What is the purpose of the scraper/wiper ring?

The scraper/wiper ring serves a dual purpose in small engine operation. Primarily, it is designed to create a seal between the piston and the cylinder, effectively preventing combustion gases from escaping into the crankcase, which maintains the pressure needed for efficient engine performance. This sealing is crucial for minimizing blow-by, where unburned fuel and air can escape, reducing the engine's efficiency.

In addition to sealing, the scraper/wiper ring also has the important function of cleaning the cylinder wall. As the piston moves up and down, the ring removes excess oil from the cylinder wall, ensuring that there is just the right amount of lubrication on the surfaces that contact the piston. This helps to maintain optimal performance and extend the lifespan of the engine components.

The other options do not accurately reflect the main functions of the scraper/wiper ring. Option A suggests it adds pressure to the piston but does not address its sealing and cleaning roles. Option B pertains to oil maintenance, which is more related to the oil control ring. Option D refers to increasing engine efficiency, but that is a broader goal of many components, not just the scraper/wiper ring specifically.