A sealed-in piston cooling system under development by Federal Mogul could enable higher running temperatures, greater energy efficiency and reduced cooling oil costs for marine four-stroke engines. A new steel piston, Monosteel EnviroKool, features an integral cooling gallery filled with coolant liquid and inert gas and sealed with a welded plug. The cooling system, which lasts the lifetime of the piston, is expected to enable the piston to run at engine temperatures of more than 100°C higher than current limits. Keri Westbrooke, director engineering & technology, Federal Mogul Powertrain, explained that higher temperature engine running would improve energy efficiency by up to 5% (in conjunction with waste heat recovery). Cooling oil costs can also be reduced by around 50% and piston condition improved, he added. “The prolonged exposure of engine oil to higher temperatures in the piston oil cooling gallery [in current piston designs] leads to degradation and carbon build-up, reducing the cooling efficiency and leading to overheating. The superior high temperature properties of the EnviroKool gallery coolant allow it to handle increased gallery temperatures reliably, with the heat subsequently removed from the undercrown – where temperatures are lower – by a standard cooling oil jet.” The piston has accumulated more than 1,400 hours of testing on heavy duty engines, and development programmes are underway with several engine builders. The company expects to begin serial production by 2021. Federal Mogul makes pistons for heavy duty engines, including high-speed marine engines for companies including MTU and Cummins.