BMW to use the latest high performance aluminium pistons by Federal-Mogul

Federal-Mogul Corporation (NASDAQ: FDML) has developed an aluminium piston that meets the higher strength and thermal performance demands of very high-power diesel engines. BMW is the first to use the piston in its triple-turbo 3.0-litre diesel (N57D30S1) engine, which with a specific power output of 93kW/litre (124bhp/litre) is the world's most powerful light diesel.

Premium vehicle manufacturers are introducing higher power diesel engines that improve dynamic performance, CO2 emissions and fuel economy, but power outputs of more than 90kW/litre have long challenged piston designs. "Increasing the specific power output produces higher mechanical loads and temperatures, making a piston's heat dissipation as important as its strength," said Gian Maria Olivetti, Federal-Mogul's vice president for Technology and Innovation, Powertrain Energy. "Our aluminium piston can operate efficiently under higher thermal and mechanical loads than previously possible, without the risk of engine oil cracking and carbon deposit formation associated with a steel piston. By combining all our process and materials expertise, Federal-Mogul has produced an aluminium piston with the durability and the thermal characteristics that high-power diesels require. These advances mean that aluminium pistons can retain their leading position in diesel engines for light vehicles for some time to come."

The aluminium piston's innovative design uses the company's DurabowlR process to create a reinforced combustion bowl rim to withstand the high mechanical and thermal loads. The thermal performance comes from a raised cooling gallery, made possible by Federal-Mogul's development of a two-dimensional (2D) ultrasonic inspection process. Federal-Mogul's DuraBowl process re-melts the alloy around the rim of the piston's combustion bowl, refining the aluminium's microstructure and improving the fatigue strength of the material. To ensure control of key parameters, every bowl is tested using the company's proprietary eddy current process, which detects imperfections below the metal's surface.

The piston's raised gallery places the cooling oil as close to the piston bowl as possible to achieve maximum cooling. "The cooler running of the piston enables durability and also reduces internal friction," said Arnd Baberg, Chief Engineer Piston Product Engineering, Federal-Mogul.

Federal-Mogul validated the technology by dissecting and sampling hundreds of pistons, correlating the ultrasonic images against destructive testing methods. The research resulted in the development of software tools as well as a number of key physical parameters such as probe geometry, wavelength, beam geometry and focus.

The piston was developed at Federal-Mogul's centre for aluminium piston development and production in Nuremberg, Germany. The company produces steel and aluminium pistons for light and heavy-duty diesel engines.