The rising demand for increasing efficiency in the commercial vehicle sector is stronger than ever before, not least because of future CO₂ standards, where the European Commission claims a reduction of 30 % by 2030. In order to meet such requirements, new technologies are necessary to reduce fuel consumption.

The demand-controlled operation of the auxiliaries facilitates potentials in the field of parasitic losses on an internal combustion engine. Therefore, a heavy-duty diesel engine was investigated on an engine dynamometer with regard to possible benefits in fuel consumption by replacing the mechanical water pump with an electric water pump (EWP). In Figure 1 it is displayed that the operation of an EWP under the same conditions as in the basis configuration (mech. WP) has a negative effect on the efficiency. The actual benefit can be gained through a decoupling from the engine speed, thus enabling a demand-controlled operation. By reducing the coolant volume flow rate by half, an increase in efficiency of 0.5 %_Pt. can be obtained in the so-called highway load point (constant drive of the truck at 85 km/h).

In addition, the application of an EWP can influence thermal management of the internal combustion engine significantly. Through the modification of the complex cooling system of the test carrier it was possible to affect the pollutant emissions – especially the nitrogen oxides.

Due to a reduction in the thermal load of one of the two vehicle coolers the remaining cooling power can be utilized to decrease the charge air temperature T21 (see Figure 2). Consequently, a reduction in T21 of 16 °C leads to 15 % savings in engine-out NO_x emissions. Regarding future emission standards, every potential reduction of pollutant emissions is beneficial.

In the course of the project the demand-controlled operation of the EWP was validated in transient cycles, thus getting quantifiable results for CO₂ reduction in test cycles as well as a simulation model will be set up in order to be able to evaluate the demand-controlled operation of further auxiliary components.