach the combustion chambers. With the help of an injector, the fuel is injected into the cylinders at an angle of 30 degrees and, depending on the engine operating characteristics, at a pressure of up to 140 bar. Here the fuel droplets and the air particles form a mixture which is guided to the spark plugs via specially shaped recesses in the pistons. By way of comparison, the fuel pressure in a four-cylinder engine incorporating conventional injection technology is approximately 3.8 bar.
In order to ensure optimum swirl in the mixture, thus making combustion fast and as complete as possible, the CGI engines have intake ports with specially calculated flow characteristics. An adjustable swirl flap is also used so as to produce high turbulence in certain operating ranges and thus improve the combustion process. The high-pressure fuel pump is driven by the intake camshaft, while a quantity control valve integrated in the pump module ensures on-demand metering of the fuel supply. A pressure regulator with its own sensor, monitored by the engine control unit, controls the pressure in the fuel line (rail), which is directly connected to the multi-hole solenoid injectors. The four-cylinder direct-injection units operate in the homogeneous range, in other words with a stoichiometric air-to-fuel ratio of 14.6 : 1 (Lambda = 1), which is important for emission control by means of three-way catalytic converter. The new four-cylinder direct-injection engines meet the requirements of the EU5 emission standard.
Balancer in the crankcase and controlled oil pump
In addition to exemplary power delivery, low fuel consumption and low exhaust emissions, the new Mercedes four-cylinder engines have a further advantage, namely outstanding refinement thanks in no small part to the newly developed Lanchester balancer: two forged shafts supported in three bearings, which are arranged below the crank mechanism and counter-rotate at twice the crankshaft speed. In so doing, they compensate for the inertia forces which are caused by the motion of the pistons, for example, and can lead to irritating vibrations. The aluminium housing that contains the bearing-mounted balancer shafts is located in the oil sump, where it is bolted to the crankcase from below. The crankcase also contains the controlled engine oil pump, which is driven by one of the two shafts by means of a gear pair.
CGI six-cylinder engine with spray-guided direct petrol injection
The E 350 CGIBlueEFFICIENCY model is equipped with the world's first petrol engine to feature spray-guided direct injection. The six-cylinder powerplant develops 215 kW/292 hp and provides a peak torque of 365 Nm from 3000 rpm. Thanks to the state-of-the-art engine technology, which Mercedes-Benz has modified right down to the last detail, fuel consumption is reduced to between 8.5 and 8.8 litres per 100 kilometres (NEDC combined figure), which is 0.5 litres per 100 kilometres less than the figure achieved by the outgoing model. These exemplary performance and fuel-consumption figures are achieved using cost-efficient premium unleaded petrol (RON 95).
What's more, the highly economical and environmentally compatible CGIpowerplant provides a unique driving experience: it takes the E 350 CGIBlueEFFICIENCY model just 6.3 seconds to accelerate from 0 to 100 km/h and a mere 4.2 seconds to complete the sprint from 80 to 120 km/h (in third gear).
Stratified-charge mode, even at higher engine speeds, thanks to multiple injection
Mercedes-Benz was the first car manufacturer to introduce spray-guided direct petrol injection into series production in 2006. Thanks to higher thermodynamic efficiency, this technology allows better use of the fuel and, therefore, lower fuel consumption and lower exhaust gas emissions. The key benefit of the six-cylinder engine is delivered in stratified-charge mode, when the powerplant operates with a high degree of excess air and, therefore, extremely fuel-efficiently. This advantageous "lean-burn operation" is now also possible when the Mercedes direct-injection unit is running in higher engine speed and load ranges because the combustion chambers are supplied with fuel several times in succession within a fraction of a second in every combustion cycle, thus improving mixture formation, combustion and consumption.
Fast and precise piezo injectors are among the key components of the second-generation direct petrol injection system. They open their nozzle points outwards, forming an annular gap that is mere micrometres in size, shaping the jet of fuel and ensuring its even, hollow-cone-shaped dispersion. Thanks to their ability to switch within milliseconds, the piezo injectors also allow the multiple injection that is also of benefit for lean-burn operation, thus playing a crucial role in achieving the engine's exemplary consumption figures. A high-pressure pump with downstream distributor and pressure valve supplies the fuel and ensures on-demand flow control. With a level of up to 200 bar, the system's fuel pressure is several times higher than that in a conventional port injection system.
The combustion process with several injections in succession per combustion cycle developed by Mercedes engineers also enhances the refinement and emission characteristics of the V6 engine. Tests show that untreated emissions (hydrocarbons) are reduced by more than half in the warm-up phase. Plus the specifically targeted injection and combustion control allows higher temperatures in the exhaust manifold, ensuring faster heating of the catalytic converters.
