Moderators: IMOC Moderators, IMOC Committee Members
(First video, aint looked at the second) Most cars will do that, It's just playing with the throttle... Just looked at the second vid.... Thats more like it 
(still not a pigeon though 
) The AFM and filter will only deaden some of the noise, but it doesn't mean its not happening. I have the AFM on my car and I was getting flutter with the stock bov and a cone filter. I guess it could depend on how loud other components of your car are as to wether you hear it or not.
***RIP Car13 ****** Now in an Evo ***cantfindausername wrote:I do agree with Matt, the air has to go somewhere.
Right take your bov off and block it up (just like i did) Metal plate 2 holes drilled and a gasket, Bolt the plate where the bov was and take your car for a run (just like i did) You will get nothing. But its nothing you can call proper full on chatter.***RIP Car13 ****** Now in an Evo ***cantfindausername wrote:One way to test the theory would be to put your hand infront of this bad boy.
http://www.youtube.com/watch?v=Y4Eme4GGXwA&NR=1
Spittinflames wrote:You ask that question like im telling a lie
No no not at all Sorry it wasn't meant to sound like that 
, I just wondered where all the air goes, and if it goes back through the turbine blades why it made no noise etc lol 
Greddy-Matt wrote:Spittinflames wrote:You ask that question like im telling a lie
Ive got sound clips of mine fully screwed in, ill post them up, i get no venting at all but a LOT of turbine noise, it doesnt sound very nice tho
It's all good i was only havin a laff 
... If i tighten the dump valve all the way then it does nothing, but its still boosting at 1.3 bar so wheres all that pressure going? In fact its bugging me so im gonna grab a camera and go out for a spin with it fully tight.... see what happens I shall return with a vid ](./images/smilies/eusa_wall.gif "Brick wall"){kind=small}
= air deflecting off the CLOSED TB and back through the 'Still foward flowing' compressor fins! the Flutter / pidgon / mutant lesbian octapus Noise or what ever people want to call it , is the noise of SURGE!! Its NOT the DV, BOV, WG !!! as the air rebounding off the TB will have nowhere to go except back the way it came. Setting the spring to its softest setting will make the LEAST noise! as the valve's spring will have little tension to resist the escaping boost air! .. If the car is running uprated ammounts of boost / larger turbo, then when the BOV opens ,the inlet pressure will instantly drop causing the bov to shut -but the turbo will STILL be in Compress mode &it will cause the inlet pressure to rise again almost instantly thus-Re-opening the BOV ... imagine it opening and closing really fast like a strobe light.. This will make your pidgon noise as each time the BOV shuts, surge occurs,and when it re-opens , it amplifies the sound!! you could remove a turbo from a car, rig it up to a household hoover and still get it to make that noise!!RyanRs wrote:
Why is it soooooooo god dam hard to understand!!! jesus! its soo dam simple people!!!
Surge
If the BOV spring is set to the position of maximum spring tension then it will act like blocking off the BOV altogeather and will cause the MOST SURGE NOISE!
Remember.
Both thoes 2 sound clips are EXACTLY THE SAME THING!!
.. Could you please explain then why when my bov is wound all the way tight i get no noise, I've even blocked it off as an experiment. I've taken a video as promised, will put it up tommorow now as i cant be ar$ed today. In fact the noise it does create sounds quite bad, its certainly not a flutter.Spittinflames wrote:RyanRs wrote:
Why is it soooooooo god dam hard to understand!!! jesus! its soo dam simple people!!!
Surge
If the BOV spring is set to the position of maximum spring tension then it will act like blocking off the BOV altogeather and will cause the MOST SURGE NOISE!
Remember.
Both thoes 2 sound clips are EXACTLY THE SAME THING!!
That all sounds very interesting.
Blocking off the bov or setting it to tight does not cause flutter.
I wonder if the AFM is acting as some kind of stop?
This is proper flutter http://uk.youtube.com/watch?v=w3TqIOVhc ... re=related
the same noise what i posted ..... that is the way every turbo car/van/lorry/bus/boat..... works..!! i had to drive some small 7.5tonne lorry thing the other day that made exactly the same 'Fluttering' noise as that 200sx did. -and as hellboy said, that noise is the same fluttering as in the clips he posted!'fluttering' noises ..yes.. but this is down to many things...like, turbo positioning,turbo type, make, Psi its hitting,spring tension on the BOV/DV etc. for example A top mounted gt35r will be louder than a bottom mount purely because its not tucked down the back of the engine near lots of heat proofing and sound deadening etc.. -check out nathan's drag run..listen to the turbo chatter on that when he does his burnout!! . Tbh tho, im a rev 3 owner and therefore not played with the MAF sensor on the earlier ones...did someone mention there is a butterfly in there?? - exactly the same as this EFI RS Turbo: My cossie had an enormous Ram Air foam effort, and the noise was epic. Switched over to a small K&N and it was much quieter and far less high pitched.(the one in the abpve example uses the EFI setup from the Fiesta) because it has a metering unit in the inlet. In much the same way as the AFM operates on a Rev1 and Rev2, at closed throttle, it acts as a solid baffle, completely dampening any sound that might emerge, which is why it will near silent. What we're talking about here is more stall than surge, as the turbo isn't surging as you are on closed throttle. ON throttle compressor surge is a very bad thing! If you've ever heard a incorrectly specced big turbo car on track that hasn't had it mapped out, or the wrong choice of cam etc, you'll know what it sounds like. It happens when the turbo overspeeds and backs off repeatedly on throttle under boost. Don't think anyone had picked up that we were actually discussing compressor stall, not surge. ***RIP Car13 ****** Now in an Evo ***- i didnt want to put up a new topic...- because of the AFM.... ?? half air goes to the air half comes back to the inlet - or whatever u set it up 4 ????***RIP Car13 ****** Now in an Evo ***, the ricirc valve works best, if you vent to Atmo its just wasted energy your allowing the car to vent. , when you re circ it returns to inlet path under force and makes throttle response that little bit quicker.