A diesel engine will lose power if fuel...

🔍 Key Concepts

• Four-stroke diesel cycle – when fuel is injected relative to top dead center (TDC) on the power stroke • Combustion pressure vs. piston position – where in the stroke you want the peak pressure to act on the piston • Difference between ignition (starting combustion) and useful work (expanding gases pushing the piston)

💭 Think About

• Think about what the piston is doing if fuel is injected too late: is it still near TDC, or already moving down? How does that change the amount of work extracted from combustion? • Which choice focuses on WHERE and WHEN the pressure from burning fuel acts on the piston, rather than on how the fuel is sprayed or whether it will ignite at all? • Among the options, which one describes a loss of mechanical advantage rather than a complete failure of ignition?

✅ Before You Answer

• Identify when, in a properly timed diesel, maximum cylinder pressure should occur relative to TDC • Decide which option best explains a reduction in power output (not total failure to fire) when injection is delayed • Eliminate any choice that describes something that would happen even with correct injection timing (e.g., normal atomization or normal ignition conditions)

A diesel engine will lose power if fuel injection occurs too late in the cycle, because the __________.

fuel droplets will burn as they leave the fuel injector

fuel will not be properly atomized in the cylinder

maximum expansion of the burned fuel cannot take place in the cylinder

compression pressure will be too low to cause fuel ignition

🔍 Key Concepts

💭 Think About

✅ Before You Answer