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Old 05-21-2006, 03:45 PM   #1
Scooby Specialist
Member#: 17256
Join Date: Apr 2002
Chapter/Region: MWSOC
Location: America's Outback
04 STi
Blue w/ custom bug splat

Default UTEC + ABC on 04 STi = Not hitting target boost.

I have been playing around quite a bit with my 04 STi/UTEC, and I can't seem to hit target boost higher than 16-17 psi, regardless of the CLB values (which I have varied as much as +50, as high as 430), and regardless of the ABC setting.

When I screw in the ABC to close it off, and open it a turn or two, I run 12-13 psi. But I can unscrew it until the top of the set screw is coming out of the ABC body (10-15 turns??), and I still only see 16-17 psi max (except for boost spiking).

I have checked the install repeatedly, and all the lines appear correct, no leaks as far as I can tell. The only thing that has me a bit confused is the "brass restrictor" that is supposed to be in the compressor side line of the factory T-fitting hosing. I just had my stock turbo replaced with another stock turbo (straight from Subaru), and it came with all the vacuum lines installed. The stock vacuum lines DID NOT have any restrictor in the compressor side of the T-fitting (nor anywhere else). I am familiar with the factory restrictors, having experimented with the 3/16 replacement on my 02 WRX years ago. But this factory setup does not contain a restrictor.

Any ideas?
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Old 05-22-2006, 12:41 PM   #2
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Member#: 44351
Join Date: Sep 2003
Chapter/Region: MWSOC
Location: Cincinnati, OH
2004 Mitsubishi Evo
701whp [email protected]


You need the restrictor else you won't make the b00st!
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Old 05-22-2006, 01:01 PM   #3
Scooby Specialist
Member#: 7194
Join Date: Jun 2001
Chapter/Region: MAIC
Location: NoVa
2011 997.2 Turbo


the restrictor is really hard to feel. It may be there.

other then that, maybe you have a boost leak?

Maybe your boost solenoid isnt working or isntl plugged in?

Put all 1's in your boost map, if your boost solenoid clicks like a mad-man, then your boost control solenoid is getting power. (still doesnt mean its working right though)

p.s. I have yet to see a STI that needed the ABC.
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Old 05-22-2006, 07:15 PM   #4
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Member#: 50582
Join Date: Dec 2003

Are you using the remote map selector? Make sure both maps show up the same on your dashboard when you are tuning, the first time mine was tuned, somehow they were reading differently and we weren't adjsuting the map we thought was operating, but were going by the switch indicator. Kept opening up the ABC as well with no effect. Once we saw the discrepancy and figured we were adjusting the wrong map, it was obvious why boost wasn't increasing.

I have an 04 STI and had to use the ABC to make the boost I wanted, but went as high as 21-22 psi on race gas. My ABC needed 3 turns open and values across the board of 500 to do it.
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Old 05-23-2006, 08:00 AM   #5
Scooby Specialist
Member#: 17256
Join Date: Apr 2002
Chapter/Region: MWSOC
Location: America's Outback
04 STi
Blue w/ custom bug splat


I have carefully checked the factory hoses, and there is no restrictor. These are brand new factory hoses that came with my new turbo from Subaru.

I can boost up to 17-18 psi in higher gears with a long pull. But in 1st and 2nd, I rarely hit 14 psi, even on hard pulls.

I am running the ABC, and have unscrewed the allen screw until it is backed out of the body of the ABC about half way. I did not count turns, but it must be about 15. When screwed in and backed off 3 turns, I run wastegate pressures.

UTEC dashboard confirms that the map selector switch is actually running my selected map (both switch and map are reading the same, correct number).

Assuming that somehow Subaru provided my local dealer with a new stock STi turbo that did not come with the restrictor, how do I go about getting one? I have heard that they are no longer available.
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Old 05-25-2006, 03:10 AM   #6
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Member#: 97642
Join Date: Oct 2005
Chapter/Region: SWIC
Location: Phoenix, AZ
2002 Wrx Sedan


Look into the gm boost solenoid.

Also, the restrictors are still available. I bought two a couple months ago for around three bucks a piece. If you cant find one I still have an extra one sitting around somewhere.
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