Flutter dump

[xenonkuraz]

I can't seem to get a straight answer on this one.

My current setup is using a hks ssqv and at low boost (<3000k revs) I get flutter dump. You can hear a bit of 'su tu tu' then 'psht'. It even happens in low vacuum.

However, when I go beyond 3psi of boost the bov dumps fully.

Is it normal for a ssqv to be doing this? my impression is that they're meant to open fully no matter what boost level.

I don't mind the sound just worried it may be detrimental to my turbo down the line...

[Riced_Civic]

ur not getting enough pressure to open the BOV

[connorling]

try to set the spring preload on the bov to softer, so it require less effort to open the bov.

[Jccck]

Basically i think your boost is forcing the BoV open, not having enough pressure to keep it open.. And it's fluttering.
This happens because the turbo is still spinning and making pressure, but not enough for a clean release.
Kinda hard to explain.. But it just opens a little bit and shuts. Has to happen a few times because you keep getting pressure in there.

I don't think you can adjust the spring on most BoVs?
If you are dumping properly from 3psi onwards you must have a very weak spring.
Mine doesn't stop fluttering until 7psi roughly.

You could either get a bigger BoV so the flutter will be shorter and quieter.
Or just plumb it back into the intake.

And to answer your question about turbo health.
BoV Flutter has nothing to do with Compressor Surge.
Your Boost is getting out the correct way, and your Turbo is safe my friend!

[mugen_ctr]

ur not getting enough pressure to open the BOV

BOV use Vacuum pressure to open em, not boost pressure :)


Basically your boost is forcing the BoV open, not having enough pressure to keep it open.. And it's fluttering.
This happens because the turbo is still spinning and making pressure, but not enough for a clean release.
Kinda hard to explain.. But it just opens a little bit and shuts. Has to happen a few times because you keep getting pressure in there.

I don't think you can adjust the spring on most BoVs?
If you are dumping properly from 3psi onwards you must have a very weak spring.
Mine doesn't stop fluttering until 7psi roughly.

You could either get a bigger BoV so the flutter will be shorter and quieter.
Or just plumb it back into the intake.

And to answer your question about turbo health.
BoV Flutter has nothing to do with Compressor Surge.
Your Boost is getting out the correct way, and your Turbo is safe my friend!

All bov like HKS, Tial, Greddy etc etc are adjustable... Just play around with the adjusting spring...

And agree about bov spring.. BUT on HKS SSQ they use a combination of spring and diaphragm which makes em one of best bov on market. Almost leak proof

BOV flutter is compressor surge! LOL... think about it, when its shut theres no were for the air to go, so it goes out back the turbo, creating that fluttering sound ;)

[XB-16-AX]

BOV use Vacuum pressure to open em, not boost pressure :)



All bov like HKS, Tial, Greddy etc etc are adjustable... Just play around with the adjusting spring...

And agree about bov spring.. BUT on HKS SSQ they use a combination of spring and diaphragm which makes em one of best bov on market. Almost leak proof

BOV flutter is compressor surge! LOL... think about it, when its shut theres no were for the air to go, so it goes out back the turbo, creating that fluttering sound ;)

Compressor flutter sounds is bad for your turbo, causes the pressure to go back to the compressor which will cause the comp wheel to spin awkwardly. Lol

S15 t28 turbos are common for this. Their either block off the bov or keep em tight closed. And they get that nice sounds of flutter almost like a screamer pipe.

But at the end, the longevity of the turbo will fail and you will get a loose comp wheel or worse fall off to your exhaust.

Not recommended.

[Jccck]

BOV use Vacuum pressure to open em, not boost pressure :)



All bov like HKS, Tial, Greddy etc etc are adjustable... Just play around with the adjusting spring...

And agree about bov spring.. BUT on HKS SSQ they use a combination of spring and diaphragm which makes em one of best bov on market. Almost leak proof

BOV flutter is compressor surge! LOL... think about it, when its shut theres no were for the air to go, so it goes out back the turbo, creating that fluttering sound ;)

But the BOV shuts because of no pressure to open it with.. So there's nothing left to cause Compressor Surge.. Until a millisecond later when the Turbo achieves pressure again and reopens the BoV.
Who knows?! I'd love a definant answer on this one.
But i'd have to think if there isn't enough pressure to open a BOV that is fully open at 3PSI, then there's not enough pressure to Surge.

I've got a TIAL 50mm Q Sports with 11PSI Spring, i know i can change the spring to a softer or harder one (6 8 10 11 12 are the avaliable iirc) but there doesn't appear to be any way to adjust it otherwise.
Atleast not a screw adjustment like my Wastegate has anyway.


Compressor flutter sounds is bad for your turbo, causes the pressure to go back to the compressor which will cause the comp wheel to spin awkwardly. Lol

S15 t28 turbos are common for this. Their either block off the bov or keep em tight closed. And they get that nice sounds of flutter almost like a screamer pipe.

But at the end, the longevity of the turbo will fail and you will get a loose comp wheel or worse fall off to your exhaust.

