|The C 350 CGI BlueEFFICIENCY.|
Mercedes-Benz will add three fuel-efficient variants to its C-Class range: the C 180 KOMPRESSOR, C 200 CDI and C 350 CGI BlueEFFICIENCY models. Fuel consumption of the high-volume C 180 KOMPRESSOR and C 200 CDI models will be reduced by up to 12%.
The BlueEFFICIENCY version of the 100 kW/136 hp C 200 CDI consumes 5.1 liters of diesel per 100 kilometers (46.1 mpg US), while the C 180 KOMPRESSOR BlueEFFICIENCY with 115 kW/156 hp covers 100 kilometers with 6.5 liters of premium gasoline (36.2 mpg US). This corresponds to 135 and 156 grams of carbon dioxide, respectively, per kilometer. The C 350 CGI BlueEFFICIENCY features spray-guided gasoline direct injection and burns around 10% less fuel than the model with the current V-6 engine.
Engines. For the C 180 KOMPRESSOR, Mercedes-Benz has reduced the overall displacement of the four-cylinder engine from 1,796 to 1,597 cubic centimeters, while retaining the same output (115 kW/156 hp) and torque (230 Nm/170 lb-ft). This downsizing of the engine’s displacement, combined with measures for optimizing the combustion chamber, mixture formation and engine friction, adds up to a total potential fuel saving of 0.35 liters per 100 kilometers. The 6.5 L/100km fuel consumption of the C 180 KOMPRESSOR BlueEFFICIENCY is 0.9 liters (12%) less than for the standard production model.
The displacement, output and torque of the CDI engine remain unchanged. The package of efficiency measures (below) has enabled the NEDC fuel consumption of the BlueEFFICIENCY version of the C 200 CDI to be cut by 0.6 liters (10.5%) to 5.1 L/100km.
The new C 350 CGI BlueEFFICIENCY is equipped with a 3.5-liter spray-guided gasoline direct injection engine with a compression ratio of 12.2. (Mercedes-Benz became the first car maker to put spray-guided direct gasoline injection into series production in 2006.) Despite generating a higher power output and even greater torque, the new model consumes around 10% less fuel than the C 350 saloon with the current V-6 engine.
The six-cylinder CGI engine delivers 215 kW/292 hp of power and 365 Nm/269 lb-ft of peak torque at 3,000 rpm—15 kW/20 hp and 15 Nm/11 lb-ft more respectively than the current V-6 unit with port injection. Fuel consumption of the C 350 CGI BlueEFFICIENCY has been cut to approximately 8.4 L/100km (28 mpg US), about 1 liter below the figure for the current C 350.
The C 350 CGI BlueEFFICIENCY takes 6.2 seconds to accelerate from 0 to 100 kph and is capable of an electronically limited top speed of 250 kph/155 mph (provisional figures).
The six-cylinder engine demonstrates its particular strengths during stratified-charge operation when the powerplant operates with a high excess of air and is thus very fuel-efficient. In the Mercedes direct injection engine, this favorable lean-burn operation with a stratified charge in the combustion chamber is also possible for the first time at higher engine speeds and load ranges because the engine’s combustion chambers are injected with several successive jets of fuel in fractions of a second during each power stroke, thereby substantially improving mixture formation, combustion and consumption.
Whereas stratified-charge operation was previously only feasible over a limited partial load range, the CGI six-cylinder engine can now be operated in stratified charging mode over a wider range.
High-speed, ultra-precise piezoelectric injectors are among the key components of the second-generation direct gasoline injection system. The piezoelectric valves open their injectors outwards to create an annular gap just a few microns wide, allowing the fuel jet to form with a uniform, hollow cone-shaped pattern. With millisecond switching times, the piezoelectric injectors also permit the multiple injection that promotes lean-burn operation and helps optimize conditions to deliver the engine’s consumption figures.
A high-pressure pump with downstream distributor and pressure valve supplies the fuel and regulates the amount delivered in accordance with requirements. With a pressure of up to 200 bar, the system develops around 50 times the fuel pressure of a conventional port-injection system.
Measurements show that untreated emissions (hydrocarbons) are reduced by more than half in the warm-up phase. Active control of injection and combustion also produces higher temperatures in the exhaust manifold, thereby warming up the catalytic converters faster.
Four-valve technology, variable camshaft adjustment for the intake and exhaust sides, two-stage intake manifold, balancer shaft and an intelligent heat management system with map-controlled thermostat are some of the other technical highlights that the direct injection engine has adopted from the port-injected C 350 engine. The crankcase and cylinder head are made out of aluminium; the cylinders are fitted with low-friction, dimensionally stable liners made out of a lightweight aluminium-silicon alloy.
For the new BlueEFFICIENCY models, Mercedes engineers also reduced weight, aerodynamic drag and rolling resistance and organized the onboard energy management more efficiently. Together, these measures add up to a fuel saving on the NEDC driving cycle of 0.9 liters per 100 kilometers for the C 180 KOMPRESSOR, and 0.6 liters for the C 200 CDI.
Lightweighting. Mercedes managed to shave off between 19 and 32 kilograms of weight depending on the model. This is in part due to a newly developed windshield made of laminated glass, which weighs around 1.2 kilograms less than before. This is made possible by a technology transfer from the Maybach luxury sedan: between the panes of glass is a new, acoustically effective plastic membrane which efficiently absorbs wind noise. This has enabled Mercedes engineers to reduce the thickness of the windscreen, achieving a further weight reduction without compromising noise comfort in any way.
