Germany's KS Kolbenschmidt patents steel piston as light as aluminum

KS Kolbenschmidt GmbH, Germany, has patented a steel piston design that consists of a one-piece forged piston with a reshaped and fully supported ring land. The piston enables very low groove deformations, and will also be able to achieve higher target values with respect to blow-by and oil consumption in the future

MOSCOW (Scrap Monster): KS Kolbenschmidt GmbH, Germany, has patented a steel piston design that consists of a one-piece forged piston with a reshaped and fully supported ring land. The piston enables very low groove deformations, and will also be able to achieve higher target values with respect to blow-by and oil consumption in the future.

 Even though aluminum is basically lighter than steel, the refined steel piston is as light as its aluminum counterpart, and has a shorter compression height as well as a longer connecting rod. This results in reduced side forces. Comprehensive tests have also shown that friction has been reduced so that a 2 to 3% lower fuel consumption can be achieved, thanks to the design with reduced piston skirt surfaces and optimized piston profile and assembly clearance.

 Furthermore, the new steel piston design can be installed in engines with reduced cylinder block height. An optimized piston cooling configuration and an adaptation of the combustion parameters compensate for the relatively lower heat conduction of steel compared to aluminum, as well as the resulting higher combustion-chamber surface temperatures. The large enclosed cooling channel is positioned directly at the temperature-critical bowl rim and cools it optimally. The favorable temperature level in the piston ring zone reduces both carbonization of the ring groove and abrasion on the piston ring groove and piston ring.

 International automobile manufacturers are currently examining the automotive steel pistons in durability tests. One premium-segment OEM has recently placed an order for an initial series development, and production is planned to begin in 2014. The piston is to be placed in a four-cylinder engine with a cylinder pressure of more than 200 bar and a specific performance of more than 100 kilowatts per liter.

 A further main focus of the development activities lies in the optimization of the noise behaviour of steel pistons - especially in combination with aluminum crankcases. The lower thermal expansion of the steel piston - which favorably affects friction reduction - has a negative effect with respect to the so-called Noise Vibration Harshness (NVH), at hot running conditions. Solutions to this issue are currently being worked out in comprehensive tests and in close collaboration among KS Kolbenschmidt engineers and customers.