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phoenixgoldskyline

Not the BOV noise the other one?

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It's the sound of the excess air coming back through the piping, being chopped by the turbo as it goes the wrong way, and you can hear it out the pod filter.

Often called fluttering.

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no you can get the fluttering with the bov just the bov may be louder than the natural one so you may not hear it as much, if at all

also you can get different bovs that make different noises not just the fluttering

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the 'fluttering' that i think you are describing is called 'compressor surge'. it happens when the bov it sprung too tight or when you don't have a bov (ie not a skyline).

when the throttle body closes (like taking the foot off the accelerator), the comressed air hits and reflects back in the direction it came. in a skyline the bov would open and air would pass out through this making a 'ppsssssshhhhhhhhhh' sound. if no bov, then the air goes back through the intercooler and passes through the compressor side of the turbo in the opposite direction to the spinning blades and as mentioned by obseshn this 'chops' the air up making a fluttering noise. as you can imagine it ain't good for the turbocharger even if it sounds good.

hope that helped.

Waz.

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Hi,

The Flutter is what WazR32GTSt stated if you block off your factory bov with a plate u will get flutter (Compressor Surge) ppl have said it is bad but i wonder how many ppls turbos have been wrecked by actual compressor surge.

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Have a friend who ran a turbo for quite a while with no BOV and it was still fine. Unsure about my car but it's making a fluttering/chattering/chopping noise so either the BOV's pretty tight or the previous owner removed it. Will have to perform a more thorough investigation but everything's in good nick!

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hi guys, my R33 does the same thing and its very loud, i have a blitz bov, im not a big fan of the fluttering noise that i get ( i like the bov sound ) is there a way of getting rid of the fluttering sound

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Remember the Sieria at Bathurst. They didn't have a BOV and suffered quite a few turbo failures compared to the GTR's which had bovs.

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definitely not wastegate. on closed throttle there's no air going through the engine so the wastegate opening and shutting wouldn't do much. Either the BOV fluttering or compressor surge with air reverting back through the turbine compressor blades.

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i always thought it was the wastegate...some ppl ive talked to about their cars they havent got bov's on them,hence making the fluttering noise and theyre turbos arent ***t and theyre running high boost say 30 psi....

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this has been explained in super high detail by myself and others! so if you want the exact answer you should find it in a search.

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This "fluttering" is also a major factor in engine stalls when comming to a stop. I was investigating stalling issues on my car a while back and did some measurements with an oscilliscope on the AFM. I've attached an image of AFM voltage with a "loose" and "tight" BOV. Note that the "tight" setting produced audible "flutter" through the AFM after a rev, and this is seen as the severe oscillations in the trace indicating reversion due to compressor surge....

phantom

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most vl turbos do the fluttering sound and the owners think their really cool when it does this noise. its a bad noise :(

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yes its definately not the best thing for the turbo but it doesnt in most cases have anything to do with an after market bov unless the tension of the spring is one that is made for high boost use and is being used on a low boost setting.

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