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Fluttering Sound From Bov

FORZA-MOTORSPORT
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mad082 Grand Master

mad082

Posted
Posted

it could be that you have a slight vacuum leak and the vacuum isn't as strong to pull the bov open as much.

where do you have the wastegate line coming from? is it off the bov hose? if it is then that may be the cause of it. could either be the extra air in the line, or the restriction of the 'T' piece. if you don't have the wastegate hooked from the bov line then it buggers me.

Rolls Grand Master

Rolls

Posted
Posted
I thought the flutter noise was the wastegate opening and closing really fast?

also, i didnt think that the standards turbo were big enough to get compressor surge?

Sorry but thats complete bollucks. What has happened is the bov is too tight/not big enough and its not opening or only partially opening letting only some of the built up pressure out. The rest of it goes back through the compressor and gets chopped up making that flutter noise. Now that you can installed a big front mount the noise is amplified so you can hear it much easier. The noise is coming out of your pod filter not the bov.

If you were to run absolutely no bov at all this is what you would hear. Try loosening the bov off a bit or you can or get a bigger one.

Theres some good discussion in here about running no bov to get the sound always.

http://www.skylinesaustralia.com/forums/in...&hl=flutter

Cubes Grand Master

Cubes

Posted
Posted

I've heard 2 types of what could be considered a flutter.

When you jump off the throttle at part boost levels and you hear a flutter due to a bov thats too tight. May very well be the case here as you are only running 8psi. :(

Under full throttle/boost acceleration the bov isn't tight enough and begins to make a fluttering noise. I've seen the last on a dyno but it was pushing over 20psi.

nissan950 Newbie

nissan950

Posted
Posted

guys,

that flutter noise is from air filter not BOV. as the air pressure cannot be realsed from BOV it comes out from the air filter, which i heard is not healthy for your turbo according to the rep from turbosmart. so most of the 200sx which has got loud flutter noise might sound cool but not healthy for their car.

VB- Veteran

VB-

Posted
Posted

fluttering under very liht load/acceleration is normal, and shouldnt do any harm, if its wen u jump off the throttle while making alot of boost and it still does it, you need to reduce preload on the spring as its too tight, and as has been said its the air going back through the turbo that makes the fluttering noise, and as well as causing compressor surge, it will also shorten the life of your turbo, or so i've been taught.

when the pressure builds up and has nowhere to go (blow off valve not setup right/not working/no blow off valve) and it makes its way back through the compressor, its will either momentarily stop/slow the compressor while the build up or air escapes, but the shaft is still trying to twist the compressor at 100-200,000rpm, and this happens 5, 10, or 20 times, every time u let off the throttle.

the other possibility is that the compressor will keep spinning at speed, but actually be forced backwards into the turbo (not necesarily causing contact) so the air can escape infront of it.

and now im going to make myself look really stupid, and tell that yes, i actually like the fluttering sound too, especially on VLs. A stock VL turbo, with a massive cooler, and no blow-off valve. love it!

Rolls Grand Master

Rolls

Posted
Posted (edited)
the other possibility is that the compressor will keep spinning at speed, but actually be forced backwards into the turbo (not necesarily causing contact) so the air can escape infront of it.

LOL

Guys do you just make up shit for fun, the compressor spinning backwards? c'mon if you dont know anything about it dont say anything, all it does is propogate misinformation.

The air will just escape between the blades slowling minimally, thats why it makes the chopping flutter sound, if it stopped the compressor completely or pushed it backwards or whatever it would sound just like a bov cause the air wouldnt be getting chopped up.

The flutter does sound fully sick though, my stock redtop rb20det R31 fluttered like crazy, they came out stock with no bov.

Edited by Rolls

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