Actually, kV is the rating for how many RPM the motor will turn unloaded per volt applied, usually without timing advance.
So, the max unloaded RPM at 1s would be
2300 * 4.2 (full battery) = 9660 RPM
2300 * 3.7 (end race voltage) = 8510 RPM
2300 * 8.4 = 19,320 RPM
2300 * 7.4 = 17,020 RPM
When you add timing on the RS, the motor can turn more RPM than the kV rating would suggest.
On my 17.5 Boosted D3 TC, I usually run around a 6k - 16k RPM range, with a 6.0-6.3 FDR.
Privateer racing lots of stuff.
Remember kids, racing isn't fair!