I just ordered a fully divided turbo manifold with dual wastegate runners. I'll be running dual Tial 38mm's, but I am a little confused on which springs I need to run in both. Will both wastegates see the total amount of boost (~23 psi), therefore needing the larger springs, or will both wastegates see only half the boost (~12 psi), needing only the smaller spring?

 

both wastegates see the same pressure.

 

Whether you run dual or single wastegates will have no effect on the spring you want to use.

Most select a spring based on the stiffest one they can run while stiff being able to run the lowest setting of boost desired. i.e. if you want to run 16-23psi of boost then get a 13-15psi spring. Assuming you are using a boost controller. Or, if not, just get a 20-22psi spring and use the adjustment screw on the top to tune it in.

Justin

 

Thanks! I was a little confused about that stuff at first, but I think I'm getting it now.