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Discussion Starter · #1 ·
I have a set of the 38mm gates with the small green springs installed and a turbo smart manual boost controller turned all the way down. The gates are both in ideal positions, right in the bends of the crossovers. Turbo is a FI stock S480 on a 408sbf with Afr225s. I'm wanting 8-10lbs on the street and 14lbs is the lowest it will make. I have read where this same combo will hold 8lbs easy on some combos. I even unhooked the boost controller just to see if it was the problem and drove the car and it jumped to 19lbs and was just crazy. What can I try or do I just need 44mm gates if I want lower boost? Boost gauge is referenced in back of intake. It's also going through a big Garrett intercooler.
 

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I'm going to say backpressure. I can't go lower than 10-12psi with that hot side and two tial 38s with an 11-1 383. I believe that is with 10lb springs. With 5-7lb springs it wouldn't make any boost until 5500rpm then shoot up to 10-12psi and higher.
 

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Discussion Starter · #3 ·
Mine is 9.5-1 and makes boost around 3800 and full boost by 4400. I wouldn't think it would be back pressure but I guess it could be. Turbo has the 1.32 a/r and exhaust is 4" all the way.
 

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I even unhooked the boost controller just to see if it was the problem and drove the car and it jumped to 19lbs and was just crazy.
That says you unhooked it maybe, but didn't plumb it back in right.

To see if its just the controller, need the vac hoses connected to the bottom port on the wastegates, leave the top open to atmo.

Try that first, see what happens.
 

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Discussion Starter · #6 ·
The gates are at good angles, cant load pics for some reason. I looked at alot of photos to determine how to mount them.

On the controller i just pulled the lines out of each side of them controller and put those together. Should i have done it another way?
 

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So just run the gates with the bottom port with the lines and leave the tops open to atmosphere?
Yes, the gates need a reference signal to the bottom so they will open to whatever spring you have in the gate. Leave the top of the gates open to atmosphere.
 
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I run the 38's on a 372 and am able to get down to 3.5psi on the street. WG's are priority, when they weren't priority on my previous setup couldn't get below 8psi or so. What is the diameter of the pipe where the WG's are located?
 

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Discussion Starter · #15 ·
The hotside is 2.5 inch and I have about 7" of 1-3/4 pipe coming out of the gates venting to atmosphere. I agree I should be able to regulate it way down. Something is off.
 

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My car made 9psi with a small green spring and single 38 tial,358ci and S475. Placement is not great and plumbed into the down pipe. Honk if parts fall off ran a single 38 with similar results using an S480.
 

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On my 363 SBF I can get my twin 38 Tials down to 4lbs with their 5lb spring also.
 

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Just my observation: Assuming the 480 has the divided hsg. So, if you have the hot side plumbed the same way, you have each 38mm gate seeing flow from a 204" engine. As others have said, a gate plumbing issue.
 

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Discussion Starter · #19 ·
I sent some pics to 93hatch. He will post them and you guys can see if i have them plumbed correctly. I think placement is not perfect but really good. I may have them vacuum lines routed wrong. Thanks for the advice and help so far.
 
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