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Compressor surge

Posted by Bud92gsx, Jan 8, 2009

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  1. Bud92gsx

    Bud92gsx Proven Member

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    Can someone please explaint to me what compressor sure is, and why it happens? I recenty put on the EVO 3 16G, and noticed when I left of the gas a flutter coming from the BOV. I was wondering why this happens, and If this will cause damage to mt turbo? MY BOV is recirculated, and I am only running on wastgate pressure at the moment.

    Thanks

    Bud
     

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    My DSM:
    1992 Mitsubishi Eclipse GSX

    13.300 @ 102.400 MPH
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  2. RyAn007

    RyAn007 Proven Member

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    Do you have an aftermarket blow off valve or is your mbc teed in through your blow off valve line? Also compressor surge is when the air is not released when load is let off and instead of releasing out of the blow off valve it goes back wards out of the turbo, yes it will cause damage because it is putting a lot of load on the thrust bearing, but it will not instantly kill a turbo, but it takes half the life away.
     
  3. JusMX141

    JusMX141 Moderator

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  4. Boosted98gsx

    Boosted98gsx Proven Member

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    Comp surge is too much air out of your compressor for your engine to digest or your blow off valve to release. Basically, your turbo makes too much air, and so instead of exiting the system through the combustion chamber, it reverts through the compressor housing.

    This is bad because it causes your compressor wheel to spin backwards, which spins your turbine backwards, and puts backpressure on your engine, normally in pulses, which can make your car jerk, and hurt your drivetrain.

    Too much load per given rpm is the main cause. Examples, going up a hill in a RPM too low, having your A/C on in an RPM too low, a turbo that spools very easily under load (small turbine / housing).

    Also, a blow off valve that doesn't release enough airflow can cause surge (or BOV "flutter").

    It can be avoided by increasing your turbine size or turbine housing A/R ratio, getting a larger BOV, or a less efficient turbo.
     
    My DSM:
    1998 Mitsubishi Eclipse GSX

    11.641 @ 114.230 MPH
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  5. Bud92gsx

    Bud92gsx Proven Member

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    Wisconsin, Wisconsin
    THe BOV recic tube is not kinked at all. SO basically by allowing the BOV to vent to atmosphere, I could prevent thrust bearing failure?
    I will definatly read the link, to gain more knowlage about this issue...

    Thank you for the responses!!:thumb:
     
    My DSM:
    1992 Mitsubishi Eclipse GSX

    13.300 @ 102.400 MPH
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  6. Bud92gsx

    Bud92gsx Proven Member

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    Wisconsin, Wisconsin
    I'm sorry I should have been more specific..I'm getting flutter not surge. Only when I let off the throttle, not under boost.
    Will flutter damage anything?
    Does flutter means the pressure is spinning my turbine backward, like BOOSTED said?

    Should I try to uncrush my BOV? You think that will help?
     
    My DSM:
    1992 Mitsubishi Eclipse GSX

    13.300 @ 102.400 MPH
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  7. Mr Peepers

    Mr Peepers DSM Wiseman

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    Janesville, Wisconsin
    A crushed BOV can't open as far as an uncrushed one and may not be bypassing enough air to keep your turbo in it's happy place to the right of the surge line when you let off the throttle. Uncrush it if you can, and/or DG mod an uncrushed one it if you are having problems with it leaking at higher pressures.

    Surge isn't actually the compressor/turbine going backwards, just cycling from stable to unstable airflow, which as stated can be very damaging.
     
    My DSM:
    1991 Eagle Talon TSi AWD

    Street Build

    10.082 @ 132.21 MPH
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  8. Bud92gsx

    Bud92gsx Proven Member

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    Wisconsin, Wisconsin
    Thanks Matt your always a big help..If I uncrush my BOV or just put an uncrushed one on and recirculate that, I will be fine??
     
    My DSM:
    1992 Mitsubishi Eclipse GSX

    13.300 @ 102.400 MPH
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  9. Bud92gsx

    Bud92gsx Proven Member

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    Wisconsin, Wisconsin
    Heres what I did today.. Went to the garage and put on 2g mas. I think i screwed something up cause my car started acting funny. I put the 1g mas back on and it fixed the problem...

    Next I put on my 1g BOV that was only crushed a small amount. That did not fix the flutter. I vented the BOV to the atmosphere just to make sure I cannot cause any damage to the turbo.

    Checked for shaft play, I had none....

    But I did notice something strange happening.. After a while at idle, the car will repeatedly go up and down in rpm. Just like if i hit the gas and let off.
    Does anyone know of why this could be happening??
     
    My DSM:
    1992 Mitsubishi Eclipse GSX

    13.300 @ 102.400 MPH
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  10. Mr Peepers

    Mr Peepers DSM Wiseman

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    Joined Oct 16, 2005
    Janesville, Wisconsin
    The surging could be due to a boost leak, possibly caused by your slightly crushed and vented 1g BOV sucking in air during idle. Base timing being too advanced can also cause idle surge, along with a list more.

    If you just threw the 2g MAS on with no other modifications, it will cause the car to run lean.
     
    My DSM:
    1991 Eagle Talon TSi AWD

    Street Build

    10.082 @ 132.21 MPH
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  11. Bud92gsx

    Bud92gsx Proven Member

    7,872
    51
    Joined Jan 16, 2008
    Wisconsin, Wisconsin
    That's what I was trying to do was to get it to lean out a bit. A wise man told me it would give me a HP gaing, by leaning it out... What other mods would I need to run the 2g MAS??

    Base timing has always been ok. I did move the CAS a bit. Maybe I'll set that back to 0...
     
    My DSM:
    1992 Mitsubishi Eclipse GSX

    13.300 @ 102.400 MPH
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