Not recommended.

So, is 'ALL' flutter caused by compressor surge?
And if so, how to eliminate it completely?
I'm running the recommended 11PSI spring based on my Vacuum level at idle being ~20In/HG.
Now i'm worried.. Haha.

[trism]

Wow. A lot of misinformation in this thread.

Let's get a few things straight first. Most of it will be obvious but I'm going to say it anyway.

1. 'Flutter' has nothing to do with the waste gate/exhaust and everything to do with the turbo/intake. In a system with no blow off valve, when you get off the throttle and the throttle plate closes, there is a whole heap of pressurised air between the turbo and the throttle body. All this air has to go somewhere, so it rushes back towards the turbo, which is spinning rapidly. As the air passes back through the turbine, it gets chopped up, which results in the characteristic flutter noise.

http://www.youtube.com/watch?v=DBb4YcfJCdQ&feature=youtube_gdata_player

Some people say it damages the turbine and others say it makes no difference.

2. A blow off valve has the job of giving this air somewhere to go. It either gets vented to atmosphere or vented back into the intake before the turbo. How it works is, when the turbo is boosting, the positive pressure in the manifold keeps the spring pressed closed, and when you get off the throttle, the intake manifold forms a vacuum which opens the BOV, venting the intake pipe.

BOVs have a spring that pushes down on the diaphragm the assist in keeping it closed, and resist it from creeping open under boost.

By tightening this spring up, what it does is stops the BOV from opening under low boost levels, and so gives this effect of flutter dump.

For example, let's say you're running 10psi. If your BOV spring is wound tight, it may not open until say, 5psi, so under low throttle loads, it won't open, it'll simply flutter.

The secondary effect of this is that under higher boost levels, when you get off the throttle, any air that is between the BOV and turbo just goes back into the turbo, and any between the BOV and throttle body goes out the BOV. This results in the flutter and dump sound you are referring to.

Make sense or would a diagram assist?

[mugen_ctr]

Compressor flutter sounds is bad for your turbo, causes the pressure to go back to the compressor which will cause the comp wheel to spin awkwardly. Lol

S15 t28 turbos are common for this. Their either block off the bov or keep em tight closed. And they get that nice sounds of flutter almost like a screamer pipe.

But at the end, the longevity of the turbo will fail and you will get a loose comp wheel or worse fall off to your exhaust.

Not recommended.

Just to correct... Regardless of what turbo u use, If u dont have any form of BOV than there will always be compressor surge, with out any form of circulation or valve to release the pressure when throttle closes, compressor surge will occur.....

And its a very debatable argument with compressor surge about damaging the turbo... Many guys have used no bov with no damage to the turbo in long period of use.

Screamer pipe = External gated waste gate pipe that vents into the atmosphere

[XB-16-AX]

Just to correct... Regardless of what turbo u use, If u dont have any form of BOV than there will always be compressor surge, with out any form of circulation or valve to release the pressure when throttle closes, compressor surge will occur.....

And its a very debatable argument with compressor surge about damaging the turbo... Many guys have used no bov with no damage to the turbo in long period of use.

Screamer pipe = External gated waste gate pipe that vents into the atmosphere

Thnx bud,

Its why i said s15 turbs are common for this. :)

Yes i knw what screamer pipes are and why i said it makes similar noises.

I used to have a 500hp GTR32 Vspec converted single T66 turbo with Tial x/gate, hks ssq2 bov all tuned on apexi pfc @ 25psi.

I knw all bout turbs, been there done that and over it... Hehe

But yes your responses are all correct bud. +1

[mugen_ctr]

Thnx bud,

Its why i said s15 turbs are common for this. :)

Yes i knw what screamer pipes are and why i said it makes similar noises.

I used to have a 500hp GTR32 Vspec converted single T66 turbo with Tial x/gate, hks ssq2 bov all tuned on apexi pfc @ 25psi.

I knw all bout turbs, been there done that and over it... Hehe

But yes your responses are all correct bud. +1

nice! always been a fan of single turbo GTR's, good to hear someone hear has experience in Nissans :D

Though i wonder, does compressor surge happen more often on bigger engine/turbo setup with high power like urs? ive numerous magazines about it but never really grasped why some bigger turbos suffer compressor surge

[XB-16-AX]

nice! always been a fan of single turbo GTR's, good to hear someone hear has experience in Nissans :D

Though i wonder, does compressor surge happen more often on bigger engine/turbo setup with high power like urs? ive numerous magazines about it but never really grasped why some bigger turbos suffer compressor surge

Thnx bud. I love my hondas as well as my nissans :)

Comp surges occurs more than so on any turbo that has increased boost levels higher than stock and no bov or blocked bov.

More common so on bigger turbos as most of them higher than a AR60 trim are mostly oil cooled only and not watercooled. Therefore more prone to heat and uses thrust bearings rather than bAll bearings.

Thats why once u start to upgrade to bigger turbos, they are generally made x/gated types due to comp surges and made for higher HP...

