The main reason for the time difference between NTSC and Pal is the display image NTSC ( 525? lines horizontal ) against Pals ( 675? ) where the processor has to work harder on a Pal machine making it run slower. What the game developer does is speed up the game engine to make the game play similar to the NTSC version. In WipEouts case they must slow down the NTSC version to make it play similar to the Pal game speed.
An unmodified NTSC version sounds ludicrous but thats what WipEouts all about though isn't it? Another level up from Pals Phantom..... rin: