gas always pushes, never pulls...gas always pushes, never pulls...and Fool pushed the proof long ago...
Take a single cylinder 'engine' charged with 2 bar helium (piston BDC) and place it in a vacuum chamber...
(1) will piston move ??? NO, cylinder pressure remains constant
(2) now chill vacuum chamber real cold, will piston move ??? NO, cylinder pressure DECREASES but gas does not "contract" and suck in piston
Your contraction BS is from bogus fantasy regarding how ambient pressure effects expansion and compression processes during a cycle. This is just as lame as the balloon video with liquid nitrogen that avoids discussing what happens to each balloon if same 'experiment' was conducted in a vacuum...