Piston rings are designed to maintain the automobile’s cylinder and combustion pressures, securing the diesel power performance. They keep oil out of the combustion chamber and seal it in the air and fuel so that it may be compressed. Almost often, each ring in a three-ring set is intended to maximize or assist the other two rings’ tasks. Thus, although each ring in the three-ring pack is unique, the ring pack as a whole is built as a system, with each ring tuned to ensure that the whole three-piece set performs optimally in the engine.
The top ring acts as a gas seal, while the second ring below it aids in sealing and modifies the oil film’s function. This requires that the combustion chamber be made as gastight as possible for the pressure created by the rapidly burning combustion gases to move the piston in the cylinder, forcing the crankshaft to revolve, producing power. Not only is gas-tightness critical for the combustion or expansion stroke, but it is also critical for the intake, compression, and exhaust strokes. This overall function is referred to as “gas sealing.”
The piston’s heat is transferred to the cylinder through the ring. The piston rings conduct heat away from the heated piston and into the cooled cylinder wall or block engine. The piston groove transfers heat energy to the piston ring, which transfers it to the cylinder wall, where it is finally transmitted to the engine coolant. This heat transfer function is critical for maintaining appropriate temperatures and stability in the piston and piston rings, which prevents the piston and piston rings from losing their sealing capacity.
The wiper ring, sometimes referred to as a Napier ring or backup compression ring, is positioned directly underneath the compression ring. Their primary duty is to remove excess oil from the liner surface and serve as a backup support ring, preventing any gas leaking farther down that escaped the top compression ring. Excessive oil consumption occurs when the wiper ring is placed improperly with the tapered angle closest to the compression ring. This happens due to the wiper ring ejecting extra oil into the combustion chamber.
The oil scraped off by the oil ring pours the piston through the oil drainage hole. The piston rings need some oil for lubrication; however, this quantity should be minimal. The rings scrape away surplus oil from the combustion chamber. In this manner, oil consumption may be kept within reasonable limits while hazardous emissions decrease.
To know more about common causes and symptoms of piston ring failures, below is an infographic from Pure Diesel Power.