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Old 04-13-2007, 10:56 AM   #1
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Default Vacuum/boost sources for everything

I have a '92na with 1.6l. I'm currently piecing together the pieces for a DIY turbo. I like the idea of having a vacuum manifold for a central location for everything for the turbo system. I understand the value of keeping pcv system isolated from boost and now need an opinion or experienced advice on my vacuum source for certain turbo system components.

My vacuum/boost effect pieces on my turbo setup will include boost gauge, tein external wastegate, vortech fmu, and recirc. valve. I would like to tie all of these components into a vacuum manifold that is tied into one source on the engine. The source I have in question is an unused vacuum nipple that is located after the throttle butterfly/TB on the top of the intake manifold. It can be seen in the picture on the bottom of this page. This guy has his used, but mine is empty. Its the one on the top.

http://www.cardomain.com/ride/2303

My question is how will the various vacuum boost components of my turbo be affected by this location? Will this location see vacuum and boost or just boost all of the time?

My wastegate instructions say to get a vacuum source before the throttle butterfly.....is this so the wastegate sees boost and vacuum? If the wastegate only sees boost what will happen? If the wastegate sees boost and vacuum, what will happen?

I believe that the vortech fmu will not be negativley affected from seeing boost and vacuum, but will it be negatively affected from only seeing boost?

Am I wrong in thinking that the recirc/bov will not be negatively affected by seeing boost and vacuum?

Anthony
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Old 04-13-2007, 11:17 AM   #2
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boost gauge : Intake manifold
wastegate : Compressor Outlet, Pre-TB
fmu : Intake manifold
recirc. valve : Intake manifold

The two nipples on the TB are Post TB...wastegate should be run off the compressor outlet nipple.

FMU is not affected by boost/vac, it doesn't do anything in vac.

check valve to your charcol canister.

PCV valve should stay is place.

breather line should be reconnect to the intake post-AFM, pre-compressor inlet.
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Old 04-13-2007, 11:30 AM   #3
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That ride is unavailable...

The recirc/bov NEEDS to see boost and vacuum, so a source AFTER the throttlebody is needed.

The wastegates instructions state before the tb, this would be boost ONLY. Typically wastegate manufacturers say this to reduce wear and tear on the actuator components and it will usually give you a smoother boost curve.

If you pull the reference for the FMU from the charge piping chances are it will be affecting your fuel pressure constantly.

Your vacuum distribution block will only be as good as its source... so would you T all of those items off of that single source?

I always give any boost and fuel control components their own dedicated reference. And despite what some companies suggest I NEVER run valves or boost controllers off of the FPR line. I've seen instructions for bleeder valves that say to tap into the FPR line... so as you increase your boost, IE a larger leak, you are potentially lowering your fuel pressure! Asinine.
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Old 04-13-2007, 11:34 AM   #4
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Brain- You need to make "Turbo Miatas For Dummies" bigger and bright green, it doesn't clash enough with your avatar i mean i hardly notice it.
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Old 04-13-2007, 12:57 PM   #5
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Thanks brain and pat!

My conclusion is this.....I will hook my vac. manifold up to the nipple that is post throttle plate on the intake manifold. Boost guage, fmu, and recirc will then be run from the vac. manifold since they all can or should see VAC and BOOST.

The wastegate will be run off the nipple on the compressor housing. Brain told me to run it off of there about a month ago. I was jw if there was a clean vacuum line routing option to referencing the WG post IC so I wouldn't be affected by the IC pressure drop compared to the compressor housing. Oh well, I like the cleanliness of sourcing off the compressor housing and can make up for the pressure drop referencing by spending a whole $3 dollars on an MBC.

Thanks guys! I really appreciate the help that you guys always give me!

Anthony
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Old 04-13-2007, 01:02 PM   #6
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your boost gauge will display exactly what the manifold is seeing, you won't even know a pressure drop exists. not a big deal at all.
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Old 04-13-2007, 01:31 PM   #7
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the boost guage won't know there is a pressure drop and either will the WG. So when the WG opens at 6psi from the compressore housing, i might have only 4psi in the intake.................It's allright, i can make up for that difference with an MBC, and like you said, the most important thing to know is what my boost gauge will tell me from reading off the intake manifold, i.e. what is actually going into the engine.
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Old 04-13-2007, 03:20 PM   #8
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exactly!
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