i dont get the whole ubec part.

im looking for a fast revo, nothing about racing. something to compare to my friend BL hyper 7.

what if i got the Warrior 9920 Brushless Car Controller , ran two 7 cell packs to power it, and the stock reciever pack as the last 5 cells, so thats 19 cells. so thats 1 under its max. would that work? im looking for more speed, so would a 7,8, or 9 be the best for more of a speedy revo? and which mod 1 pinion works on the xl's which one in the store. (if you can show me, thanks. i need a budget ).