Welcome to the North American Subaru Impreza Owners Club Thursday March 28, 2024
Home Forums Images WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Go Back   NASIOC > NASIOC Technical > Factory 2.5L Turbo Powertrain (EJ Series Factory 2.5L Turbo)

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.







* As an Amazon Associate I earn from qualifying purchases. 
* Registered users of the site do not see these ads. 
Reply
 
Thread Tools Display Modes
Old 09-21-2020, 11:09 PM   #1
MattZ
Scooby Newbie
 
Member#: 270623
Join Date: Jan 2011
Default 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!
* Registered users of the site do not see these ads.
MattZ is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 09-21-2020, 11:20 PM   #2
truck7575
Scooby Newbie
 
Member#: 516780
Join Date: Jul 2020
Location: Georgetown Kentucky
Vehicle:
2008 Subaru wrx sti
WRB

Default

Does the wastegate lever need adjusted? U didnt mention where you got your turbo or what kind
truck7575 is offline   Reply With Quote
Old 09-21-2020, 11:41 PM   #3
BoostedBubz
Scooby Newbie
 
Member#: 506756
Join Date: Sep 2019
Default

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.
BoostedBubz is offline   Reply With Quote
Old 09-22-2020, 12:16 AM   #4
MattZ
Scooby Newbie
 
Member#: 270623
Join Date: Jan 2011
Default

Quote:
Originally Posted by BoostedBubz View Post
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.
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.
MattZ is offline   Reply With Quote
Old 09-22-2020, 12:16 AM   #5
MattZ
Scooby Newbie
 
Member#: 270623
Join Date: Jan 2011
Default

Quote:
Originally Posted by truck7575 View Post
Does the wastegate lever need adjusted? U didnt mention where you got your turbo or what kind
As stated, stock VF39 - no WG lever adjustment
MattZ is offline   Reply With Quote
Old 09-22-2020, 01:12 AM   #6
murrdogg24
Scooby Guru
 
Member#: 50586
Join Date: Dec 2003
Chapter/Region: BAIC
Location: Chiraq
Vehicle:
64 Impala

Default

do you have TGV's or did you delete them?
murrdogg24 is offline   Reply With Quote
Old 09-22-2020, 05:41 AM   #7
dryvby
Scooby Newbie
 
Member#: 49931
Join Date: Dec 2003
Chapter/Region: MWSOC
Location: Grand Rapids, MI
Vehicle:
0305 wrx/Xt
black/black

Default

Quote:
Originally Posted by MattZ View Post
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.

Not true. I’ve witnessed the oem bcs not function with the lines reversed. Swap them and see what happens.
dryvby is offline   Reply With Quote
Old 09-22-2020, 11:42 AM   #8
MattZ
Scooby Newbie
 
Member#: 270623
Join Date: Jan 2011
Default

Quote:
Originally Posted by dryvby View Post
Not true. I’ve witnessed the oem bcs not function with the lines reversed. Swap them and see what happens.
Tried it already, no change!
MattZ is offline   Reply With Quote
Old 09-22-2020, 11:43 AM   #9
MattZ
Scooby Newbie
 
Member#: 270623
Join Date: Jan 2011
Default

Quote:
Originally Posted by murrdogg24 View Post
do you have TGV's or did you delete them?
Car completely stock except for a DP
MattZ is offline   Reply With Quote
Old 09-22-2020, 11:46 AM   #10
MattZ
Scooby Newbie
 
Member#: 270623
Join Date: Jan 2011
Default

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
MattZ is offline   Reply With Quote
Old 09-22-2020, 12:41 PM   #11
subaru_gc8
Scooby Specialist
 
Member#: 29292
Join Date: Nov 2002
Chapter/Region: SCIC
Location: Orange County CA
Vehicle:
2004 WRX wagon
silver

Default

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.
subaru_gc8 is offline   Reply With Quote
Old 09-22-2020, 02:48 PM   #12
MattZ
Scooby Newbie
 
Member#: 270623
Join Date: Jan 2011
Default

Quote:
Originally Posted by subaru_gc8 View Post
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.
As stated, i bridged the lines that the BCS controls and she boosts as normal. Not an exhaust leak, not a boost leak, not the BCS, not the lines, not the pill.
MattZ is offline   Reply With Quote
Old 09-22-2020, 03:51 PM   #13
dryvby
Scooby Newbie
 
