🔍 Key Concepts

• Notice the horizontal axis is crankshaft degrees, marked from 90 degrees before TDC, through TDC (Top Dead Center), to 90 degrees after TDC. • Relate what is plotted on the vertical axis (pressure in cylinder) to what normally happens during compression and power around TDC in a diesel engine. • Compare whether this diagram is showing specific engine events (intake/exhaust vs compression/power) or simply pressure variation over a span of crank angle.

💭 Think About

• How many total degrees of crankshaft rotation are actually shown on the horizontal scale, from the left 90 mark through TDC to the right 90 mark? • Does the shape of the pressure curve match the low-pressure intake/exhaust events, or the high-pressure compression and firing period around TDC? • Which answer choices talk about a simple angular span (degrees of rotation) versus particular strokes or events in a specific engine cycle?

✅ Before You Answer

• Count the total degrees of crankshaft rotation represented on the bottom scale before choosing between options A and B. • Verify whether the curve reaches very high pressure near TDC, which would correspond to compression and firing, not intake or exhaust. • Make sure your choice’s wording matches what the diagram actually labels on the axes: crank angle (degrees) on the bottom and cylinder pressure on the side.