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Old 07-22-2019, 04:45 PM   #1
Phengkaen21
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Member#: 491791
Join Date: Sep 2018
Default 7-8 psi of boost??

Whatís up guys? as you can tell by the title Iím only making 8psi of boost and I donít know why.

Backstory: I blew my first ever motor on my 2012 WRX and needed a replacement motor asap since I have work and school. Thatís when I found an affordable replacement motor, a jdm Ej20x/y out of an 04 Legacy GT. I finished the swap little over 5 months ago but havenít been hitting nearly the same amount of boost I had with my ej255. (Targeted boost was 26psi).

I havenít gotten the car retune yet so I think that might be the issue but idk. I do have a CEL code due to the jdm motor not having the secondary air system for emission so I also believe that might be another reason Iím only hitting 7-8psi but like I said idk man. I donít have any leaks, I checked the throttle body hose and that was fine (plan on replacing that with a mitshimoto one). I read somewhere that 7-8psi is wastegate pressure or something like that and the cause of that is not having the restricter pill in the turbo vacuum lines, which I also checked and have of the pink restricter in but but not the yellow one. I plan on buy a new vacuum line with both restricters in them but Iím also hesitant because the same vacuum line are the same one I used in my ej255 and I didnít have any problem with boosting. So rn Iím at a loss so any advice/information will be really helpful. Thanks bros
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Old 07-22-2019, 10:03 PM   #2
bdubblu
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Member#: 251046
Join Date: Jul 2010
Chapter/Region: MAIC
Location: Mostly at my home
Vehicle:
2004 WRX Wagon
Stage 5.1.2a.2

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7-8 lbs is wastegate pressure.

Is your ebcs working? Swap for a known good one. You can put power to it and should hear the relay click.

If you blow into the wastegate vacuum line it should leak sloooooooooowwwwwly. If you can blow right thru, the diaphragm is torn.

Or your car is in some limp mode because as you stated, you havenít tuned it or something. Youíve left an awful lot out when it comes to that.
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Old 08-08-2019, 01:55 PM   #3
Jedi03
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Member#: 491095
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Chapter/Region: SWIC
Location: New Mexico
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2009 STi Blue
Blue

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also make sure the restrictor pill is on the correct side...accidentally swapped mine and found doesn't work lol!
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Old 08-08-2019, 02:27 PM   #4
JSR84
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Quote:
Originally Posted by bdubblu View Post
7-8 lbs is wastegate pressure.

Is your ebcs working? Swap for a known good one. You can put power to it and should hear the relay click.

If you blow into the wastegate vacuum line it should leak sloooooooooowwwwwly. If you can blow right thru, the diaphragm is torn.

Or your car is in some limp mode because as you stated, you havenít tuned it or something. Youíve left an awful lot out when it comes to that.
He would hardly be able to drive it if it was in Limp Mode. Unplug your accelerator pedal and start the car if you want a demo of limp mode.


Step 1 - Confirm the vehicle mechanically including the boost control circuit. Cobb has an article on how the factory boost control system works if you need a reference.
Step 2 - Take it to a reputable tuner to have it tuned. Preferably before you decide to completely depress the acceleration pedal again, unless you want another blown engine.

Last edited by JSR84; 08-08-2019 at 02:39 PM.
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