Flutter dump

[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.

Tell us more

[XB-16-AX]

Tell us more

Trollin in the hood...









Srs



























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.

[senna]

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

[ericl33]

Wow,






Sounds too good to be true.

[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.










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.