Car not boosting more than 11 psi.

[JeanDSM]

My best friends car (97 GST) only boost 11 psi. no more than that

Here are the Specs:

Rebuilt block
Eagle Rods
Wiseco 8.5:1 pistons
ARP Studs
Cometic HG
Balance shafts eliminated
Fully balance block
Stock Head
Stock intake Manifold & T/B
Custom FMIC
Tial 38mm w/g
2.5in turbo back with exhaust cut off
Underdrive pulley
NGK Wires & BPR7es
Apexi S-AFC 2
Apexi AVC-R
Walbro 255lph
Aeromotive FPR
FIC 650cc
ACT 2100
Garrett T3/TO4E 60 Trim .63 A/R

We went last week to the dyno and with a 1 bar on the Boost controler the car only went 6 psi and got 143whp and 155 tq. We chek out if the Boost controler was well conected and everything was fine, The problems continues so we disconected the Boost controler and put the vacum line from the w/g to the compresor cover. (9 psi spring) The car went 9 psi and gave 189 whp and 175 tq. We tried with a manual controler and didnt want to pass 9 psi we even disconected all vacumm lines to see if even overboost to 20+psi and stayed at 9 psi WTF
Still at 189whp, we tested on the road and went up 10 psi. We tried for leaks and Nothing everything is well sealed The turbo is 2K miles old and 5K since the engine rebuilt. It has 185psi on all cylinders. We dont understand whats going on here.
Also it reaches 9 psi at 5250 rpms WTF

Whats the problem here?

 

[oldman]

If the system was able to hold 20psi during the leak test, there really isn't much left.

1. Huge exhaust leaks before O2 housing.

2. Wastegate being blown open after 9psi.

3. Defective turbo or failure caused by oil feed/return/pressure issues. Did the turbo ever boosted over 9psi?

I must say, you have done well troubleshooting so far.

 

[JeanDSM]

No the car never run more than 9 spi on the dyno when we tested it on the street only wen up to 11 psi. We even diconected the vacum lines to see if it overboost and nothing just ran 10 to 11 psi.

It has a custom O2 eliminator downpipe. We already cheked for all kinds of leaks including exhaust manifold

 

[pballer]

cracked exhaust housing?

 

[oldman]

No the car never run more than 9 spi on the dyno when we tested it on the street only wen up to 11 psi. We even diconected the vacum lines to see if it overboost and nothing just ran 10 to 11 psi.

It has a custom O2 eliminator downpipe. We already cheked for all kinds of leaks including exhaust manifold

Then basically the only two possibilities left is a defective wastegate or turbo.

 

[JeanDSM]

When we went to the dyno the car had a Turbonetics deltagate and we thought it was the wastegate so my friend bought a brand new Tial 38mm. The Turbo has no play and it dosent smoke. We event talked to one of the best dsm tuners here in Puerto Rico and he said that the turbo is on great conditions. We modified the stock exh. manifold to accept a T3 turbine housing. and the fabrication that my friend did could cause some turbolance on the manifold. but i dont think that this could be the mayor problem.

 

[oldman]

Remove the wastegate and block off the flange with piece of metal plate cut to fit the flange. If you get all out boost, the wastegate is being blown open by exhaust flow. If problem persists, it has to be the turbo unless it's related to the T3 modification which can only be answered by you and your friend.