🔍 Key Concepts

• Trunk vs crosshead piston – look at how the connecting rod attaches to the piston in the illustration. • Two-stroke scavenging patterns – difference between uniflow and loop scavenging and where air enters/exhaust leaves. • How to tell two‑stroke vs four‑stroke from the presence of ports in the liner and valve arrangement in the cylinder head.

💭 Think About

• From the picture, does the piston have a separate piston rod and crosshead guides, or is the connecting rod pinned directly to the piston? What does that tell you about piston type? • Where does fresh air enter the cylinder and where does exhaust gas leave? Does the gas flow mostly in one direction or does it loop around? • Do you see intake and exhaust handled only by poppet valves in the head (typical of four‑stroke), or do you see ports in the cylinder wall uncovered by the piston (a strong clue about a two‑stroke diesel)?

✅ Before You Answer

• Be sure you can clearly identify whether the piston is trunk or crosshead before eliminating any choices that name the wrong type. • Confirm whether scavenging is uniflow (air in through ports, out through valves at the top) or loop (both in and out through ports with a looping path). • Verify that your chosen option’s operating cycle (two‑stroke or four‑stroke) matches the port/valve arrangement you observe in the illustration.