Complex-ish physics/maths question on the speed a car would need to take to go around a loop.

I basically want to know what formula they used in this video what steps did he take, so I could work out similar problems.
http://www.youtube.com/watch?v=wiZoVAZGgsw
I know basic projectile motion and masses on inclined planes, etc the basic stuff but I haven’t come across a question like this before.