Fluttering Sound From Bov

[FORZA-MOTORSPORT]

I just changed from a stock cooler to a front mount and now my aftermarket bov has a fluttering sound is this normal??

[HR32_GTS-T]

wat kind of blow off valve is it?

Does it do it all the time, or just wen u drive normally?

[BezerkR32]

thats sick bro

I just changed from a stock cooler to a front mount and now my aftermarket bov has a fluttering sound is this normal??

[FORZA-MOTORSPORT]

Not sure havent pushed it hard enough to see if it makes the same kind of sound, must be compressor surge, it is a sheep dog bov see attached pic

[krzysiu]

Depends how tight the spring is (are the sheepdogs adjustable?) So if you dont give it enough boot it wont open up and vent. So your just getting compressor surge.

[HR32_GTS-T]

the flutter sound is cool, my v-pot type 2 does it as well untill u boot it.

[mad082]

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.

[paulr33]

http://www.skylinesaustralia.com/forums/in...c=60654&hl=

[mad082]

he is asking how to get rid of it, not how to make it do it.

[jazza08]

He's not askin to get rid of it? More is this normal, yes flutter can be normal and many ppl think its fully sik, personally i just like it lol

[hayden49]

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?

[Cubes]

When Does it do it?

During light/hard acceleration or when jumping off the throttle?

Most likely just a greater volume of air in the system causing a different bov noise when you jump off the throttle.

[Rolls]

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]

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]

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.

[Cubes]

If that is the case *most likely* on 8psi.. I wouldn't be concerned.

[VB-]

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!

[FORZA-MOTORSPORT]

The fluttering noise only happens when i dont push her full throttle, i think it is compressor surge...

[Rolls]

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 July 15, 2006 by Rolls

[FORZA-MOTORSPORT]

As long as it doesnt damage my turbo in the long run then good , so if i do tighten the bov this wont happen anymore???