Car Design News: Mercedes B-Class Facelift In Detail

Diesel engines: fuel consumption reduced by a further seven percent

The B-Class continues to be available with a choice of six engines � two direct-injection diesel units (80 kW/109 hp and 103 kW/140 hp) delivering up to 300 Newton metres of torque, as well as four petrol engines with a peak power output of up to 142 kW/193 hp and a maximum torque of 280 Newton metres. The four-cylinder power units have undergone a series of detailed improvements in order to further reduce fuel consumption.

For the diesel models, this means that the combined NEDC fuel consumption
of the B 180 CDI and B 200 CDI has dropped by as much as seven percent � depending on tyre size � to 5.2 - 5.4 and 5.4 - 5.6 litres per 100 kilometres, respectively. The two turbodiesel models will therefore be an even less seldom sight at the filling station from now on; the B 180 CDI can clock up over 1000 kilometres on a single tank of fuel (54 litres).

Petrol models: new fuel-saving ECO start/stop function

Depending on the model and engine output, the four petrol variants of the B Class return fuel consumption figures of between 6.6 and 8.1 litres per 100 kilometres on the NEDC driving cycle. From autumn 2008, motoring is set to become even more economical with the arrival of the B 150 and B 170 BlueEFFICIENCY models featuring the ECO start/stop function (optional). This newly developed function automatically switches the engine off when the driver shifts to neutral at low speed whilst depressing the brake pedal. If the criteria for stopping the engine are fulfilled, a special display appears in the instrument cluster to inform the driver.

The moment the clutch is pressed or the brake pedal released, the engine springs back to life almost noiselessly and in a fraction of a second. This ability to restart the engine swiftly yet smoothly gives the ECO start/stop function a key edge over other systems of this type. To achieve this, Mercedes-Benz fits a starter-generator which is connected to the crankshaft via the belt drive. This allows the engine to start much faster and far more quietly than with the conventional starter. During the journey, the starter-generator feeds the electrical system on board the B-Class with energy.

In practical operation, substantial fuel savings of up to nine percent can be achieved with the ECO start/stop function, particularly when driving in city traffic with frequent stops at traffic lights or in tailbacks.

Natural-gas drive: a clean and economical alternative

A further new addition to the B-Class range bears the initials "NGT" on the right-hand side of its tailgate. They stand for "Natural Gas Technology" and identify a model variant which is as economical as it is environmentally compatible, courtesy of its bi-fuel drive: the B 170 NGT BlueEFFICIENCY is able to run on both natural gas and premium grade petrol while delivering an identical maximum output of 85 kW/116 hp.

In addition to the petrol tank, there are five natural gas reservoirs whose total capacity of 16 kilograms equates to a range of over 300 kilometres. With overall NEDC consumption figures of 7.3 litres of premium petrol and 4.9 kilograms of natural gas per 100 kilometres, the new B 170 NGT BlueEFFICIENCY is therefore able to attain a total range in excess of 1000 kilometres. The driver determines which power source the engine is run on at the touch of a button using the multifunction steering wheel; an electronic control unit carries out the switch instantaneously without any jolts � even while on the move.

The four-cylinder engine has been modified by Mercedes-Benz to include additional gas injectors on the underside of the intake manifold. A close-coupled pressure governor with electromagnetic shut-off valve regulates the supply of natural gas and keeps the pressure within the system constant.

The installation of the gas reservoirs, which are located in the rear and underneath the front passenger footwell, reduces the boot capacity of the B Class by 128 to 422 litres (as per the VDA measurement method), but there is still sufficient space for carrying a family's luggage.

The lower carbon dioxide emissions and cheaper fuel costs make natural gas an attractive alternative to petrol and diesel, both ecologically and economically speaking. On the NEDC cycle, the CO2 emissions are 17 percent lower than in the petrol-powered B 170 at 135 grams per kilometre. If the 4.9 kilograms (7.5 m�) of natural gas consumed per 100 kilometres by the new B 170 NGT BlueEFFICIENCY is converted into the equivalent quantity of petrol energy, the fuel cost per kilometre is around 50 percent less than when running on petrol.

Key B-Class engine, performance and fuel consumption figures at a glance:

	B 180 CDI	B 200 CDI	B 150	B 170	B 170 NGT	B 200	B 200 TURBO
Displacement cm�	1991	1991	1498	1699	2034	2034	2034
Output kW/hp	80/109	103/140	70/95	85/116	85/116	100/136	142/193
Max. torque Nm	250 at 1600- 2600 rpm	300 at 1600- 3000 rpm	140 at 3500- 4000 rpm	155 at 3500- 4000 rpm	165 at 3500- 4000 rpm	185 at 3500- 4000 rpm	280 at 1800- 4850 rpm
0-100 km/h s	11.3	9.6	13.2	11.3	12.4	10.1	7.6
Top speed km/h	183	200	174	184	184	196	225
NEDC consumption l/100 km*	5.2-5.4	5.4-5.6	6.6-6.8	6.8-7.1	7.5 m�	7.2-7.5	7.9-8.1
CO2 emissions g/km**	137-140	140-148	158-163	163-171	135	173-180	190-195

*combined consumption; **in NEDC driving cycle

Environmental Certificate: first ever lifecycle assessment for NGT drive too

Mercedes engineers have, for the first time, compiled an eco balance sheet for the natural-gas drive. It forms one element of the Environmental Certificate awarded to the B-Class by Germany's T�V Technical Inspection Authority. Mercedes-Benz is the only automotive brand in the world to have been granted this certificate, which is based on the stringent international standard ISO 14062 "Design For Environment". It is a confirmation of the Stuttgart-based brand's total commitment to all aspects of environmental protection. In contrast to just the standardised measurement of exhaust emissions and fuel consumption on the roller dynamometer, Mercedes engineers analyse the environmental compatibility of vehicles over their entire lifecycle � starting with their manufacture, continuing with their many years of use and finishing with their end-of-life disposal.

In all, over 40,000 individual processes come under scrutiny, whose analysis, computation and evaluation ultimately produce a comprehensive eco profile. This in turn forms the basis for the environmental certificate of the B-Class.

The results of this integrated analysis over a total distance travelled of 150,000 kilometres highlight, for example, a number of clear advantages for the natural-gas drive. The overall CO2 emissions are some 20 percent below the figure for the comparable petrol-engined model. Nitrogen oxide emissions are eleven percent lower, while the experts have calculated a 54 percent difference in carbon monoxide emissions over the entire lifecycle in favour of the natural-gas drive. The greater ecological cost of the manufacturing process for the new B 170 NGT is therefore balanced out after a distance of 17,300 kilometres.

The environmentally driven concept of the B-Class is clearly evident from its use of high-quality recycled plastics, for instance, or its components made from natural materials, including flax, cotton, coconut fibre, wood veneer and fibres from the abaca banana.

Source: Daimler AG

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