Hence cooling and tuning is a cruicial factor in boosted cars...the cooler the better. And the less lag the better.

[EKVTIR-T]

Thnx bud. I love my hondas as well as my nissans :)

Comp surges occurs more than so on any turbo that has increased boost levels higher than stock and no bov or blocked bov.

More common so on bigger turbos as most of them higher than a AR60 trim are mostly oil cooled only and not watercooled. Therefore more prone to heat and uses thrust bearings rather than bAll bearings.

Thats why once u start to upgrade to bigger turbos, they are generally made x/gated types due to comp surges and made for higher HP...

Hence cooling and tuning is a cruicial factor in boosted cars...the cooler the better. And the less lag the better.
http://deadhomersociety.files.wordpress.com/2012/01/lemonoftroy61.png

Tell us more

[XB-16-AX]

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Trollin in the hood...

:)







Srs
























http://oyster.ignimgs.com/wordpress/write.ign.com/65272/2012/03/You-Think-This-Is-A-Game-Cat-Meme-300x289.png


Gtfkdm8

[EKVTIR-T]

Huh? What game

My civic had very long pronounced flutter from its gt28 even with huge bov,I want to learn the why and how :)

[XB-16-AX]

Wow,






Sounds too good to be true.





http://swiftor.com/attachments/f7/10452d1330210107t-new-spiderman-meme-face-df790206-13e8-4c7b-9dd9-89dfc8c2ee0e.jpg

[senna]

I've never heard a blow off valve or flutter that sounded like a screamer...

[ericl33]

Wow,






Sounds too good to be true.





http://swiftor.com/attachments/f7/10452d1330210107t-new-spiderman-meme-face-df790206-13e8-4c7b-9dd9-89dfc8c2ee0e.jpg
http://www.profilebrand.com/funny-pictures/category/cats/608_stop-posting.gif

[mugen_ctr]

Huh? What game

My civic had very long pronounced flutter from its gt28 even with huge bov,I want to learn the why and how :)

IF wondering about the sound, comes down to how the piping is routed + length, turbo intake size and length... Alot of the drifters tend to use shorter piping with short turbo intake so it creates a more deep tone and shorter sound

On the muzza tek VL turbo, they tend to run a long turbo intake as it amplifies the compressor surge and noise

[EKVTIR-T]

IF wondering about the sound, comes down to how the piping is routed + length, turbo intake size and length... Alot of the drifters tend to use shorter piping with short turbo intake so it creates a more deep tone and shorter sound

On the muzza tek VL turbo, they tend to run a long turbo intake as it amplifies the compressor surge and noise
The pipe was about 500mm leading to pod

[DLO01]

I can't seem to get a straight answer on this one.

My current setup is using a hks ssqv and at low boost (<3000k revs) I get flutter dump. You can hear a bit of 'su tu tu' then 'psht'. It even happens in low vacuum.

However, when I go beyond 3psi of boost the bov dumps fully.

Is it normal for a ssqv to be doing this? my impression is that they're meant to open fully no matter what boost level.

I don't mind the sound just worried it may be detrimental to my turbo down the line...


As said the 'flutter' noise is the boosted air passing back through the turbo compressor blades when throttle off (butterfly closed) as the boosted air can only escape this way (no blow off valve). The concern with damage to the turbo is the pressure it puts on the turbos shaft/bearings as the air faces the compressor blades in the opposing direction. This causes a shearing affect on the shaft and therefore more pressure on the bearings. Its of course better not to have it then to have it, but really would be more of an issue higher rpm, with big boost and or larger turbos. Surge at low rpm I don't think there is much concern at all.

Most BOV's can act very similar as you've described. ie flutter at low rpm and no flutter and total blow off at higher rpm where boost is higher. It just comes down to the reaction time of the BOV. Most BOV's can be adjusted by the spring, so you can play around with it and see what suits best. As said though, it probably won't solve you early flutter issue, but again as said above, flutter at low rpm is not an issue. Its common for most diaphram/piston traditional BOVS act this way.

A BOV does not work just on boost or just on vacuum alone. It works BOTH on boost AND vacuum.

Explain:
Theres 2 'opposing' sides to a BOV. The boost side where the bov is connected to. Which is your intake pipe (before Throttle body). And theres the vacuum side usually connected to the top of the BOV, this is connected to the Intake Manifold (after the Throttle body). Both these connections work on a push/pull basis and oppose each other.

When your Accelerating in gear, foot down on the gass Butterfly is open right? The intake pipe side of BOV sees boost, lets say 8psi. What does the Vacuum side see? 8psi as well. Why? Because your foot is down on the gas and Butterfly is open. So you have equal pressure on both sides of the Throttle body. The BOV stays closed (which is what you want). Its because the 8psi in the intake piping is trying to push open the BOV (pre throttle body), but it can't because you have 8psi trying to keep it closed from the intake manifold (after throttle body) and also the spring. To sum up: In gear > on the gas > bov remains closed.

