ah, i see. makes sense how he went from DM to SM2

 

DM is for production cars under 2L, with a LOT of allowances on chassis modification. Drivetrain is totally open, other than displacement and a few multipliers for things like FI.

AM, BM, CM, and FM are the classes for the various formula type cars. DM and EM are production based cars, with either above or below 2L of displacement after whatever correction factors.