🔍 Key Concepts

• air-fuel ratio and what causes a rich mixture • relationship between engine load and exhaust temperature • how incomplete combustion shows up as black smoke

💭 Think About

• Which conditions tend to make the engine burn too much fuel for the amount of air available? • Think about situations where the engine is working harder than it should for the speed or load it is carrying—what happens to exhaust temperature then? • Which options would normally improve combustion and cleanliness of exhaust rather than make it dirtier and hotter?

✅ Before You Answer

• Identify which choices would increase fuel burned per power produced (poor efficiency). • Decide which conditions usually cause black, sooty smoke versus white or blue smoke. • Ask: does this condition make combustion hotter and less complete, or cooler and more complete?