"The BIG BOV thread" (Where all bov question threads get merged) - Page 722
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This is a discussion on "The BIG BOV thread" (Where all bov question threads get merged) within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; So i got a stock bpv, but its making kind of a funny sound when you let off the gas. ...

  1. #10816
    Registered User Silversubie05's Avatar
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    So i got a stock bpv, but its making kind of a funny sound when you let off the gas. Its obviously not as loud as the HKS so its hard to tell, but the HKS you could tell was definately open when it bled pressure, this stock one makes kind of a fluttery sound, almost like when you let off the gas it kind of vibrates quickly open and closed until the excess pressure is gone. Do your stock bpv's do this? I noticed the HKS had some sort of little check valve on the vacuum line, does the stock one need that because I don't have it on there, i just have a straight piece of hose running to it.

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  3. #10817
    Sammich Makin' Pwincess wrxtreme06's Avatar
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    Quote Originally Posted by Silversubie05 View Post
    So i got a stock bpv, but its making kind of a funny sound when you let off the gas.
    do you have a snorkus delete or an intake? these will cause your stock BPV to be louder but less obnoxious than a BOV

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    i have a no name ebay cold air intake (it came with the car, I'm trying to find a stock airbox to replace it). I don't mind hearing it, I just want to make sure that its bleeding off enough pressure, because the HKS obviously was one big PSSHHH when you let off the throttle, and obviously this isnt going to make as much noise, but my concern is that the noise is different, its more like a bunch of really quick little psh psh psh 's. It sounds like when you blow air out your mouth and flick your tongue like when your trying to learn to rolls your r's in spanish...if that makes any sense, thats the closest thing I can think of that it sounds like.

  5. #10819
    UnBanned Sinister's Avatar
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    You're fine. Replace the intake quick though!

    I personally like and recommend the K&N Short Ram.... SPT and Cobb are quality pieces though
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  6. #10820
    Registered User Silversubie05's Avatar
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    I'm on it! Thanks for the quick responses

  7. #10821
    UnBanned Sinister's Avatar
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    Quote Originally Posted by Silversubie05 View Post
    I'm on it! Thanks for the quick responses
    Sure... The quick "pshh" sound you're talking about is more than likely wastegate flutter. It's mostly heard on upgraded turbos with internal wastegates, but can be heard if you have an aftermarket downpipe.

    It usually happens in 3rd, 4th, and 5th gears because you're hitting full boost, and it only occurs when you're full throttle
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  8. #10822
    Pro Manscaper Mikie13's Avatar
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    Quote Originally Posted by Sinister View Post
    Sure... The quick "pshh" sound you're talking about is more than likely wastegate flutter. It's mostly heard on upgraded turbos with internal wastegates, but can be heard if you have an aftermarket downpipe.

    It usually happens in 3rd, 4th, and 5th gears because you're hitting full boost, and it only occurs when you're full throttle
    ^^^This.

    Unless you specify the flutter sound is occurring when you let off the gas to shift, as in the normal point for blow off to occur...then it may actually be something with the piston/valve in the stock BPV. Do you have a boost gauge to see what you're boosting at?
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  9. #10823
    Admiral Ackbar the 1st mycologist's Avatar
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    My experience with wastegate flutter, which was always VERY pronounced on my car until I adjusted it to run Testes' map:

    It was most pronounced at part throttle/part boost - i.e. right about when it was supposed to start opening and the pressure was very near the spring pressure. It could get louder with a slight lift depending.

    At full throttle it is primarily reacting to wastegate duty cycle and the boost control solenoid is in control - the spring is mostly out of the picture but is still acting a little (e.g. the boost increase you can get with spring pre-load is small). I actually didn't hear any flutter at full throttle even with the stock exhaust.
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  10. #10824
    Moderator Donkey's Avatar
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    Quote Originally Posted by Sinister View Post
    Sure... The quick "pshh" sound you're talking about is more than likely wastegate flutter. It's mostly heard on upgraded turbos with internal wastegates, but can be heard if you have an aftermarket downpipe.

