What is this... Boost hissing?
08-03-2009, 11:11 AM
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What is this... Boost hissing?
Just yesterday I noticed that I hear a sharp brief "hiss" when my boost level drops. It sounds like the air pressure is being "released". From 5psi and under there is none, 5 to 10psi it is barely noticable, from 10 to 15psi it is very noticable, and from 15psi and up it is pretty loud. It seems to be coming from under the hood on the passanger side. My first thought was a loose charge piping, but the last time my piping came loose I had no boost at all. Can anyone guide me as to what this is and how maybe to fix it? Thanks in advance!
08-03-2009, 11:41 AM
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Yeah it just started happening yesterday... I have had the tune now for about two months. It sounds really cool when it happens, I am just worried something is wrong. The CEL came on about 2 days before this started happening, but went off after a few hours. I have not noticed a drop in power or anything else... just that cool hiss sound when changing gears or letting off the gas when boosting...
08-03-2009, 12:06 PM
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I noticed it after my K&N drop in and its a very quick sharp air movement sound. Not a hiss or vent but its definitely on the passenger side.
What does the BPV sound like?
What does the BPV sound like?
08-03-2009, 01:46 PM
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08-03-2009, 02:56 PM
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Seriously, it is very loud and noticable "all of a sudden". I am by no means a car guru. I read all sorts of things on these forums most of which is news to me. Does this have something to do with the "LEARN" feature the ECU has that a tune unlocks? Or is that just a fairy tale that I saw on some random post. I know it took about two weeks for my CEL to go off after having a loose gas cap trip it. I could really do without the smartass responses 
I was always told that the stupid question was the one you did not ask. I dunno... until just recently I couldnt even change the oil in a car. Now I am able to reconnect my charge piping. For most of you that might seem pretty mundane, but that was a big accomplishment for me as I am ignorant to most things dealing with cars.
If one of you asked me a computer question(something I am very good with) I would do my best to help and not infer that you were some sort of idiot
I was always told that the stupid question was the one you did not ask. I dunno... until just recently I couldnt even change the oil in a car. Now I am able to reconnect my charge piping. For most of you that might seem pretty mundane, but that was a big accomplishment for me as I am ignorant to most things dealing with cars. If one of you asked me a computer question(something I am very good with) I would do my best to help and not infer that you were some sort of idiot
08-03-2009, 03:03 PM
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if you have stock charge pipes, you should be fine. but that sound you hear when you let off is called a blow off, or in this case the bypass valve doing its job on a turbo car. Turbo's build up air pressure in your charge pipes, when you let off the gas the throttle body closes and that pressurized air needs somewhere to go. It starts heading back twords the turbo. In order to stop the air from getting to the turbo and slowing it down and bending the blades it has to purge and release that air. It releases it back before your turbo and runs it through again making use of that excess air. This is called a bypass valve. That excess air being purged around makes that PSST sound.
If you believe there is a problem with a piping, check to make sure everything is snug and tight. Otherwise your fine. You no longer have CEL, your car is running good and making cool sounds, just enjoy it. Its a turbo
As for the sudden'ness, these turbos like to break in over time. I noticed mine get much louder after i drove my car more. Then after intake and etc it really got loud. But now i have a Greddy BOV and its like disconnecting an airhose from a house at 21psi
If you believe there is a problem with a piping, check to make sure everything is snug and tight. Otherwise your fine. You no longer have CEL, your car is running good and making cool sounds, just enjoy it. Its a turbo
As for the sudden'ness, these turbos like to break in over time. I noticed mine get much louder after i drove my car more. Then after intake and etc it really got loud. But now i have a Greddy BOV and its like disconnecting an airhose from a house at 21psi
08-03-2009, 03:52 PM
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^^^Very true...I now have a little over 2000 miles on mine, and the BPV and exhaust note is noticebly louder than when I first got it. It is starting to sound really good. Before I couldn't even hear it running.
Last edited by reed; 08-08-2009 at 04:48 PM.
08-03-2009, 05:10 PM
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if you have stock charge pipes, you should be fine. but that sound you hear when you let off is called a blow off, or in this case the bypass valve doing its job on a turbo car. Turbo's build up air pressure in your charge pipes, when you let off the gas the throttle body closes and that pressurized air needs somewhere to go. It starts heading back twords the turbo. In order to stop the air from getting to the turbo and slowing it down and bending the blades it has to purge and release that air. It releases it back before your turbo and runs it through again making use of that excess air. This is called a bypass valve. That excess air being purged around makes that PSST sound.
If you believe there is a problem with a piping, check to make sure everything is snug and tight. Otherwise your fine. You no longer have CEL, your car is running good and making cool sounds, just enjoy it. Its a turbo
As for the sudden'ness, these turbos like to break in over time. I noticed mine get much louder after i drove my car more. Then after intake and etc it really got loud. But now i have a Greddy BOV and its like disconnecting an airhose from a house at 21psi
If you believe there is a problem with a piping, check to make sure everything is snug and tight. Otherwise your fine. You no longer have CEL, your car is running good and making cool sounds, just enjoy it. Its a turbo
As for the sudden'ness, these turbos like to break in over time. I noticed mine get much louder after i drove my car more. Then after intake and etc it really got loud. But now i have a Greddy BOV and its like disconnecting an airhose from a house at 21psi
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