only 10lbs of boost!help=(
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This is a discussion on only 10lbs of boost!help=( within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; hello forum! i just bought an 07 sti with 100k miles ( i know it was risky) and I thought ...

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    only 10lbs of boost!help=(

    hello forum! i just bought an 07 sti with 100k miles ( i know it was risky) and I thought it was perfect condition but come to find out I am only boosting 10lbs! Ive done a little research and did the Boost Solenoid trick of unpluging the hose that connects from the boost solenoid to the intake. I am still boosting 10lbs so I think it might be the boost solenoid??? Any ideas of what else if you think it is this, what should i get to replace it? Like an electronic boost controller or Can i just buy the solenoid?? A bit confused any info can help please it is my first subi!!

    Also can i just change the boost from my cobb accesport? the owner gave me this to use for 'mini tuning' im wondering if he changed the boost from stock to 10lbs?! help? any reccs of certain bc or like an electronic boost controller??

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    Subaru Newb MainFrame's Avatar
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    What are the car's mods? Is the boost control system hooked up properly (ie, is the restrictor pill in place)?





    I highly doubt someone would have purposely dialed in less boost. Boost can be adjusted via the AP using Race Tuner (or whatever it's called), but you don't want to go messing with that when you know it already isn't functioning properly. You need to figure out what is wrong with it before you start messing with something else.

    Have you logged the car, and if so can you post the logs? Have you put the car into test mode and listened for the EBCS clicking to ensure it is functioning properly? If all those things are in order start checking for leaks, both boost leaks and preturbo exhaust leaks.

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    Admiral Ackbar the 1st mycologist's Avatar
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    Removing line 4 tells you nothing, the BCS just vents to atmosphere then which will skew your MAF reading but will not affect boost.

    Don't remove line 3 without plugging the T off at the turbo end (or else you will have run-away boost) - that will tell you your wastegate spring pressure. That is worth checking as if your spring is weak you will boost less. I'd test it by running a new line directly from the compressor to the wastegate actuator though.

    It is likely your BCS or possibly the restrictor pill, vacuum line size, or T-fitting size.
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    Registered User benson156's Avatar
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    I've never messed with the lower boost maps on the AP, but could it possibly be in economy mode? I'm not sure what the boost is reduced to but there is a 5800 RPM rev-limiter when this map is in use according to Cobb.
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    Admiral Ackbar the 1st mycologist's Avatar
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    I didn't notice it was a Cobb car.

    It would be wise to log it and look at the map with the AP. Log just the IAM, boost, boost error, wastegate duty cycle, RPM, and throttle position. Do it in third from 2K rpm to redline (somewhere safe).

    Leaks in the vacuum lines related to the boost control system can only increase boost, they can't decrease it directly. The ECU can pull boost if it isn't happy due to knocking, which can result from various leaks. The log will tell us if so.


    Also, do you know what modifications there are? If not take a pic of the area the exhaust comes out of the turbo and the intake.
    Last edited by mycologist; 10-15-2012 at 11:50 AM.
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    Pro Manscaper Mikie13's Avatar
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    Quote Originally Posted by benson156 View Post
    I've never messed with the lower boost maps on the AP, but could it possibly be in economy mode? I'm not sure what the boost is reduced to but there is a 5800 RPM rev-limiter when this map is in use according to Cobb.
    I was under the impression that Boost was virtually removed all together with the economy mode.
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    They can't drop it below ~8psi as that is mechanical due to the spring. I wonder if the boost gauge is reading a little high and he is on spring pressure, or maybe reading low enough that his boost is normal.

    The log will clear that up.
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    Registered User benson156's Avatar
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    Quote Originally Posted by Mikie13 View Post
    I was under the impression that Boost was virtually removed all together with the economy mode.
    I guess it could be, Cobb's mapping notes specify:

    Economy mode intended for 2007 Subaru WRX STi stock or cat-back exhaust, stock or COBB SF intake system only. Requires a minimum of 91 octane petrol. Low boost, AVCS tuning, increased ignition timing, leaner fuel curve, and lower Rev Limiter for optimal fuel savings. Not a performance calibration and not recommended for aggressive driving. THIS MAP IS NOT INTENDED FORSPIRITED DRIVING. Rev Limit lowered to 5800 RPM.

