🔍 Key Concepts

• Relationship between injection timing and peak firing pressure in a diesel cylinder • How air supply and scavenging affect exhaust temperature and combustion quality • Effect of exhaust back pressure on cylinder performance and temperatures

💭 Think About

• If firing pressure is low but exhaust temperature is high, what does that say about when most of the fuel is burning in relation to top dead center (TDC)? • Which condition would tend to make combustion slower and more prolonged into the expansion stroke, raising exhaust temperature but not peak pressure? • Would restricted air intake or low back pressure typically cause BOTH low firing pressure AND high exhaust temperature, or mainly affect one of these?

✅ Before You Answer

• Match the condition that causes combustion to shift later in the power stroke, lowering peak pressure but heating the exhaust more. • Eliminate any choice that would normally increase peak firing pressure when everything else is normal. • Consider which option would most likely cause after-burning (fuel still burning as gases leave the cylinder), leading to high exhaust temperature.