the compression chamber thereby providing an different compression capacity than shown in fig2 a although fig2 b shows a substantially circular disengageable eccentric cam 203 shape when rotating in one direction the geometry of the disenageable eccentric cam 203 is not limited to a circular shape and may be an eccentric or other geometry that permits the piston to compress gas in the compression chamber at a different capacity than the capacity shown in fig2 a during operation the engagement of the second side of the dog 205 and the second stop surface 209 is a result of the rotation of the crankpin 201 the rotational direction illustrated in fig2 b results in the compressor operating at a reduced capacity in addition little or no noise is produced by the disenageable eccentric cam 203 from disengagement of the disengageable eccentric cam 203 from the dog 205 having the reduced or eliminated compression capacity because the presence of reexpansion gas is reduced or eliminated due to the reduced motion of the piston fig3 through 6 illustrates various embodiments of a piston assembly 300 incorporating the reexpansion gas discharge assembly of the invention piston assembly 300 illustrates a compressor piston at or near the completion of the compression stroke the piston assembly 300 includes a piston head 301 inside of a cylinder wall 303 the piston head 301 includes a piston ring groove 305 which is capable of receiving a piston ring a valve plate.