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Fuel economy improvement efforts in engines have focused on reducing parasitic losses. This paper addresses the friction losses in the valve train chain drive system where about half of the losses is caused by the chain sliding on plastic guide and tensioner arm faces (Figure 1). Efforts have been made to reduce these friction losses by optimizing the chain link profile, the geometry of the guide and tensioner arm rails, and developments towards low friction materials. This paper describes the approach taken for the development of new low-friction chain tensioner arm plastic materials. The approach is characterized by building an understanding of the friction mechanisms and identifying the most critical material’s properties. A lab-scale test is used for a first assessment of the friction performance of materials. The correlation between this lab-scale test and the actual chain-on-tensioner arm application is discussed.

The requirements on engine components are becoming tougher. On the one hand, the load of the components is increasing due to the optimization of the engines to make them more efficient. New materials and/or coatings and surface treatments are needed to fulfill the new requirements. On the other hand, changes of oil additives and the introduction of alternative fuels are challenging the engine materials as well. In addition, there is a high demand to reduce the friction of the engine for improved fuel consumption. One-way to support this is the application of friction reduced coatings and/or surface treatments. DLC coatings seem to be a promising candidate. But what differentiates DLC coatings on the market and within different lubrication conditions in regards to friction? Standard valve train bucket tappets coated with different DLC coatings will be compared regarding friction to uncoated steel bucket tappets by using a special self build test rig.