Please read the manual I sent

The BARC has a momentum feature that can be turned on.. You set this with the left stick before you start the tank. What it does is add a small amount of speed up and wind down to the ESC so the tank doesn't act like a Jack Rabbit. Ie It won't go instantly from forward to reverse. It will auto slowdown and speed up in the other direction. It is not a lot of momentum, but it is enough to smooth out the tank and improves the performance of the ESC.( RX18) It blends on the speed steps together so you end up with a very proportional response from the RX18

Cheers