Influence of Piston Ring Gaps on Lubricating Oil Flow into the Combustion Chamber

The authors have utilized a modified automobile engine with a transparent glass cylinder, which was driven by an electric motor. The effects of the positions of the piston ring gaps, the end clearance size and the shape of the piston ring gaps on the lubricating oil flow were examined using the modified engine.

The results indicate that the main stream of the lubricating oil flow goes from the lower ring gap to the upper ring gap in all of the positions of the piston ring gaps and that the position of the oil ring upper side rail gap has a great influence on the lubricating oil flow. We have also found that the lubricating oil flow is reduced by up to 26 % by utilizing the oil ring side rails with the optimized upper and lower side rail gaps as compared to the standard end clearance (standard production tolerances) and that the lubricating oil flow is reduced by up to 69 % utilizing the top ring with the special joint (triangle step joint) as compared to the standard joint (straight joint).