Piston coating

Cleaner finish

Who

Federal-Mogul has developed a new coated piston for petrol engines that it says combines the properties of low wear and low friction in a single application.

Technology

The company says that the new EcoTough-coated piston offers superior wear resistance and reduces fuel consumption up to 0.8%, as well as reducing CO2 emissions, compared to conventional piston coatings. The piston is compatible with existing and advanced cylinder bore finishes and can be introduced in volume engine production as a running change.

The key behind the technology is the composition of the coating, which is comprised of solid lubricants, including graphite, molybdenum disulphide (MoS2) and carbon fibre. In applications requiring additional protection, for example with a rough cylinder honing structure, the piston offers a greater coating thickness than pistons with conventional coatings. The technology suits high-volume manufacturing and is less sensitive to pre-treatment process variations, says the firm. 

Customer and governmental mandates to reduce CO2 emissions and fuel consumption make the reduction of parasitic friction losses between the piston and the cylinder bore a priority for vehicle manufacturers. At the same time, the power output per litre of engine displacement is increasing as engines are downsized and boosted by turbo- or super-charging, subjecting pistons to higher mechanical and thermal loads.

In laboratory testing, Federal-Mogul says that EcoTough-coated pistons show an 18% reduction in piston friction and an improvement of up to 3% in entire engine parasitic losses. Engine bench tests confirm a fuel economy benefit of 0.4-0.8% in normal driving conditions. In wear resistance testing at full load and after 50 cold-start cycles, EcoTough-coated pistons demonstrate a major reduction in wear on the piston surfaces in contact with the cylinder.

Application

EcoTough-coated pistons have entered production for a high-volume vehicle by a major European manufacturer. Dr Frank Doernenburg, Federal-Mogul’s director of technology, pistons and pins, says: “EcoTough offers vehicle manufacturers a combination of benefits – a reduction in fuel consumption and CO2 emissions, coupled with improved wear resistance and straightforward implementation.”