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=DBb4Y...e_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

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

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.