OEM Boost Solenoid/Low Boost Concerns
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This is a discussion on OEM Boost Solenoid/Low Boost Concerns within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; I'm new to the Subaru as well as boosted arena so please bear with my seemingly naive questions. Engine: 1998 ...

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    OEM Boost Solenoid/Low Boost Concerns

    I'm new to the Subaru as well as boosted arena so please bear with my seemingly naive questions.

    Engine: 1998 WRX STI Version V RA 2.0L EJ207 (Completely stock internals)
    ECU: 6S
    Turbo: Stock VF28
    Exhaust: 3'' Turboback 5zigen exhaust.

    I currently have an aftermarket MBC (Halman) installed running approximately 10 psi of boost (its a daily driven car).

    1. Are there any issues running such low boost? Research suggests that these engines ran 17-18psi stock.
    2. Wastegate pressure (if I remember correctly) is circa 7-9psi. I don't quite understand how I can reconnect the OEM Boost Solenoid, I'll appreciate if anyone can supply me with some images of an engine bay and the appropriate connections etc. Effectively then, will adjusting the MBC to run the desired 18psi be equivalent to reconnecting the OEM Boost Solenoid? IMO reconnecting the OEM solenoid seems safer as proper adjustments can be accurately made by the ECU.

    I recently installed an AEM Wideband and A/F ratio at idle was averaged to be 14.70.2 and 10.0 at WOT. The WOT A/F ratio seems to be quite rich which prompted my question regarding running LOWER than stock boost pressures and its effect on the ability of the ECU to compensate effectively.

    Prompt replies and any knowledgeable insight will be hugely appreciated.

    Thanks in advance!

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    Subaru Newb MainFrame's Avatar
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    Turning up the boost via the MBC will not be equivalent to running the OEM EBCS. We mostly deal with USDM cars here, so I'm not entirely sure what your options are in your area for tuning, but 10.0:1 is pretty rich (and I would guess that's pegging out your sensor, so it's likely even richer than that).

    With the aftermarket exhaust and MBC, I suggest getting a custom tune.. but not knowing where you're located (probably not USA?), it's difficult to give a recommendation as to where to go for a tune.

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    Quote Originally Posted by MainFrame View Post
    Turning up the boost via the MBC will not be equivalent to running the OEM EBCS. We mostly deal with USDM cars here, so I'm not entirely sure what your options are in your area for tuning, but 10.0:1 is pretty rich (and I would guess that's pegging out your sensor, so it's likely even richer than that).

    With the aftermarket exhaust and MBC, I suggest getting a custom tune.. but not knowing where you're located (probably not USA?), it's difficult to give a recommendation as to where to go for a tune.
    It turns out I've got a 2 port boost solenoid and somehow I managed to find that restrictor pill to properly set back up the EBCS. Gonna do that shortly and I'll post the stock PSI rating as well as if that influences the rich situation I've been getting at WOT. And nope, I'm from the Caribbean, Trinidad specifically so the variety of tuners are indeed limited. I'll consider the local consensus regarding tuners available before I venture blindly into management. What's your opinion regarding choice of ECUs for these particular engines?

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    Subaru Newb MainFrame's Avatar
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    Quote Originally Posted by gboson View Post
    What's your opinion regarding choice of ECUs for these particular engines?


    That's one of the problems.. the WRX wasn't introduced to the US market until 2002, so all of my experience has to do with 2002 and newer USDM ECUs. In which case, there are a variety of methods you can use to reprogram the factory ECU which is the best option for 98% of people. I know before that, in the UK, Prodrive had some modified ECUs you could get that were designed to work with a limited variety of modifications.. and there were also piggy back ECU type things that we used to use in 2002-2003 like the Unichip and UTEC, but AFIK they wouldn't work with your ECU.


    I know the UK and Australian markets had a few different tuning options for WRX/STi back in the 90s, but that's well out of my area of expertise. Maybe someone with more knowledge of international market cars could chime in..

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