Fluttering Sound From Bov

[Rolls]

As long as it doesnt damage my turbo in the long run then good , so if i do tighten the bov this wont happen anymore???

Im not quite sure how yours works but I think you would want to loosen it, dont loosen it so much that it leaks at idle though, ultimately youd want a really small amount of flutter at very low boost 3psi etc. That way you can be certain its not leaking vacuum at idle. Just play with it until it sounds right, its not going to do any damage either way, worst case itll pop and wont idle properly because its too loose and leaking.

[FORZA-MOTORSPORT]

Ok thanks for all the help guys, i have noticed that she will stall sometimes on down gearing and when i rev her on idle or hunt so ill have a play with the bov, so losening is the best solution?

[VB-]

LOL

Guys do you just make up shit for fun, the compressor spinning backwards? c'mon if you dont know anything about it dont say anything, all it does is propogate misinformation.

The air will just escape between the blades slowling minimally, thats why it makes the chopping flutter sound, if it stopped the compressor completely or pushed it backwards or whatever it would sound just like a bov cause the air wouldnt be getting chopped up.

The flutter does sound fully sick though, my stock redtop rb20det R31 fluttered like crazy, they came out stock with no bov.

sorry, i didnt word it very well. i didnt mean that the compress will spin backwards, but the wheel is forced towards the turbine wheel. if you were looking at the intake, it would be forced backwards.

oh and as for the slowing of the blades and pushing it back, it wouldnt just sound like a normal BOV, from my understanding, the pressure builds up, causes the comp wheel to slow down, force it back a bit, then this relieves the pressure, and comp wheel will speed up again, comp wheel will come back into place, then the pressure builds up again and so on

Edited July 15, 2006 by VB-

[Cubes]

The fluttering noise only happens when i dont push her full throttle, i think it is compressor surge...

Ok thanks for all the help guys, i have noticed that she will stall sometimes on down gearing and when i rev her on idle or hunt so ill have a play with the bov, so losening is the best solution?

]

Its 100% not compressor surge. The GT35r .82 on an RB30 won't experience compressor surge unless you some how manage to get it making 1bar at 2500rpm.

RE: The stalling.... Atmo bov, try playing with the off throttle fuel cut I showed u last time, bump it up a little higher. I don't believe shaun would have done this as he would have loaded another map in to it erasing what you already have.

[Rolls]

oh and as for the slowing of the blades and pushing it back, it wouldnt just sound like a normal BOV, from my understanding, the pressure builds up, causes the comp wheel to slow down, force it back a bit, then this relieves the pressure, and comp wheel will speed up again, comp wheel will come back into place, then the pressure builds up again and so on

So what your saying is the compressor/shaft has slack in it causing it to move backwards and forwards? surely itd break pretty quickly if that was the case? do you have anything to back that up?

[FORZA-MOTORSPORT]

Joel come around and have a bit of a play if you want? Then you can hear the fluttering too

[RB SANDY]

I have seen a stock gtr with the bov taken of and it does not flutter could this have someting to do with twin turbos

[VB-]

So what your saying is the compressor/shaft has slack in it causing it to move backwards and forwards? surely itd break pretty quickly if that was the case? do you have anything to back that up?

shaft owuldnt have slack in it. when you say backwards and forwrds, do you mean rotation wise? or laterally, from compressor to exhaust turbine? no i dont have anything to back this up, its what i was taught, and i believe it, to me it makes sense.

[Rolls]

shaft owuldnt have slack in it. when you say backwards and forwrds, do you mean rotation wise? or laterally, from compressor to exhaust turbine?

you tell me?

I didnt understand what you were saying, I figured the air just came back out the inlet getting chopped up by the turbine as it wouldnt be spinning with it causes a pulse of air which sounds like the flutter you hear.

[VB-]

i always thought that it was a build up of pressure, coz the compressor is still spinning wen u back off the throttle, and still forcing more air in, and the air trying to escape is met with heaps more air being forced in, then the pressure builds up to much and slows the compressor while the pressurised air escapes, then when the pressure drops, more air is still fed in by the compressor, pressure builds up again, and slows the compressor and goes through it all again.

kinda like the overboost valve on idny cars, except its just going back through the turbo rather than a valve if u get me? pressure builds up to much, it gets released, and then when the pressure drops, the valve closes (the turbos compressor is spinning at speed, forcing air in while there is lower pressure in the inlet piping/coller etc) this is a sh*tty example but its the only thing i could think of to give you an idea of what i mean

lol im not good at explaining things, but i do try aint that worth sumthin?

