Yesterday, I did some training with some new students on a Nextstar with the new 46FXi and a Alpha with the Evolution 46. Both motors appear to be made very well. The Evolution 46 has a angled back glow plug more like a 4-stroke that is good to get your hands away from the prop. The Evolution engines are suppose to be pre-broken in and ran at the factory before shipping. The Evolution 46 has more fins on the rear of the head to better cool the motor. The OS FXi is basically a rebadged FX with no differences except for the name plate. Both motors have a remote high speed needle and a air bleed low end screw. When flying the engines, there is a huge difference in power although they have the same displacement. The FXi had a ton more power compared to the Evolution, however the Evolution had very little vibration due to the shaft counter balancer. The Evolution 46 did not have the power to accelerate into the air quickly. It literally creep on up in altitude slowly, but the FXi really gained altitude quickly and has more power to get out of a bad situation if it arouse. Much more pull. The Alpha did however have a 3 blade and the Nextstar had a two blade, but the difference was significant. Both engines were running optimally with the mixture. If OS ever starts selling this FXi engine separately, I would buy one especially if it is cheaper than the FX. It has the same power as a FX version. I doubt they will ever sell the FXi separately because people wouldn't go buy a higher dollar FX line then, but would be basically getting the same motor.

The FXi engine seriously could be taken off the Nextstar and used on another plane as a sport engine unlike the 40LA that comes on the RTF versions of the Avistar or Super Star 40 (HobbyTown USA does not carry the RTF version of this anymore).

Both, the Nextstar and Alpha has it's bad points, but they are easily correctly. In my opinion the engine choice and simulator software that comes with the Nextstar alone is a great deal for the money besides the fact that there is a warranty of not crashing. I do feel the Evolution is a good motor and would like to better compare the two with the same prop and fuel.

I read an article that compared the Evolution 46 and the normal OS 46FX. The FX would spin a MAS 10x6 at 13,700 rpm on 10% nitro with 88 dB (noise). The Evolution with the same prop and fuel would spin at 13,700 also with 87 dB (insignificant difference), but as RTF trainer versions with these two motor choices I would choose the model with the OS FXi motor (Nextstar).
DTB