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09-21-2020, 11:09 PM | #1 |
Scooby Newbie
Member#: 270623
Join Date: Jan 2011
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Low boost issue, out of ideas...$20 to your venmo
2006 sti, recently rebuilt with new OEM shortblock.
Only mod = cobb catted downpipe. Running cobb stg2 91 OTS map in anticipation of being pro tuned. Just got through the break in period and getting on the throttle into boost. I can't seem to get past spring pressure of ~9psi peak boost. Engine runs great, idles great, no misfires, solid AFR at idle, some minor knock numbers in low load which i attribute to noise as DAM = 1.0. Things I've tried so far - new vacuum lines, retaining the pill between the Tee and Turbo nipple. Swapped the BCS 3 times, 1 from a functioning car! Flashed all the stage 2 WG maps and even tried S1 - no change. Triple quadruple checked all vacuum and charged lines - everything was upgraded to silicone during rebuilt. One off the wall idea i had was to verify the system was capable of boost so i by passed the BCS and jumped the turbo tee directly to the inlet hose. Boosts as far as i want - so i know i don't have a major vacuum or exhaust leak preventing me from physically making boost. My WGDC has been active, although i plan to log and investigate that further... still doesn't really help me find the root cause of WHY....in either its not calling for boost (no hints here why not), or if it is calling for boost and i know my system is capable of it (minus the electrical from ECU to BCS - maybe i have bad wire?) Im out of ideas. $20 to your venmo if you have the proper solution!
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09-21-2020, 11:20 PM | #2 |
Scooby Newbie
Member#: 516780
Join Date: Jul 2020
Location: Georgetown Kentucky
Vehicle:2008 Subaru wrx sti WRB |
Does the wastegate lever need adjusted? U didnt mention where you got your turbo or what kind
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09-21-2020, 11:41 PM | #3 |
Scooby Newbie
Member#: 506756
Join Date: Sep 2019
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I'd double check the wires that connect to the BCS and make sure that they are not damaged, also double check that you're connecting the vacuum lines from the BCS to the correct location.
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09-22-2020, 12:16 AM | #4 |
Scooby Newbie
Member#: 270623
Join Date: Jan 2011
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Wires look fine, going to look down them with my multimeter tomorrow. You can't mess up the BCS lines... there is no direction its just a valve open or closed. ... but i do have the right ones to the factory locations.
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09-22-2020, 12:16 AM | #5 |
Scooby Newbie
Member#: 270623
Join Date: Jan 2011
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09-22-2020, 01:12 AM | #6 |
Scooby Guru
Member#: 50586
Join Date: Dec 2003
Chapter/Region:
BAIC
Location: Chiraq
Vehicle:64 Impala |
do you have TGV's or did you delete them?
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09-22-2020, 05:41 AM | #7 | |
Scooby Newbie
Member#: 49931
Join Date: Dec 2003
Chapter/Region:
MWSOC
Location: Grand Rapids, MI
Vehicle:0305 wrx/Xt black/black |
Quote:
Not true. I’ve witnessed the oem bcs not function with the lines reversed. Swap them and see what happens. |
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09-22-2020, 11:42 AM | #8 |
Scooby Newbie
Member#: 270623
Join Date: Jan 2011
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09-22-2020, 11:43 AM | #9 |
Scooby Newbie
Member#: 270623
Join Date: Jan 2011
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09-22-2020, 11:46 AM | #10 |
Scooby Newbie
Member#: 270623
Join Date: Jan 2011
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Have been reading everything i can on this subject. Trying to do some data logs to see if theres something "hidden" in the ECU that isn't popping a code, but keeping me out of boost. Areas of interest... FPR, MAP sensor, MAF sensor in that order. Now deciding what to log and how to interpret it
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09-22-2020, 12:41 PM | #11 |
Scooby Specialist
Member#: 29292
Join Date: Nov 2002
Chapter/Region:
SCIC
Location: Orange County CA
Vehicle:2004 WRX wagon silver |
so the first thing you have to do is to track down what is not working, so what you want to do is disconect the wastesgate vacuum line and see if it will boost normally, if it does then you know its not the turbo or a exhuast leak. if not go from there an start to eliminate other stuff.
