Engine: Expired / Motor Plants and Auxiliary Boilers

1. A allow the exhaust ports to open and close before the inlet ports close
2. B allow the scavenge ports to open and close simultaneously with the exhaust ports
3. C prevent scavenge air pressure buildup in the cylinders
4. D prevent the exhaust piston from reaching TDC and BDC before the intake piston

Tip: press A-D to answer