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How much boost can the stock turbo on an 04' STi put out?
It will peak with proper support mods at around 17-18 psi. Anything higher and it's efficiency plummets.
 

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FP green rotated mount setup with supporting mods (FMIC, TBE, Injectors, BOV, Fuel Pump, Tune, and possibley a different WG solenoid).

This puts out consistent 360+ to the wheels.

Toss in some meth injection for a bit more power and much safer AFRs.

Appropriate guages should be a necessity at this point. Wideband 02, EGT, Oil Press, Oil Temp.

Don't forget your brake lines, pads and fluid as you'll need to stop the beast better too! Small investment for a big payoff. SS lines, Ferodo 2500S pads, motul blue fluid.

Check out the STi forum for the stickey on modification path.

BTW...you are putting out 311 to the wheels with no EMS? I would guess that it a mistake and your fogot to post that as a mod. Or perhaps you are running an EBC or MBC? If so, hopefully it is using feedback from the ECU or 02 sensor.

Also, are the headers tuned or not? Manufacturer? These typically lower EGT temps, but there are some on the market that can actually interfere with the exhaust flow path and raise temps. Not a good thing.
 

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How much it can handle is based on how you drive and how well it is tuned. They seem to be able to reliably handle low 400 to the wheels, but that is with something like a GT35r turbo, meth or water injection, and some fairly safe tuning. There are cases of some stock motors in the 500s, but those are very, very rare.

So...do you have an MBC or EBC on your car? I'm sure you realize that without one of those items, or EMS, you probably aren't putting out anywhere near your stated number.
 

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Nevermind the fact that running all that with no EM and not having serious boost creep issues is almost impossible.The VF39's were notorius for creeping once you started upping the boost.
 

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Discussion Starter #13
How much it can handle is based on how you drive and how well it is tuned. They seem to be able to reliably handle low 400 to the wheels, but that is with something like a GT35r turbo, meth or water injection, and some fairly safe tuning. There are cases of some stock motors in the 500s, but those are very, very rare.

So...do you have an MBC or EBC on your car? I'm sure you realize that without one of those items, or EMS, you probably aren't putting out anywhere near your stated number.
I'm have a mbc.
 

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I'm have a mbc.
I hope you are being careful in your boost settings then. A MBC without feedback control based on AFR is just asking for things to go boom once you start uping the boost. I personally wouldn't run over 16-16.5 psi, and even then I wouldn't count on the longevity. An MBC basically fights the ECU, and when this happens, the boost level is not what the ECU is asking for, and thus, your AFRs can get screwy (re....very, very lean).

In short, I would be careful with that setup. Especially if you are truly putting out 311 HP.
 

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Discussion Starter #16
I hope you are being careful in your boost settings then. A MBC without feedback control based on AFR is just asking for things to go boom once you start uping the boost. I personally wouldn't run over 16-16.5 psi, and even then I wouldn't count on the longevity. An MBC basically fights the ECU, and when this happens, the boost level is not what the ECU is asking for, and thus, your AFRs can get screwy (re....very, very lean).

In short, I would be careful with that setup. Especially if you are truly putting out 311 HP.
I had the car dyno tuned, they installed the mbc. All my afr are fine. :)
 

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I had the car dyno tuned, they installed the mbc. All my afr are fine. :)
Wow. A new MBC that allows dyno tuning. Can you give us some information on this manual boost controller?
 
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