🔍 Key Concepts

• How diesel engines ignite fuel without a spark plug (compression ignition principle) • The difference between when fuel is injected and when it actually starts burning • Common terminology in diesel cycle: injection, ignition, compression, and mixture turbulence

💭 Think About

• Think about the full sequence inside a diesel cylinder: air is compressed, fuel is injected, then it must heat up and vaporize before burning—what is the name for that waiting period? • Which term from the choices refers specifically to a time delay between two events, not the event of injection itself? • Which options describe a type of process (like a mode of ignition or air motion) rather than a time interval?

✅ Before You Answer

• Identify which option clearly implies a time delay between fuel injection and combustion. • Separate the term that describes the mode of ignition in a diesel engine from the term that describes the delay time before it starts. • Eliminate any term that mainly refers to air motion in the cylinder instead of timing.