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Old 07-09-2014, 08:18 PM   #1
TurboJac
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Default Need Help with this Turbo Paradigm!


Fully connected = 15.7 Still


As the picture shows, I can only hit target boost (kind of) when my vacuum line from the turbo is removed entirely. I'm protuned at 21 PSI. I also replaced the turbo actuator with one known to work with no difference..

When I remove the boost solenoid side line, nothing changes at all! Same PSI regardless (15.7 ish)

When I change pill sizes, the smaller I go, the more boost I make (.025 = 19 PSI)(Stock =.047 = 15.7 PSI)

When I removed the turbo side line, I hit 21 PSI MAX. It was to the floor, wide open on a straight road.


So.. what gives? I've asked quite a few people and no one knows for sure..
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Old 07-09-2014, 10:21 PM   #2
Shiftace420
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post log.... your tune may not be shooting for the target you think...
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Old 07-10-2014, 12:17 AM   #3
Andrewxxcarlson
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Idk 2-port..and never had a 3 port buuuuh is there supposed to a pill in the line anymore??
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Old 07-10-2014, 06:32 AM   #4
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sounds like the wg door is sticking partially open or ya got a boost leak or exhaust leak
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Old 07-10-2014, 05:28 PM   #5
TurboJac
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I'll post a log when I get off work, but I assure you my target boost is 21psi. And I have gone through multiple sizes of pills.

Also, when I changed the WG actuator, I could very easily move the wastegate flapper and it was making a metal on metal clanking noise when I closed it which I assume means it's seating correctly. I've both boost and exhaust leak check until I turned blue in the face.
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Old 07-10-2014, 06:26 PM   #6
Shiftace420
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You may need to preload the wastegate up to 12-15psi to get your 21psi due to high pressure on the exhaust manifolds.

Likely a spring will have to be added to get a stock one that high.
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Old 07-10-2014, 07:14 PM   #7
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if the wg actuator has the wrong spring in it it wont hold boost

a VERY general rule of thumb is that you want the wg spring pressure to be at LEAST = to 1/2 of what your target max boost will be

so if ya doin 20psi...ya want at least a 10psi wg spring
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Old 07-11-2014, 12:36 PM   #8
TurboJac
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Well that makes sense to what I feel is the problem. My wastegate. I'll have to see how much it'll be for a good aftermarket actuator.

I'd go to an EWG, but it's my daily and already pretty obnoxious.
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Old 07-11-2014, 05:19 PM   #9
TurboJac
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Doing some research online, it seems as though most people are using their stock actuator to hit boost targets around 19-21 PSI.

Is this generally true? Because with the stock pill, I'm a far cry from 21. Around 16 with both old and new actuator.
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Old 07-11-2014, 10:25 PM   #10
Shiftace420
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Goto the cobb website or search "how a subaru boost control system works"

It tells you how to adjust your wastegate arm to the proper spring load.
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Old 07-12-2014, 02:11 PM   #11
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If you're talking about the adjustable arm, it's a VF39 turbo with a non adjustable actuator. But I'll read through the entire thing nevertheless.
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Old 07-12-2014, 04:55 PM   #12
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you can still adjust them. Just takes some bends in the right places or a spring.

There are aftermarket ones as well but a spring would be a really cheap fix until you got the cash.
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Old 07-12-2014, 09:24 PM   #13
TurboJac
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I've heard some bad things about the helper springs, but I may do some bending of my old actuator.

I may ride with someone who has a EWG and see how obnoxious it really is. Then buy a really cheap used setup.

The only aftermarket actuator I can find is 180 dollars, and for that much I can have a used EWG which I hear is better anyway.

Edit: ... Scratch that, it appears as though another protune would be needed.

Last edited by TurboJac; 07-12-2014 at 10:27 PM.
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Old 07-13-2014, 12:43 AM   #14
Shiftace420
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Just try the spring to see if that is what the problem accually is. If it boosts than you should plan on fitting some other accuator onto the thing.

As long as you check the crack pressure with a mityvac it really wont matter if you just use just about anything with a strong enough spring.
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Old 07-13-2014, 08:18 PM   #15
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Wow. I have be having this exact problem for months now. Please post up if you get any results. Just popped into my head yesterday that Maybe the Wastegate spring is getting too tired. I have a vf48 too without the adjuster.
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Old 09-12-2014, 09:54 PM   #16
TurboJac
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Updating this thread to say I have found the solution to my low boost.

I ended up buying a Forge actuator with a yellow spring (10-15 PSI I believe) and installed it. Without much adjustment (yet), I can hit 20 PSI in 3rd/4th and I actually over boost slightly in 5th/6th to 22 PSI.

My turbo spools quicker, smoother, and simply revving the car (rev matching even) is smoother and without an annoying stutter I once thought was merely turbo lag.

I believe the spring in the stock actuator was simply much too wimpy and blew open at the first sign of pressure. There was/is a huge difference between the 2 actuator spring constants and the fact I can preload to my liking is a major plus the non-IHI turbo guys have been enjoying for far too long.

Overall, with a little more tuning, my problem will be fixed and the extra bottom and top end power is very much enjoyed now.

Blah blah, ramble ramble, hope this helps someone one day!
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