IW STi Forum banner
1 - 16 of 16 Posts

· Registered
Joined
·
35 Posts
Discussion Starter · #1 ·
I've searched hi and low and cannot find any useful information.

I am troubleshooting a boost problem and would like to know the boost I should be seeing on my boost gauge when i turn my Greddy Profec B Spec II boost controller OFF.

1> I thought I would be seeing the factory spring pressure which I think is around 7-8psi per all the threads I have read. Instead, I see 14.5psi. Is this correct?

2> If i bypass the boost control solenoid and plug the hose from the turbo compressor housing directly to the wastegate actuator nipple, I should see the factory spring boost pressure correct?

Thanks for all the help.
 

· Registered
Joined
·
35 Posts
Discussion Starter · #3 · (Edited)
Yes 14.5 is correct. Normal stock boost is between 14.5 and 14.7 so your fine.
i agree that normal stock boost is 14.5-14.7psi but with the installation of an EBC, the stock wastegate solenoid has been removed and replaced by the Greddy solenoid. Does that mean that if the EBC is OFF, it defaults to 14.5? What is controlling the wastegate then or am I mistaken in thinking the mechanical spring in the wastegate is 7-8psi when it actually is 14.5?

Thanks.
 

· Registered
Joined
·
2,165 Posts
i agree that normal stock boost is 14.5-14.7psi but with the installation of an EBC, the stock wastegate solenoid has been removed and replaced by the Greddy solenoid. Does that mean that if the EBC is OFF, it defaults to 14.5? What is controlling the wastegate then or am I mistaken in thinking the mechanical spring in the wastegate is 7-8psi when it actually is 14.5?

Thanks.
the spring rate is different in the wastegate then it is in the EBC, alot of people get either get a harder or softer spring depending on turbo and boost pressure applications. what do you have your EBC eletroniclly set to?
 

· Registered
Joined
·
35 Posts
Discussion Starter · #5 ·
the spring rate is different in the wastegate then it is in the EBC, alot of people get either get a harder or softer spring depending on turbo and boost pressure applications. what do you have your EBC eletroniclly set to?
The wastegate spring on a IHI is non-changeable.

I've turned my EBC OFF hense this thread.
 

· Registered
Joined
·
804 Posts
Stock turbo? The mechanical spring in the wastegate is approximately 1 bar. Even if you have installed an EBC, if it is "TURNED OFF", you will run what ever rated spring you have. My AVCR has 2 maps. A and B. When I turn it off, my car runs wastegate pressure which is 1 bar on mine.
 

· Registered
Joined
·
35 Posts
Discussion Starter · #9 · (Edited)
Stock turbo? The mechanical spring in the wastegate is approximately 1 bar. Even if you have installed an EBC, if it is "TURNED OFF", you will run what ever rated spring you have. My AVCR has 2 maps. A and B. When I turn it off, my car runs wastegate pressure which is 1 bar on mine.
Yes, stock 05 STi turbo.

Thank you very much.

Believe it or not, i've searched 3 different forums looking for the STi stock mechanical spring pressure for the wastegate and found nothing. The only numbers I got were 7-8psi but I think that would be a WRX setting.

Just curious but if you were to hook the compressor side nipple directly to the wastegate actuator nipple thus bypassing the solenoid, theoretically, this would give you mechanical spring pressure boost correct?
 

· Registered
Joined
·
199 Posts
I just bought a 07 STI and it has Greddy Profec B Spec II boost controller on it. The boost controller is turned off, but im not sure on how to read this boost controller to make sure the car is running 14.5psi. Also im not really sure on how to make the boost controller read in psi form? Any help would be greatly appreciated
 

· Registered
Joined
·
172 Posts
if you EBC is off it should act on spring pressure alone... as if you had the lines looped back on its self and no boost controller present. I have a VF43 off a 07 sti on a Forester right now no boost controller what so ever and it only spools 8lbs of boost.
 

· Registered
Joined
·
350 Posts
Just curious but if you were to hook the compressor side nipple directly to the wastegate actuator nipple thus bypassing the solenoid, theoretically, this would give you mechanical spring pressure boost correct?
That is correct.
 

· Registered
Joined
·
173 Posts
I would think that it depends on how your EBC solenoid is plumbed. If the lines running to it are configured for a "bleed" type set up then you would likely run higher than wastegate spring level boost because some of the pressure is being bled off before reaching the wastegate actuator thus it takes more pressure to overcome the spring. I would try taking the solenoid out of the loop and trying with just a hose from the complressor to the w/g actuator to see what you get.
 

· Registered
Joined
·
10 Posts
Turbos waste gate springs are set at a pressure where the waste gate should open fully when the boost pressure reaches the set pressure. So if you have a 15 psi spring and you run the full pressure of the intake back to actuator you will be limited to 15 psi of boost. However if you vent that pressure back to the air intake, you can get much more boost. This is what the boost controller does. Basically to target boost above the spring if vents some of the pressure which would have been used to open the waste gate. I believe you can request 2-3 times the waste gate soring pressure.
 
1 - 16 of 16 Posts
Top