So the Tamiya Championship Series for North America has announced their rules. Finally, F1 will allow 21.5/no timing esc in the class, which is a huge step. I realize there are a fair amount of racers who are fans of the 540J, but I hate those motors. Formula one should definitely be embracing brushless technology. While it is as good as class as any to get started in, it's still a challenge for the advanced racer.
I am certainly not a silver can guru by any stretch of the imagination, but I put enough time into it to get decent motors. It's pretty much time I could have used doing something more useful, instead of dynoing overhyped drill motors and interviewing old time 1/12 racers to find out what they where doing in 1982 to Igarashi closed endbell motors.
You could dyno up the brushless motors as the oval racers do, but it's not going to produce the same gains they may see. .05 sec per lap is real when you are doing 3 second laps, but on a 10 turn race track, you have ten opportunities to fritter away a pretty small advantage. Most of the time you'd be better off making your car work better. In the unlimited silver can days, the massive advantage you could gain is worth the work, but the return is not there in brushless trying to hunt down the perfect stator/rotor combination, in terms of raw numbers. The manufacturing tolerances are not as bad a brush motors, from what I can tell.
Looking at what I have seen in 17.5 and 21.5 no timing sedan racing, the vast majority of the speed is in the amount of timing that can be put into the motor. The newer motors like Thunder Power, SpeedPassion MMM, Trinity D3 and Revtech all allow up to and even north of 50* of timing. Most other parts of the motor have been specified, so timing is where the bulk of the advantage is gained. I came to believe this due to a race I had with 21.5 "Gt" style touring cars. One racer showed up with the new Thunder Power motor, which was indeed very fast. I had a Novak Ballistic in my car, and I had a hard time keeping up on the straights especially. The secret of the Ballistic motor is that there is no mechanical stop in the endbells timing ring. Novak provides a sticker on the motor to show the timing range up to 45*, but nothing stop you from going past. So i just thought, "What would happen if I went past the sticker?", as I had no other reason to think the TP motor was faster except advanced timing. Sure enough, exceeding the timing sticker by about 2-3mm produced the desired speed with no discernible ill effects.
The bigger issue is the allowance of "any rotor" in the rules. There are 2 ways to go in my opinion, if you are thinking of experimenting. One would be a smaller diameter rotor to get more rpm. This will also produce less torque, which may be an advantage in outdoor situations where traction may be at a premium. The other would be a bigger rotor, and advanced timing to bring the rpm back. At an indoor facility, this could be an advantage on high traction. I have seen this combo work in 17.5 sedan, i know it could be feasible.
As far as a starting point for a 21.5, 66-67mm rollout on a small track is a decent start. On a bigger track, 70mm would be appropriate. This is with a lot of timing advance on a Ballistic.
As far as what ultimately, will be the best motor, I don't know. I know there is a perception that the Thunder Power and Trinity/Revtech products are very good, but I have had the above experience with the Novak, and I have also seen some ridiculous Speed Passion motors recently as well (with 40 or 50* sensor boards in them). More than anything, the main factor would be possibilities with the rotors, if it pans out...but until somebody puts the work in, I think that pretty much anything with a boat load of timing will be serviceable.