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Fluttering blow off valve

Guest barneyrubble

By Guest barneyrubble,
in Engines & Forced Induction

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TTT Grand Master

TTT

Posted
Posted

Dude..

Listen.

the fluttering noise is the air being chopped by the turbo blade.

it doesn't matter if there is a air filter or not. it is just the sound caused by the air having to go back through the turbo blade cause the BOV didn't open to let it out with a psshhh.

I just said air filter cause on most cars, you have an air filter (if you've got half a brain - without it, who knows what would end up in your engine).

but the sound is caused by the air being returned through the pipes to the turbo blades because the BOV didn't open to let it out during gear changes or when you back off from the throttle.

do you get me.?

If you look at a turbo's inlet blades, they are on an angle which when spun, sucks air inwards. so when the air in the pipes gets stuck and no bov to vent it out, it has to escape from somewhere and in goes back to the turbo and of course the blades are designed to suck air in and not blow out, this causes a weird fluttering sound as the air pushes through and gets chopped up.

huh??

Jay95R33 Grand Master

Jay95R33

Posted
Posted

GTST is right (from my experiences).

The fluttering is from air being forced back out through the turbo and back out the inlet track.

The adjustable BOV will make the noise only becuase they have been adjusted too tight, so they don't actually do anything with low boost - off throttle.

J

XrSiSt Grand Master

XrSiSt

Posted
Posted

:)

Fluttering noise = BOV tight = to hold high boost = releasing

at low rpm.

This is air being "chop" by the turbo impellors and sound coming

back through the air filter. If there's no air filter it will be more

likely be louder because the sound doesn't have to travel

through the piping and filter element.

Psshh = BOV = as we all know

Wastegate = release excess pressure produced by BIG turbo.

eg. set to it to 18psi and the more pressure produced by this

will be bleed through here.

If your all still in doubt, do this. Get an aftermarket vent BOV or

someone with one. Get them to tighten it all the way and tell

them to take you for a spin. Remember how many turns u do

so you know how much to wind it back afterwards. If your down

my way, i'll be happy to show you the difference.

Mine at low rpm doesn't have enough pressure to push the

spring in the BOV to make the psshhh... so it has no other option

but to go backwards hence makes the fluttering noise. When

enough boost is made, it goes psssh...

to make the pshhh... s

hitnrun Collaborator

hitnrun

Posted
Posted

Hey GTST,

True about the fluttering sounds, but you can also get a slightly different sounds depending on the BOV. Yes it is the sound of the blades "chopping" the air, but some BOV also can give off multiple, quieter, phssst noises, not the whoo whoop whoo noise that the air going throught the turbo makes.

If anyone wants to know what noise GTST is talking about, on Mario's site he has a video of a dyno run, I think it is the Supra 8thsin, can't remember, but it is a damn sweet noise, pity about the damage it can cause.

http://www.exvitermini.com

  • 4 weeks later...
Gerds Rising Star

Gerds

Posted
Posted

I have a wooshing sound now on my HKS SSq BOV after installing an Apexi pod with fibreglass partition. Under 3,000 RPM, there is just a wooshing sound. Past 3,000 RPMS and releasing the accelator quickly gets the wooosh sound. The wooshing sound under low boost is really annoying. How can i get rid of this? With the original air box and filter the BOV was not making a wooshing sound or a sound at all. I h8 the wooshing sound and thinkin of disconnecting the BOV.

Help?

inark Grand Master

inark

Posted
Posted
Originally posted by Gerds

I have a wooshing sound now on my HKS SSq BOV after installing an Apexi pod with fibreglass partition. Under 3,000 RPM, there is just a wooshing sound. Past 3,000 RPMS and releasing the accelator quickly gets the wooosh sound. The wooshing sound under low boost is really annoying. How can i get rid of this? With the original air box and filter the BOV was not making a wooshing sound or a sound at all. I h8 the wooshing sound and thinkin of disconnecting the BOV.

Help?

as far as im aware that wooshing sound is the actual filter it self isnt?

