Ok so here is the deal. I'm running an 8 blade wh1c on a stock 1jz. I had a Garrett .63 Single scroll turbine housing machined to fit. on 18psi with a t3 open scroll manifold I was able to make..




Now I would like to convert to Twin Scroll manifold and Turbine housing. I'm hoping to have it come on earlier and breath better up top. My question is.. what Twin scroll Cm2 housing is equivalent to my open scroll .63? It seems i have a few options to choose from here http://www.gillettdiesel.com/DodgeCummins.aspx

 

No one knows?

 

9cm2 is equal to .65 a/r that is your best option.

8cm2 = .57 a/r
10cm2 = .73 a/r

 

Am I correct in assuming that I should stay around the size of my .63 in order to get similar spool? or does that number not mean the same thing when you factor in a twin scroll setup? in other words should I be looking for the sizes you mentioned or bigger?