os 0.18 cv-rx produces 1.35hp @ 28.000rpm. I recently found out the best 0.18 money can buy is the LRP Z.18S PRO SPEC.2 PULLSTART producing 1.58hp @ 33.000rpm see for yourself: http://www.lrp-electronic.de/e/lis/ I also read that LRP is in assosiaton with HPI so the nitro star 18ss engine is practicly the same because it comes from LRP. HPI claims 1.5 and the engine is rated at 1.52hp @ 32.000. So lrp took the Z18S shortened one port a bit to slightly reduce rpm (engines for cooperative companies never produce the same power as the original it's marketing policy!!!) and there's the nitro star 18ss! If you have a problem finding LRP or HPI distributors nearby, buy the OS .18 it is for sure faster than your stock.