    And

    Valet Mode for 2007 Subaru Impreza WRX STI vehicles with stock or COBB SF intake system only. Rev limiter set to 3200 RPM and turns off boost control. The turbo will still produce wastegate pressure boost, which can be anything from 4 to 10 psi, as this is mechanical.

    Hope that helps some!
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    i dont know much of how to put the data or logs seeing as i berly got this car and just registered it yesterday. I do not think it has the rest. pill on that hose so on wednesday I am going to subaru to buy the pill with the hose and see if that works...

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    mods are. spt cold air intake, perrin exhaust. perrin downpipe, perrin headers, and i think that is it besides spt sway bars and other suspension parts.

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    Quote Originally Posted by scobby07 View Post
    i dont know much of how to put the data or logs seeing as i berly got this car and just registered it yesterday. I do not think it has the rest. pill on that hose so on wednesday I am going to subaru to buy the pill with the hose and see if that works...
    Data-logging is easy and I recommend that you do before you go out and purchase/order components that you may not even need. Here's a link for data-logging.

    How-To Datalog Using Your AccessPORT (Subaru) » PERRIN Performance Official Blog

    As for the restrictor pill, you should be able to disconnect the vacuum hose that connects to the turbo and see the tiny brass reducer inside. Also there is a dot on the vacuum line where the restrictor should be so you should be able to squeeze the line and feel it.

    Click image for larger version. 

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    Quote Originally Posted by scobby07 View Post
    Ive done a little research and did the Boost Solenoid trick of unpluging the hose that connects from the boost solenoid to the intake
    This is not a trick, it is just flat-out irresponsible!! Unplugging the vacuum end of the EBCS can result in the car drastically overshooting the boost targets, leading to severe damage to the car. I think you need to spend some time reading up on the stock boost control system before doing anything further to your car...
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    Admiral Ackbar the 1st mycologist's Avatar
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    Quote Originally Posted by zax View Post
    This is not a trick, it is just flat-out irresponsible!! Unplugging the vacuum end of the EBCS can result in the car drastically overshooting the boost targets, leading to severe damage to the car. I think you need to spend some time reading up on the stock boost control system before doing anything further to your car...
    Zax -

    I think he means line 4 and you are referring to line 3. Line three will eliminate any pressure getting to the WGA, and will lead to dangerous overboosting for sure.

    In my thinking line 4 is just going to vent to atmosphere instead of the intake tract - not having the vacuum of the intake would seem hypothetically to possibly reduce boost, not cause overboost. I could be wrong though....
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    Quote Originally Posted by mycologist View Post
    Zax -

    I think he means line 4 and you are referring to line 3. Line three will eliminate any pressure getting to the WGA, and will lead to dangerous overboosting for sure.

    In my thinking line 4 is just going to vent to atmosphere instead of the intake tract - not having the vacuum of the intake would seem hypothetically to possibly reduce boost, not cause overboost. I could be wrong though....
    Yeah, you're right. I thought he was referring to line 3. Unplugging line 4 will not allow the pressure to bleed off fast enough leading to a difficulty hitting target boost.
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    Pro Manscaper Mikie13's Avatar
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    Quote Originally Posted by benson156 View Post
    I guess it could be, Cobb's mapping notes specify:

    Economy mode intended for 2007 Subaru WRX STi stock or cat-back exhaust, stock or COBB SF intake system only. Requires a minimum of 91 octane petrol. Low boost, AVCS tuning, increased ignition timing, leaner fuel curve, and lower Rev Limiter for optimal fuel savings. Not a performance calibration and not recommended for aggressive driving. THIS MAP IS NOT INTENDED FORSPIRITED DRIVING. Rev Limit lowered to 5800 RPM.

    And

    Valet Mode for 2007 Subaru Impreza WRX STI vehicles with stock or COBB SF intake system only. Rev limiter set to 3200 RPM and turns off boost control. The turbo will still produce wastegate pressure boost, which can be anything from 4 to 10 psi, as this is mechanical.

    Hope that helps some!
    Thanks for clearing that up. I guess I could have looked it up myself. You've further helped my laziness
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