(dont slap me i have no idea and just regurgitate what i hear if it sounds right to me :D)

TTT Grand Master

TTT

Posted
Posted

If you disconnect the BOV, you will get a constant fluttering sound.. Sounds sort of like fffrrrrrrrrr sort of sound.

As you have read in the post earlier, this sound is not goot for the turbo in the long run.

if you don't like the low rpm whoosh, then you will have to remove that noce air filter pod you put on and put in the original one which keeps quiet.

Blitz Grand Master

Blitz

Posted
Posted
Originally posted by adam 32

it happens when you run without an air filter

have you seen the hard tuned imports video? when they run the cars down at central circuit they mke th flutter on thir burnout and you see an after shot of the engine bay, THERES NO AIR FILTER!

ITS THE BOV WHICH MAKES THIS NOISE!!

it is NOT the bov that makes that sound its the filter.... ps the HKS SSQV is a heap of sh-ite bov so steer clear of it

I believe Blitz is the best bov available on the market... but thats just my opinion:uh-huh:

Blitz Grand Master

Blitz

Posted
Posted

Hey Gerds... how did you go on Saturday? happy with the partition?

Answer is yes, if you put a lid on the partion you are effectively making it an air box which will conceal the pod filter and greatly reduce the induction noice including the fluttering which you will hear....

makes it more legal though which is a good thing.

Nicko

raist60 Community Regular

raist60

Posted
Posted

I can sort this out nice and easy.

Anyone here your pipes banging when you shut the tap of real quick?

SAME PHYSICS

Air flowing fast in one direction you let throttle snap close the air that was moving one way bounces off the throttle body butterfly going the other way back through the turbo causing it to slow quickly :D

Now i can say that this DEFINITELY does cause damage your jarring the entire wheel / shaft assembly in your turbo.

And people with BOVs do NOT get this noise. A BOV will vent when the throttle snaps shut thus releasing the air before it hits the butterfly in the throttlebody.

TTT Grand Master

TTT

Posted
Posted
Air flowing fast in one direction you let throttle snap close the air that was moving one way bounces off the throttle body butterfly going the other way back through the turbo causing it to SPIN BACKWARDS multiple times sort of jolting back and forth.

Almost true.

Only incorrect part of that is that the SPIN BACKWARDS bit.

The turbo will not spin backwards.

that sound is not the turbo spinning backwards.

It's the air getting chopped up by the turbo as it goes back through it.

A turbo blade will spin at over 100,000rpm easily.

There is no way that air can make that stop and go the other way.

If you look at the blades of the turbo, they are on a slight angle. As it spins, it causes the air to get sucked in in a swirling manner..

this causes a whistling sound as the air is sucked in.

Because the blades are on a certain angle to suck air in, when the air tries to go back out through the same gap, it gets chopped by the turbo blades. This is sort of like blowing air on to the back of a fan. It makes a frrrrrrr sort of sound.

But because between gear changes the turbo slows down a little until you hit the go pedal again, the frrrr sound is in slightly slower motion so it goes.. fffch ch ch ch (or what ever fluttering sounds like)

This compressed air trying to get out of the turbo blade will slow the turbo down more than if it hadn't gone through and this is why the theory is that it will cause premature death to your turbo, cause it is sort of like puting the brakes on rather than letting it slow down naturally, when the thing is spining up at 100,000 rpm..

ok?

TTT Grand Master

TTT

Posted
Posted

it will reduce it but it won't eliminate it.

Look at it like this.

The old config (with the standard air box)

you have a complately sealed (almost water proof) air box and a filter in it which flows OK but not very freely. then after all of that, there is a whole host of piping that is used for cold air.

You have removed all of that and added a large free flowing pod. So the induction sound is going to be much more. When you accelerate, you will hear the air being sucked through the turbo and when you change gears, it will make a whosh noise that you didn't hear before cause it was so muffled.

I don't think that puting a box around the filter will eliminate it. It might reduce it but I doubt it would eliminate it.

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