🔍 Key Concepts

• compression temperature vs. compression pressure in a diesel engine • how fuel ignition happens in a compression‑ignition (diesel) engine • effect of air supply (scavenge air) and exhaust back pressure on combustion

💭 Think About

• Ask yourself: in a diesel engine, does the fuel ignite because of high pressure alone, or because of the temperature reached by compressing the air? • Which of these options would make it harder for the injected fuel to reach its self‑ignition temperature at the end of compression? • Which listed conditions (high scavenge air pressure, high compression pressure, low exhaust pressure) would normally improve air charging and scavenging rather than cause poor combustion?

✅ Before You Answer

• Be clear on the difference between pressure that helps raise temperature and a condition where the final compression temperature is too low. • Consider which items are generally viewed as beneficial to combustion quality (better charging, better scavenging) and which would clearly reduce ignition quality. • Visualize the end of the compression stroke: which condition would result in air not being hot enough to properly ignite the injected fuel?