Hello
@Chris Cheung .
Firstly try to check id your controller is correctly setup (I recommend checking CPanel options in Windows, and then use the wizard in-game).
If that is ok, 2nd thing to check is car setup ingame. Turn-in is affected by toe-in, anti roll-bar, etc..
If you indeed need to play with the data.acd.. can't really help you for the moment - I'm away from all my documentation. And will be for another 1 month or so.