Power (expansion) stroke timing in a four-stroke diesel engine Identify the typical angular span for the expansion stroke (combustion/expansion period) in a four-stroke diesel engine. Choose the correct option.

Concept
In a diesel engine, fuel injection begins near TDC and continues slightly after; peak pressure follows soon after TDC. The useful expansion then proceeds until exhaust opens typically some degrees before BDC (≈ 30–50°), ending the effective expansion early.

Reasoning
Thus, a representative textbook span is: start ≈ few degrees after TDC, end ≈ some degrees before BDC — matching option C.

Final Answer
Starts at 15° after TDC and ends at 30° before BDC