How to make a car drive on walls and upside down?

I am trying to make a racing game that uses car physics similar to Grip and Rollcage. I have searched the internet for help, but I can’t seem to find anything that is useful. I want my car to be able to drive on walls and upside down, but still hit jumps off the ground.

There isn’t a built-in way. But you can disable regular gravity and implement your own gravity, like this guy did (read down the thread a bit and he explains).