Controlling the boost on '03-'04 STi
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This is a discussion on Controlling the boost on '03-'04 STi within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; How do I control/change the boost level on the '03-'04 STi (all standard)? I know that in theory I can ...

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    Registered User knfevg's Avatar
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    Controlling the boost on '03-'04 STi

    How do I control/change the boost level on the '03-'04 STi (all standard)? I know that in theory I can "play" with the spring on the wastegate, but I also know that on the STi/WRX you can change a small hose for a different diameter and this will change the boost.
    Please let me know how it works on the Imprezas.
    Thanks,
    Evgeny

    Subaru Impreza WRX STi ProDrive 2.0 MT6 2003
    Mazda 6 2.0 AT 2008

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    Are there any Subaru tuning shops in Israel?

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    Registered User knfevg's Avatar
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    Quote Originally Posted by brfatal View Post
    Are there any Subaru tuning shops in Israel?
    Ofcourse there are! but I'm asking because I want to know. Thats always the easiest way out to say "go to a pro", but there is a reason why I asked.
    Thanks,
    Evgeny

    Subaru Impreza WRX STi ProDrive 2.0 MT6 2003
    Mazda 6 2.0 AT 2008

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    It's the easiest, and by far the best way to go about it: getting professionally tuned. You will get infinitely better results.

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    Registered User knfevg's Avatar
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    Quote Originally Posted by brfatal View Post
    It's the easiest, and by far the best way to go about it: getting professionally tuned. You will get infinitely better results.
    OK.

    Does someone know how to tune the boost on a STi?
    Thanks,
    Evgeny

    Subaru Impreza WRX STi ProDrive 2.0 MT6 2003
    Mazda 6 2.0 AT 2008

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    Registered User Kjott21's Avatar
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    Quote Originally Posted by knfevg View Post
    OK.

    Does someone know how to tune the boost on a STi?
    The easiest way for you to change your boost is to get a manual boost controller, but I advise against it. Turning up the boost without changing the fuel or the timing is dangerous.

    If you want to tune the car yourself you can get yourself a Tactrix cable and download EcuFlash and RomRaider to edit the maps on your ECU. I don't know if they have definitions for your ECU or not though.

    RomRaider - Open Source ECU Tools | Documentation / Getting Started
    RomRaider - Open Source ECU Tools | Documentation / Supported ECU Revision List

    Other than doing that you will probably need to go to a professional tuner and buy an EcuTec license or something similar and have them tune your car.

    Being that you are from Isreal I don't know if there are any other options available to you. I am used to dealing with USDM tuning solutions.

    Bottom line there is no cheap way to do it right.
    My name is Ken and I am a HP Junkie.

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    Registered User knfevg's Avatar
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    Quote Originally Posted by Kjott21 View Post
    The easiest way for you to change your boost is to get a manual boost controller, but I advise against it. Turning up the boost without changing the fuel or the timing is dangerous.

    If you want to tune the car yourself you can get yourself a Tactrix cable and download EcuFlash and RomRaider to edit the maps on your ECU. I don't know if they have definitions for your ECU or not though.

    RomRaider - Open Source ECU Tools | Documentation / Getting Started
    RomRaider - Open Source ECU Tools | Documentation / Supported ECU Revision List

    Other than doing that you will probably need to go to a professional tuner and buy an EcuTec license or something similar and have them tune your car.

    Being that you are from Isreal I don't know if there are any other options available to you. I am used to dealing with USDM tuning solutions.

    Bottom line there is no cheap way to do it right.
    I guess I didnít explain my self clear enough. I'm NOT looking to tune my car and I know all about different ECU tuning options.
    All I asked is if there is any small hoses somewhere on the turbo/inlet system that can control/effect the maximum boost?
    Here is the reason I'm asking:
    My car was boosting ~0.9-1.1BAR
    On my last visit to the service center (yesterday) the guy said that it should boost higher (up-to 1.4-1.5) and that the last owner (he knows him) tuned down the boost for his own reasons (fuel, safety, etc...). In order to bring the boost up, he changed a small (maybe 2 inches long) piece of hose for a wider diameter. He said that the one that was installed is for WRX (which boost around 1bar) and the one he put in is a STi one.
    I didnít have a chance to drive my car strong enough to see what changed, but it does seems more responsive and the turbo can be heard at 3K rpm (instead of 4K before). The mechanic told me that this is what I should notice.
    So, I'm just interested to know what EXACTLY he did...
    Thanks,
    Evgeny

    Subaru Impreza WRX STi ProDrive 2.0 MT6 2003
    Mazda 6 2.0 AT 2008

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    Quote Originally Posted by knfevg View Post
    I guess I didn’t explain my self clear enough. I'm NOT looking to tune my car and I know all about different ECU tuning options.
    All I asked is if there is any small hoses somewhere on the turbo/inlet system that can control/effect the maximum boost?
    Here is the reason I'm asking:
    My car was boosting ~0.9-1.1BAR
    On my last visit to the service center (yesterday) the guy said that it should boost higher (up-to 1.4-1.5) and that the last owner (he knows him) tuned down the boost for his own reasons (fuel, safety, etc...). In order to bring the boost up, he changed a small (maybe 2 inches long) piece of hose for a wider diameter. He said that the one that was installed is for WRX (which boost around 1bar) and the one he put in is a STi one.
    I didn’t have a chance to drive my car strong enough to see what changed, but it does seems more responsive and the turbo can be heard at 3K rpm (instead of 4K before). The mechanic told me that this is what I should notice.
    So, I'm just interested to know what EXACTLY he did...
    If your mechanic actually told you that you could crank your boost up 50% on a whim, I suggest never going to him again.

