Captivating design, passion-fuelled driving enjoyment and outstandingly low CO2 emissions – these are the hallmarks of the new Mercedes-Benz E-Class Coupe. Its sporty temperament is largely attributable to newly developed and modified engines, including a new four-cylinder powerplant with direct injection, which outperforms engines that boast a far higher displacement yet still succeeds in saving fuel. With a displacement of 2.2 liters, the engine in the Mercedes-Benz E 250 CDI BlueEFFICIENCY Coupe develops 150 kW/204 hp and consumes 5.1 liters of diesel per 100 kilometers; equivalent to CO2 emissions of 135 g/km. Mercedes-Benz offers a total of five powerful engines – four of them with direct injection – for the new E-Class Coupe. These exemplary fuel-consumption and CO2 figures, achieved without compromising on agility or driving enjoyment, are down to BlueEFFICIENCY measures as well as to the new engines. These measures include optimised aerodynamics with the world-best cd (drag-coefficient) figure for any series-production car. And that is not to mention a sophisticated energy management system, a shift-point and fuel-consumption indicator in the cockpit, and tires with low rolling resistance. All of the engines for the new E-Class Coupe meet the requirements of the EU5 emission standard. Thanks to its innovative technology, the E-Class Coupe proves that excitement, driving enjoyment and ecology can go hand in hand.
It is now possible to combine the temperament of a sports car and the stylistic allure of a coupe with ambitious ecological aims. As proven by Mercedes-Benz with the new E-Class Coupe, whose motto is "more power and more driving enjoyment with even lower fuel consumption". Thanks in no small part to the Mercedes strategy, which involves substituting large-displacement, non-turbocharged engines for turbocharged powerplants with a lower displacement. Key benefits of this concept include lighter weight, reduced internal friction and a more economical fuel-consumption map. As a consequence, the newly developed and modified four-cylinder powerplants have a lower displacement yet develop more power than earlier six-cylinder units whilst also posting impressive fuel-consumption figures only previously achievable on a regular basis by compact cars.
The engine line-up for the new E-Class Coupe comprises four-, six- and eight-cylinder powerplants with outputs ranging from 150 kW/204 hp to 285 kW/ 388 hp.
Fuel consumption of 5.1 liters per 100 km and CO2 emissions of 135 g per km
With its newly developed four-cylinder powerplant, the E-Class Coupe is a generation ahead when it comes to diesel technology. The new engine features latest-generation common-rail direct injection, fast piezo injectors, enhanced exhaust gas recirculation, and new twin turbochargers that ensure spontaneous power delivery and excellent performance characteristics. To put this into figures, the E 250 CDIBlueEFFICIENCY Coupe with an output of 150 kW/204 hp and a torque of 500 Nm is around 36 more powerful and produces 47 percent more torque than the previous four-cylinder engine in the outgoing model, yet it consumes around 17 percent less fuel: 5.1 liters per 100 kilometers (provisional NEDC combined figure), equivalent to 135 grams of CO2 per kilometer. All of which makes the new CDICoupe more fuel efficient than comparable models in this output category.
Topping the range of diesel models is the E 350 CDIBlueEFFICIENCY Coupe with six cylinders and an output of 170 kW/231 hp. Despite the higher output and torque produced by this sophisticated compression-ignition engine, fuel consumption is considerably less than that of the previous model, amounting to just 6.8 liters per 100 kilometers, equivalent to 179 grams of CO2 per kilometer. Petrol models with up to 12 percent lower fuel consumption thanks to direct injection The petrol models are equally impressive, boasting a higher output and lower fuel consumption than their predecessors. The new E 250 CGIBlueEFFICIENCY Coupe model with direct petrol injection has a displacement of 1.8 liters and an output of 150 kW/204 hp yet consumes a mere 7.2 liters of premium unleaded petrol per 100 kilometers (provisional NEDC combined figure) – around one liter per 100 kilometers (12 percent) less than the previous four-cylinder engine (135 kW/184 hp) with conventional fuel injection and a supercharger. The CO2 emissions of the new direct-injection model have been cut to 167 grams per kilometer.
The E 350 CGIBlueEFFICIENCY Coupe is powered by the world's first petrol engine with 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 8.5 liters per 100 kilo-meters (NEDC combined figure), which is 14 percent lower than the figure for the previous model, whose V6 engine featured port injection.
