Regardless of what it happening in the specification, the mechanism is a simulation of some sort.
If you have a "servo motor" that you are tracking the RPM, then you are asking for a trigger. I am not sure this is a mechanism definition, but rather an if statement in relations which triggers a display state or family table instance. I am not sure how best to "program" this requirement in Creo or Mechanism.
If it were me and I needed to -simulate- the action for a presentation, I might have two completely separate features driven by their own servo motor and defining a user defined motor profile. The 1st mechanism would be a tachometer and the second may be a servo driving a cam to show valve actuation.
Maybe a little more information on what you are trying to achieve or what purpose you are trying to achieve may help.
Also be warned that showing springs being actuated in an animation is tricky. Only one method that I know of works in showing a spring being compressed in each frame, and it is a trick by "hinging" coils all along the spring with relations.