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  1. #1
    Active Member Two Rings
    Join Date
    Mar 17 2016
    AZ Member #
    370415
    Location
    CO

    Whistling noise when letting off throttle @ 5k+ rpm

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    Tried searching the forums and all I could get describing similar noise was in the A4 forums.

    I'm hearing a high pitch whistle or possible mechanical noise when letting off the gas above 5k rpm. I hear a couple short whistles (super high pitch, almost like a dog whistle) at like 5k and again around 4.5k rpm as the rpm drops.

    Anyone else get this noise? Could this be normal / possibly bypass valve related?

    It sounds similar to the vacuum / suction chirp noise I hear when first getting on the throttle, which I assume is actually the bypass valve closing. But this noise is sharper / higher pitched. I've got an open intake installed for the record.

    Sent from my SM-G955U using Tapatalk
    2014 B8.5 S4 Ice Silver DSG

    EPL Stage 2 DP::EPL TCU Tune::Merc Racing HX::iABED 75mm TB::ECS Luft-Technik Carbon Fiber CAI::Bilstein B12::ECS Transmission Mount::ECS Slotted Geomet Rotors::EBC Red Stuff Pads::19" Black AG M510 Wheels

  2. #2
    Established Member Two Rings
    Join Date
    Jul 23 2018
    AZ Member #
    422941
    Location
    Vicenza, Italy

    Does it ‘wind down’ with respect to engine speed? I get a very faint, high pitched sound too when letting off the throttle, but it sounds to me like the supercharger winding down (in ‘reverse’ so to speak).. Not sure if this is what it is, or what your experiencing, but I do experience something..

  3. #3
    Established Member Two Rings BlueSteW8's Avatar
    Join Date
    Apr 24 2011
    AZ Member #
    74517
    Location
    Ft. Myers FL USA

    I could the TB adapter plate, as others with 75mm throttle body have experienced the same thing

  4. #4
    Active Member Two Rings
    Join Date
    Mar 17 2016
    AZ Member #
    370415
    Location
    CO

    Quote Originally Posted by Allan691 View Post
    Does it ‘wind down’ with respect to engine speed? I get a very faint, high pitched sound too when letting off the throttle, but it sounds to me like the supercharger winding down (in ‘reverse’ so to speak).. Not sure if this is what it is, or what your experiencing, but I do experience something..
    Not sure it is a wind-down, as I dont hear the whistle when the RPMs fall lowe, but maybe? Can you actually hear the SC winding down? Separate from the SC whine?

    I only hear the 2 little chirps/peeps. Maybe like the bypass valve being forced open/closed ever so slightly a couple of times as the RPMs fall?

    Sent from my SM-G955U using Tapatalk
    2014 B8.5 S4 Ice Silver DSG

    EPL Stage 2 DP::EPL TCU Tune::Merc Racing HX::iABED 75mm TB::ECS Luft-Technik Carbon Fiber CAI::Bilstein B12::ECS Transmission Mount::ECS Slotted Geomet Rotors::EBC Red Stuff Pads::19" Black AG M510 Wheels

  5. #5
    Active Member Two Rings
    Join Date
    Mar 17 2016
    AZ Member #
    370415
    Location
    CO

    Quote Originally Posted by BlueSteW8 View Post
    I could the TB adapter plate, as others with 75mm throttle body have experienced the same thing
    But I don't hear it while accelerating at all? Still think it might be the adapter plate? I was under the impression the adapter plate whistle was a loud consistent whistle from the meth injection port.

    I only get the 2 whistles. The noise happens when I completely let off the gas after getting up past 5000rpm, only noticed because I was engine braking. Happened pretty consistently during that drive - does not make the noise accelerating 3k-5.5k, but only when I let off. Super high pitch dog whistles (probably close to the limit of my hearing) @ 5k and 4.5k.

    Sent from my SM-G955U using Tapatalk
    2014 B8.5 S4 Ice Silver DSG

    EPL Stage 2 DP::EPL TCU Tune::Merc Racing HX::iABED 75mm TB::ECS Luft-Technik Carbon Fiber CAI::Bilstein B12::ECS Transmission Mount::ECS Slotted Geomet Rotors::EBC Red Stuff Pads::19" Black AG M510 Wheels

  6. #6
    Established Member Two Rings
    Join Date
    Jul 23 2018
    AZ Member #
    422941
    Location
    Vicenza, Italy

    Quote Originally Posted by k186 View Post
    Not sure it is a wind-down, as I dont hear the whistle when the RPMs fall lowe, but maybe? Can you actually hear the SC winding down? Separate from the SC whine?

    I only hear the 2 little chirps/peeps. Maybe like the bypass valve being forced open/closed ever so slightly a couple of times as the RPMs fall?

    Sent from my SM-G955U using Tapatalk
    I actually don’t know what I hear. lol But it is a high pitched whistle.. Only constant. Not peeps or chirps. So probably not the same thing.

    As for actually hearing the SC ‘winding down’ - IDK.. Just don’t know how else to describe it.



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