🔍 Key Concepts

• diesel engine combustion timing and what happens if injection is too early vs too late • relationship between combustion efficiency and fuel consumption • signs of incomplete combustion in exhaust and how that relates to wasted fuel

💭 Think About

• Think about what happens to the air temperature and pressure in the cylinder after top dead center if fuel is injected late—will conditions still be ideal for complete burning? • If fuel does not burn under ideal pressure and temperature, what happens to the amount of useful work you get from the same quantity of fuel? • Which choice best matches the typical result of inefficient combustion: is it usually lower fuel use, higher fuel use, or perfectly clean exhaust?

✅ Before You Answer

• Compare which options describe efficient operation versus inefficient operation, then ask yourself which category "late injection" belongs to. • Ask: would late injection tend to make the exhaust cleaner or dirtier? Eliminate any choice that conflicts with typical symptoms of poor timing. • Verify which option logically matches wasted fuel energy—that is, fuel going out the stack instead of being fully turned into power.