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09-22-2020, 02:48 PM | #12 | |
Scooby Newbie
Member#: 270623
Join Date: Jan 2011
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Quote:
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09-22-2020, 03:51 PM | #13 |
Scooby Newbie
Member#: 49931
Join Date: Dec 2003
Chapter/Region:
MWSOC
Location: Grand Rapids, MI
Vehicle:0305 wrx/Xt black/black |
It sure seems like it is in the bcs circuit. Do you have a multimeter? It would be an idea to see that there is voltage being supplied by the ecu at the plug in when its being commanded by the computer. But that may prove difficult.
When you tested the bcs on a bench, does it energize/deenergize and allow air to pass thru it if you pulse the voltage at it? And also stay open when constant voltage is there? |
09-22-2020, 03:52 PM | #14 |
Scooby Newbie
Member#: 49931
Join Date: Dec 2003
Chapter/Region:
MWSOC
Location: Grand Rapids, MI
Vehicle:0305 wrx/Xt black/black |
Dumb point- make sure you’re not on the valet map.
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09-22-2020, 04:06 PM | #15 | |
Scooby Newbie
Member#: 270623
Join Date: Jan 2011
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Via green connectors it clicks, and functions. I can blow through it when I hear it click and fee pressure build when it’s closed. It’s working. Data logs coming soon
Quote:
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09-22-2020, 04:08 PM | #16 |
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09-22-2020, 04:40 PM | #17 |
Scooby Specialist
Member#: 29292
Join Date: Nov 2002
Chapter/Region:
SCIC
Location: Orange County CA
Vehicle:2004 WRX wagon silver |
why dont you take off the map and see if its acts normal. it seems like you are totally convinced its mechanical why is that?
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09-25-2020, 12:39 AM | #18 |
Scooby Newbie
Member#: 518888
Join Date: Sep 2020
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Regardless of anything just take the OTS off. That OTS stage 2 Cobb tune specifically has now sent multiple vehicles with ringland to the shop I use
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05-19-2022, 11:39 AM | #19 |
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Member#: 530099
Join Date: May 2022
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Anyone ever figure this out. Im having the same problem for last 10,000 miles and still no trouble codes pointing to the issue. Bcs is confirmed function on bench and with green connectors. Wgdc stays at 0 and all other logs seem fine
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05-19-2022, 04:08 PM | #20 |
Scooby Newbie
Member#: 518830
Join Date: Sep 2020
Chapter/Region:
RMIC
Location: Colorado
Vehicle:2009 WRX dark grey metallic |
if your wgdc stays at 0 then your computer is not saying to build boost to the wastegate and so you will be straight spring pressure. there's a few things that can cause this- is your IAM staying at 1 or dropping?
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05-20-2022, 09:42 PM | #21 |
Scooby Newbie
Member#: 530099
Join Date: May 2022
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Everything to do with knock is good, accessport logs it as DAM and that stays at 1. Fine knock learn stays at zero. I have very few knock events logged. I switched MAF's with a known good one. Only thing is right now my shield joint connector failed so a few things aren't properly grounded but i'm going to fix that soon, it only recently happened but I haven't made boost for 10000 miles.
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05-21-2022, 12:54 PM | #22 |
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Member#: 511807
Join Date: Feb 2020
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What about the baro pressure sensor? Is that plugged in?
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05-21-2022, 10:25 PM | #23 |
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05-23-2022, 09:13 PM | #24 | |
Scooby Guru
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Join Date: Aug 2002
Chapter/Region:
SWIC
Location: Albuquerque, NM
Vehicle:2024 Legacy Sport |
Quote:
I had very similar issues when I had the shortblock replaced in my car due to a spun bearing a few years back - I took it easy until I was past 1000 miles, then started getting on it and found i would only hit wastegate boost. One thing to check - if you reset the ECU (pull the battery cable, tap the brakes or something to drain charge) then drive, can you still only hit wastegate boost? I was able to boost per normal for one or two pulls, then back to wastegate boost. They took it in, opened a techline with subaru, etc. and eventually fixed it, but couldn't figure out what they did (which I am guessing means something was loose or not connected properly and they found it and didn't want to fess up) - that was 3 years ago and it's been just fine ever since. Anyway - resetting the system will help you determine if it's a purely mechanical issue or if the ECU is seeing something it doesn't like and going into limp mode. |
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05-27-2022, 11:45 AM | #25 |
Scooby Newbie
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Join Date: May 2022
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Problem fixed. PO didn't keep barometric pressure sensor when removing SAI. New sensor and hitting all the boost I could dream of.
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