Emissions are controlled by two close-coupled three-way catalytic converters
with linear lambda control, which are activated immediately after a cold start. Mercedes-Benz reduces nitrogen-oxide emissions by means of two-pipe electrically controlled exhaust gas recirculation, which directs up to 40 percent of the exhaust gases back into the cylinders, depending on the engine's operation, and by means of two NOx storage catalytic converters on the underbody. During lean-burn operation, these catalytic converters absorb the nitrogen oxides and re-release them in short regeneration phases so that they react chemically to form harmless nitrogen.
Four valves per cylinder, variable intake and exhaust camshaft adjustment, a two-stage intake manifold, a balancer shaft and intelligent thermal management are further highlights of the V6 engine with direct injection. The crankcase and cylinder head are made of aluminium; the cylinders are equipped with liners that have a low-friction aluminium-silicon coating.
Precision-modified eight-cylinder engine
The eight-cylinder unit in the E 500 model – the flagship powerplant in the new generation of Mercedes-Benz V engines – incorporates an extensive technology package to create a blend of high output and torque yield with exemplary refinement and effortlessly superior agility. The extent of the powerplant's capability is highlighted by the performance figures for the new top-of-the-range E-Class model, which is equipped with the 7G-TRONIC 7-speed automatic transmission as standard:
- 0 to 100 km/h: 5.3 seconds
- 80 to 120 km/h: 3.6 seconds (in 3rd gear)
By incorporating an intelligent valve-timing concept, the Mercedes engineers achieve advances that are a major factor behind the excellent torque and output characteristics. An optimum supply of fresh gas for the cylinders is assured thanks to four-valve technology and, above all, continuously variable and continuous intake and exhaust camshaft adjustment. The valves always open at the just the right time, in line with the current driving situation, thus substantially improving the gas cycle in the combustion chambers and reducing the amount of lost energy.
The "quadruple" continuously variable camshaft adjustment process is further enhanced by shifting camshafts, which are used to enable opening of the exhaust valves and, therefore, further improve the engine's gas cycle. The exhaust cams are designed so that the valves open at different times during the exhaust process, depending on the firing order. As a consequence, the pressure fluctuations inherent in a V8 engine's exhaust train are reduced. Thanks to a more constant residual-gas content, a higher knock limit and improved bottom-end and mid-range cylinder charging, the shifting camshafts increase the V8 engine's torque and refinement. The effective mean pressure at 2000 rpm, for example, is around six percent (10.3 : 11.0 bar) higher than in a comparable engine not fitted with shifting camshafts.
The key data for the new E-Class petrol models at a glance:
Modified manual transmission and consumption-optimised automatic
The Mercedes engineers have adapted the tried-and-tested six-speed manual transmission to suit the high torques of the four-cylinder engines. For instance, they equip the new E 250 CDI BlueEFFICIENCY model with a modified transmission which, thanks to more effective gearing, a dual-mass flywheel and a larger clutch, is capable of transmitting the peak torque of 500 Nm. On account of the larger gears, the transmission is around 78 millimetres longer than its counterpart for the other four-cylinder models.
The five-speed automatic transmission, available as an option for the petrol models and four-cylinder diesel models (standard for the E 250 CGI BlueEFFICIENCY) has likewise been precision-modified and features a newly developed converter that reduces the hydraulic losses and, therefore, operates even more fuel-efficiently than previously.
Standard equipment for the new V6 and V8 E-Class models includes a seven-speed automatic transmission. In "C" mode, the 7G-TRONIC offers a consumption-optimised transmission mode that is always active after the engine is started. Earlier upshifts mean the powerplant operates at a lower engine speed level and, therefore, consumes less fuel. A further new development is the standstill decoupling function: if the car is stopped at traffic lights or stuck in traffic, for example, the transmission shifts to "N" position and thus reduces the engine load.
4MATIC: new all-wheel-drive technology saves up to 0.9 litres of fuel per 100 kilometres
For the E-Class, Mercedes-Benz offers a new generation of the 4MATIC all-wheel-drive system, which is even more efficient, even lighter and even more compact than the previously installed all-wheel-drive technology. These advantages over the outgoing model are evident in the improved traction and lower fuel consumption.
Three of the models are available with all-wheel drive: the E 350 4MATIC with a six-cylinder engine developing 200 kW/272 hp consumes 9.7 litres of premium unleaded petrol per 100 kilometres (provisional NEDC combined figure), making it 0.7 litres per 100 kilometres more economical than before.
In the case of the E 350 CDI 4MATIC BlueEFFICIENCY model (170 kW/231 hp), the fuel saving compared to the comparable predecessor model amounts to 0.6 litres per 100 kilometres. The V6 direct-injection diesel engine posts a fuel consumption figure of 7.3 litres per 100 kilometres (provisional NEDC combined figures). With the E 500 4MATIC model, meanwhile, the Mercedes engineers have succeeded in reducing the fuel consumption by 0.9 litres per 100 kilometres compared to the outgoing model.
