Maurizi, M. and Hrdina, D., "New MAHLE Steel Piston and Pin Coating System for Reduced TCO of CV Engines," SAE Int. J. Commer. Veh. 9(2):270-275, 2016, doi:10.4271/2016-01-8066.
Total cost of ownership is requiring further improvements to piston friction reduction as well as additional gains in thermal efficiency. A piston compression height reduction in combination with carbon based piston pin coatings is enabling advancements in both demands. MAHLE implemented a new innovative metal joining technology by using laser welding to generate a cooling gallery. The MonoLite concept offers design flexibility which cannot be matched by any other welding process. Especially an optimum design and position of the cooling gallery as well as durability for very high peak cylinder pressures can be matched. This is particularly advantageous for complex combustion bowl geometries that are needed in modern diesel engines to meet fuel economy and emission requirements. The MonoLite steel piston technology offers a superior compression height reduction potential compared to typical friction welded designs. Using this benefit to reduce side forces by a longer connecting rod, the full friction reduction potential is achieved by a combination with a new low friction carbon based coating on the piston pin. The new coating shows best-in-class performance in terms of friction and high temperature resistance compared to currently available pin coatings.The shorter compression height also results in reduced oscillating masses. This can be used for further weight reduction in the whole drivetrain, which allows the implementation of further systems for better fuel efficiency, e.g. waste heat recovery, without reducing payload.