🔍 Key Concepts

• Cetane rating measures the ignition quality of diesel fuel (how easily and quickly it ignites under compression). • Low cetane number is associated with longer ignition delay between fuel injection and actual combustion. • Long ignition delay affects combustion smoothness, noise, and starting characteristics, especially in cold weather.

💭 Think About

• Ask yourself: If the fuel is slower to ignite, what happens to the pressure rise and noise inside the cylinder when combustion finally starts? • Think about which options describe benefits (good performance) and which describe problems usually associated with poor-quality or incorrect diesel fuel. • How does ignition lag relate to knocking or rough running compared to smooth operation and easy starting?

✅ Before You Answer

• Verify which choice is linked to longer ignition lag (a known effect of low cetane fuel). • Identify which options describe improvements (smoother operation, reduced lag, better starting) and which describe a harmful symptom. • Make sure the option you select matches typical engine knock / rough running behavior tied to poor ignition quality in diesel engines.