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Old 03-26-2021, 06:07 AM   #1
TristanLudvig
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Member#: 522096
Join Date: Feb 2021
Vehicle:
2005 Saab 92x aero
Brilliant Red

Default Need some new ideas, 2005 wrx overboost and fluctuations

Hello Nasioc

My 2005 wrx (215k) has been overboosting and then boost fluctuates, dropping to about 10 psi then doing it again...again...again when under wot. This problem gets worse once the car gets up to temperature, and even worse when the car heat soaks.

Things I have tried mostly off my friends car (my friend has an 05 wrx also):
Boost controller
Redid all of the boost controller plumbing with high quality silicone hose, and cleaned the restrictor pill
Cobb stage 1(car was stage 1 at one point and was thinking possibly the base map got messed while sitting on the cobb)
Messed with the wastegate actuator (went to 2 turns out, to attempt to lower the wastegate duty cycle 1/2 turn at a time, have not tried in yet)
Different Stock intake (2 different maf's)
Stock BPV
Different intercooler
Tightening the downpipe bolts
Unplugging the boost controller (shoots right to 7 and stays there no problem so I don't think faulty wastegate or wastegate actuator)

The car is not triggering fuel cut and shows no codes for fuel cut

I kinda don't know what to do anymore...

I was thinking there could be a large vacuum leak pre turbo, perhaps a ripped turbo inlet? That likes to leak a lot under high boost and high temperature but not always.

or the journal where the wastegate rides likes to stick when it needs to open a lot and my turbos bad?

or digging around some old forum posts said it could be clogged up pipe cat (but I dont rly understand how that relates to overboosting)

I recently bought a tactrix cable and decided to some datalogging to see if I make sense of anything.
This is a third gear pull 100 percent throttle the entire time.
You can see boost initially spike to ~17 then drops to ~9 then does the same thing again. The car will continue to do this if kept WOT.

https://imgur.com/a/gMDga7t

I appreciate any help or ideas.
and also some input on what I should actually be logging would be great.

Thanks
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Old 03-26-2021, 11:03 AM   #2
D-Rodman
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Member#: 110078
Join Date: Mar 2006
Location: Long Island N.Y.
Vehicle:
02 Bugeye JDM STi
OBP BLACK

Default

Have tested for boost leak ?
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Old 03-27-2021, 07:43 AM   #3
TristanLudvig
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Member#: 522096
Join Date: Feb 2021
Vehicle:
2005 Saab 92x aero
Brilliant Red

Default

Not yet.
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Old 03-27-2021, 10:11 AM   #4
subaru_gc8
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Member#: 29292
Join Date: Nov 2002
Chapter/Region: SCIC
Location: Orange County CA
Vehicle:
2004 WRX wagon
silver

Default

disconnect the wastegate vacuum line and drive around, if you don't feel the fluctuations you know is a boost control issue if its still there its something else...
be careful though since you are disconnecting the boost control system you can over boost very easily
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Old 03-27-2021, 02:27 PM   #5
D-Rodman
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Member#: 110078
Join Date: Mar 2006
Location: Long Island N.Y.
Vehicle:
02 Bugeye JDM STi
OBP BLACK

Default

Quote:
Originally Posted by TristanLudvig View Post
Not yet.


It would be a good move.
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Old 03-29-2021, 04:00 AM   #6
TristanLudvig
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Member#: 522096
Join Date: Feb 2021
Vehicle:
2005 Saab 92x aero
Brilliant Red

Default

Update: What I have found and what I think I should do next.

I tried removing the boost control lines for the wastegate actuator. The car "held" 15 psi fine but it was hard to control and im not sure if this was actually the case. But the car made an odd squealing noise. I don't know if this is just air squealing through the port on the turbo. Or, what I really think is happening is a leak in the turbo inlet. I think air is getting in post maf and messing everything up.

For fun I tried my friends restrictor pill line. No luck.

I think the lines are fine for my boost controller because when I unplugged the boost controller the car held 7 pounds fine. And the boost controller lines that control the wastegate, should never see more than 7 psi, I think...

because my understanding is the wastegate will open when it sees 7 psi of boost. So to get > than 7 psi of boost you must divert air away from the wastegate actuator. I also think my wastegate actuator is fine because the car holds 7 psi no problem.


I think I have the problem down to 1 of 3 things.

An electrical issue (least likely in my eyes, but the car had subs so )
An issue with another sensor somewhere in the engine (but car isn't throwing any codes except tps, which I don't think would cause it)

Or a large vacuum leak involving the turbo inlet or one of the hoses running to the turbo inlet (I think this is by far the most likely scenario, the turbos sucking more than it should causing boost to spike)

I kindve want to try a diy leak test, but I am nervous with my cars age and how hard all of the vacuum lines are I might get a local shop to do it.

Any other ideas or if I sound like an idiot and someone can point out something obviously wrong with my ideas that would be great


It's only gotten worse and I want my car to work again
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Old 03-29-2021, 07:35 AM   #7
D-Rodman
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Member#: 110078
Join Date: Mar 2006
Location: Long Island N.Y.
Vehicle:
02 Bugeye JDM STi
OBP BLACK

Default

Start by replacing all the hardened hoses, a leak test should be next.
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