The innovation will be debuted in V6 diesel versions of the company's E-Class medium-large saloon in September.
The company's engineers have managed to use the different heat properties of aluminium and steel and reduce the friction in the cylinders of an engine at working temperature. Using steel means the pistons can be smaller, with less frictional surface area against the cylinder walls. Up to 50 percent of friction losses in an engine are related to the piston/cylinder elements. The denser characteristics of steel are more or less offset by the smaller depth of metal used in the new pistons.
Steel pistons have been used in diesel engines for years, but with cast-iron blocks and mainly heavy duty applications. For passenger cars, where light aluminium blocks are preferable, aluminium pistons have been used. Using steel pistons also allows higher and more efficient combustion temperatures to be achieved.
Mercedes-Benz was the first carmaker to roll out a diesel engine in a production car, in 1936.
