🔍 Key Concepts

• Relationship between compression ratio / clearance volume and peak firing pressure in a diesel engine • How injection timing (early vs late) affects both firing pressure and exhaust temperature • Effects of nozzle condition and fuel cetane number on combustion characteristics

💭 Think About

• Which option would increase peak cylinder pressure without necessarily increasing the amount of heat in the exhaust? • For each choice, ask: does this mainly change when the fuel burns, how much fuel burns, or how much space the gases have to expand in? • Which condition could slowly develop over time inside the cylinder and quietly raise firing pressures while normal operating temperatures are still observed at the exhaust?

✅ Before You Answer

• Compare how early vs late injection typically affects both maximum firing pressure and exhaust temperature trends • Decide which option would most directly reduce the clearance volume or effectively raise compression ratio inside the cylinder • Verify which conditions (nozzle wear, cetane number) are more often associated with abnormal exhaust temperatures or smoke rather than normal exhaust readings with only high firing pressure