2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.

vac/boost line questions

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Old Apr 1, 2003 | 06:03 PM
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Ryde _Or_Die's Avatar
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vac/boost line questions

Ok I have a hose coming from the UIM that goes to a "Y." One end from the Y goes to my aftermarket boost gauge sensor. The other end goes to a "T." One end of the T goes to my stock boost sensor and the other to my BOV. Is this a good setup? Any other ways that would be better? Thanks for any help.
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Old Apr 1, 2003 | 06:06 PM
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Scott 89t2's Avatar
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that's what mine is. but I have 2 "T"s instead of a Y
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Old Apr 1, 2003 | 06:11 PM
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Ryde _Or_Die's Avatar
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Alright thanks. I have a Y because thats what my Greddy boost gauge came with.
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Old Apr 1, 2003 | 07:50 PM
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Im not sure that is the best way of doing things. Personally I would have a seperate vacuum line running to the factory boost sensor. That sensor gave me a lean condition when I was running the stock fuel injection because I had too many things Y'd off of it.
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Old Apr 1, 2003 | 10:29 PM
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Ryde _Or_Die's Avatar
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Heres the thing that kinda bothers me. When you have a Y or a T, then the 2 things each is going to couldn't possibly get the same force(vac or boost pressure), right? Basically a certain pressure reaches a point where it is relieved(at the Y or T), correct? What other point could I run one hose to my boost sensor and one to my BOV? I have the nipple on the side of my UIM I can continue to use for my Boost gauge already.
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Old Apr 2, 2003 | 04:56 AM
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Re: vac/boost line questions

Originally posted by Ryde _Or_Die
Ok I have a hose coming from the UIM that goes to a "Y." One end from the Y goes to my aftermarket boost gauge sensor. The other end goes to a "T." One end of the T goes to my stock boost sensor and the other to my BOV. Is this a good setup?
This is basically what I have, and probably the same as everyone else who's removed their ACV. While it may not seem like the ideal set-up, in practice it works fine. Remember these lines don't actually flow any air, they just get a little more air squeezed in under pressure.
In theory the more vac line attached to one point, the more air that has to be pushed in to match manifold pressure. This would slow the response time of anything connected. But in reality the difference would be tiny, certainly not enough to notice.
One thing to note is that the factory line for the pressure sensor has the small restriction ("pill") in it to stops spikes, and the pill in at the UIM end. Any tees in this line will be downstream of the pill, so whatever's connected to the tee will have its repsonse slowed. I originally had my boost gauge teed into that line, and it's resonse improved noticably when I relocated the pill to after the tee. I rearranged the tees so there's basically one line going from the UIM to the pressure sensor, but has two tees along the way for the boost gauge and BOV.
When you have a Y or a T, then the 2 things each is going to couldn't possibly get the same force(vac or boost pressure), right?
When you apply pressure to any volume, the pressure will quickly equalise so that's it the same at every point. This is exactly what will happen in all your hoses. It does take time to pressurise all the hoses, and the shortest one will reach peak pressure first and the longest one last, but the actual time difference is tiny. Basically your boost gauge, pressure sensor and BOV will all see the same pressure at the same time. That's just how pressure works.

Last edited by NZConvertible; Apr 2, 2003 at 05:05 AM.
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