The new E-Class 4MATIC models at a glance:
The latest-generation 4MATIC is a Mercedes development that only adds 50 to 70 kilograms of extra weight (depending on model) and boasts a compact design that takes up very little space in the transfer case area. It can therefore be installed without any modifications to the body and without impeding the front-passenger footwell. What's more, the compact design makes for lower noise and vibration levels.
The permanent all-wheel-drive system, which works in tandem with the standard-fit Electronic Stability Program (ESP®), really comes into its own in poor weather conditions such as rain, snow or black ice as well as when starting off, accelerating, cornering at speed or driving on poor road surfaces. In these situations, the electronically controlled 4MATIC system greatly enhances traction, directional stability and road adhesion.
These exemplary handling qualities go hand in hand with hallmark Mercedes comfort thanks on the one hand to the selected damper control and on the other hand to the meticulous spring and damper tuning for the all-wheel-drive models, which largely replicates that for the rear-wheel-drive models. The modified AIRMATIC air suspension system is fitted as standard for the E 500 4MATIC model or as an optional extra for the two other all-wheel-drive Saloons. A further comfort-related aspect of the 4MATIC is the omission of conventional differential locks which, as other all-wheel-drive passenger cars show, affect steerability and handling.
Transfer case integrated in 7G-TRONIC automatic transmission
Unlike before, the transfer case is now integrated directly in the 7G-TRONIC transmission. The transfer case consists of a planetary centre differential and two bevel gears, which form the side output to the front axle. The centre differential produces the newly defined torque distribution between the front and rear axles – 45 to 55 percent (previously 40 to 60 percent) – which is noticeable above all in the improved directional stability, road adhesion and traction compared to the outgoing models.
A further highlight of the new powertrain concept is the compact side output to the front axle gear, which is based on a one-stage concept, meaning that a complete gear stage can be omitted compared to the previous 4MATIC drive system. Furthermore, the rear universal joint on the propshaft is integrated in the power take-off output gear. This space-saving design allows the propshaft to the front axle to be routed very close to the transmission without having to make modifications to the bodyshell.
The significantly higher efficiency of the 4MATIC drive system and the resulting lower fuel consumption compared to the predecessor models is largely down to the omission of the gear stage for the transfer case power take-off and an improved oil supply, since the integral design means that the transmission and the transfer case share the same oil circuit.
Multiple-disc clutch with lock between the front and rear axles
The new double-disc clutch located on the centre differential produces a basic locking torque of around 50 Nm between the front and rear axles. In this system, a cup spring preloads the clutch pack with a permanent force. If the wheels on one of the two axles start to spin, the relative movement of the discs causes a friction torque to be transmitted from the faster-turning axle to its slower-turning counterpart.
This principle of variable torque displacement between the front and rear axles improves the traction, directional stability and road adhesion of the 4MATIC models. The traction assistance provided by the double-disc clutch is especially noticeable when the friction ratio between the tyres and the road is low, since the clutch locks the powertrain mechanically during moderate starting if the friction coefficient between the tyres and the road is less than µ = 0.3 (more or less equivalent to snow). The wheels are prevented from spinning in such a way as to avoid what is known as the "polishing effect", which leads to a reduction in the friction coefficient. Another advantage of the double-disc clutch is the improved load-change characteristics of the 4MATIC models.
Electronic traction system in place of differential locks
4MATIC uses the Electronic Traction System (4ETS), an additional component of the Electronic Stability Program (ESP®), in place of conventional differential locks. It has been modified and now provides a even higher level of comfort and even better traction. 4ETS is activated automatically when one or more wheels lose grip on the road. In this event, 4ETS brakes these wheels automatically and individually, thus increasing the drive torque at the wheels offering sufficient traction at the same time. These millisecond-fast braking pulses achieve the same effect as three differential locks. In addition, the 4ETS automatic braking pulses are based on the speed of the car.
Copyright © 2009, Mercedes-Benz-Blog. All rights reserved.
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- The new Mercedes-Benz E-Class - PART X
- The new Mercedes-Benz E-Class - PART IX
- The new Mercedes-Benz E-Class - PART VIII
- The new Mercedes-Benz E-Class - PART VII
- The new Mercedes-Benz E-Class - PART VI
- The new Mercedes-Benz E-Class - PART V
- The new Mercedes-Benz E-Class - PART IV
- The new Mercedes-Benz E-Class - PART III
- The new Mercedes-Benz E-Class - PART II
- The new Mercedes-Benz E-Class - PART I
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- Daimler Heritage: TOPICS FOR APRIL 2009
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