Fluttering blow off valve

[Guest barneyrubble]

Ive heard plenty of turbo cars with with bov's that flutter, what are these and who makes these, are there disadvantages of this type. Ive seen no advertisements for this type.

Does anyone know?

[hitnrun]

Hey BarneyRubble,

Correct me if I'm wrong, but I was under the impression that cars that do that either are letting the accelerator off before full boost hence not enough pressure to hold the BOV open the whole time,

EI. opens releases pressure, closes, pressure builds up slightly again, opens etc. That's why the sounds dies down.

From my experience with EXA's and Silvias, usually because the BOV is adjusted incorrectly. If it was tightened more, it wouldn't open until it was able to hold it long enough to let all pressure vent off.

Also you can get funny noises from air travelling backwards through a pod filter.

Cheers

[PranK]

true.

My BOV doesn't open til about 5 or 6psi under load, so it flutters at low rev gear changes etc...

my pulsar was running 16psi and no BOV, it had a straight metal pipe from air filter to turbo and it made a fantastic high pitched flutter - it was AWESOME! a few of the dudes on here have heard it.

[Jay95R33]

My R33 used to do it too, until one day I noticed that my stock BOV had been blanked off so it wasn't being used.

That fluttering is sometimes air being pushed back passed the turbo and out the filter :eek: :eek:

Not really a good thing

[Guest | hype^ |]

dam right it aint a good thing..

wont that stuff ur turbo prank?

i heard its really bad for it..

[XrSiSt]

So the question remains... how much do u adjust it to get the

most life out of your turbo?

[PranK]

all the people i have spoken to about it have told me that unless you are running mega boost (18 and upwards) it wont be doing much damage to your turbo... i am only running 9psi, its all good.

if i kill the turbo, i get a T04, easy!

[initialD]

so fluttering hurts turbos?????

when i got my front mount done....my trust bov flutters alot,

took it for service, told me my BOV wasnt tightning enuff

shud i buy a new 1????

[TTT]

I can answer this..

The flutter is not coming from the valve..

I have a R32 GTST (as in the picture)

It has a SARD R2D2 racing BOV.

I also have a pod filte..

No other mods.

The BOV makes a normal PSSHHHHH sound.

If I am driving along and say in 3rd gear I put my foot down and the boost goes up to 7 psi and I back off but not right off the throttle, I get a light fluttering sound... this is because the throttle partially closes the butterfly valve and the compressed air turns back and goes back through the intercooler and through the turbo blades.. causing a sound that sounds like you are blowing air on to a fan.. like a frrrr sort of sound..

On tuesday I got a FRONT mount intercooler put on.

This cooler is about 3 times the size of the standard unit and because it is front mounted and the inlet and outlet are on either side of the intercooler, there is haeps of extra piping.

Now. When driving in the same situation as above.. 3rd gear and getting to about 7 or whatever psi then backing off partially, the fluttering noise that is caused by the bov not opening is excellent.

it is much louder and sounds sort of like ssssch ch ch ch ch..

If I back right off the throttle i still get the normal psshhh sound.

The BOV I have works perfectly and I doubt that I am causing any damage because it only hapens at like 5 psi or whatever..

The reason this gets louder with the front mount is because there is extra piping to be filled with air and at standard boost, with the new longer pipes, there is less pressure in there and so the BOV does not open as easy as it used to..

But like I said, it will open and give a psshh sound if I drive normally and change gears.. even at like 2 psi..

I hope this explains it.

If anyone wants a presentation, just ask.. I'll take you for a quick spin.

[TTT]

By the way..

One of my previous cars was a 1987 4wd Ford laser Tx3.

It was an EX-RALLY car.

The BOV was taken out and the wholes blocked off.

It was running 15psi boost with no BOV and all the air would go back through the turbo and you could hear this thing flutter through the air filter..

My point is that I had no problems with the turbo on that car..

There were hundreds of other issues but not Turbo.

I am not recommending you go out and take your BOV off..

Just sharing some experience.

[SilverSlyder]

I'm going to be taking my BOV off and plumbing it back in, I heard that I might have more lag when bov is removed. Is this true?

[TTT]

I don't have the writen proof but I can see why people say that there will be more lag.

Think about it..

You hit the throttle, the turbo screams as it spins to like 150,000rpm, forcing all this air through.

All of a sudden, you back off or change gears, your foot comes off the throttle, the throttle butterfly slams shut, the air that is currently in the pipes smashes against the throttle butterfly, has no where to go but back.

The air gets forced back throught the spining turbo blades which are designed to really suck the air inwards and not have it go the other way, but the air gets through causing the fluttering sound.

So because it forces it's way through the turbo blades, this causes the blades to slow down heaps to get all the air out.

WITH a BOV.. same at the begining.. the turbo screams sucking the air in. you change gears or back off, the butterfly closes, the air hits it, goes to turn back around and because the manifold in your car has vacuum, it makes your BOV open up and all the air goes screaming out of there going pppsshhhhhh.

Now because the air didn't go back to your turbo blade to slow it down, when you sellect the next gear, the turbo hasn't slowed down as much as it would with the air being forced back through it, and therefore, picks up boost quicker..

You have to realise that when changing gears, all of this happens like in a fraction of a second..

The standard BOV on the skylines or any car really, releases the air back to the inlet, AFTER the turbo.. so basically, it gets re-circulated and dumped in between the air filter and the turbo

make sense?

[SilverSlyder]

Thanks GTST. That's pretty much what i was told. Still...good to get a second or third opinion.

[Guest barneyrubble]

thanks guys

I guess the answer to my question is that there is no such blow off valve.

Learning something new every day

[adam 32]

yeh there is, HKS SSQ makes the sound under low boost ie not enough boost to hold valve open to make the pshhh noise

[TTT]

Adam... it's not your BOV that causes that sound..

when it doesn't open under low boost, it's as if there is no valve there at all.

So it's not your BOV making the fluttering noise.

[002 NVS]

Most BOV's make this noise when not under full acceleration/boost...I know the turbo smart typre 3 makes this shutter noise, the HKS ssq, the blitz sequential i think it is, the GFB mach1 as well as many more..

It depends how u set it and how u drive, most BOV's make the loud psshhh noise that every one knows when under full boost and acceleration, but when just cruising makes the shutter noise, alot like some external wastegates....

Just my thoughts...

I hate the ppsshhh and want the shutter...choo choo choo..

[TTT]

002 NVS

Did you even read what I wrote?

THERE IS NO BOV THAT MAKES THE CHOOO CHOOO CHOOO OR FLUTTER OR WHATEVER YOU WANT TO CALL THAT NOISE...

wastegates do not make that sound either...

all BOV's make some sort of PSSSHHH noise when they open.

the other chattering/fluttering noise is coming from your air filter as the air gets chopped through the turbo blades and goes back out of your air filter

As for the external WASTEGATE... the only thing that a wastegate does is open up to prevent over boosting.

it doesn't flutter or phhhsst or anything.

if you have a pipe that goes from the wastegate straight out to atmosphere instead of plumbing back in to the exhaust, then once the set boost is reached, the wastegate will open up and allow the excess exhaust gasses to flow out of that gap instead of going through the turbo.

When this happens you will hear a very loud screaming/roaring sound because it is like having a very short exhaust pipe with no muffler.

OK??

[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!!

[adam 32]

that is also why on a HKS SSQ when you loosed the plate it doesnt make the flutter anymore, only a pshh