Equivalence Chart Round To Oval Exaust Pipe - to achieve same flow  

I need to go OVAL exhaust tubing instead of round due to clearance underneath and did a lot of research so I thought I might post this up to help people in the same case as me

Equivalence chart from the leading oval guys in USA who have done race cars for years showing what size oval exhaust tube you need to go to, to get the same flow as round tube.

Attached

Hope it helps someone..