Which of the following sequences correctly represents the four steps of a compression cycle?

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

Answer: (A)

The sequence starts with expansion to create a low-pressure condition inside the chamber, which draws in fresh working gas through the intake. Once the chamber is filled, the gas is compressed to raise its pressure for the next stage. After reaching the desired pressure, the exhaust phase removes the gas from the chamber to move it on in the process. This order—expansion, then intake, then compression, then exhaust—ensures the chamber fills properly and the gas is delivered at the correct pressure. If you tried to start with intake or compression, there wouldn’t be gas present to fill the expansion space or be properly compressed, and expelling gas before completion would vent it prematurely.