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Old 04-14-2012, 09:35 PM   #1
cargod78
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Default installed 15g now only getting 5psi boost

ok, i have a 1992 745 tic, my old 13c had gone up so i decided to do a 15g swap. got a good one with little play, rebuilt it anyway... reclocked it, installed it... test drove and .... 5psi max! any ideas on what i f'ed up? my old turbo (13c) would do 12psi with the manual boost controller.. this new 15g is only putting out 5psi and takes a while to get there.
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Old 04-14-2012, 10:23 PM   #2
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pulled out the CBV diaphram, it has two very small holes in it. Is that enough to cause my issue?
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Old 04-14-2012, 10:38 PM   #3
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Yes.
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Old 04-14-2012, 10:47 PM   #4
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awesome, i was hoping it was something simple. i tried pulling off the valve and shimming the spring as well as disconnecting the wastegate, but still only 3-5psi.. thanks for the input... now to find one..
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Old 04-14-2012, 11:05 PM   #5
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Quote:
Originally Posted by cargod78 View Post
awesome, i was hoping it was something simple. i tried pulling off the valve and shimming the spring as well as disconnecting the wastegate, but still only 3-5psi.. thanks for the input... now to find one..
same one as 13c, use that one.
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Old 04-14-2012, 11:22 PM   #6
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Make sure the weastgate has the rite pre-load (10mm).
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Old 04-14-2012, 11:46 PM   #7
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Originally Posted by 740volvo View Post
Make sure the weastgate has the rite pre-load (10mm).
This is my thought, wastegate preload. The CBV is the second thought.

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Old 04-14-2012, 11:50 PM   #8
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Should only need 3-5mm according to Karl Buchka.
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Old 04-15-2012, 10:25 AM   #9
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I think the poster above is correct @ 5mm is a good preload.

GET THE IPD CBV IT IS GREAT!!!
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Old 04-15-2012, 12:18 PM   #10
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Ok, I'm going to silicone up the two small holes in the cbv for testing. I don't know if my preload is correct, I'll check that too. Thanks for the info
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Old 04-15-2012, 04:10 PM   #11
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the 850 wastegates are only set to like 5psi factory, they have a solenoid to control it on the 850s
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Old 04-15-2012, 09:39 PM   #12
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is your actuator hooked up? I.E. on the flapper arm?
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Old 04-15-2012, 10:11 PM   #13
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F the silcone, reuse the 13c diaphragm
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Old 04-15-2012, 11:50 PM   #14
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The cbvon my old stock turbo is completely different. It sets down in it wit an o-ring of some sort.
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Old 04-15-2012, 11:51 PM   #15
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Quote:
Originally Posted by falunbrick View Post
the 850 wastegates are only set to like 5psi factory, they have a solenoid to control it on the 850s
Even on a 94? That's what the turbo came off of. So I guess if I hook my mbc back up I should be good
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Old 04-16-2012, 12:02 AM   #16
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yep hook up your mbc and boost away. i know that will fix it
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Old 04-16-2012, 12:22 AM   #17
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Lol, the simplest things... I'll give that a try in the morning.
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Old 04-16-2012, 12:23 AM   #18
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Speaking of wastegates, anyone know where I can get a rwd 15g bracket? The one I made is a bit cheesebally
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Old 04-16-2012, 12:44 AM   #19
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I believe tryingbe reclocks 15gs, so he may have a wastegate bracket that he can sell you.
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Old 04-16-2012, 12:57 AM   #20
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what is the 15g from? yeaR?
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Old 04-16-2012, 08:13 AM   #21
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The 15g was from a 1994 850 turbo sedan


I tried pulling the wastegate vac line off and no change, still 3-5 psi
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Old 04-16-2012, 09:38 AM   #22
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the dia. in the act. is nfg. I know the dia that came off my 13c was no stronger than a rubber band. I got a new(1.2 bar) dia and a ipd cbv and the turbo spools very quick and the cbv is perfect!

Looking back I would get a .8 bar and put the mbc back in.You can e-bay the wg act. for cheap from I think authenticboosting.com
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Old 04-16-2012, 10:40 AM   #23
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The actuator feels strong, has a good bit of spring tension to it... And I shimmed up the cbv to put more pressure holding it closed
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Old 04-16-2012, 02:07 PM   #24
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did the shim help? You would be amazed at how much pressure is on the little wg door and dia. If that is the orig. 94 part it's OLD.

My car ran with the old dia. but what a HUGE DIFFERENCE the new one made! It is worth the few bucks not to have a prob. later; dont you think?
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Old 04-16-2012, 02:51 PM   #25
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No, it didn't help. I agree, it is worth the money.. If that is the problem. I just want to make sure I find the true cause before I buy parts. Perhaps I'll wire it shut as a test. If it still has low boost I know the problem is elsewhere.
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