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Stupid Flutter

R34NRG

By R34NRG,
in Engines & Forced Induction

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R34NRG Grand Master

R34NRG

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even better chuck on the std BOV, they're pretty good until you start running high boost levels.

maybe i got something diff but what ever i removed to install the aftermarket BOV never made any sound. all i ever herd was the turbo whine

govich Community Regular

govich

Posted
Posted
OMG - The flutter sound does not come from the BOV....It just means your aftermarket BOV is set too tightly and most of the air is reversing back through the turbo getting chopped up by the impeller hence the 'flutter' sound...You couldn't hear it b4 because your airbox muffled the sound.

Sure? I wanted to confirm what was making this noise the other day and watched my blow-off valve open and close repeatedly after opening the throttle small amounts and then closing it. The flutter was coming from the blow-off valve, and it makes sense from an engineering point of view.

Lowering the spring tension would allow the valve to open completely at lower pressures and not 'bounce' between open and closed. That might fix it for you.

Primordial Grand Master

Primordial

Posted
Posted

I've currently got no BOV at all (blocked off the hole in the intake), I can still hear the psshht and then flutter. Is the sound of the air 'blowing off' just the rush of air coming back out the pod?

govich Community Regular

govich

Posted
Posted (edited)

What i'm saying is it's not necessarily air running back through the intake (if you have a BOV). Primordial in your case it'll just be air rushing back and doing funny things :happy:. You can check for yourself though, just pop the bonnet, rev your car and see if you can feel air coming out of the filter and match it to whatever noise you hear.

Edited by govich
chrissso Proficient

chrissso

Posted
Posted

This is basicly what ^ said with some instructions.

Make sure car is off... Take off the blue hose from the BOV and undo the bolt with the red circle around it one revolution. Then reconect the Blue hose. Start car and test. Repeat all steps until you are satified.

post-19015-1154349934.jpg

chrissso Proficient

chrissso

Posted
Posted
Sure? I wanted to confirm what was making this noise the other day and watched my blow-off valve open and close repeatedly after opening the throttle small amounts and then closing it. The flutter was coming from the blow-off valve, and it makes sense from an engineering point of view.

Still caused from a surge buddy. Noise comes from pod and sometimes bov.

govich Community Regular

govich

Posted
Posted
Still caused from a surge buddy. Noise comes from pod and sometimes bov.

My blow-off valve bounces between open and closed (this is visually obvious), air comes out of it and this makes a fluttering noise. There is no other audible fluttering or whooshing associated with the air, from the pod or otherwise.

satanic Grand Master

satanic

Posted
Posted

Flutter is NOT caused by the BOV! I had no BOV for a month, fluttered like no tomorrow... Now I've got the stock BOV back on (with some mods) and I get both the flutter and PSSSSSHHHHTTT

Jeeez; it's just a sound!

govich Community Regular

govich

Posted
Posted
Flutter is NOT caused by the BOV! I had no BOV for a month, fluttered like no tomorrow... Now I've got the stock BOV back on (with some mods) and I get both the flutter and PSSSSSHHHHTTT

Jeeez; it's just a sound!

OK.

With the stock blow-off valve on, my car does not flutter. At all. Ever.

With the aftermarket atmospheric-vent blow-off valve, the car flutters on trailing throttle or after closing the throttle after light openings. I have visually confirmed this sound as coming from the blow-off valve bouncing open and closed.

If the throttle is closed after being open wide, the blow-off valve dumps completely and there is no flutter. At all. Just whoosh.

How is the noise (in my car) not coming from the blow-off valve bouncing open and closed?

I'm not posting about this again :cheers:.

Modena Grand Master

Modena

Posted
Posted (edited)

I had the exact same GFB BOV and it fluttered even thbough all pipes were connected and closed off. The flutter IS due to ur BOV. Read the manuell, it says flutter at low rpm is normal, u can probably eliminate is by following the advice other guys gave u.

Edited by Sir-D
CSNet Collaborator

CSNet

Posted
Posted (edited)

An aftermarket BOV is probably a lot tighter than your stock one. Fluttering at low RPM would occur because the blow of valve would not open at lower revs/boost, thus the air going back through the intake (as in going back against the turbines spinning direction, shopping the air), amplified by your FMIC and pod and wellah, flutter for you.

A blow of valve can help effect it, but it doesn't directly make the noise. Forgive me if it doesn't make sense, I need sleep :cheers:

More info:

http://www.nissansilvia.com/forums/index.p...60&hl=stock

Edited by ReeceR
Baz Experienced

Baz

Posted
Posted

Ok I'm going to settle this once and for all..

The fluttering you here is the pressure created by the turbo changing directions and flowing back through the turbo when the throttle snaps shut. The factory BOV's have a weak spring to let through air at idle so that fluttering does not occur. This air recirculates from the cross over pipe and goes through a pipe which is realeased in front of the turbo again. Disconnect this pipe and vent the factory BOV to atmosphere and you will create a idling problem on the car. You will NOT have a true turbo flutter created through a aftermarket BOV. The only time it will create a noise like a flutter is if the spring is stuffed in the BOV or if the BOV is created to make a similar noise to a flutter.

It sounds to me like you BOV is way too tight, loosen it off and it will fix it. You cant hear a flutter through a air box so hence why you couldnt hear it before.

ODessA Collaborator

ODessA

Posted
Posted (edited)

guys isnt the flutter the sound the air going back and forth between the throttle body as it snaps shut off throttle and the turbo, and the sound is heard once u get a pod, stock intake u cant hear it.

there is bovs that also make that noise or similar noises but they arent compressor surge they are just noise the bov makes instead of compressor surge

hence the reason of getting a bov.

most cars with aftermarket bovs will have to set how lose or tight they are, if they are too tight u will get compressor surge, too lose and u could leak boost depending on the bov and the boost level.

generally to get it right u need to find a setting somewhere inbetween where on low psi u get the flutter because its not enough pressure to open the bov generally below 7psi or so and that on higher boost over 10psi etc the bov opens and no compressor surge, no back pressure on the turbo it keeps velocity and u dont lag as much between gear changes.

i could be wrong but i dont think i am, would like to be corrected if am.

Edited by ODessA
sloutch Mentor

sloutch

Posted
Posted

If i'm not wrong, the flutter is commonly caused when the air goes back into your turbo fins.

Without a BOV installed, u'll get the flutter all the time. With a BOV, you will get both the flutter ( at lower RPMs ) and most of the time u'll hear the BOV sound that's IF it's an atmospheric BOV. If it's plumback BOV, u'll hear the flutter too.

Anyone care to input their knowledge? :cheers:

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