Fuel consumption lowered by a variable high-pressure pump

Despite this impressive performance increase, the fuel consumption remains at the same, exemplary level for which the Mercedes compact class is known. The specific fuel consumption of the diesel engines has now seen an improvement over the previous CDI engines of the C-Class to 205 g/kWh, which means that NEDC fuel consumption values of just five litres per 100 kilometres may be expected.

This result is largely thanks to the second-generation common-rail injection system, which allows even more precise control of the solenoid valves on the injectors and demand-related regulation of the high-pressure pump. In the first-generation CDI engines this pump always operated at maximum output, which required a high energy input at the expense of fuel consumption and also caused a large increase in fuel temperature. This conflict of aims has now been resolved with a newly developed high-pressure pump, which is demand-controlled by means of a vacuum throttle. Depending on the fuel pressure calculated by the engine management system, the delivery chambers of the pump are only partly filled and enable the delivery volume to be demand-related. This technology considerably reduces the energy input required by the pump, and therefore the fuel consumption.