When your off the gas changing gears. Now that your off the gas, butterfly is now fully closed and you want it to blow off. But whats happening? The turbo is still spinning. Intake side is still boosted as the butterfly is now closed, so theres 8psi trying to push open the BOV. But whats happening on the other side of the BOV? now that the butterfly is closed it cannot see boost, in fact it now sees vacuum / negative psi, because the engine is still trying to suck in, but the butterfly is fully closed. So we have 8psi one side of the BOV and vacuum on the opposing side of the BOV. You have a push/pull affect. Pressure (push) on one side of the BOV and sucking vacuum pulling the BOV open. So the BOV fully opens and blows off.

If your interested Synapse makes a fast action BOV which does away with the delay of the traditional diaphragm design of every other BOV. See here:
http://www.phantasmusa.com/synapse-blow-off-valves.html

[XB-16-AX]

I've never heard a blow off valve or flutter that sounded like a screamer...

Watch out for modified VL calais turbos RB30 with external gate and screamer pipe combo will sound like a high pitched flutter.


http://www.youtube.com/watch?v=3B5bJPFh3Xc&feature=youtube_gdata_player








tru story mun..

[senna]

I disagree, dosing sounds like dosing, screamers sound like screamers.

[DLO01]

Is that supposed to sound like a screamer? Cause it don't if us spose to.

[senna]

http://www.youtube.com/watch?v=5JM5knbdDB0&feature=youtube_gdata_player

This is screamer

[XB-16-AX]

On idle and revving, there is no heavy load, therefore the boost will be below 8psi. If you have a hks ssq depending on the spring setting, the bov will remain shut (if spring is hard) which will cause the boost pressure to return back into the compressor housing which will then cause your internal/external w/gate to release this rather than the bov. Hence why u get the flutter sound put of the intake filter or screamer pipe.

But if your bov spring is not as aggressive, then you can hear this both in the filter or screamer pipe or bov - just all depends on boost pressure & boost load.


Ninja - your def right its a hard one to explain, as ive seen many forced induction cars and they all work differently and will also depend on quality of parts, engine components etc etc the list goes on aswell as the debate..


Lol

[XB-16-AX]

http://www.youtube.com/watch?v=5JM5knbdDB0&feature=youtube_gdata_player

This is screamer

I know this is also the sound of screamer pipe wthout the flutter.


But i have seen and experienced the screamer/ex gated combo and output that flutter sound

Keyword: Combo

V&E Rigolli & Queen St loves these setup..


Yallah performance... Lol

[EKVTIR-T]

http://www.youtube.com/watch?v=5JM5knbdDB0&feature=youtube_gdata_player

This is screamer
They sound crap I reckon

It overpowers everything,not to mention your ears if youre next to them

[XB-16-AX]

They sound crap I reckon

It overpowers everything,not to mention your ears if youre next to them

If u have heard this in the carpark of westfields parra on a thurs shopping nite,

There is a custom queen st vl turbo screaming shit out of the flutter X/gated combo in the carpark and its loud as fck... Lol

They love this shit.

[senna]

You do realise that air cannot pass through the compressor side of the turbo onto the turbine side right?

The wastegate has nothing to do with the intake or charge air. The wastegate controls the amount of exhaust gas that flows through the turbine housing, which in turn determines the speed of the turbo and the amount of boost created.

DL's explanation is accurate. The flutter is more apparent on smaller or highly efficient turbo setups because they spool quickly without a large amount of load.

The T28 is a small turbo so it only requires a small displacment engine to spool it quickly. I get a lot of flutter on my falcon since the GT3582R and 4L motor is a similar turbo-motor ratio

[EKVTIR-T]

Yeah but some bananas run screamer pipes on dailys

I didnt say it had anything to do with flutter :p

[senna]

Sorry I should've quoted XB16AX

[mugen_ctr]

As said the 'flutter' noise is the boosted air passing back through the turbo compressor blades when throttle off (butterfly closed) as the boosted air can only escape this way (no blow off valve). The concern with damage to the turbo is the pressure it puts on the turbos shaft/bearings as the air faces the compressor blades in the opposing direction. This causes a shearing affect on the shaft and therefore more pressure on the bearings. Its of course better not to have it then to have it, but really would be more of an issue higher rpm, with big boost and or larger turbos. Surge at low rpm I don't think there is much concern at all.

Most BOV's can act very similar as you've described. ie flutter at low rpm and no flutter and total blow off at higher rpm where boost is higher. It just comes down to the reaction time of the BOV. Most BOV's can be adjusted by the spring, so you can play around with it and see what suits best. As said though, it probably won't solve you early flutter issue, but again as said above, flutter at low rpm is not an issue. Its common for most diaphram/piston traditional BOVS act this way.

A BOV does not work just on boost or just on vacuum alone. It works BOTH on boost AND vacuum.

Explain:
Theres 2 'opposing' sides to a BOV. The boost side where the bov is connected to. Which is your intake pipe (before Throttle body). And theres the vacuum side usually connected to the top of the BOV, this is connected to the Intake Manifold (after the Throttle body). Both these connections work on a push/pull basis and oppose each other.

