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2fst4urtrk

OHIM2FST4U
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Whats up everyone, need some help taking out an issue I'm having.

cg hot side, dual 39mm wastegates, spring pressure 2psi (i have tried 9.5psi springs and 15.5psi), car always spike to 20psi. top of wastegate venting to atmosphere, pt7675 turbo, 4in down pipe bumper dumper. Boost lines from turbo to T which goes to bottoms of wastegates with push lock fittings, and goes to boost solenoid, from solenoid to tops of wastegates.

when I do a pull in 4th I see spring pressure +2psi from 2000-5000rpm, after 5000 my boost will climb like crazy to 20psi.

with no wastegates opening i see 31.5psi (2000-6800rpm)

My tune is setup for 20psi, i just am trying to get my electric boost controller to do its job instead of letting my wastegates do all the work, so i can have a low boost safety.

My question, are my two 39mm wastegates only able to bleed 10psi from the turbo which is why i keep seeing 20psi? placement looks good but can be moved if completely necessary. Would rather not drop 800+ on larger wastegates but can be done.

20200830_003300.jpeg
20181215_193658.jpeg


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cobranick01

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Have you tried it with your wg dump pipes removed? Wonder if there is some sort of restriction with them merged together and the pipe size remaining the same.

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MG0h3

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I’d say either they aren’t sufficient or your reference isn’t strong enough.

I’d think two 39s would be enough but I’ve never run dual. Maybe you need a dedicated line to each?


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2fst4urtrk

OHIM2FST4U
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Have you tried it with your wg dump pipes removed? Wonder if there is some sort of restriction with them merged together and the pipe size remaining the same.

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Interesting point, since the dump tubes are the same size they could be fighting each other. ill pull the dumps off and see how it reacts. Thank you for the suggestion.

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2fst4urtrk

OHIM2FST4U
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I’d say either they aren’t sufficient or your reference isn’t strong enough.

I’d think two 39s would be enough but I’ve never run dual. Maybe you need a dedicated line to each?


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Good point, reference is off of the turbo where they recommend, i can try a Y from turbo straight to bottoms of wastegates. Thank you for the suggestion!

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cobranick01

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What kind of boost controller? I always thought regerence line went from turbo to boost controller and boost controller to waste gate. And then vent would be on the boost solenoid. I would doblue check the boost controller manufacturers recommendation for running a reference line. Im not saying yours is wrong. I would just double check.

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2fst4urtrk

OHIM2FST4U
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What kind of boost controller? I always thought regerence line went from turbo to boost controller and boost controller to waste gate. And then vent would be on the boost solenoid. I would doblue check the boost controller manufacturers recommendation for running a reference line. Im not saying yours is wrong. I would just double check.

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its a innovate scg-1.


its plumbed exactly line innovate wants. i just added 2 T fittings so I can hit the second wastegate. They plumb it different for a low boost cut (spring pressure) if you go lean or overboost.

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cobranick01

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That last one deleted, I would definitely eliminate the controller for testing purposes only. And run a line from the turbo to the bottom of the wastegate. And leave the top of the wastegate open to atmosphere. Then you can see if your wastegates and piping is efficient for what your wanting. If it still climbs out of control then i would remove dump pipes as a process of elimination. If neither of those 2 work. Then either your wastegates or the way the wastegate pipes come off the up pipes needs correction

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cobranick01

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If that does work, then you have a controller issue or you need to step up to a co2 bottle with your controller for the ultimate control of boost. I went almost a year on 1 2.5lb bottle. So I wouldn't stress about refills. Report back your findings

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9397SVTs

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Why are you using 2 gates on a single turbo? A properly sized and placed gate will work just fine.

I can't tell from the pictures, but the ideal location for the wastegate is between the turbo and the merging of both headers with a direct path towards the wastegate, no sharp angles.

If you keep what you have, dump them independently.
 

2fst4urtrk

OHIM2FST4U
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Why are you using 2 gates on a single turbo? A properly sized and placed gate will work just fine.

I can't tell from the pictures, but the ideal location for the wastegate is between the turbo and the merging of both headers with a direct path towards the wastegate, no sharp angles.

If you keep what you have, dump them independently.
got them for a great price new and also wanted some residency if anything fails. May go twins later so keeps my options open.

Im going to pull the dumps and see how it does. i plan to rebuild a full exhaust out the back in the next month or 2 so i can rework dumps then.

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