ok im pretty sure that the compression in a rotary can be changed...at least i think it can... im not sure how this is done tho...i've been thinking about it and i can't come up with an answer, except that their could be different compression rotors...if you know anything about this it would be very helpful

 

yes, the simplest way is to change the rotors between compatible engines.

Check out the chart in this: Compression Thread