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Old 06-25-2017, 08:20 PM   #1
brisketrobot
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Member#: 444985
Join Date: Apr 2016
Vehicle:
2016 STi
Pearl White

Default Tech Help

Hey Subie fam,

I finally got a chance to take my STi to the track yesterday. After about 3 to 4 laps, at WOT in 4th I started to get fuel cut off. I checked my AP and the stock boost gauge and noticed overboost with the stock boost gauge reading 24psi. Target boost pressures on the tune were 19.5psi in S#. Checked vacuum lines (visible ones) and no leaks. Tried baby-ing the car but no matter what after a few laps, same issue.

2016 STi
Engine mods are as follows:
Cobb AP
Cobb SF Intake and Box
Nameless Performance Turboback exhaust - thermal wrapped
Grimmspeed EBCS
NGK Iridium One Step Colder Spark Plugs
Cobb Flex Fuel Kit
1100cc FIC Injectors
AEM Fuel Pump
IAG AOS
Protuned on e85

I did data log the runs I just need to upload them to see what's going on. Can anybody help point me in the right direction about what could be failing? I was thinking maybe having to change my turbo inlet piping and intercooler piping so that I'm not running crazy A/F ratios, otherwise is next step putting a block plate on the turbo and running EWG?

Any other ideas would be a ton of help!
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Old 06-26-2017, 12:54 PM   #2
whispering_eye
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Member#: 348882
Join Date: Mar 2013
Chapter/Region: MWSOC
Location: Royal Oak, MI
Vehicle:
2012 WRX Hatch
WRB

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catted or catless?
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Old 06-26-2017, 01:54 PM   #3
brisketrobot
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Member#: 444985
Join Date: Apr 2016
Vehicle:
2016 STi
Pearl White

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Catted DP from Nameless Performance
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Old 06-26-2017, 02:55 PM   #4
nofriends
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Member#: 65169
Join Date: Jun 2004
Chapter/Region: RMIC
Location: Colorado Springs
Vehicle:
2010 Outback
2016 STI CBS

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Shouldn't have boost creep/spike with those mods. I used to have a very similar setup and it was never an issue.

Double-check your vacuum lines on the wastegate itself. I had one pop off and would see boost in the 24-25psi range like you.
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Old 06-26-2017, 03:01 PM   #5
whispering_eye
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Member#: 348882
Join Date: Mar 2013
Chapter/Region: MWSOC
Location: Royal Oak, MI
Vehicle:
2012 WRX Hatch
WRB

Default

Agree with nofriends on the creep. You should also verify that the restrictor pills going to the wastegate are still there. I would also verify that the gauge is reading correctly by comparing absolute manifold pressure. Datalogs will help diagnose the issue better if you have them.
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Old 06-29-2017, 09:03 PM   #6
brisketrobot
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2016 STi
Pearl White

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All lines look good. I was thinking its possible given summer heat that the stock hoses were collapsing under track conditions. It wasn't happening until 3 or 4 laps in usually and more towards the high heat part of the day.
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