🔍 Key Concepts

• Two-stroke vs four-stroke diesel cycles and how often each has a power stroke per crankshaft revolution • Meaning of mean effective pressure (MEP) and how it relates to power and temperature • How scavenging air flow and valve overlap affect exhaust gas temperature

💭 Think About

• Think about how many times each engine type fires for the same displacement and speed, and what that means for heat in the cylinder and exhaust. • Ask yourself: Does lower or higher mean effective pressure generally correspond to lower exhaust gas temperature, and why? • Consider how scavenging air in a two-stroke and valve overlap in a four-stroke change the amount of fresh/cool air mixing with hot exhaust gases.

✅ Before You Answer

• Be clear on whether two-stroke engines have continuous flow of scavenging air through ports and how that would cool exhaust gases. • Verify if MEP in a two-stroke of the same displacement and power is typically lower or higher than in a four-stroke, and how that affects thermal loading. • Check whether valve overlap is generally greater in four-stroke diesels and whether that would increase or decrease exhaust temperatures.