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This is a discussion on Need tuning advice. within the Tuning: Electronic Engine Management forums, part of the Tech & Modifying & General Repairs category; 2002 bugeye ej25 vf39 up pipe catless downpipe perrin exhaust sti pink injectors turbo XS tmic (greedy type S bov) ...

  1. #1
    Registered User ronzonothebugeye's Avatar
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    Need tuning advice.

    2002 bugeye
    ej25
    vf39
    up pipe
    catless downpipe
    perrin exhaust
    sti pink injectors
    turbo XS tmic (greedy type S bov)
    open source tuning
    307hp 319tq 18psi

    I need tuneing advice. My vf39 is on its last leg, it burns a quart of oil about every 500 miles...about once a week. I am replacing the vf39 this weekend with a very slightly used VF48, out of a 2012 sti, along with an upgraded compressor wheel (which is said to flow up to 15% more). If I am to go back to get it re tuned on a dyno, it is going to cost me 500 dollars and a drive from San Diego to Los Angeles (and a full day off of work). There are a few tuners in San Diego that will do a street tune for 250 dollars, just running it down the street. I would save 250 dollars plus a full days work gas and time if I did a local street tune. My question is do I need a complete tune, or can a street tune with minor adustments be fine?

    I also plan on installing a grimspeed 3 port solenoid before either tune.
    LS stocker to a VTEC rocker!

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  3. #2
    zax
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    Do you have a WBO2? If not, invest in one now and a street tune will be just as good as a dyno tune (and in some ways better).

    Difficult to judge since IHI does not publish compressor maps, but the VF48 should be nearly identical to the VF39. I am also HIGHLY skeptical about this "rebuilt" VF48 since IHI has never released a rebuild kit... who rebuilt the turbo? Is it the stock CHRA?
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    Registered User ronzonothebugeye's Avatar
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    The VF48 is not rebuilt. It has appoximitly 6000 miles on it. All I did to the turbo was install an upgraded billet compressor wheel. A turbo shop here in San Diego called Action Turbo(a repitable shop) said they have used the wheels before, and they come pre balanced. I put the wheel in myself, and it works fine.

    https://www.xsboostturbochargers.com...f39-vf43-vf48/

    Question? when tuning, does the factory o2 sensor read as a wideband?...I thought they made a kit that can hook to the factory o2 sensor? so that would mean the tuner can read fuel ratios when tuneing with his computer, on a street tune, correct? or am I wrong?



    Quote Originally Posted by zax View Post
    Do you have a WBO2? If not, invest in one now and a street tune will be just as good as a dyno tune (and in some ways better).

    Difficult to judge since IHI does not publish compressor maps, but the VF48 should be nearly identical to the VF39. I am also HIGHLY skeptical about this "rebuilt" VF48 since IHI has never released a rebuild kit... who rebuilt the turbo? Is it the stock CHRA?
    THANKS ZAX!!!
    LS stocker to a VTEC rocker!

  5. #4
    zax
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    Quote Originally Posted by ronzonothebugeye View Post
    The VF48 is not rebuilt. It has appoximitly 6000 miles on it. All I did to the turbo was install an upgraded billet compressor wheel. A turbo shop here in San Diego called Action Turbo(a repitable shop) said they have used the wheels before, and they come pre balanced. I put the wheel in myself, and it works fine.
    ... Still skeptical

    Quote Originally Posted by ronzonothebugeye View Post
    Question? when tuning, does the factory o2 sensor read as a wideband?...I thought they made a kit that can hook to the factory o2 sensor? so that would mean the tuner can read fuel ratios when tuneing with his computer, on a street tune, correct? or am I wrong?
    Not to sound condescending, but yes, you are wrong. The front O2 sensor actually is a zirconia WBO2 sensor, but the ECU cannot use this sensor as a WBO2 sensor. Even WBO2 sensors will change sensor scaling as the ambient pressure changes. The exhaust gas pressure pre-turbo can actually rise as high as 50 PSI, which makes any reading (besides a rich/lean assessment) useless. As such, the ECU registers the rich and lean condition in cyclic fueling logic -- if lean, then increase pulse width; if rich then decrease pulse width. With an NA car, precisely what you have stated could be performed, but not with the WRX. Unfortunately the rear O2 sensor is a standard zirconia narrow-band O2 sensor with the primary purpose of monitoring catalyst efficiency. Dyno tunes can be performed using a full EGA (exhaust gas analyzer) and are extremely flexible, also monitoring NOx emissions which are useful in judgement of EGTs.