[hayden49]

From what ive been told, the flutter has NOTHING to do with your bov.

its actually the noise of the waste gate opeing and closing really fast.

i was told it has somthing to do with the pressure difference in the plenum and the differnt pressure in the cooler pipes.

Whether the spring is loose as it can be, or tight as can be it will still make the flutter.

also when i installed my fmic, i didnt have a nipple on the cooler pipes so i used the vacum line running to the bov to run the vacum line was attached to the cooler, after that it started fluttering like crazy, and i was told as the vacum line running to the wastegate is now longer, the gate opens and closes continuously when you back off the throttle.

Meh everyone has their own theory about what causes it.

[Rolls]

From what ive been told, the flutter has NOTHING to do with your bov.

its actually the noise of the waste gate opeing and closing really fast.

i was told it has somthing to do with the pressure difference in the plenum and the differnt pressure in the cooler pipes.

Whether the spring is loose as it can be, or tight as can be it will still make the flutter.

also when i installed my fmic, i didnt have a nipple on the cooler pipes so i used the vacum line running to the bov to run the vacum line was attached to the cooler, after that it started fluttering like crazy, and i was told as the vacum line running to the wastegate is now longer, the gate opens and closes continuously when you back off the throttle.

Meh everyone has their own theory about what causes it.

Did you even read the thread? its not the f**king wastegate opening and closing, everyone doesnt have their own theory, people just spout bullshit over and over again. It is clear what is happening and why it happens and its been said several times in this thread.

Man im sick of people.

edit: http://ausrotary.dntinternet.com/forums/vi...bov&start=0

read this thread, namely the posts by riceracing, he knows his stuff, I think he is on these forums as well. Theres more information regarding flutter there then anywhere.

Edited July 16, 2006 by Rolls

[Cubes]

From what ive been told, the flutter has NOTHING to do with your bov.

its actually the noise of the waste gate opeing and closing really fast.

i was told it has somthing to do with the pressure difference in the plenum and the differnt pressure in the cooler pipes.

Whether the spring is loose as it can be, or tight as can be it will still make the flutter.

also when i installed my fmic, i didnt have a nipple on the cooler pipes so i used the vacum line running to the bov to run the vacum line was attached to the cooler, after that it started fluttering like crazy, and i was told as the vacum line running to the wastegate is now longer, the gate opens and closes continuously when you back off the throttle.

Meh everyone has their own theory about what causes it.

Well hasn't some one been pissing in your ear..

lol @ Rolls...

[Rolls]

lol @ Rolls...

After telling people for 2 years that waste gate flutter is some bs term some hektik in his vl calias turbs made up you get kind of sick of hearing it

[FORZA-MOTORSPORT]

So anyone want to make a good summary on why the fluttering noise happens, if it causes any turbo problems even later on down the track and if so whats the best way to combant the issue? I havent had a chance yet to adjust my bov as my bonnet is cable tied shut

[Rolls]

So anyone want to make a good summary on why the fluttering noise happens, if it causes any turbo problems even later on down the track and if so whats the best way to combant the issue? I havent had a chance yet to adjust my bov as my bonnet is cable tied shut

That ausrotary thread and the one earlier from here are good discussions to read. No one has really prove either way it will or wont damage your turbo, so its really up to you to make your own decision on what you think.

Personally I dont think you are likely to see any damage as alot of cars back in the 80s were fitted stock without bovs (R31s/DR30s etc and the VL turbos) and managed to see 80kms before they were required to service their turbos. The maintanance intervals are now more like 120kms but whether this is from the fitting of a recirc bov or just because they are manafactured better you dont know.

Why the fluttering happens? because when you dont have a bov or it is so tight it doesnt open properly the compressed air has to go somewhere as the butterfly is closed. Now normally it'd go out of the bov but instead it moves backwards back through the compressor wheel getting chopped up as it slides past the blades (still spinning) then back out your pod filter. If you have a big intercooler it will bounce around and amplify the sound even more. All this talk about wastegates is complete non sense and has nothing to do with it. If you can be bothere searching theres about 10 other threads about this that explain it fairly similarly