The eight-cylinder engine in the E 500 Coupe – the flagship powerplant in the new generation of Mercedes-Benz V-engines – develops 285 kW/388 hp with a relatively low fuel consumption of 10.9 liters per 100 kilometers. Attributes of this variant of the new Coupe include high output and torque yield as well as exemplary refinement and effortlessly superior agility.
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 specified by previous standards.
Lower fuel consumption thanks to BlueEFFICIENCY
Like the new engines, the BlueEFFICIENCY package for the E-Class Coupe helps to reduce fuel consumption. A team of development engineers drawn from every key discipline has optimised the parts and components – by reducing their weight, modifying their form, improving their functioning or ensuring more efficient energy management – in order to save fuel.
The work performed in the wind tunnel has proven particularly successful: with a drag coefficient (cd figure) of 0.24, the new E-Class Coupe is the world's most aerodynamic series-production car. Further BlueEFFICIENCY measures include newly developed tires which have had their rolling resistance reduced by up to 17 percent as well as energy-saving control of the alternator, fuel pump, air-conditioning compressor and power steering. Displays on the speedometer inform the driver of the current fuel consumption and when it is best to change up a gear in order to ensure economical and ecoconscious driving.
With its newly developed direct-injection diesel and petrol engines, Mercedes-Benz has taken further major strides forward in its quest to reduce both fuel consumption and exhaust emissions – without compromising on agility and driving enjoyment.
The new four-cylinder diesel engine in the E 250 CDIBlueEFFICIENCY Coupe, for example, shows just how much progress has been made: with an output of 150 kW/204 hp, a peak torque of 500 Nm and a displacement of 2.2 liters, it develops around 36 percent more power and delivers 47 percent more torque than the previous four-cylinder diesel engine yet consumes around 17 percent less fuel: 5.1 liters per 100 kilometers (provisional NEDC combined figure). What's more, CO2 emissions are just 135 grams per kilometer. All of which means that the new CDICoupe is more fuel-efficient than comparable models in this output category.
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 250 CGI BlueEFFICIENCY Coupe model with direct petrol injection has a displacement of 1.8 liters and an output of 150 kW/204 hp, consuming a mere 7.2 liters of premium unleaded petrol per 100 kilometers (provisional NEDC combined figure) – around one liter per 100 kilometers (12 percent) less than the previous four-cylinder engine (135 kW/184 hp) with conventional fuel injection and a supercharger. The CO2 emissions of the new direct-injection model have been cut to 167 grams per kilometer.
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 specified by previous standards.
Diesel engines: new four-cylinder unit featuring state-of-the-art common-rail technology
As well as being economical and ecofriendly, the four-cylinder CDIengine impresses with its exceptional agility, effortlessly superior power delivery and exemplary refinement. The former is reflected in the performance figures: the new E 250 CDIBlueEFFICIENCY Coupe needs just 7.4 seconds to accelerate from 0 to 100 km/h, while the sprint from 80 to 120 km/h takes the two-door model a mere 6.6 seconds. The engine is part of a new series of four-cylinder powerplants, which sees Mercedes-Benz introducing the fourth generation of its tried-and-trusted common-rail direct-injection units into series production. One of its hallmarks is a 400-bar increase in the maximum rail pressure, which now stands at 2000 bar. 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 reduction in untreated emissions.
Newly developed piezo injectors are key components in the latest CDIengine generation. 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 new injectors are equipped with a stack of thin piezo-ceramic 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 even 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 low emissions, low fuel consumption at full load and peak output is the ignition pressure of 200 bar, which puts the new four-cylinder diesel model at the head of the field when it comes to diesel engines for passenger cars.
Torque: two-stage turbocharging for exceptional pulling power
The new diesel engine in the E 250 CDIBlueEFFICIENCY Coupe model marks the debut of two-stage turbocharging in a series-production diesel engine for Mercedes-Benz passenger cars. The aim is to achieve further advantages compared to a single-stage turbocharger, for example an improvement in start-up performance and peak output.
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 initially 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, distributing the exhaust gas energy to the turbines with optimum efficiency. Downstream of the HP turbine, the two exhaust gas streams join up again, and the remaining exhaust gas energy drives the LP turbine at a maximum speed of up to 185,000 revolutions per minute. To protect against overloading, the LP turbine is 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 harmoni ous 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 up to 140 degrees Celsius so that a larger volume of air can enter the combustion chambers.