    It usually happens in 3rd, 4th, and 5th gears because you're hitting full boost, and it only occurs when you're full throttle
    Or it is compressor surge. I the valve has to much spring pressure on it then the valve won't open (or open enough) at lower boost pressures (like around 3-7 psi). My moddifed stock valve would do this at 5psi and below.
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  11. #10825
    Registered User Impreza2.0's Avatar
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    The question has been answered. The problem will go away when you install a properly tuned intake, one from a reputable manufacturer. eBay intakes are mandrel bent and very roughly measured, and work poorly.

  12. #10826
    Admiral Ackbar the 1st mycologist's Avatar
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    Quote Originally Posted by Impreza2.0 View Post
    The question has been answered. The problem will go away when you install a properly tuned intake, one from a reputable manufacturer. eBay intakes are mandrel bent and very roughly measured, and work poorly.
    The possibilities have been outlined but the question is not answered. I'm leaning with Donkey that the BPV needs to be adjusted which can seriously affect the turbo.

    If you read the instructions you can adjust you wastegate arm slightly and see if that affects the sound - if it is just that then no worries.

    The intake just lets you hear it better and is its own separate issue. Whatever is causing the noise is still going to be happening regardless of correcting the intake.
    Last edited by mycologist; 09-17-2009 at 08:24 AM.
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  13. #10827
    UnBanned Sinister's Avatar
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    Quote Originally Posted by Impreza2.0 View Post
    The problem will go away when you install a properly tuned intake, one from a reputable manufacturer.
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  14. #10828
    Registered User Impreza2.0's Avatar
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    Not sure if Sinister is giving me a thumbs up or telling me to shut up and keep reading...

    I learned from use of a bad intake that my turbo DID get a lot louder, but that it valved poorly, and did have a shuddering action to it. I got an Apex'i intake, and it fixed the issue completely.

    There is a bit of development that goes into creating an intake for a car engine. It is similar to the tuning of a port for a bass reflex, or ported woofer in a speaker. If the port is too long, it will filter a frequency which does not compliment the speaker. If it is too short, it will either filter the wrong frequency again, or filter nothing at all. The tubing length and it's bends should compliment an even and balanced flow of air which changes only due to call from the throttle. If it has turbulence or is in some way restricted, it will have many negative effects, one of which is the one you describe.

    I do hope that this is not coming off as an attempt at newbish misinformation, and I hope that my vocabulary is not leading you all further into the bushes, I want the OP to have a good time solving this problem, and to enjoy the car in question.

    Please let me know which way I am leading the OP.

    I do stand by the comment I made, that a good and proper intake which was built and tested for the car intended will solve many engine related problems which exist where an economy-type performance intake was used in place of the OEM part.

  15. #10829
    Moderator Donkey's Avatar
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    Creating an intake on a turbocharged car is very different than a N/A car. The only thing an intake effects is the MAF signal.....and that is not going to effect how a BPV/BOV operates or compressor surge or wastegate flutter.
    Last edited by Donkey; 09-17-2009 at 05:26 PM.
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  16. #10830
    Registered User Silversubie05's Avatar
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    Quote Originally Posted by Mikie13 View Post
    Unless you specify the flutter sound is occurring when you let off the gas to shift, as in the normal point for blow off to occur...then it may actually be something with the piston/valve in the stock BPV. Do you have a boost gauge to see what you're boosting at?
    Yes, this is when it occurs, and I'm 99% sure its coming from the BPV and not the wastegate, I can hear it pretty much directly in front of me to the center of the car, if it were the wastegate I'd be hearing it off to the passenger side by the turbo right? I'll try to get a video clip of it tomorrow, hopefully my camera can hear it.

    And as a side note, I'm looking at getting a stock airbox because I've already spent too much money lately, I found one that looks good, does $65 shipped from the east coast to the west coast sound reasonable for the complete setup? It only has about 10,000 miles on it, and its off an 07, that will fit my 05 right? Sorry to change the subject, I know this is a BOV thread.

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