🔍 Key Concepts

• Diesel combustion timing and how injection after top dead center affects peak pressure • Relationship between combustion pressure vs. crank angle and useful work on the piston • Effects of late fuel injection on temperature, pressure, and efficiency in a diesel engine

💭 Think About

• Think about when fuel should ideally be injected in a diesel engine relative to top dead center for maximum power and efficiency. • If combustion starts too late (after top dead center), what happens to the pressure in the cylinder while the piston is already moving down? • Consider how late combustion affects both the useful work on the crankshaft and the amount of unburned or partially burned fuel.

✅ Before You Answer

• Compare ideal injection timing (just before vs. just after top dead center) and what that does to cylinder pressure at the start of the power stroke. • Decide whether late injection makes the engine do more useful work or less useful work on each power stroke. • Ask yourself whether poor combustion timing is more likely to improve power, increase load/stress, reduce power, or improve fuel economy.