13.5T or 17.5T?

[xlDooM]

I'm under the impression that my Amp's 20T motor is losing power. It does get quite hot (2 second finger test failure hot) as I run it on the grass non-stop typically.

So, if I were to get a brushless motor, where would a 17.5T put me? And a 13.5T? Both would be Turnigy Trackstar sensored (my 4 year old needs to be able to drive slowly and smoothly), same 80A ESC.

I just have no reference point for brushless, so I'm clueless as to whether the 17.5T is actually faster than stock or not, or how much faster the 13.5T would be than stock. Opinions appreciated.

 

[X]

I believe a 13.5T is about 3300kV and a 17.5T is about 2200kV. Ofcourse, that varies by motor. I have a 3300kV in my circuit (stock BL) and it is alot more powerful than my sons stock amp (20T). Without the AVC on it's hard to get it to go straight if you nail the throttle. Both running 2s.

 

[xlDooM]

See that helps, thanks! So 3300KV is quite hot for these cars (yours is 4WD right?). The motors I'm considering are roughly 2300KV and 3000KV but they do punch above their weight according to the testimonials I read.

I'm still undecided though. I'm thinking if I make the Amp much faster it's going to end up costing a lot more in replacement parts. The front linkages already took quite a beating.

 

[X]

Yes, the BL circuit is 4wd. Truth be told, I wish I could use 3s, but if you read my other thread I can no longer do. The nice part about the amp is that it doesn't have much for driveline components, so there isn't much to break. You can change to a metal mod 1 spur and pinion, for the BL circuit (hot racing). And ECX makes a metal geared diff.

 

[i_r_beej]

When I switched to brushless in my Boost I installed a Reedy Sonic Mach2 and kept the same final gearing (87/23) and the performance of the car was... virtually the same.

The 17.5 motors apparently generate a fair amount of torque so when I changed the final gearing to 72/33 the car really came alive. I could coast around a tight turn and then punch the throttle and clear a double-jump easily. I can easily keep up with other "stock" cars on the straight sections.

So if you are going to keep the stock gearing go with a motor in the neighborhood of 3000kv (personally i think the "kv" rating is too damn confusing). If you do run a 17.5t be prepared to get a smaller spur and larger pinion to take advantage of the motor's torque.

 

[xlDooM]

Thanks for your input! I was sort of planning to go for a 32P spur and pinion anyway, so right now the 17.5 sounds very good. If it's not hot enough I can always get the better motor later.