BMW announced that by autumn 2007, 22 models in the BMW Group (BMW, MINI, Rolls Royce) for model year 2008—about 40%—will meet or exceed the European voluntary CO2 target of 140 g/km. Three of these 22 vehicles are MINIs and two belong to an additional BMW model line.
The increase in the number of more fuel-efficient models is due to a number of factors, including the introduction of a number of new, smaller vehicles, the development of new four-cylinder gasoline and diesel engines (earlier post), and the deployment of micro-hybrid functionality (start/stop and regenerative braking) (earlier post).
|Overview of BMW models meeting or exceeding the 140g/km target for 2008. Click to enlarge.|
BMW is applying start/stop functionality as standard in all models with 4-cylinder engine (gasoline and diesel) and manual transmission in the 3 Series and 1 Series. All models of the 6, 5, 3 and 1 Series as well as the BMW X5 will feature regenerative braking, according to BMW.
Other features applied in different models across the line-up to enhance fuel economy include the needs-oriented control of ancillary units, the use of electrical steering and a Varioserv steering pump and the decoupling of the air conditioning compressor.
For example, needs-oriented control of the coolant pump uses significantly less energy than conventional systems which run permanently at full capacity. The servomotor of the electric steering is only activated when steering boost is required or desired by the driver.
With the Varioserv steering pump, the cam ring is adjusted in relation to pressure and volumetric flow so as to avoid the loss of drive train power as the engine speed increases.
The power dissipation of conventional air conditioning compressors can also be reduced by means of intelligent regulation. In the new BMW models, the compressor is separated from the belt drive by means of a magnetic coupling as soon as the air conditioning system is out of operation. These measures reduce the amount of electrical energy required, and as a result the generator has to convert significantly less primary energy into electrical current.
A special low viscosity transmission oil contributes to the reduction of frictional loss. Optimized heat management for the rear-axle drive ensures that frictional resistance is reduced more quickly after starting.
BMW is also using reduced rolling resistance tires as standard in select 5 Series models and in all models of the 3 Series and 1 Series. Active aerodynamics (cooling air flaps which open or close depending on the driving situation and which are actively controlled in some models) also contributes to the reduction of aerodynamic resistance.
The driver also receives support in the choice of the most economical driving style from the gear shift indicator. This system uses data provided by the engine control unit to calculate in each situation the most favorable point at which to shift down or up from the point of view of economical fuel consumption.
For model year 2008, 4-cylinder gasoline engines with second-generation High Precision Injection in lean combustion operation are used in all versions of the BMW 3 Series and the BMW 1 Series. In addition to the two engines already introduced with a capacity of 2.0 liters each, a new 1.6 liter gasoline direct injection engine in the new BMW 116i is now premiering. Compared to the predecessor engine in each case, the three new 4-cylinders feature increased output of between 5 and 15 kW, but decreased fuel consumption of up to 23%.
The 4-cylinder diesels now include the variable twin turbo unit. For MY 2008, the 2.0-liter lightweight aluminium units are available in up to three output levels for the BMW 5 Series, the BMW 3 Series and the BMW 1 Series as well as the BMW X3.