Cooled exhaust gas recirculation to reduce NOx emissions
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.
Pedestrian protection: 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 a short chain drive.
Six-cylinder CDI: increased output and fuel consumption of 6.8 liters per 100 kilometers
In a similar vein, the V6 diesel engine for the E 350 CDI BlueEFFICIENCY Coupe 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 torque of 540 Nm alone – compared to the 510 Nm developed by the previous model – which is available between 1600 and 2400 rpm, ensuring outstanding agility when accelerating from rest and exemplary flexibility when accelerating in any gear. The figures are impressive to say the least: the E 350 CDI BlueEFFICIENCY Coupe accelerates from 0 to 100 km/h in 6.7 seconds and from 80 to 120 km/h in 4.6 seconds. The six-cylinder unit now has an output of 170 kW/231 hp instead of 165 kW/224 hp as before.
Despite the higher output and torque, fuel consumption is considerably less than that of the previous model, amounting to just 6.8 liters per 100 kilometers, equivalent to 179 grams of CO2 per kilometer. The 7G-TRONIC seven-speed automatic transmission is specified as standard for the E 350 CDI BlueEFFICIENCY Coupe.
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 and enhancing the turbocharger with a more efficient EGR cooling zone, switchable bypass duct, ceramic glow system, modified injection nozzles and optimised air ducting.
The range of diesel engines for the new E-Class at a glance:
*Provisional figures; **NEDC combined fuel consumption; ***NED
Petrol engines: new four-cylinder unit with direct injection
CGIappears at the end of the model designation of the four- and six-cylinder petrol engines for the new E-Class Coupe, signifying that Mercedes-Benz uses direct petrol injection for all of 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 powerplant consumes up to 13 percent less fuel than the previously installed supercharged engine with port injection. Power and torque, however, are much higher than in the case of the outgoing model: 150 kW/204 hp instead of 135 kW/184 hp and 310 Nm instead of 250 Nm. Hence the new CGI Coupe also boasts even more impressive performance figures:
0 to 100 km/h: 7.2 seconds instead of 9.1 seconds as before
80 to 120 km/h: 5.0 seconds (in 3rd gear) instead of 6.7 seconds as before
Mercedes-Benz equips the E 250 CGI BlueEFFICIENCY Coupe with a five-speed automatic transmission. The four-cylinder engine is made almost entirely of aluminium: the crankcase is made of diecast 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.
Thermal management: coolant circulation based on engine temperature
The Mercedes engineers have paid special attention to the engine's warm-up governor because also has a major effect on 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, welded to the exhaust manifold on the engine's exhaust side, 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, is around four kilograms lighter and, in addition, 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.
Direct injection: pressure of up to 140 bar and new multi-hole injectors
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 CGIengine has 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 a homogeneous range, in other words with a stoichiometric air-to-fuel ratio of 14.7 : 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 EU 5 emission standard.
Comfort-enhancing measure: balancer in the crankcase
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 that are caused by the motion of the pistons, for example, which 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.
Six-cylinder engine: CGI technology with spray-guided direct petrol injection
The E 350 CGIBlueEFFICIENCY Coupe is powered by the world's first petrol engine with 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 8.5 liters per 100 kilometers (NEDC combined figure), which is 14 percent lower than the figure for the previous model, whose V6 engine featured port injection. These exemplary performance and fuel-consumption figures are achieved using cost-efficient premium unleaded petrol (RON 95). The seven-speed automatic transmission is fitted as standard. What's more, the highly economical and environmentally compatible CGIpowerplant provides a unique driving experience: it takes the V6 Coupe just 6.3 seconds to accelerate from 0 to 100 km/h and a mere 3.8 seconds to complete the burst from 80 to 120 km/h (in second gear).
Mode of operation: stratified-charge mode, even at higher engine speeds
Mercedes-Benz was the first car manufacturer to introduce the spray-guided combustion system into series production in 2006. Thanks to higher thermo-dynamic 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 vastly improving mixture formation, combustion and consumption.
Fast and highly 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 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-Benz 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 with a logic-controlled thermostat are further technical 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 lightweight, low-friction aluminium-silicon coating that is stable in shape.
