I understand that first you pick a turbo, then your a/r is limited by what's available for that turbo. And you look at what others have used on similar combos, and especially someone with a similar combo who tried different turbine housings, and which they found worked best. But even if the combos are similar, doesnt it depend on how you use the car that can change which housing works best?

 

Smaller housings generally have small wheels and will spool fast, a .48a/r is a decent compromise for the beta motor and will help build boost faster than say a .63a/r. There are a few Tib owners I know running larger turbine housings but they don't build boost until around 4200rpm.



If you want top end power a small turbine wheel/housing will choke, its air becomes too hot as the compressor falls off its efficiency area. A larger turbine/wheel will take more exhaust to spin and allow better top end power.



I find my .63 is great because it doesn't build boost unless I want it to so my blow off valve doesn't attract negative attention.