A ‘New Twist’ on Twisted Rings

Facing monumental challenges in the tightening constraints of friction reduction, oil control, and blowby, piston ring designs are becoming intricately more complex. Within this complex matrix of design criteria, minute changes can have a big impact on the performance of engines, which are operating under conditions of higher temperatures and speeds. At the same time there is a general requirement to reduce the overall mass of the components. Thus, the piston rings must have inherent design properties (more finely tuned) to withstand the elevated operations of the engine, maintain longevity, and perform within the expected performance criteria. To help meet these challenges, this paper gives a brief introduction to the axial formed process as an improvement of the twist characteristic on the upper compression ring (UCR) design, along with representative supporting performance data based on engine tests and computer simulation. The goal is to show some successes across different engine types involving the axial formed process. The main topics covered include a) historical role and design of twisted rings in the engine, b) advantages of improved twisted rings, c) example of engine test data and d) example simulation results.