Precision-modified eight-cylinder engine
The eight-cylinder unit in the E 500 Coupe – the flagship powerplant in the new generation of Mercedes-Benz V engines – provides 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 Coupe, which is equipped with the 7G-TRONIC 7-speed automatic transmission as standard:
0 to 100 km/h: 5.1 seconds
80 to 120 km/h: 2.8 seconds (in 2nd gear)
Mercedes engineers use an intelligent valve-timing concept, achieving a level of progress that is a major factor behind the excellent torque and output characteristics. An optimum supply of fresh mixture for the cylinders is assured thanks to four-valve technology and, above all, continuously variable and continuous intake and exhaust camshaft adjustment. The valves are always opened at precisely the right moment in any driving situation, significantly improving the gas cycle in the combustion chambers and reducing energy losses.
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 engine's torque and refinement.
The key data for the new E-Class Coupe petrol models at a glance:
*Provisional figures; **NEDC combined fuel consumption; ***NEDC
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 CDIBlueEFFICIENCY Coupe with a modified transmission which, thanks to more effective gearing and a newly developed dual-mass flywheel, is capable of transmitting the peak torque of 500 Nm with the utmost reliability. On account of the larger gears, the transmission is around 78 milli-metres longer than its counterpart for the other four-cylinder models.
The five-speed automatic transmission, available as an option for the four-cylinder CDICoupé (standard for the E 250 CGI) has likewise been precision-modified by the Mercedes engineers and features a newly developed converter that reduces the hydraulic losses and, therefore, operates even more fuel-efficiently than previously. In "C" mode, the transmission meets the most stringent of requirements in terms of fuel consumption, comfort and output, while "S" mode offers a more sportier configuration with an appropriately adapted gear-change strategy and accelerator pedal characteristic. Optional extras for the AMGSports package include "M" mode, which has been specially configured for the keenest of drivers. Standard equipment for the new V6 and V8 E-Class Coupe 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.
BlueEFFICIENCY – the trademark for exceptionally economical and ecofriendly Mercedes passenger cars – is a package of measures compiled by development engineers across all disciplines, the main aims being to reduce weight, aerodynamic drag and rolling resistance, to further optimise the engine technology, and to make energy management even more efficient.
Mercedes-Benz's commitment to reducing fuel consumption and carbon-dioxide emissions targets actual driver usage profiles. As part of a large-scale field trial, the typical driving profiles of Mercedes customers were ascertained and combined in an inhouse fuel-consumption test covering a total of almost two million kilometers. Hence the positive effects of the BlueEFFICIENCY concept are most noticeable during everyday use of the cars.
For the new E-Class Coupe, Mercedes-Benz has developed an extensive raft of measures, which is one of the key factors behind the reduction in fuel consumption. From the power steering to the tires, from the fuel pump to the alternator, the development engineers scrutinised a wide range of components to determine if and how lightweight designs, new forms, more efficient control or enhanced functioning could be employed to save fuel. Although many of the individual measures only improved fuel economy by the odd percentage point or two, together they add up to a substantial saving.
Fan shutter adapts the flow of air through the engine compartment in line with the current driving situation By performing complex computer calculations and meticulous work in the wind tunnel, the Mercedes engineers have succeeded in aerodynamically optimising the body, achieving an impressive overall result: with a cd figure as low as 0.24 (depending on model version), the E-Class Coupe is the world's most aerodynamic series-production car.
One of the main reasons behind the reduction in wind resistance is the new, electropneumatically controlled fan shutter. Its development is based on the knowledge that the air flowing through the radiator and the engine compartment accounts for up to ten percent of a car body's total aerodynamic drag. The fan shutter allows the engine's cooling air quantity to be limited in line with requirements, thus saving fuel. In essence, this means that, when the engine is running under part load and requires relatively little cooling, the radiator grille is closed by a circular system of louvres located behind the radiator. For minimum cooling, the shutter allows just a small amount of residual air to enter the engine compartment, but opens completely when the sensors signal that more cooling air is required.
