CO2 emission reduction is currently the most important market driver in the automotive industry. However, Rheinmetall Automotive development divisions had already been placing a high priority on reducing the fuel consumption directly linked to CO2 emissions long before the current discussions about the environment. The automotive supplier is therefore a longstanding specialist in CO2 reduction. To achieve this, the engineers of Rheinmetall Automotive adjust many small variables in the advanced development and refinement of existing products and the conception of new models in order to be able to demonstrate as great a total CO2 reduction as possible. At the same time, it is very challenging to properly evaluate the savings potential of each individual measure as a component in the entire system: "Individual developments often interact with one another and combine to result in lower CO2," explains Heinrich Dismon, Head of Research & Technology at Rheinmetall Automotive.
Elaborate simulation process
Rheinmetall Automotive then looked into the savings potential of its automotive components with regard to CO2 emissions. "We used the most modern, state-of-the-art vehicle simulation processes for this purpose," says Dismon. The calculation is supported by test results obtained through engine test bench trials and a CO2 competency demonstrator that was constructed in-house. The test conditions under which the vehicle simulation transpires exert a great influence on the results of the investigations.
The consumption-reducing effect of the Rheinmetall Automotive product range was therefore determined for various legally prescribed approval cycles: for the current New European Driving Cycle NEDC, the more globally oriented WLTP and the high-performance cycle FTP 75. When selecting the baseline vehicle, Rheinmetall Automotive decided upon a compact model with a petrol engine from the so-called C-segment.
This will make it more difficult for vehicles with petrol engines to fulfil the European legal CO2 limit
On the one hand, this is because the C-segment is very widespread in the marketplace. On the other hand, for technical reasons, petrol engines have greater specific fuel consumption and higher CO2 emissions than diesel engines of equal performance rating. "This will make it more difficult for vehicles with petrol engines to fulfil the European legal CO2 limit of 95 g CO2/km for 2020. As engineers, our task is therefore even more demanding," says Dismon. Within the context of the full vehicle simulation, Rheinmetall Automotive ascertained the effects of reducing weight by employing lightweight aluminium structural components in place of standard parts, variable oil and coolant pumps and a comprehensively optimised cylinder system together with a piston assembly and bearing points in the basic engine. Moreover, the engine was equipped with a fully variable intake valve control -system, including two electric camshaft phase shifters, and cooled low-pressure exhaust gas recirculation.
13% lower emissions
For the variable oil pumps, the simulations in the NEDC resulted in a CO2 reduction of about 1 g/km. Reduced friction in the cylinder groups and engine mountings as well as the use of a variable mechanical or electric coolant pump each reduced CO2 by 3g/km. The fully variable intake valve control system with two electric camshaft phase shifters even posted 7 g less CO2/km. A 50 kg lighter vehicle weight thanks to lightweight aluminium structural components saved an additional 2 g of CO2/km. In total, there was an overall reduction of about 18 g CO2/km in the NEDC and in the FTP 75. Even in the new WLTP cycle, which is said to correspond more strongly with real driving behaviour, there was still a reduction of 15 g CO2/km. "In relation to the currently valid NEDC, 120 g CO2/km corresponds to a reduction of approximately 13% as compared with the baseline emission of 138 g CO2/km," says Dismon, summarising the results.