Can you hear your turbo bypass?

Discussion in 'Fiesta ST Chat and Discussion' started by WScottCross, Jun 5, 2014.


Can you hear the turbo Bypass?

  1. Yes

    33 vote(s)
  2. No

    3 vote(s)
  1. ghostwhite

    ghostwhite Active Member

    Yeah with an injen intake it's super loud. Love it

    Sent from my iPhone using Tapatalk
  2. Register or Sign in

    Advertisement Sponsor

  3. dislegal

    dislegal Member

    jimclark, I get a noise that matches your description above. My thought was that it's just the sound of the air getting sucked in through the intake when the turbo is under load.

    I could be wrong however as I'm far from an expert on forced induction.
  4. jimclark

    jimclark Active Member

    And I'm in the same boat, with regard to expertise--know just enough to get confused, it seems. I'd be more comfortable with it if it were actually more consistent, and had it not suddenly come up a couple weeks ago. That said, I'm just "watching" it at the moment, and should I think I can get by the dealer and have a good, knowledgeable technician take a listen when it's readily observable, I'll try again to do so. I can't help but wonder if there's a leak in the intake somewhere, but I can't find it.
    dislegal likes this.
  5. Firesail

    Firesail Active Member

    If you think there might be a leak, check all of the hose clamps and tighten them. It wouldn't be the first time that has happened to one of these cars.
    jimclark likes this.
  6. Dyn085

    Dyn085 Active Member

    There should be two separate and easily identifiable sounds, and it will be relatively easy to replicate. With all of your windows down, AC and radio off, roll into your throttle in second gear around 1500-2k rpm and pin it. There will be an audible and constant 'hiss' that you will primarily hear on the drivers side. That is your intake. Around 3k rpm, jump off the throttle and throw in the clutch. You should hear a 'psshh' sound very briefly, and it should appear to come from the passenger side. That is your bypass valve releasing the pressure and preserving your turbo's lifespan.

    It is all load dependent because you aren't always off-boost and you aren't always at max-boost-a lot of the time you will be somewhere in between. While driving normally on a flat road you may only hear it on acceleration, if at all. When on CC in a hilly area you will probably hear the intake as it's building boost while climbing hills. When racing people you'll hear the intake with the throttle pinned and the bypass when you lift and depress the clutch. The higher the intensity of work that the car is doing, the more audible the sounds will be and vice-versa.

    To further quiet the engine to test, you can pull the sound-symposer tube and muffle it with some more foam. I did this for a permanent sound-change, but you can remove it after your testing if you prefer the sound as it comes from the factory. This will just help to quiet things down a little bit more so that you can hear what you're listening for.
    Neely2005 and jimclark like this.
  7. BlackBird

    BlackBird Active Member Staff Member

    I can hear my BPV/Diverter. I've got the COBB AP Stage 1 93 (v102) and that's it--a couple guys have said my car sounds slightly different than stock, and I reckon that's down to changes in the TiVCT. But the extra spool and boost pressure at different parts of the power band means I regularly hear turbo spool and the diverter venting excess charge-line pressure. If I get on it hard, you bet. Can't wait to get an intake and hear it all of the time, and louder...
  8. jimclark

    jimclark Active Member

    Thanks, Dyn085--I'm gonna have to do some careful listening and comparing of my observations to what you describe. At the moment, I'm not sure that what I'm hearing is what you describe, but I'm also not sure it isn't. [I know what I'm concerned about is not the bypass valve release--given the good descriptions before, and what proved to my correct understanding of what and when, I can now pick that up pretty easily, and it's certainly a different sound.] I very much appreciate your description and explanation of what sorts of things I can/should hear. Thank you.
  9. jimclark

    jimclark Active Member

    Thanks for the suggestion. I already did this--no difference. Although there are a couple of clamps that are plenty hard to get to, so it's possible I didn't get 'em fully tightened. Assuming I did get 'em all tight, and assuming it is an intake-leak-sound, then it would mean the leak is somewhere else in the system that I can't see/find. Good news, I think, would be that if the techs at the dealer come around to hearing it and thinking that might be the issue, I'd think it would be fairy easy to check pressures, seeing if the relative vacuum in the intake is less than it should be, for instance.
  10. D1JL

    D1JL Well-Known Member

    Are you implying that there IS foam in the sound-symposer tube from the factory?

    BTW, I made some adjustments and now I hear the bypass.

  11. Dyn085

    Dyn085 Active Member

    There is, it's just super small. About an inch long and grey, with a hole through the length of it. Mine is at home in my garage, I'll take a pic of it when I get back if no one has posted one by then.
  12. Dyn085

    Dyn085 Active Member

    The end that attaches to the symposer box. When you pull the tube look into it and you'll see it about an inch in.
  13. D1JL

    D1JL Well-Known Member


  14. dislegal

    dislegal Member

    Does removing that foam change the noise you hear in the cabin, or did you mean you added more foam to muffle yours...?
  15. Dyn085

    Dyn085 Active Member

    I added foam to mine. I basically cut up a foam polishing bonnet, rolled it up, and jammed it there. It cut out the majority of the symposer noise. I didn't like that the symposer made noise all the time as opposed to my FoST which only opens up under certain rpm and throttle input.

    It sounds much better to me now, there's no vibration, and I can drive without hearing it at all if I'm driving easy. When I get on it it still sounds great and not overwhelming.
    jimclark and dislegal like this.
  16. Dyn085

    Dyn085 Active Member

    Ok, some pics.

    The grey foam piece-

    How my tube is currently-

    The piece removed and unrolled-

    Not super-pretty but nobody sees it anyways. And if it's too quiet you can cut it down some more. I'm going to go drive it with neither piece installed to see what it sounds like...
    dislegal likes this.
  17. envyist

    envyist New Member

    I only really noticed it since adding my custom exhaust.
    dislegal likes this.
  18. ST-in-Mich

    ST-in-Mich Member

    Were you ever able to do this? I'm curios how it sounds removed.
    dislegal likes this.
  19. Dyn085

    Dyn085 Active Member

    I did and personally wasn't a fan. It doesn't change much from just having the grey piece installed honestly.

Share This Page