Daimler wins Steel Innovation Award for diesel car pistons

11 June 2015

Daimler AG has been awarded the Steel Innovation Award 2015 in the category “products made of steel”. The prestigious award of the German Steel Federation—awarded every three years—honors this year the newly developed steel pistons for passenger car diesel engines, with a potential for CO₂ emission reductions and high performance.

In September 2014, the new steel piston celebrated its world premiere in a production car—the V6 diesel engine of the Mercedes-Benz E 350 BlueTEC. The innovative steel pistons, in conjunction with lightweight aluminum engine housings, lower the fuel consumption and CO₂ emissions by two to four percent, according to Daimler. The fuel consumption advantages are even more pronounced for the everyday low and medium engine speed ranges, said the company.

At first glance, the combination of aluminum housing and steel pistons seems problematic because steel expands less when heated than aluminum; it has a lower heat conductivity and is heavier—noted Daimler. Therefore, aluminum pistons have traditionally been used. However, the Stuttgart engine designers were able to combine these apparent disadvantages into benefits. For example, the low expansion of steel through rising operating temperatures ensures a growing interplay between piston and aluminum housing, and reduces friction by 40-50%. The higher strength of steels allows, at the same time, a very compact designed, lightweight pistons, for even extra strength reserves. Finally, the lower thermal conductivity of steel leads to increased component temperatures, thus improving the thermodynamic efficiency with higher ignition performance and reduced burn time.

The steel pistons previously used were poorly suited for a combination with engine housings made of aluminum. Therefore, Mercedes-Benz had to completely redesign the piston. The new steel pistons used in the V6 diesel in the E 350 BlueTEC are forged from high-grade strong steel and are installed in the aluminum crankcase with NANOSLIDE® cylinder liner coating.

Source: Daimler