The noise-insulating lining of the firewall has also been weight-optimized with the help of special materials and computer simulations. Mercedes-Benz recalculated the required firewall insulation and precisely redefined the material thickness of the sound-absorbing resinous foam in line with the noise input. This needs-driven redesign reduces the weight of the lining by around 20%.
Forged lightweight wheels also have a positive effect on the weight. These weigh around 1.8 kilograms less than conventional light-alloy wheels, saving a total of more than seven kilograms per vehicle. These new lightweight wheels (6 J x 16 ET 39), which have aerodynamic benefits too, are standard equipment for the new BlueEFFICIENCY variants of the C 180 KOMPRESSOR and C 200 CDI.
Aerodynamics. At 120 kph/75 mph, the aerodynamic drag of the vehicle body already accounts for around 50% of all the dynamic resistance a passenger car must overcome, according to Mercedes. With a Cd of 0.27, the C-Class is among the most aerodynamically efficient notchback saloons in its market segment. The Cd figure for the new BlueEFFICIENCY models has been reduced by 7% to 0.25. Aerodynamic enhancements include:
Smooth underbody cladding ensures that the air can flow beneath the vehicle body without turbulences. The full engine compartment and underbody panelling of the diesel models is also standard equipment in the BlueEFFICIENCY version of the C 180 KOMPRESSOR.
Partially blanking off the radiator grille reduces the airflow into the engine compartment, thereby lowering wind resistance. Adequate cooling of the four-cylinder engines is of course uncompromised by this measure.
Sealing the joins between the hood and headlamps, as well as between the bumper and headlamps, improves the airflow around the front end.
The housings of the exterior mirrors were developed in the wind tunnel, and are particularly streamlined in form.
Lowering the suspension by 15 millimeters reduces aerodynamic drag, and has a particularly noticeable effect at higher speeds.
The design of the new lightweight wheels also meets aerodynamic requirements, and improves the airflow around the vehicle flanks.
Rolling resistance. In addition to lightweight construction measures, Mercedes-Benz also collaborate with Michelin to develop lightweight tires with a particularly low rolling resistance. These are now receiving their series production premiere in the C-Class, and help to reduce fuel consumption.
Rolling resistance is primarily caused by tire deformation as the tire contacts the road surface. This has a braking effect on the car, since additional energy is required to overcome this deformation resistance. Up to around 100 kph, rolling resistance has a greater effect on fuel consumption than aerodynamic drag, according to Mercedes.
The belt of this newly developed tire for the C-Class contains a multi-layered mesh of high-strength steel for less deformation. It is also lighter in weight than conventional designs, enabling a further 1.7 kilograms or so to be saved per set of tires. The secret, however, mainly lies in the chemical composition: the rubber compound for the treads and side walls is designed to ensure that rolling resistance is reduced by 17%, while retaining the same good handling and braking characteristics.
Energy management. Intelligent control of ancillary units and the reduction of friction losses also contribute to the increased fuel economy. In the BlueEFFICIENCY models of the C-Class, the power steering system is controlled on a needs-driven basis. The standard power steering in the C-Class has an additional valve which switches off the servo pump when it is not required.
While this pump operates continuously in all driving situations in conventional steering systems, the new valve interrupts the flow of hydraulic fluid when the car has followed a straight course for a while, switching off the servo pump. This has the advantage that the engine no longer needs to provide energy to drive the servo pump, meaning that it operates more economically. Thanks to this technology, the NEDC fuel consumption is cut by 0.14 liters per 100 kilometers&mash;which equates to a reduction of 2.5% in the case of the C 200 CDI.
Drive and transmission. As a further contribution to reduced weight and friction, the BlueEFFICIENCY C 180 KOMPRESSOR and C 200 CDI saloons are equipped with a newly developed final drive featuring further-improved antifriction bearings, forged differential gears and a lightweight construction. These measures reduce the friction forces within the transmission, hence the engine expends less energy in overcoming them. The longer final-drive ratios of the BlueEFFICIENCY versions also help to reduce fuel consumption. These are as follows:
C 180 KOMPRESSOR: 2.87 : 1 (rather than 3.07 : 1)
C 200 CDI: 2.47 : 1 (rather than 2.65 : 1)
The C 180 KOMPRESSOR and C 200 CDI models are both equipped with the six-speed manual transmission with overdrive characteristics as standard. With a ratio of 0.838 : 1 and 0.828 : 1, respectively, sixth gear considerably lowers the engine speed, contributing to more fuel-efficient driving.
A newly developed gearshift display in the cockpit informs the driver when he or she should change gear to save fuel. Experience gained during the Mercedes-Benz ECO Training courses has shown that drivers are able to make average fuel savings of up to 15% with an economical and energy-conscious style of driving. In addition to gearshift recommendations, the instrument cluster features a newly developed display showing the present fuel consumption. This will appear in the centre of the speedometer as an easily legible bar chart. A brief glance at the display is sufficient to tell the driver the current fuel consumption in liters per 100 kilometers. The bar chart responds immediately when the driver changes to a higher gear or takes his foot off the accelerator to use the deceleration fuel cut-off function.