jeepsking: An existing hard plastic vacuum line for the "purge control valve" is replaced with a vacuum hose with 2 "T" fittings. The wastegate and BOV sensing lines connect to the two T's on that vacuum line.
Given the above diagram, both the wastegate and BOV are connected to "C" using a vacuum line shared with each other and the purge control valve.
This is not the ideal setup.
Ideally, the BOV should have its own dedicated line connected directly to the intake manifold, rather than teed into an existing line. Having a dedicated line ensures the quickest possible response of the BOV.
The wastegate should ideally not be connected to a vacuum source. Even TiAL (manufacturer of the wastegate) specifically says to use a pre-throttle-body boost source. It should be connected to either "A" or "B" in the diagram. Here's a good read about wastegate boost source options: http://www.miataturbo.net/diy-turbo-...eed-ebc-47532/
Post #15 in that thread specifically talks about why the wastegate should NOT be connected to the intake manifold (position "C" in the diagram).
I have asked Prodigy about this, and they say they have zero issues with their setup. Also, they say they tested the wastegate boost source both before (position "B" ) and after (position "C") the throttle body and found no difference. They chose position "C" and shared vacuum lines for ease of installation.
I'm not too concerned about the BOV having its own dedicated vacuum line. If the BOV responds quickly with a shared line, then it's fine.
I'm more concerned about the potential part throttle issues with the wastegate being connected to position "C" (see post #15 in the linked thread above).
Connecting the wastegate to the intake manifold seems to be a controversial subject on the internet. Many people on forums say they have run that way for years with no problems. Other people report part-throttle drivability issues and part-throttle high load compressor surge (like when driving up a long hill). Some people say the intake manifold source will give you quicker spooling and faster throttle response. I'm sure the exact outcome depends on many factors and the entire turbo/engine system as a whole. I've read many threads on the topic and talked to both TiAL and Prodigy directly. Based on all of that, I have concluded for myself that there's no good reason to disregard TiAL's instructions to specifically use a pre-throttle-body boost-only (no vacuum) source to control the wastegate.
For this reason, I decided to order one of these that I will use to add a boost source to the silicone coupler/elbow that connects to the throttle body (position "B" in the diagram):
http://www.atpturbo.com/mm5/merchant...egory_Code=BCS
It's a very simple/inexpensive modification to make me happy that I've done it the "right way". I will probably try both the Prodigy setup and my modified setup to see if I notice any differences.
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