When your Accelerating in gear, foot down on the gass Butterfly is open right? The intake pipe side of BOV sees boost, lets say 8psi. What does the Vacuum side see? 8psi as well. Why? Because your foot is down on the gas and Butterfly is open. So you have equal pressure on both sides of the Throttle body. The BOV stays closed (which is what you want). Its because the 8psi in the intake piping is trying to push open the BOV (pre throttle body), but it can't because you have 8psi trying to keep it closed from the intake manifold (after throttle body) and also the spring. To sum up: In gear > on the gas > bov remains closed.

When your off the gas changing gears. Now that your off the gas, butterfly is now fully closed and you want it to blow off. But whats happening? The turbo is still spinning. Intake side is still boosted as the butterfly is now closed, so theres 8psi trying to push open the BOV. But whats happening on the other side of the BOV? now that the butterfly is closed it cannot see boost, in fact it now sees vacuum / negative psi, because the engine is still trying to suck in, but the butterfly is fully closed. So we have 8psi one side of the BOV and vacuum on the opposing side of the BOV. You have a push/pull affect. Pressure (push) on one side of the BOV and sucking vacuum pulling the BOV open. So the BOV fully opens and blows off.

If your interested Synapse makes a fast action BOV which does away with the delay of the traditional diaphragm design of every other BOV. See here:
http://www.phantasmusa.com/synapse-blow-off-valves.html

Looks awfully like direct knock off of HKS SSQ ;)

Heres how the HKS operates to give some ppl a better understanding... ive had one on turbo b4, sounds nice, and defs well worth the money, and i mean buying the original one lol

http://members.generationdub.com/footose/hksworks.jpg

[nigs]

Holy shit, 3 pages on "flutter"
Only OzHonda.

If it's that much of a concern then:
http://i123.photobucket.com/albums/o304/jonnnny28/IMG_0053.jpg

http://carphotos.cardomain.com/ride_images/3/1838/1921/29593460009_large.jpg

[Emnesty]

Holy shit, 3 pages on "flutter"
Only OzHonda.

If it's that much of a concern then:
http://i123.photobucket.com/albums/o304/jonnnny28/IMG_0053.jpg

http://carphotos.cardomain.com/ride_images/3/1838/1921/29593460009_large.jpg

wow that is a nice snail. would love to put one of these in my daily beat rush (toyota T18)

[mugen_ctr]

Holy shit, 3 pages on "flutter"
Only OzHonda.

If it's that much of a concern then:
http://i123.photobucket.com/albums/o304/jonnnny28/IMG_0053.jpg

http://carphotos.cardomain.com/ride_images/3/1838/1921/29593460009_large.jpg

http://www.myfacewhen.net/uploads/1297-problem-meme.jpg

And anyways u fail to see the bigger picture here....

[senna]

Holy shit, 3 pages on "flutter"
Only OzHonda.

If it's that much of a concern then:
http://i123.photobucket.com/albums/o304/jonnnny28/IMG_0053.jpg

http://carphotos.cardomain.com/ride_images/3/1838/1921/29593460009_large.jpg

I assume that because you linked pics of turbos with surge slot covers you are mistaken by what we are talking about being compressor surge, the flutter sound being discussed could be described as one form of compressor surge.

Compressor surge is when the turbo is being pushed past its normal operating RPM and it starts to "chop" the intake air and not pump it efficiently. The slots in the compressor housing allow turbulence to be created before the compressor wheel which in turn slows the intake air speed and allows the turbo to run efficiently.

Compressor surge can also happen when the motor cannot accept or i guess you could say "ingest" the amount of air the turbo is sending it. This results in the charge air "backing up" in the hotside pipes back to the compressor wheel which can cause a noise that kind of sounds like a half open blow off valve...

[nigs]

Are you saying it doesn't aid in the reduction of said "flutter" at all?

[mugen_ctr]

Are you saying it doesn't aid in the reduction of said "flutter" at all?

It aids in the reduction of compressor surge, there are few ways to combat compressor surge

What many say an hear is common compressor surge as they dont wanna use BOV or have BOV set to open at set level boost... When u start talking about turbo compressor surge, as in what senna has described, its a different thing... especially when ur chasing power, its the last thing u want to happen... really robs u of power... though ive never really experience it as bad as the youtube link, any form of compressor surge to the turbo isnt what u want as it creates a form of unstable air flow, hence why ALL manufactures equip there cars with recirculating bov


http://www.youtube.com/watch?v=nCj6Spwl1CU&feature=player_embedded

[nigs]

Didn't answer my question.

Are you saying it does nothing for "flutter" ?

[mugen_ctr]

Didn't answer my question.

Are you saying it does nothing for "flutter" ?

LOL... Flutter = Compressor surge... So yessss, having that type of compressor housing, or anti surge housing will remove it... BUT as ive said, having no BOV to induce compressor surge isnt ideal, but having compressor surge occurring whilst driving is much much worse...

