FLUTTER SOUND PLEASE HELP

[JuanSTI]

so i got an 06 sti and i want it to flutter like this guys car http://www.youtube.com/watch?v=DyWc5yMGuRA
what can i do ??? for mine to do that

 

[finallymysti]

U can block off the bps and mess up ur turbo

 

[finallymysti]

Bpv not bps

 

[JuanSTI]

oh so that means when that flutter noise happens its not a good thing huh thats a bummer i love that sound but oh well. thanks.

 

[Batmobile_Engage]

U can block off the bps and mess up ur turbo

I believe you are referring to the sound of compressor surge. To me, the car in the video
does not sound like it's experiencing compressor surge. It sounds to me that the aftermarket
bov that is installed is making that noise.

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The bov I have on my STi does this a little bit when the engine is cold and/or when I'm revving
while sitting still. The turbo isn't making a much boost because with no load on the engine, there's
not a whole lot of exhaust being produced. When you let off the gas, the valve barely reacts to
the slight pressure difference and opens (let's say for the sake of example) 10% dumping a little
bit of boost and equalizing the pressure, but the turbo is still spooling down and producing a bit
of positive boost. So until the turbo is spooled down to an idle rpm, this continues, 10% open,
close, 10% open, close and so on...which sounds a little like flutter.

However, when I'm under load, at WOT producing max boost, the valve opens 100%, closes....done.
PSSSSSSSHHHHH!

If I were to OVER tighten the valve, this happens...60% open, close, 20% open, close, 10%, close...
etc. (OR the valve opens too late, both scenarios causing "flutterdump")
http://www.youtube.com/watch?v=jEUWEsqoWz8&NR=1&feature=endscreen

Every setup is different. The turbo, intercooler, bpv/bov all are variables in this. It's hard to describe
this unless you've experienced it, but bpv/bov adjustments can make a difference in your times around
an auto-x course. Sometimes the valve dumps too much boost by staying open too long. This of course
adds time before the boost is back at peak. HOWEVER, if you adjust the valve to be too constrictive
creating flutterdump, a pressure wave returns to the turbo and hits the compressor wheel (almost the
same thing as compressor surge that destroys turbos) causing a momentary (or in the case of compressor
surge, total) stall of the turbo. Not only is this hard on the turbo, but when this happens, it takes even
longer to get back to peak boost than if the valve dumped too much boost.

So, in the end, there are a couple valves out there that operate properly and make that noise at the same
time, but generally people don't have their valve adjusted properly, which causes this sound due to surge,
and that's not good for performance or turbo health.

 

[JuanSTI]

ok cool i always thought that flutter sound came from the intake