Four-stroke cycle temperature profile: identify when the minimum cylinder temperature occurs. Choose the stroke position at which the in-cylinder temperature is at its minimum during a cycle.

Concept/ApproachDuring the suction stroke, relatively cool fresh charge is inducted. The mixture has the longest time to exchange heat before compression begins.

ReasoningBy the end of suction, the cylinder contains the coolest charge of the cycle (before compression raises its temperature), hence the minimum in-cylinder temperature typically occurs at this point.

Final AnswerEnd of suction stroke.