🔍 Key Concepts

• Cetane rating as a measure of how easily diesel fuel auto-ignites under compression • The meaning of ignition lag in a diesel engine (time between start of injection and start of combustion) • How poor combustion affects fuel consumption and engine smoothness

💭 Think About

• If a fuel auto-ignites less readily, what happens to the delay between injection and combustion? Longer or shorter? • When combustion starts later than ideal, what does that do to pressure rise in the cylinder and how smoothly the engine runs? • Would a harder-to-ignite fuel generally improve or worsen cold starting and overall efficiency?

✅ Before You Answer

• Be clear on the definition: high cetane = easy ignition, low cetane = hard ignition • Link ignition quality to cold starting performance and smoothness of operation • Decide which option best matches the typical effects of delayed, less-controlled combustion in a diesel engine