Ok I here of people running 3s in there flux.... I called my local hobby store to ask and they also were unclear so I decided to skip the middle man and go directly to the source and CALL HPI DIRECTLY. I called them and talked to a dude on the phone that worked in the tech department!! I asked him if I could infact run 3s in my car! He said "YES YOU CAN, YOU MAY NEED TO ADJUST YOUR GEARING IN YOU HPI SPRINT FLUX, hang in sir let me double check.." a moment later "yes sir it's good to roll with 3s" Ok sweet thanks alot dude. I hung up and plugged in a 3s and it worked fine on the bench. The tires ballooned like crazy. So I put the body on and headed out side Half way up my drive way I heard a sizzle sound.... And I glanced thru the window of my car and THERE WAS FIRE AND SMOKE AND OMG IT WAS AWEFUL!!! I don't think i have ever ran and unplugged a battery so fast in my entire life!!! So now I get to call HPI tomorrow and tell them what happend. And they had better be replacing my friggin ESC for free cause to be honest I am FRIGGING CHEESED. After one of there customer service tech people told me it was fine. When obviously it is t ok to do. So basicly do not put 3a in your sprint!! Brushed or brushless 2s IS THE MAX YOU CAN USE. I am not saying I hate HPI I am just saying maybe the guy was an idiot or having an off day who knows.. I will keep you all posted on how this turns out.