🔍 Key Concepts

• Diesel engine basic principle (compression ignition vs. spark ignition) • What actually gets compressed in a diesel cylinder before fuel is injected (air only, not fuel) • How very high compression affects temperature inside the cylinder

💭 Think About

• In a diesel engine, is the fuel ignited by a spark or by the conditions inside the cylinder? Think about how diesel differs from a gasoline engine. • Before fuel is injected, what is happening to the air in the cylinder as the piston moves up? How does that affect its temperature? • Which option describes something that happens every power cycle in a diesel engine, not just occasionally or in auxiliary equipment?

✅ Before You Answer

• Verify which system is used only in gasoline engines (spark/electronic ignition). • Identify which choice directly involves high pressure and temperature created inside the cylinder itself. • Eliminate any option that sounds like external or auxiliary heating rather than the normal, continuous operating principle of a diesel engine.