    Everything I've stated above applies to GD WRXs. As an interesting side-note, both EJ257 and Heide264 have informed me that the logic in the newer CANbus ECUs actually utilizes a component of the rear O2 sensor readings to establish closed-loop control of the AFRs. Given this information, I do wonder if the rear O2 sensor on the CANbus WRXs actually is a WBO2 sensor. Anyone want to chime in or look up part numbers?

    EDIT:
    Here is something that helped me quite a bit to understand the hardware difference between a WBO2 and a narrow-band Oxygen sensor (pictures taken from Wikipedia):

    WBO2:


    Narrow-band O2:
    Last edited by zax; 02-11-2014 at 12:50 PM.
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  6. #5
    Registered User ronzonothebugeye's Avatar
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    Quote Originally Posted by zax View Post
    ... Still skeptical



    Not to sound condescending, but yes, you are wrong. The front O2 sensor actually is a zirconia WBO2 sensor, but the ECU cannot use this sensor as a WBO2 sensor. Even WBO2 sensors will change sensor scaling as the ambient pressure changes. The exhaust gas pressure pre-turbo can actually rise as high as 50 PSI, which makes any reading (besides a rich/lean assessment) useless. As such, the ECU registers the rich and lean condition in cyclic fueling logic -- if lean, then increase pulse width; if rich then decrease pulse width. With an NA car, precisely what you have stated could be performed, but not with the WRX. Unfortunately the rear O2 sensor is a standard zirconia narrow-band O2 sensor with the primary purpose of monitoring catalyst efficiency. Dyno tunes can be performed using a full EGA (exhaust gas analyzer) and are extremely flexible, also monitoring NOx emissions which are useful in judgement of EGTs.

    Everything I've stated above applies to GD WRXs. As an interesting side-note, both EJ257 and Heide264 have informed me that the logic in the newer CANbus ECUs actually utilizes a component of the rear O2 sensor readings to establish closed-loop control of the AFRs. Given this information, I do wonder if the rear O2 sensor on the CANbus WRXs actually is a WBO2 sensor. Anyone want to chime in or look up part numbers?
    Not condesending at all, I appriciate the information. I'm on a budget just like everyone else, so pulling more money from wife is going to be hard...lol. Im probably not going to buy the 3 port boost solenoid which I was planning to buy, and instead I'm going to buy a wideband o2sensor and gauge. Do you think the stock boost solenoid is sufficaint, or does the 3 port solenoid really make a big differnece?
    LS stocker to a VTEC rocker!

  7. #6
    zax
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    Quote Originally Posted by ronzonothebugeye View Post
    Not condesending at all, I appriciate the information. I'm on a budget just like everyone else, so pulling more money from wife is going to be hard...lol. Im probably not going to buy the 3 port boost solenoid which I was planning to buy, and instead I'm going to buy a wideband o2sensor and gauge. Do you think the stock boost solenoid is sufficaint, or does the 3 port solenoid really make a big differnece?
    3 port would be a good plan. Bleed-type BCS have clear shortcomings.
    2015 CWP WRX STi ... But how did I get roped back into an EJ motor?!
    Zax's utterly unimaginably stock 2015 STi build thread
    Zax's Shaggin' Wagon Build Thread Now tuned for 99% pure Unicorn Jizz!

    Zach | Moderator -- Mid-Atlantic States, Tech & Modifying & General Repairs
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    OMG WTF MainFrame's Avatar
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    Eat in instead of going out one night and you can afford the 3-port.. GM 3 port BCS Turbo Boost Control Solenoid Valve 1997152 : Amazon.com : Automotive

  9. #8
    Registered User ronzonothebugeye's Avatar
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    Quote Originally Posted by MainFrame View Post
    Eat in instead of going out one night and you can afford the 3-port.. GM 3 port BCS Turbo Boost Control Solenoid Valve 1997152 : Amazon.com : Automotive
    hahaha...your right...I'm just impatient, I put the turbo in on Sunday, and I want to boost already. Ive been driving it, and I punched it once....feels about the same as the vf39, not sure if the vf48 is even any differnet....
    LS stocker to a VTEC rocker!

  10. #9
    Master Baiter EJ257's Avatar
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    Quote Originally Posted by zax
    As an interesting side-note, both EJ257 and Heide264 have informed me that the logic in the newer CANbus ECUs actually utilizes a component of the rear O2 sensor readings to establish closed-loop control of the AFRs. Given this information, I do wonder if the rear O2 sensor on the CANbus WRXs actually is a WBO2 sensor. Anyone want to chime in or look up part numbers?
    All 32-bit ECUs (including the '06/'07 WRX will have fueling issues without the presence of a rear O2 sensor).
    2005 WRX STi (Mods | Virtual Dyno)

    Resident Tuner @ WTF Tuning

    "Never trust anything that bleeds for a week and lives ..."

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