IF u dont want compressor surge because u didnt have a bov on, whack on a OEM Skyline GTR bov, and plumb it back into the turbo intake..... why? because OEM cars dont have any form of compressor surge :)

[nigs]

Yeah, regardless of what the primary purpose of those compressor housing are.
So no, I was not mistaken into thinking "flutter" was compressor surge. The 2 are different but the ported housings can be applied to both.

I never implied or suggested "flutter" was surge or otherwise.

[XB-16-AX]

http://www.wiichat.com/forum/attachments/anime-lounge/8648d1311055173-hanamaru-kindergarten-plz-stop-post.jpg

[senna]

Didn't answer my question.

Are you saying it does nothing for "flutter" ?

I'm saying that the flutter the guys are talking about has more to do with BOV selection and not turbo housing design or wastegates.

Surge slot cover equipped turbos will still suffer from this flutter since compressed air is still pushing against the compressor, or more specifically the exducer blades.

Namsayin...lol

[trism]

And this is where all the confusion comes in.

The term "compressor surge" must be used exclusively for what we see in the video of the R33 above.

The lack of BOV resulting in the typical sound when you get off the throttle is called flutter or dose. It has never been called, and never shall be called "compressor surge"

[EKVTIR-T]

And this is where all the confusion comes in.

The term "compressor surge" must be used exclusively for what we see in the video of the R33 above.

The lack of BOV resulting in the typical sound when you get off the throttle is called flutter or dose. It has never been called, and never shall be called "compressor surge"

So what is actually producing the flutter sound?

[mugen_ctr]

And this is where all the confusion comes in.

The term "compressor surge" must be used exclusively for what we see in the video of the R33 above.

The lack of BOV resulting in the typical sound when you get off the throttle is called flutter or dose. It has never been called, and never shall be called "compressor surge"

disagree here, there all just nick names for the same thing "compressor surge", so does GFB and few other BOV manufactures... dose/flutter same thing as compressor surge, its been explained previously....

http://gfb.com.au/images/stories/downloads/gfb_dp_compressorsurge.pdf

[trism]

So what is actually producing the flutter sound?

Are you talking about the flutter when you get off the throttle?

I explained it earlier in this thread.

Rather than going out the BOV, it rushes back at the turbo, because it has nowhere to go since the throttle plate shut, where it gets chopped up and makes that noise.

[trism]

disagree here, there all just nick names for the same thing "compressor surge", so does GFB and few other BOV manufactures... dose/flutter same thing as compressor surge, its been explained previously....

http://gfb.com.au/images/stories/downloads/gfb_dp_compressorsurge.pdf

Yeah, and they're doing nothing to help the confusion. As we already know, there is a very distinct difference between "compressor surge" at full throttle, full boost, and flutter/dose when you are getting off the throttle.

[XB-16-AX]

Are you talking about the flutter when you get off the throttle?

I explained it earlier in this thread.

Rather than going out the BOV, it rushes back at the turbo, because it has nowhere to go since the throttle plate shut, where it gets chopped up and makes that noise.


i think i mentioned this earlier in my posts.. Well something along the lines of compressed air or wasted air going back to the turbo if the BOV is too tight which will cause this flutter via the wastegate/screamer pipe.


Simple: if u dont like the flutter bov sound then buy a plumpback bov.

But if u like shitloads of noise then buy a trumpet bov and add a screamer pipe for the extra noise.

Bear in mind that if the spring on the bov is too tight then u will experience a flutter sound rather than a loudass whooosh...

Nomsayin?

[EKVTIR-T]

Its not via the wastegate/screamer at all.

The flutter is produced from the throttle closing causing a pressure wave against the compressor blades and sounding out via the intake pipe


Axi-symmetric stall, more commonly known as compressor surge; or pressure surge, is a complete breakdown in compression resulting in a reversal of flow and the violent expulsion of previously compressed air out through the engine intake, due to the compressor's inability to continue working against the already-compressed air behind it.

[trism]

[/b]


i think i mentioned this earlier in my posts.. Well something along the lines of compressed air or wasted air going back to the turbo if the BOV is too tight which will cause this flutter via the wastegate/screamer pipe.


Simple: if u dont like the flutter bov sound then buy a plumpback bov.

But if u like shitloads of noise then buy a trumpet bov and add a screamer pipe for the extra noise.

Bear in mind that if the spring on the bov is too tight then u will experience a flutter sound rather than a loudass whooosh...

Nomsayin?

Nope, I don't know what you're saying, because its incorrect.

The waste gate is on the exhaust side. The flutter/compressor surge comes from the intake side.

They are totally unrelated.

[XB-16-AX]

Its not via the wastegate/screamer at all.

The flutter is produced from the throttle closing causing a pressure wave against the compressor blades and sounding out via the intake pipe

Flutter can occur in two ways.

1) slight throttle response then release. The hot pressurised air from the turb -> passing the IC -> cold air to the TB. If the throttle was eased off whilst air was travelling then this cold air should release gently out of the BOV causing a flutter as the boost levels are low.- not enuf to fully open or release air to the bov.

