🔍 Key Concepts

• Fuel injection system basics – what the injection pump must overcome to push fuel into the cylinder • Relationship between cylinder pressure near TDC (top dead center) and required injection pressure • Difference between combustion process characteristics (turbulence, duration) and purely mechanical pressure requirements

💭 Think About

• During injection, what is happening inside the cylinder in terms of pressure and piston position? • Which factor directly opposes the flow of fuel from the injector nozzle into the combustion chamber? • Are turbulence, combustion duration, or compression ratio acting as immediate resistance to the fuel flow, or is something else providing that resistance at the moment of injection?

✅ Before You Answer

• Identify which choice is most directly related to actual cylinder pressure at the time of injection. • Separate factors that affect quality of combustion (smoothness, completeness) from those that affect minimum pressure needed just to get fuel into the cylinder. • Verify which option describes a condition that the injection pump must mechanically overcome to open the nozzle and inject fuel.