    Unless you know exactly what you are doing, playing with boost control is a very dangerous and expensive game. I still suggest tuning as your option; otherwise, I wouldn't touch it.
    Last edited by brfatal; 09-14-2009 at 10:05 PM.

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    Registered User Kjott21's Avatar
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    http://www.cobbforums.com/forums/ima...mWorksv109.pdf

    Quote Originally Posted by knfevg View Post
    So, I'm just interested to know what EXACTLY he did...
    Why didn't you just ask him?

    Changing the diameter of the hose is a very poor way to adjust the boost. There is no way to tell for sure how the car will react to that mod. It will change the spool characteristics drastically and could cause some pretty bad spiking without adjusting the wastegate duty cycle.
    Last edited by Kjott21; 09-14-2009 at 10:10 PM.
    My name is Ken and I am a HP Junkie.

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    Registered User knfevg's Avatar
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    Well, I trust this guy 110%. He used to be the first owner of this car and he absolutly INLOVE with it (or any other STi).
    He DIDNT tell me I can bring the boost higher JUST LIKE THAT
    What he DID say is that the original boost of this car is 1.4Bar, the last owner (whom serviced the car with him also), took it down to 1Bar. Now he brought it back to 1.4
    BTW, the car has a full PRODRIVE kit, which includes an ECU upgrade. This software supposed to be able to handle up to 1.5BAR
    Thanks,
    Evgeny

    Subaru Impreza WRX STi ProDrive 2.0 MT6 2003
    Mazda 6 2.0 AT 2008

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    Moderator Donkey's Avatar
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    Quote Originally Posted by knfevg View Post
    Well, I trust this guy 110%. He used to be the first owner of this car and he absolutly INLOVE with it (or any other STi).
    He DIDNT tell me I can bring the boost higher JUST LIKE THAT
    What he DID say is that the original boost of this car is 1.4Bar, the last owner (whom serviced the car with him also), took it down to 1Bar. Now he brought it back to 1.4
    BTW, the car has a full PRODRIVE kit, which includes an ECU upgrade. This software supposed to be able to handle up to 1.5BAR
    The problem is the ECU not only controls the boost on these cars it also uses the boost control as one of the safety devices. Boost is controlled by altering the wastegate duty cycle of the solenoid. Changing hoses is not a good idea and is not the smart way of trying to get more boost,as the other have said, because now the wastegate duty cycle is no longer controlling the wastegate properly. There are preset "boost cut" limits that can be easily hit with a spike and will make the car a pain to drive. Not to mention the boost surging and oscillations that can occur a well by changing those hoses. Plus it also throws other boost control tables out of whack as well (Turbo dynamic's and IAT compensation)

    Boost Control FAQ: Read if you are thinking of buying one! - NASIOC
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    Registered User knfevg's Avatar
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    OK, after reading COBBS guide to boost, I've learned that what he did is probably installing a new (smaller) restrictive pill.
    This should put the boost higher but alos makes it more "spiky".
    I do feel the difference in the responsivnes of the engine. However, the boost gauge still read the same ~1BAR tops. After it hits the max boost, it slowly drops back to 0.6-0.7
    I can not be sure that the gauge is OK (probably will buy a cheap chinese gauge just to see how it responds).
    Do you know what is the original pill size and the maximum boost of an ProDRIVE STI?
    Thanks,
    Evgeny

    Subaru Impreza WRX STi ProDrive 2.0 MT6 2003
    Mazda 6 2.0 AT 2008

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    Registered User Kjott21's Avatar
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    The new pill will not change what the ECU is set to make as far as peak boost. All it will do is change the spool up characteristics and possibly make it spike higher if the boost overshoots it's target. No matter what size pill you put in there it will not change the peak boost that the ECU is set to make.
    My name is Ken and I am a HP Junkie.

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    Registered User knfevg's Avatar
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    Quote Originally Posted by Kjott21 View Post
    The new pill will not change what the ECU is set to make as far as peak boost. All it will do is change the spool up characteristics and possibly make it spike higher if the boost overshoots it's target. No matter what size pill you put in there it will not change the peak boost that the ECU is set to make.
    OK, thanks
    Can it be that with this new pill the car is more responsive?
    BTW, do you know what is the size of the original pill in a 2.0l STI?
    Thanks,
    Evgeny

    Subaru Impreza WRX STi ProDrive 2.0 MT6 2003
    Mazda 6 2.0 AT 2008

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