SP is Speed Passion, I was running a SP V3 13.5 motor before switching to the Epic D3 13.5
With the SP I was running a 7.6 FDR which for me had the best balance of infield rip and top end speed, so then when I got the D3 I read the other comments about them needing more gear than other motors and when m-technic suggested 6.3 I was very surprised but his advice was good. I've only had limited time to get to the track and so far I'm at 6.45 FDR and the motor has good rip and the speed is good too and temps are between 170 and 175.