nitro to brushless

[Serum]

The 7XL is rated at ~2200 kv (the kv value you gave is without a load, the 2200 is with load)

I used the 7XL on 3S, but it was geared for about 25mph, which makes more sense. you need 4S for the speed you want.

And on 4S i would use either a 8 or 9XL.

for the 7XL on 3S; i used it geared on 25 mph, and it gave me a good 20 minutes runtime (rather slow bashing) on a 3000mAh lipo pack.