🔍 Key Concepts

• Diesel engine piston ring function and movement in the groove • Different clearances on a piston ring: side, back, end (gap), and radial • How carbon, varnish, and thermal expansion can cause rings to stick

💭 Think About

• Think about which surface of the ring actually slides against the groove when the piston moves up and down. • Which clearance, if too small, would most directly prevent the ring from moving freely and scraping oil and gases as designed? • Consider how thermal expansion during normal engine operation would reduce which specific clearance first and make sticking more likely.

✅ Before You Answer

• Identify which part of the ring contacts the ring groove surfaces during normal motion. • Decide which clearance mainly controls the ring’s ability to move freely in and out and up and down in the groove. • Eliminate any option that deals mainly with end-to-end fit in the cylinder bore rather than fit inside the groove.