2) the other flutter is same as above but before the hot air reaches the IC. This hot pressurised air will travel back to the Turbo compressor which will then in turn cause the wastegate (internal) to open/close releasing this hot air out to the dump pipe.

In an external gated scenarios - the pressurised air will be released out via screamer pipe.

Yet again, this will depend on how much boost you are running before you decide to ease off the throttle pedalstool.


The reason why u can hear the flutter noise from the filter is because the air is pressurised and is chain of parts that works together.

If u get a 2nd person to listen for a flutter noise from the IC - u will notice and hear that same flutter from all the above locations simultaneously. Try it.


Tru story mun.

Its logical man.

[XB-16-AX]

Nope, I don't know what you're saying, because its incorrect.

The waste gate is on the exhaust side. The flutter/compressor surge comes from the intake side.

They are totally unrelated.

My response on other post.

Flutter occurs both in exhaust housing and compressor (intake) pressurised air.

Turbos work all in unison - its a chain of pressured air that increases output power. All has to work together not just 1 side of the hot vs cold pressured air.


Nomsayin

[senna]

OK, i don't think you are getting it.

http://www.wrx.com.au/denis/turbo/65z4187.jpg

See in the picture how the air does not flow through the turbo from inlet to exhaust?

The screamer pipe is attached to the external wastegate, which is generally mounted to the exhaust manifold or the turbine housing of the turbo.

http://inlinethumb16.webshots.com/31887/2344531400064171239S425x425Q85.jpg

http://sphotos.ak.fbcdn.net/hphotos-ak-ash1/hs547.ash1/31976_407737283549_612643549_4289194_5502043_n.jpg

The wastegate only opens when the desired boost level is achieved and the exhaust gas is bled off away from the turbine housing. This is why in the Video i posted last night you here the screamer pipe as the car comes on to boost.

Again, a screamer pipe has nothing to do with flutter.

[trism]

Flutter can occur in two ways.

1) slight throttle response then release. The hot pressurised air from the turb -> passing the IC -> cold air to the TB. If the throttle was eased off whilst air was travelling then this cold air should release gently out of the BOV causing a flutter as the boost levels are low.- not enuf to fully open or release air to the bov.

2) the other flutter is same as above but before the hot air reaches the IC. This hot pressurised air will travel back to the Turbo compressor which will then in turn cause the wastegate (internal) to open/close releasing this hot air out to the dump pipe.

In an external gated scenarios - the pressurised air will be released out via screamer pipe.

Yet again, this will depend on how much boost you are running before you decide to ease off the throttle pedalstool.


The reason why u can hear the flutter noise from the filter is because the air is pressurised and is chain of parts that works together.

If u get a 2nd person to listen for a flutter noise from the IC - u will notice and hear that same flutter from all the above locations simultaneously. Try it.


Tru story mun.

Its logical man.


LOLOLOLOLOLOLOLOLOLOOLOLKOKLKOLLLLLLOLOLOLOLOLOLLO OL

Seriously dude. You've got the completely wrong idea about how turbos work.

[XB-16-AX]

if i can only draw what im trying to say/explain ... LOL.

ive learned information info here guys. thnx

all good were all entitled to opinions and comments. :p

[trism]

but that's the thing dude.

You're trying to say that the air charge goes out the waste gate dump pipe. But it doesn't. It doesn't go anywhere near it.

[XB-16-AX]

but that's the thing dude.

You're trying to say that the air charge goes out the waste gate dump pipe. But it doesn't. It doesn't go anywhere near it.

ill try to explain it here and my editted dodgy pic.. lol

i know there is no way that the air can travel between the comp wheel to the exhaust wheel (internal gated release valve). (CIRCLED IN RED)

im talking about the unused pressured air marked in Orange box which relates to my example before (2) air filter..

then the yellow box relates to my example (1) (BOV - green circle)



its ok mun, your prob right .. i could be getting all confused from being in the turbo scene for 10+ yrs and have owned/build high powered turbos.

juzz sayin :)

[trism]

OK. I understand what you're talking about. Some of the air goes out the BOV and some goes back through the compressor wheel, making the flutter noise.


But you are using the term waste gate and screamer pipe when they have nothing to do what we are talking about.

Also, don't try and fxuking big note yourself and talk about how long you've been in the scene.

I know xunts that have been in the modified car scene for 30 years and still don't understand shit. It's all right not to know everything, you've just gotta admit it

[XB-16-AX]

OK. I understand what you're talking about. Some of the air goes out the BOV and some goes back through the compressor wheel.


But you are using the term waste gate and screamer pipe when they have nothing to do what we are talking about.

Also, don't try and fxuking big note yourself and talk about how long you've been in the scene.

I know xunts that have been in the modified car scene for 30 years and still don't understand shit. It's all right not to know everything, you've just gotta admit it

Thnx mun.

Yeh i just prob got confused with the terminology and shiet.

Nah no big note. Just saying incase people think im a troller or 101% dont know shiet.


Nomsayin?




Regards

Ryan
xoxoxox

[Jccck]

Nomsayin?

