🔍 Key Concepts

• Relationship between camshaft speed and crankshaft speed in a four-stroke diesel engine • How air swirl/turbulence is usually created in a turbocharged four-stroke diesel (port shape vs. piston bowl/combustion chamber) • Location and purpose of a heat dam on a piston vs. the visible piston ring grooves in the illustration

💭 Think About

• From the illustration, does this appear to be a two-stroke or four-stroke engine, and what does that imply about the relative speeds of the camshaft and crankshaft? • Look closely at the valve gear in the picture: is the rocker arm currently compressing the valve spring more than its free length, or is the valve fully closed and the spring relaxed? • Examine the top of the piston: can you clearly see a separate groove above the top ring land that would act as a heat dam, or do the rings sit close to the crown?

✅ Before You Answer

• Confirm whether a four-stroke diesel’s camshaft normally turns at the same speed or half the speed of the crankshaft. • Visually check the valve spring: compare the compressed height under the rocker to what an uncompressed spring would look like. • Inspect the piston crown and ring area in the illustration for a distinct heat dam groove above the top ring before accepting any statement about heat-dam cooling.