Indicator diagrams for a two-stroke engine are used to compute which parameter and assess what aspects?

• A. Bores diameter; oil viscosity; fuel grade; exhaust gas temperature
• B. IMEP and valve timing, scavenging quality, and overall engine health
• C. Crankshaft journal wear
• D. Piston ring end gap

Answer: (B)

Indicator diagrams chart the cylinder pressure versus crank angle (or volume) during a cycle, letting you quantify the actual work produced and relate it to engine size. From the area inside the pressure–volume loop you calculate the indicated mean effective pressure (IMEP), which is a direct measure of the engine’s power capability independent of displacement. In a two-stroke, the diagram also reveals how well the scavenging process is working and how the port timing supports that flow; the pressure waveform during scavenging shows whether the fresh charge is effectively displacing the exhaust or if it’s escaping, which affects IMEP. The overall shape and timing of the curve can indicate engine health—abnormalities point to issues like leakage, improper timing, or poor compression. The other items listed—bore diameter, oil viscosity, fuel grade, exhaust gas temperature, or piston ring end gap—aren’t determined from indicator diagrams and require separate measurements.