🔍 Key Concepts

• Function and purpose of compression rings on diesel engine pistons • How combustion gas pressure acts on piston rings to improve sealing • Relationship between ring side clearance and movement of gases, carbon, and lubricating oil

💭 Think About

• Think about what has to happen to make the compression ring seal tightly against the cylinder wall. What must be able to get behind the ring? • Consider what would happen if there were almost no side clearance at all. Which of the listed functions would be most affected? • Which of the options describes a primary design purpose of the side clearance, rather than a secondary or side benefit?

✅ Before You Answer

• Identify which choice directly supports ring sealing during the power stroke • Decide whether side clearance mainly controls gas flow, carbon buildup, or oil drainage for proper ring action • Ask: if this feature were removed, which of these four outcomes would most seriously reduce compression and engine efficiency?