I think its the frameratesmoothing option that can be found in the advanced settings menu. There are four submenues. I think its in the last of them. With that you can disable the cap. To change the cap i think its in the UDKEngine.ini file somewhere. Sry im on mobile arm, cant check. But it is definatly in some of the inis. You can try googling for frameratesmoothing in UT3/UDK and you should find explanations for it.