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Can you hear the turbo Bypass?

  • Yes

    Votes: 33 91.7%
  • No

    Votes: 3 8.3%

Can you hear your turbo bypass?

12129 Views 38 Replies 21 Participants Last post by  Dalcala75
I can definitely hear my turbo spool and especially bypass when shifting. Some folks can't hear it. Can you? What is your setup if you can?
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WScottCross, dislegal, BRGT350, others: could you guys please describe the sound you're hearing, and when you can best hear it? I'm chasing an extra couple of sounds that may or may not be related. Techs at the dealer are less than helpful thus far. It might be embarrassing if the sounds that are bugging me are all turbo-related, but I would sleep better at night not worrying about the baby. :bucktooth:
Perfect! Thanks, guys. I believe that's exactly the sound I hear that I was thinking of as "turbo spool/spin-down". I see that bypass is the preferred term. Good. Unfortunately, that still leaves me with the sound(s) (primarily, at least, a single sound) I'm hearing, which seems to come from the same side of the engine bay, and is heard in the same RPM range (typically, though slightly variable, in 2-3K range) in all gears (best in lower gears, as there is lower ambient noise). It is variable in its intensity, at times being fairly easily discerned, at others difficult to make out. The sound reminds me of the sort of whistling sound that air can make rushing through a cracked-open window. It does not occur with the car in neutral and the engine revved. When it's fairly easy to hear, as it was yesterday evening, for instance, I can get it to become more or less continuous if I can run the same RPM under the same load (as, for instance, on a flat stretch of road, constant speed, constant RPMs of, say, 2.5K) for a bit (up to 5-10 secs). It's driving me just a little batty.
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hmmm, so the sound is load dependant. I was thinking the sound symposer tube, but that would make the noise at all times. Can you hear it from outside the car when it drives by?
I've not had the chance to listen from outside the vehicle. (Wife doesn't drive manual.) I've been told by one ostensibly reliable observer that he could hear it, though it wasn't loud.
And because it's variable in intensity--so much so that when I took it to the dealer, in fairness even I had a hard time making it out, yet at other times even my wife readily notices it--I have a hard time classifying it as purely incidental/normal. Especially as two weeks ago I'd never noticed it. Combining all these factors--obviously related to mechanical function, load-dependent, variable intensity, and new--it's in the category I have to call abnormal, and potentially indicative of malfunction of some sort. (I'm obviously hoping that any malfunction is mild and of no consequence.) Thus, my increasing obsession with the thing.
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.
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.
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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.
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.
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.
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.
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