Choosing a turbine housing

So, I have a turbo. Info on that is here.

Currently said turbo (it was pulled from a 4 cyl piece of heavy equipment) has a .70 A/R turbine housing with a T25 style flange. I'm thinking that is way too big for a TDI application, and I'll be at red line before I build any significant boost.

I have access to 2 other turbine housings that will fit this turbo. Both are T3 flanged, but one is a .36 A/R and the other is a .48.

My question is, which one will suit my 1Z application better (with all else equal)?

I know .36 A/R will spool pretty quickly on this little TDI, but at what point am I sacrificing flow with such a small housing? If I can run a .48 A/R turbine without sacrificing response too much, I would go with that one because I know it will flow better on the top end.

in order to chose a turbo for your application you need to know more than the A/R of the compressor housing. You also need to know the specs of your compressor wheel and hot side wheel. The you also need to ask yourself how quicky do you want it to spool, max boost, and maybe a few other things that I missed. Look in the turbo database to get and Idea of what combinations other turbo have like the gt1749B(VNT-17 I think) and gt2052(VNT-20). After you have gathered information from there come back and ask for more specific help about the combinations you have. good luck

Yeh, what he says

http://www.turbobygarrett.com/turbobygarrett/turbine_housing_AR_and_housing_sizing


(Not that I have a clue myself though lol)