Reply With QuotePickles, I'll take pictures of the set up. I'll get them this evening.
Thanks Nola for pictures. Usually boost sensor comes after the throttle body. So it might be fitted on the intake beneath the engine cover.
Pickles, I'll take pictures of the set up. I'll get them this evening.
Ahh yes! I'll get some pics up of that as well this evening.Originally Posted by jeepsking
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.
Thanks Jeff for these info's. What about the boost sensor pick up point to the gauge. As far as I know it should be in position "C".
Oh, yeah. Boost gauge should always be at position "C". Ideally, each component should have its own dedicated line, rather than using T fittings to split/share lines to a vacuum/boost source. But that would require adding new barbed hose fittings to the intake manifold for the BOV and boost gauge. I haven't found any good info on how to add fittings to a plastic intake manifold yet.
This what your looking for? Looks like they used the T fitting method.
Yes it is. So adding T fitting gives inaccurate boost reading?
Last edited by jeepsking; 08-28-2014 at 06:16 AM.
Not inaccurate. Just potentially slower response, and probably on the scale of hundredths of a second difference. It wouldn't matter at all for the boost gauge. For the BOV, as long as it responds quickly enough to avoid compressor surge, then the T fitting for that is fine too. A dedicated vacuum source for the BOV might possibly keep the turbo spooled a bit better during gear changes, but whether or not the difference is worth the effort of creating a dedicated vacuum source would require testing and data logging to determine.
Testing and Data logging! Yeah!
staying spooled with the turbo is my main concern with it. If there was a way to blend an sc with a turbo, so that it worked of the engine low, and exhaust high it would solve all problems.
Work that out, will you pickles?
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