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Old 10-24-2011, 02:41 AM   #1
BobbyGF8
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Join Date: Sep 2011
Location: Guatemala, CA
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1998 JDM WRX GF8
RED

Question stock GF8 turbo psi...

Hi all, I'm new to the forum and is my first turbo car.

I have a JDM 1998 GF8 WRX, it has an EJ20G with a TD04L, all stock. (not STI)

The problem is that a few weeks ago at WOT, I was getting 11.5psi on gauge. Then it drops to 10 psi, so I inspect all the vacuum lines and noted a few leaks, so I replace them with new hoses and right now I'm getting 7psi all the way with out any drop.

I been making a lot of research and can not tell for sure what psi should I get with this turbo on stock conditions. I been reading 7 to 10 psi on stock turbo. But I'm not sure right now. The specs for my car says that it should be making 250hp since is a JDM.

So, now the question is, what would be the normal stock boost for a JDM 1998 EJ20G with a TD04L?

I feel my car slower than before when getting 7psi in stead of 11.5psi. It is not an STI and does not have forged pistons or rods. (I rebuilt my engine a few months ago)

Thanks for any info...
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Old 10-24-2011, 01:43 PM   #2
elislider
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at 7psi you are most likely just seeing wastegate spring pressure. did you replace the short lines from the turbo to the boost controller? if so, there is a metal pill that is supposed to be in the lines and youre probably missing that now
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Old 10-24-2011, 04:24 PM   #3
TommyAtomic
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Make sure the new hoses are using any factory clamps that were present on the old hoses and also use zipties on all hose ends including the ones that have factory clamps to make sure you have perfect seals.

Does your GF8 have the factory intake resonator? if so there is a vacuum line running from the intake resonator to the boost controller that can easily get disconnected and forgotten when you are replacing vacuum lines.
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Old 10-24-2011, 06:33 PM   #4
BobbyGF8
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Ok, the turbo has a nipple that is connected to the wastegate trough a T, and the T has a larger hose to the Boost Controller I guess. I replace these hoses.

If that is the boost controller has two wires, a black and a red, and is a Denso and says 12v and a big number. I checked all the nipples and hoses and there is no leak, sure of that.

Asking to a friend, he told me since the age of my car the diaphragm of the wastegate could be broken.

What do you think?
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Old 10-24-2011, 07:22 PM   #5
TommyAtomic
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I think depending on milage its entirely possible that your turbo although stock may have been rebuilt in the past. Imported JDM's are usually really well maintained in their past lives. Its usually jackasses on this side of the pond that dont maintain them well.
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Old 10-24-2011, 08:13 PM   #6
BobbyGF8
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hehehehe! thats true!

Another thing I realize, my Scooby doesn't have the restrictor pill, should I have one?

It can be normal for a JDM WRX be on 7psi of boost? if yes, what can I do to increase it to 12psi?
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Old 10-25-2011, 06:20 PM   #7
TommyAtomic
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My understanding although possibly wrong is that the restrictor pill is for adjusting and preventing over boost in high rpm/high gear. I dont think it shouldnt effect your peak boost off the line that much. Although I've replaced most of my vacuum hoses I've never checked for my restrictor pill and I dont have any issues hitting 12psi.

If it were me I would be looking for a boost leak or a vacuum leak. Check you hoses, coupling, and all of your clamps. Might be a good time to upgrade to some new silicon couplings and t-bolt clamps.
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Old 10-25-2011, 11:58 PM   #8
BobbyGF8
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I all ready check all the boost houses, so before of that, it have a leak and it was boosting at 11.5psi with out the restrictor pill.

What I think is that my WG is set at 7psi, because the hose that comes from the fitting of the turbo housing and connects to the WG was broken so it did not had the enough pressure to open the WG, therefor giving more boost.

Should I buy a WG set to 11 or 12psi? or installing a MBC?
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Old 03-02-2012, 11:55 PM   #9
BobbyGF8
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Well, I have been making some test and looking some info about the restrictor pill and the bottom line is that with a 1.2mm restrictor pill works steady on 12 psi.

I did try with a 0.9mm (STI) and was getting boost spike of 15.5 or even 16psi but in one pull I guess I hit boost cut off. Then I try with a 1.0 mm and had boost spike of 14.5. But above 12psi the stock boost controller gets crazy and lazy.

So in one thread I read that the GF8 with TD04 uses a 1.2mm restrictor pill, so I tried and all is working Ok with out boost spike all the way. On other test I tried with a 1.5mm and was getting 8-9 psi. The Forester uses a 1.5mm restrictor pill.

Just FYI....
It is important to notice that my car has a 2 port solenoid. With the 3 port solenoid it work different the restrictor pill.
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Old 03-03-2012, 08:37 AM   #10
gtu89rx7
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EJ20G swapped

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i have a EJ20G that came out of a out of a wagon.. using a 3 port solenoid with no restrictors, and it makes steady ~13 psi, dropping to ~11 at redline

i do know that sometimes the ecu will limit boost if something funkys going on. i remember when i first did the IAC/TB coolant bypass, for a couple drives after it would only boost 7psi. but after that back to the normal 13psi

Last edited by gtu89rx7; 03-03-2012 at 08:48 AM.
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