🔍 Key Concepts

• Relationship between fuel injection timing and peak cylinder pressure in a diesel engine • How combustion timing affects exhaust gas temperature • What happens when fuel burns too early in the compression stroke

💭 Think About

• If fuel is injected earlier than normal, does the pressure peak occur sooner or later in the power stroke? How would that affect the maximum cylinder pressure? • When combustion finishes earlier in the stroke, what happens to the heat energy before the exhaust valve opens—does more or less of it get turned into mechanical work? How would that change exhaust temperature? • Compare a case where combustion is too early versus too late: in which case would you expect more unburned heat going out the exhaust?

✅ Before You Answer

• Decide whether early injection tends to produce higher or lower peak cylinder pressure than normal • Decide whether more efficient expansion of gases in the cylinder leads to higher or lower exhaust temperature • Match the combination of cylinder pressure trend (above/below normal) and exhaust temperature trend (above/below/normal) that best fits early fuel injection timing