🔍 Key Concepts

• Compression ignition vs. spark ignition in engines • Basic operating principle of a four‑stroke marine diesel engine • Role of air temperature and pressure at the end of the compression stroke

💭 Think About

• Think about whether a typical large marine diesel engine uses an external electrical spark, or relies on conditions created inside the cylinder itself. • Consider what happens to the temperature of air when it is compressed into a much smaller volume inside the cylinder. • Which of the listed devices are commonly found on gasoline engines, and which are associated with starting aids or older/smaller diesels rather than normal running?

✅ Before You Answer

• Identify whether a standard marine diesel normally has spark plugs or magnetos during regular operation. • Recall that diesel fuel is injected near the end of the compression stroke – what is the state (temperature/pressure) of the air at that moment? • Separate the idea of a starting aid from the normal, continuous ignition process once the engine is running.