Among components produced by the firm's Global Valvetrain business are sodium-cooled valves with ultra-small stem diameters, claimed to deliver not only reduced weight, but also greater resistance to high temperatures that can be a limiting factor in downsized engines.
"As vehicle manufacturers continue to pursue reduced CO2 emissions with more efficient engines that are often downsized and turbocharged, cylinder temperatures and pressures are increasing," explains Global Valvetrain Technology director Guido Bayard.
"Our sodium-cooled, hollow stem valves allow the temperature of the valve heads to be reduced using a wide range of steel materials, and also enable a reduction in valvetrain mass that cuts friction," he adds.
Bayard explains that unlike a conventional valve with a solid stem, which conducts almost 75% of its heat away through the head and seat, the new hollow stem technology reduces heat flow through the valve head to around 50% of the total by transmitting a greater share through the stem and guide.
This allows the valve head to run between 80°C and 150°C cooler – and hence their primary use exhaust valves – although hollow valves can also be used on the intake side to save weight.
Bayard states that Federal-Mogul uses a range of material combinations to maximise corrosion resistance and/or high-temperature durability – and adds that the technology is also compatible with established treatments for wear resistance, such as nitriding, chrome plating and hard facing.
As for how the valves are made, he says that high-precision deep hole drilling combined with friction welding techniques are key to producing the hollow stems down to 5mm diameter.
Although already established in motorsport applications, making this technology available for volume production required several developments, says Bayard, including a single weld to close the hollow cavity.
"Hollow valve stems are both an enabling technology and a direct contributor to the reduction of CO2 emissions," comments Gian Maria Olivetti, chief technology officer, Federal-Mogul Powertain.
"By lowering the valve head temperature they allow more efficient downsizing strategies and by reducing mass they cut the energy absorbed through friction," he adds.