https://www.lsxmag.com/tech-stories/answers-on-the-second-ring-the-science-of-the-second-piston-ring/Since the invention of the metal piston ring at the start of the industrial revolution (which, you could argue, finally made steam power practical), there’s been constant innovation and improvement in cylinder sealing technology for these seemingly simple parts. The ring package has three primary goals: Keep pressure confined to the combustion chamber on both the compression and power strokes, transfer heat from the piston to the cylinder walls where it can be removed via air or liquid cooling, and control lubrication to limit oil consumption and unwanted emissions.
While it’s easy to look at the top ring or the oil ring at the bottom and intuitively understand their contribution to meeting these objectives, the second ring is more of a mystery. What’s it supposed to be doing, and why is it necessary? How do the materials used and the physical properties of the second ring affect performance? To answer these questions, we turned to Wiseco Senior Technical Account Manager Alan Stevenson, the go-to source for knowledge about piston rings.