I think you need to stop saying 'Nomsayin' personally.
And holy hell i had to re-read this thread twice to make sure i wasn't corrupted by any of the Screamer Pipe nonsense (And i feel like a total jerk saying that word in a thread about Flutter and further confusing the issue)

Plenty of info here though, some is good.. Some is alright i guess.
But i still don't understand this;

I've got a TiAL Q Sport 50mm BoV.. 11PSI Spring (Which is the correct pressure based on my In/HG Vaccum at Idle) And i'm running Wastegate Spring of 9PSI (Gauge confirms 9 also)
So my car goes 'Flutter Flutter Flutter Chhh" when i get off the gas mid-throttle.
And at WOT/Full Boost it's a quick "Chhh"
Yet at low RPM (less than 3000, my turbo isn't even making boost yet?) it has a very quiet and slightly slower "Chhhh" noise (No flutter that i can hear though!)
Kinda suggests i have enough pressure/vacuum in combination to open the BoV enough to let the air out.
So if it happens as it should at low rpm/no boost and high rpm/full boost.. Why not at mid rpm/mid boost?

And it's said here that if i don't like the flutter.. Install a Plumbback?
TiAL BYPASS 50mm BOV is the choice, with 11PSI Spring and 1.5" Outlet.

But what i don't understand is.. How changing my BOV to the Plumbback will STOP the Flutter?
Or doesn't it stop it? It just stops the noise because it's all fed back into the intake?
So i still have this 'flutter' but i just can't hear it?

If that's the case.. Is it impossible to stop the flutter when i get off the pedal at a mid-RPM / mid boost level?
Ofcourse i'm talking within reason, because if i put a 6PSI Spring in my BoV it would just open.. But it wouldn't suit the Vacuum and the BOV may creep open during high boost? So that's out of the question.

[DLO01]

Depending on the type of plumback, you'll still get the flutter. We are still talking response time of the Bov, so depending, you'll still prol get it. On the other note, a plumback is supposed to make the blow off quiet. But contrary to popular belief, this also is not always the case and you'll hear the blow off as well. In this case though the sound instead of going directly from bov to atmosphere, it goes bov, plumback pipe, intake pipe and then sound out the intake arm (pre turbo) and out the filter. The sound is less that if 'directly' to atmosphere of course, but you can hear it noticably. This really depends on your (mainly on custom) setups, bigger pipe sizes and shorter lengths. Of course on a OEM turbo setup, you cannot hear the bov blow off cause of the narrow pipe sizes, mazes of pipes, lengths and the effort to 'design' out the noise emission.

[Jccck]

Alrighty, well the pre-turbo intake is very short and sweet.. Airbox top is mounted on a custom base too (Rather high flow, lmao)
Legality is moreso what i'm aiming for, and if the sound is muffled a fair bit then it's a win also.

From what TiAL says, these BOV's are extremely responsive.
And the control hose to the Intake Manifold (Using the PCV Inlet) is absolutely huge (5/16th ID iirc?)
Guess i'll find out when it arrives and i install it.
Cheers!

[mugen_ctr]

Depending on the type of plumback, you'll still get the flutter. We are still talking response time of the Bov, so depending, you'll still prol get it. On the other note, a plumback is supposed to make the blow off quiet. But contrary to popular belief, this also is not always the case and you'll hear the blow off as well. In this case though the sound instead of going directly from bov to atmosphere, it goes bov, plumback pipe, intake pipe and then sound out the intake arm (pre turbo) and out the filter. The sound is less that if 'directly' to atmosphere of course, but you can hear it noticably. This really depends on your (mainly on custom) setups, bigger pipe sizes and shorter lengths. Of course on a OEM turbo setup, you cannot hear the bov blow off cause of the narrow pipe sizes, mazes of pipes, lengths and the effort to 'design' out the noise emission.

Adding to this, if u ever driven a Stock evo/S15/GTR/Wrx etc etc... u will barely notice it, infact when i last drove my brothers old car, s15, i really didnt notice it at all :/

Alot of stock BOV are designed to leak on low level boost as it makes it easier to open... I remember modding a stock GTST bov to stop it leaking on low boost... well to say, it did work... but it was hella cheap ahahaha...

IMO, if u want a good BOV, stick to OEM bov, either weld on a flange an wack it on or do some other way, aftermarkets aint designed for DD, hence why its RACE/RALLY use only.

[xenonkuraz]

Wow I've started a great debate here. Didn't mean to get an education on flutter/compressor surge/screamer pipes/etc. I just wanted to know why my SSQV being a SEQUENTIAL valve would STILL flutter at LOW rpms (sorry sticky caps lock button :D)

I'm used to it now and it doesn't bother me as much and weirdly...

it now only flutters on COLD STARTS

when the car is warm it will VTA 99.99999999% of the time even if I'm hitting .01 bar boost.

Thanks to everyone for the friendly and intuitive replies.

I learnt a fair bit going through the pages, especially the difference between flutter and compressor surge. That video really helped (never heard such a noise before).