The steel piston has the lower friction and less thermal expansion. So, the running clearance can be kept low, too. It is smaller, lighter and has up to 30 percent less compression height. Although steel has 2.5 times the density of aluminum the steel piston even achieves 5 percent less installation weight.

The much lower compression height can be utilized variously. One can for example install longer connecting rods, which ensure that the piston is pressed with approximately 1.7° less inclination and 10 percent less force to the cylinder wall. The results are again less friction and thus less losses. You can use the lower compression height for shorter connecting rods and less height of the cylinder block, which in turn causes a lower weight of the engine and, if possible, even a lower hood line.

Ever the steel pistons for the future seems to be better prepared, because its melting point is more than twice as high as that of aluminum. It may be assumed that with further CO2 savings Diesel engines will be operated hotter by even stronger charge. Overall, by the transition from aluminum to steel pistons in high-speed diesel engines, 2 to 5 percent less CO₂ is expected. 02/16

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