In the four-step compression cycle, which step occurs first?

• A. Expansion
• B. Intake
• C. Compression
• D. Exhaust

Answer: (A)

Expansion is the first step because the cycle begins with the gas doing work and releasing its stored energy. During expansion, the gas pushes against the piston, lowering the cylinder’s pressure and setting up a condition where a fresh charge can be drawn in on the next stroke. After expansion, the intake step brings in new working gas at low pressure, then compression raises the pressure for the following expansion, and finally exhaust releases the spent gas. Seeing expansion first helps you visualize how the cycle moves from energy release to preparing the next charge, keeping the sequence logical and continuous.