After owing a Mazda RX-7 roadster for about 4 years (now sorry I ever sold it) I really got to like the little rotary engine.
If you want a pretty good rundown on all the Mazda rotary engine incarnations I suggest you checkout the Renesis web site.
http://www.transporteon.com/Superlatives-R/Renesis.phpThe most common engines are the 12 and the 13. The 12 has a swept volume of 1146cc and the 13 has a swept volume of 1308cc (some references say 1310cc)
The SCTA factor is 3 to get the factored displacement for engine class.
(1146cc x 3 = 3438cc) which is near the lower middle of the E class.
(1308cc x 3 = 3924cc) which is near the top of the E class.
Mazda had an earlier version (1974 and earlier) called the 10 which had about 982cc.
(982cc x 3 = 2946cc) which is right at the top of the F class.
One of these posts mentions that different sanctioning groups have different factors for rotaries. Actually that makes some sense when you consider that they are trying to equate performance in vastly different situations. I don't know what factor would be fair but for sure one size does not fit all when comparing road racing, drag racing and LSR.
An example of such a difference is that ECTA factors rotaries at 2.3 rather than 3.0. I am not sure what the rationale was but for sure the different venue had something to do with it. A Mazda 12 or 13 would be in the F class at Maxton. ECTA also has separate rotary classes for rotary motorcycles but not for cars.
FIA lists separate classes for Rotary records. I haven't heard of any other group that has separate classes just for rotaries in cars.