ideola

Functionally speaking, what is the difference between these two different styles of plumbing a dual port / tee style manual boost controller (MBC)?

carreracoupe997

It depends on how the wastegate design is. The top diagram shows a vacuum line which is actually incorrect. There will never be vacuum on a boosted car AFTER the throttle body EXCEPT at idle or very very low rpm's. There will always be pressure in the lines. But getting back to your question. The two different paths out of the MBC control the wastegate. The pressure in both lines counteract each other. What I am trying to say is that one line (carrying the full pressure) either closes (1 wastegate design) or opens (the other design) the wastegate AFTER a certain amount of pressure in the other line(coming from the adjustable side of the MBC) in achieved. In other words one design the pressure opens it, the other, it keeps it closed. Does that make sense?

ideola

Hmmm...
...not sure why the first image shows vacuum. This is actually the same design as the Lindsey Racing MBC, and the same diagram. The second diagram is actually a "T" style controller, where the T is integral to the controller itself, like this Forge product:


The L-R version is widely used on 951s, and can be configured for single or dual port use. On my 931, I have the 930-style dual port wastegate...the second diagram in the OP was drawn by another 931 owner...just trying to decide if either approach is superior, so I know which MBC to purchase...

carreracoupe997

One is not superior over the other. I do prefer the Lindsey products because you can talk to them about all your mods, just not the boost controller.