The movie car had an empty supercharger case. There was a little electric motor under the hood that turned the belt. The SC was not functional. If you think about it, the supercharger would need to free wheel while not being driven by the motor. Otherwise, it would not allow any air into the motor. The one on Max's car did not freewheel while not in use.
BTW-Nomad Trash is my alias which is a line from that movie.