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2015 STI Stage 1+ low boost
2015 STI Stage 1+ low boost
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Old 07-04-17, 08:04 PM   #1
awdboxer
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Default 2015 STI Stage 1+ low boost

So I currently have a Stage 1+ STI that can only hit around 10-12psi with the OTS Cobb map.. and I'm running out of ideas on what to check next.

But first, a little back story.

I purchased a 2015 STI about a month or so ago and I'm currently trying to get it etuned (Brentuning) but having issues reaching target boost with the Cobb Stage 1 +SF map. When I purchased the car, it had an IAG AOS, AEM CAI, Cobb EBCS, and Tomei UEL headers (wrapped) on it. I could swear when I test drove it I was able to hit around 17psi a couple times. I know, I know... don't buy a used modded STI. But I've had three Stage 2 WRX's in the past, so I'm somewhat knowledgeable.

Since it wasn't tuned, I babied it until the AP arrived.

After purchasing the AP and swapping the AEM out with the Cobb SF intake (didn't want to pay $300 for the stock setup and couldn't find a used one), flashing the stage 1+SF map, I'm now only able to hit around 10-12psi in S#. During the install, I also unwrapped the headers because I wasn't sure what the previous owner had installed.... surprise, Tomei UEL headers.

I reflashed with the HWG map, but still only hitting about 12-13psi.
Went back and forth a few times with Bren, they even cranked the boost up to like 22psi but I was only able to hit 15psi.

I've checked all the hoses/clamps around the intake and bpv. I've also taken the intercooler off and inspected the couplers and hoses and everything looks to be in good shape.

The EBCS was also inspected and verified the hoses are good and plugged into the correct ports.

I've reset the ECU a few times, but no luck. So I'm kind of at a loss on what to check next. Planning on inspecting the header for any cracks since I noticed it was pretty oxidized after taking the wrap off. Should I re-wrap it?

I have an appt next week with a local shop to see if they can diagnose the issue, but wanted to see if anyone had any other ideas.

Current mods:
Cobb AP w/Stage1 +SF map
Cobb EBCS
Cobb SF intake
Tomei UEL headers
12psi
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Old 07-06-17, 11:17 AM   #2
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Default Re: 2015 STI Stage 1+ low boost

Probably a vacuum leak of some kind. But, I would definitely check with a pro on this one.
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Old 07-11-17, 05:32 AM   #3
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Default Re: 2015 STI Stage 1+ low boost

So I finally got the car into the shop this morning and.... no leaks.
They did a smoke test but didn't find anything.

Notes from the shop:

Test drove vehicle, hit 16.3psi in 3rd (on the TEST1 map that Bren cranked up to 22psi).

Removed wastegate signal line and test drove, hit 21.2psi in 3rd (again, on the TEST1 map).

EBCS inspected and verified it's installed correctly.

Leakdown/compression results:

Cyl1 - 13%, 118psi
Cly2 - 14%, 111psi
Cyl3 - 13%, 120psi
Cyl4 - 18%, 110psi

They said everything looked great. I was kind of expecting the compression numbers to be a little higher, but at least they're all fairly consistent.

So there's still some sort of restriction somewhere or something's up with the boost control since it can hit 21psi with the wastegate line off. The shop recommended a catless dp, but I'm not sure that would fix the issue.

I guess I'll try and see if I can swap my EBCS out with a stock boost solenoid.

Any other ideas on what to check?
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Old 07-11-17, 09:48 AM   #4
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Default Re: 2015 STI Stage 1+ low boost

".......... Stage 1+ STI that can only hit around 10-12psi with the OTS Cobb map.........."
Correct me if I'm wrong but COBB OTS maps are NOT for EBCS other than stock.

Wasegate duty cycles has to be corrected in order to accommodate for aftermarket EBCS
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Old 07-11-17, 10:08 AM   #5
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Default Re: 2015 STI Stage 1+ low boost

Quote:
Originally Posted by Qkizz View Post
".......... Stage 1+ STI that can only hit around 10-12psi with the OTS Cobb map.........."
Correct me if I'm wrong but COBB OTS maps are NOT for EBCS other than stock.

Wasegate duty cycles has to be corrected in order to accommodate for aftermarket EBCS
Nope, you are correct... the OTS map does not support the EBCS, so it should be over boosting. However, the test map from Bren does support it and I'm still under boosting by quite a bit.

So not sure what else would be causing a restriction in boost. Could it be a bad cat in the downpipe?

I'm kind of leaning towards it not being an ebcs issue either, but it's the cheapest to rule out by swapping in a stock boost solenoid.
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Old 07-11-17, 10:30 AM   #6
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Default Re: 2015 STI Stage 1+ low boost

what about restrictor pill?
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Old 07-11-17, 10:34 AM   #7
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Default Re: 2015 STI Stage 1+ low boost

Quote:
Originally Posted by Qkizz View Post
what about restrictor pill?
No need for the restrictor pill, it gets removed when installing the ebcs.
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Old 07-11-17, 12:43 PM   #8
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Default Re: 2015 STI Stage 1+ low boost

no way of going back to stock ebcs to just rule out an ebcs issue?

edit: oh sorry, didnt see this:

Quote:
Originally Posted by awdboxer View Post
I'm kind of leaning towards it not being an ebcs issue either, but it's the cheapest to rule out by swapping in a stock boost solenoid.
yeah... u know how it goes, rule out anything possible and whats left is the culprit.
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Old 07-14-17, 09:54 AM   #9
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Default Re: 2015 STI Stage 1+ low boost

[QUOTE=awdboxer;4322830]So I currently have a Stage 1+ STI that can only hit around 10-12psi with the OTS Cobb map.. and I'm running out of ideas on what to check next.

I got my AP yesterday and was having the same issue. I called Cobb and the guy said to uninstall and reinstall it. I did this and it worked for me.

He obviously also tried selling me the Cobb SF intake but my data logs were fine so I'm not convinced it's necessary.

Current mods:
Cobb AP w/Stage1 +SF
K&N typhoon intake
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Old 07-14-17, 04:21 PM   #10
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Default Re: 2015 STI Stage 1+ low boost

[QUOTE=Emmbee;4324199]
Quote:
Originally Posted by awdboxer View Post
So I currently have a Stage 1+ STI that can only hit around 10-12psi with the OTS Cobb map.. and I'm running out of ideas on what to check next.

I got my AP yesterday and was having the same issue. I called Cobb and the guy said to uninstall and reinstall it. I did this and it worked for me.

He obviously also tried selling me the Cobb SF intake but my data logs were fine so I'm not convinced it's necessary.

Current mods:
Cobb AP w/Stage1 +SF
K&N typhoon intake
You had me excited for a minute... but just uninstalled, went for a drive and it was pulling timing hard. Flashed back and still at around 12psi when it should be around 17-18psi.

I just ordered the stock bcs and hoses a couple days ago. Not expecting it to fix the issue... but fingers crossed.
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