External Wastegate on Twins

[dieselpolaris]

Just wondering what is accomplished by running an external wastegate on a set of twin turbos if your secondary turbo is already internally wastegated. Just curious if this is something i should consider on my twin setup i have right now?

 

[White Knight]

Usually if you have two wastegates the external would gate the primary or even gate around both turbos depending on how you plumb it.

If you primary is perfectly sized or even too small then you wouldn't see any gain.