The fact that the area around the radiator is hermetically sealed ensures that the fan shutter works extremely effectively, allowing precise control of the air flowing into the engine compartment. When the fan shutter is closed, the cd figure falls by 0.013, which is equivalent to a fuel saving of up to 0.2 liters per 100 kilometers when travelling at the motorway speed of 130 km/h. The fan shutter is fitted as standard on the four-cylinder models and on the E 350 CGIBlueEFFICIENCY Coupe model.
Energy management: intelligent detail solutions beneath the bonnet
The most important aspect when trying to save fuel and reduce CO2 emissions is to avoid unnecessary energy losses – both internal losses caused by friction in the powertrain and losses due to drag and rolling resistance.
By way of example, the use of a turbocharger in place of the previous mechanical supercharger in the new models with direct petrol injection allows even more efficient energy management, since the mechanical drive power from the belt drive required to operate the supercharger is no longer needed. The biggest plus point in favour of the new four-cylinder engines is the homogeneously operated direct injection system, which brings about a major increase in thermodynamic efficiency compared to the previous port injection system. The fuel vaporising in the cylinders lowers the temperature in the combustion chambers, thereby reducing the engine's tendency to knock and allowing higher compression.
The engine developers have succeeded in cutting fuel consumption further still by incorporating an intelligent thermal management system which prevents coolant from being pumped through the cylinders when the engine is cold, meaning that the combustion chambers can heat up more quickly.
Another aspect of the BlueEFFICIENCY concept involved optimising the automatic transmissions: the newly developed converter for the five-speed automatic transmission reduces hydraulic losses and, therefore, uses up less fuel. For the seven-speed automatic transmission in the E 350 CDI BlueEFFICIENCY Coupe, Mercedes-Benz has developed a decoupling device which is activated when the car is stationary: at traffic lights or in traffic jams, the transmission switches to "N" position so as to reduce the engine load.
The standard-fit power steering system is based on an intelligent solution designed to prevent energy losses and, therefore, cut fuel consumption. Unlike conventional steering systems, in which the power steering pumps operate at full power on a permanent basis, the power steering pump in the new Coupe features an additional valve for on-demand control. This means that, when the driver does not require steering assistance, an electronic control unit minimises the operating power of the power steering pump. The advantage of this system is that less energy from the engine is required to drive the pump.
The delivery rate of the power steering pump is increased again spontaneously when the driver moves the steering wheel. In this instance too, the system operates on-demand, adjusting itself in line with the current steering speed and vehicle speed.
In order to ensure on-demand energy management, Mercedes-Benz is for the first time using controlled fuel pumps in the petrol engines for the new E-Class Coupe (all diesel engines will also incorporate this feature from market launch). In this setup, the engine control unit only calls for the maximum pump output during full-load operation. In all other driving situations, the pump adapts the delivery volume and pressure in line with the current driving situation, resulting in a fuel saving of 0.15 liters per 100 kilometers (NEDC). The tires also help to minimise fuel consumption. The E-Class Coupe is fitted with newly developed tires whose rolling resistance has been reduced by up to 17 percent without impairing their outstanding handling and braking character-ristics.
Alternator: power from braking energy
Each time the car is braked, kinetic energy is converted into heat and therefore goes to waste. This is why the new E-Class Coupe incorporates efficient alternator management. This means that, whenever the engine is coasting and whenever the vehicle is braked, the voltage level in the vehicle electrical system is increased and the battery is charged. This increased alternator load assists the driver with braking and also helps to recuperate part of the braking energy, which is converted into electrical energy. This is why experts refer to recuperation. Conversely, the alternator switches to no-load operation in certain situations – for example when accelerating or when the battery charge level is high – thus relieving the strain on the drive system. This process saves fuel to the tune of around 0.1 liters per 100 kilometers (NEDC) and up to 0.2 liters per 100 kilo-metres when in city traffic, where coasting and braking are more frequent than in the NEDC test cycle.
Cockpit information: current fuel consumption displayed
Drivers can also help to save fuel, aided in the new E-Class Coupe by a display in the centre of the speedometer, which indicates the current fuel consumption – converted into liters per 100 kilometers. Drivers are therefore able to check whether their driving style is fuel-efficient and, consequently, environmentally friendly. In addition to showing this information, the display also advises the driver when to change up a gear (manual models).
Mercedes-Benz "ECO driver training" courses have shown that adopting an economical and energy-efficient driving style alone can cut fuel consumption by up to 15 percent on average.
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