Hey all! Pardon my newbieness with nitro engines, but I'm a bit confused about the differences between the .12, .15, and .21 engines for the RC10GT2 which I intend on buying. First of all Associated claims the .15 is best for backyard bashing, which I would understand because it's that much more powerful then the .12. However, they recommend the .12 for racing! Is that because since the car will never reach top speed or be over-torqued anyway, the .12 is more fuel effecient and/or lighter? Or is the difference more than just in HP? I had assumed that the RPMs would be the same between the three engines, and just the HP would change, but is this correct at all? Also, where does the .21 fit into any of this?

you can only use .12 engines in races. A .15 is NOT always faster then a .12. The OS. Speed .12 TZP-T3 is a crazy fast .12 engine...but then again it is around $299.99

a .12 is a speed engine and a .15 and .18 is a torque engine

Ok, so if I wanted to race it I'd have to get myself a .12 and swap it out?

Another quick question... I've heard that the .15X isn't race legal if it's carberator restrictor is removed so that it can run at full power. Does this mean it's race legal with it in?

I believe the RTR .15 Engines are race leagal. I'm not sure, but I think if you have a carb restrictor in it, and its a RTR .15, then I think its race legal. (Feel free to correct me if I'm wrong on this)