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Thread: pls help w/ SC noise

  1. #1
    Join Date
    Dec 2016
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    vero beach, FL
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    1997 328ic

    pls help w/ SC noise



    hi guys, any clue on what the 4-6s sound is in this clip? It’s coming from intake side when I’m in boost and press in the the clutch to shift - ie it sounds like the diverter valve noise fluttering. Has anyone heard this before and should I address it ASAP? replace DV?

    thank you!!

    this is on AA c38 setup
    m50 mani / AA c38-81 stage 2 / 12psi / AEM progressive w/m kit / stg3 SB endurance clutch + SS / 3.38 LSD / cdv + asc delete / stromung catback + cat delete / ebay coilovers + GC RSMs / square CSL wheels / ski-pass 8" sub


  2. #2
    Join Date
    Mar 2015
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    Philadelphia, PA
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    03 BMW 540i M-Tech 6spd
    Sounds like compressor surge to me, as in the DV is not functioning/opening. Does your DV have any adjustment?

  3. #3
    Join Date
    Mar 2013
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    Sounds awesome haha imo, but yes possibly surge or your blow off isn't working right.

  4. #4
    Join Date
    Dec 2016
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    vero beach, FL
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    1997 328ic
    Hi jeeve that doesn’t sound good. Yes valve is adjustable but the noise came up recently when everything has been functioning smoothly so I’m not sure why the issue came up now. I will get it checked out ASAP then


    Sent from my iPhone using Tapatalk
    m50 mani / AA c38-81 stage 2 / 12psi / AEM progressive w/m kit / stg3 SB endurance clutch + SS / 3.38 LSD / cdv + asc delete / stromung catback + cat delete / ebay coilovers + GC RSMs / square CSL wheels / ski-pass 8" sub


  5. #5
    Join Date
    Mar 2015
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    03 BMW 540i M-Tech 6spd
    Sounds very similar to the surge on my turbo Maxima, the spring in the valve may be too strong- hitting the clutch makes a low vac situation where the valve does not open. Since you have not experienced it before, it can be a leaky line to the valve not providing a strong vac source or the adjustment went out of whack over time.

  6. #6
    Join Date
    Feb 2015
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    2000 540i SC'd | 2001 M5
    This is surge and its happening when you're dropping the throttle. Either your relief valve is undersized or not functioning properly.

    If this suddenly happened and it worked fine before, then inspect the valve. Make sure it opens up if you plug it to a vac pump and holds open, check the vac line connections and check for holes.

    Did everything with the setup you have no work before or is this a new setup?
    Sold: 2000-BMW-E39-540i/Biarritz-Blue/Gray-Interior/DSP Sound.
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  7. #7
    Join Date
    Dec 2016
    Location
    vero beach, FL
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    1997 328ic
    Just an update: replaced dv diaphragm, set adjustment bolt is at the lowest setting so its not preventing DV to open, they checked vacuum and DV still flutters releasing the boost. Waiting for further suggestions from AA at this point but at a loss.
    Last edited by verobeach97; 02-23-2018 at 04:40 PM.
    m50 mani / AA c38-81 stage 2 / 12psi / AEM progressive w/m kit / stg3 SB endurance clutch + SS / 3.38 LSD / cdv + asc delete / stromung catback + cat delete / ebay coilovers + GC RSMs / square CSL wheels / ski-pass 8" sub


  8. #8
    Join Date
    Nov 2008
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    Indiana
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    97' 328is, 07' Titan
    What vacuum reading are you getting at idle?
    1997 328is - Megasquirt PNP, Holset HX35, Deka 80lb injectors, SPA T3, Precision PW39 WG, Synapse Synchronic BOV, DKM Organic Twin Disc Clutch, Innovate LC-2 W/B, Mishimoto Intercooler, Mishimoto Catch Can, Mishimoto Rad, Devils Own Meth, Porsche 911 calipers with E46 M3 rotors, Corsa Exhaust

  9. #9
    Join Date
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    1997 328ic
    Update: Visited AA today -that place is always full of awesome projects. They did smoke test without any leaks and the vacuum holds perfectly at -24. No kinks in the DV hose. The noise is less noticeable than in the video after replacing the diaphragm, but they will send me a softer spring to try to eliminate it completely. It’s not necessarily a compressor surge but more of valve noise itself apparently. Still a little strange and unsettling.

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