Member#: 49931
Join Date: Dec 2003
Chapter/Region: MWSOC
Location: Grand Rapids, MI
Vehicle:
0305 wrx/Xt
black/black

Default

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?
dryvby is offline   Reply With Quote
Old 09-22-2020, 03:52 PM   #14
dryvby
Scooby Newbie
 
Member#: 49931
Join Date: Dec 2003
Chapter/Region: MWSOC
Location: Grand Rapids, MI
Vehicle:
0305 wrx/Xt
black/black

Default

Dumb point- make sure you’re not on the valet map.
dryvby is offline   Reply With Quote
Old 09-22-2020, 04:06 PM   #15
MattZ
Scooby Newbie
 
Member#: 270623
Join Date: Jan 2011
Default

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:
Originally Posted by dryvby View Post
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?
MattZ is offline   Reply With Quote
Old 09-22-2020, 04:08 PM   #16
MattZ
Scooby Newbie
 
Member#: 270623
Join Date: Jan 2011
Default

Just did a hard flash to stage 2 highwg.

Quote:
Originally Posted by dryvby View Post
Dumb point- make sure you’re not on the valet map.
MattZ is offline   Reply With Quote
Old 09-22-2020, 04:40 PM   #17
subaru_gc8
Scooby Specialist
 
Member#: 29292
Join Date: Nov 2002
Chapter/Region: SCIC
Location: Orange County CA
Vehicle:
2004 WRX wagon
silver

Default

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?
subaru_gc8 is offline   Reply With Quote
Old 09-25-2020, 12:39 AM   #18
BuiltWRXFL
Scooby Newbie
 
Member#: 518888
Join Date: Sep 2020
Default

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
BuiltWRXFL is offline   Reply With Quote
Old 05-19-2022, 11:39 AM   #19
Pee_Gang
Scooby Newbie
 
Member#: 530099
Join Date: May 2022
Default

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
Pee_Gang is offline   Reply With Quote
Old 05-19-2022, 04:08 PM   #20
GeoNV
Scooby Newbie
 
Member#: 518830
Join Date: Sep 2020
Chapter/Region: RMIC
Location: Colorado
Vehicle:
2009 WRX
dark grey metallic

Default

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?
GeoNV is offline   Reply With Quote
Old 05-20-2022, 09:42 PM   #21
Pee_Gang
Scooby Newbie
 
Member#: 530099
Join Date: May 2022
Default

Quote:
Originally Posted by GeoNV View Post
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?
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.
Pee_Gang is offline   Reply With Quote
Old 05-21-2022, 12:54 PM   #22
casey_jones
Scooby Newbie
 
Member#: 511807
Join Date: Feb 2020
Default

What about the baro pressure sensor? Is that plugged in?
casey_jones is offline   Reply With Quote
Old 05-21-2022, 10:25 PM   #23
Pee_Gang
Scooby Newbie
 
Member#: 530099
Join Date: May 2022
Default

Quote:
Originally Posted by casey_jones View Post
What about the baro pressure sensor? Is that plugged in?
It should be, the car is pretty much stock. I'll have to check next time I get a chance, but I think I remember seeing it being logged on the accessport.
Pee_Gang is offline   Reply With Quote
Old 05-23-2022, 09:13 PM   #24
DrD
Scooby Guru
 
Member#: 22412
Join Date: Aug 2002
Chapter/Region: SWIC
Location: Albuquerque, NM
Vehicle:
2024 Legacy Sport

Default

Quote:
Originally Posted by Pee_Gang View Post
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.
So by not making boost do you mean only making mechanically limited boost (so wastegate boost - somewhere around 7-8 psi) or you are actually unable to hit any boost? I am guessing the former, but just wanted to check.


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.
DrD is offline   Reply With Quote
Old 05-27-2022, 11:45 AM   #25
Pee_Gang
Scooby Newbie
 
Member#: 530099
Join Date: May 2022
Default

Problem fixed. PO didn't keep barometric pressure sensor when removing SAI. New sensor and hitting all the boost I could dream of.
Pee_Gang is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

All times are GMT -4. The time now is 07:35 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2024 Axivo Inc.
Copyright ©1999 - 2019, North American Subaru Impreza Owners Club, Inc.

As an Amazon Associate I earn from qualifying purchases.

When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission
Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.