Flutter, Yes or No?

[JelloBello]

After being inspired by Rake's current project where he's setting up his car so he can select in-cabin either flutter or BOV when he releases the throttle (see here). I went out and simply 'disabled' by BOV so now whenever there is positive pressure when the throttle is closed the air goes backwards through the turbo creating a flutter sound.

videos:
Outside- http://youtube.com/watch?v=FOcFtj0Ytj8 (mmmmm... hear that turbo spool )
Inside- http://youtube.com/watch?v=qD-eKwcKpes

Now I have read in various locations on the net that this flutter will destroy your turbo over time, and I understand why especially if the car is running higher boost levels. I'm just after your opinions on flutter, referring to bluebirds (not all the dose vl turbo's). I think it sounds pretty cool, but in saying that it does take away from the sleeper aspect that's so great about bluebirds. I'll probably only keep my car set up like this for a week at the most because I'm running 12psi.

Let me know what you think

[Budgie]

Fully

Sounds funny in auto turbo cars I reckon, because the throttle is only ever backed off on de-celeration, not acceleration.

Sounds very similar to mine, except more 'tinny' ??  Hard to explain.  Might be the youtube audio quality however.

[rathies]

flutter is hot, you never heard mine jamie but it was teh sex, at full boost it really went 'ahh-choo' back through the pod, that was funny too. If you've got a crappy turbo you intend on upgrading i dont see why you shouldn't disconnect your BOV.

[JelloBello]

yeh, but I'm not gonna upgrade it until later on - like next yearish, once I've actually bought a new turbo I'll disconnect it but until then i can't really afford for the current one to be porking (and 160 000km doesn't help the situation, although 155 000 of those were on 7psi)

[Budgie]

If thats the original turbo, then thats good millage Jello   Shows its been well looked after.

[JelloBello]

afaik the previous owner (john) never replaced it, he did however take it to a turbo place before he sold it to check how it was going and they said it was fine

Also I got the impression that john really did look after this car.

[Ammerty]

sounds really good mate but you do know that its bad fof the turbo - the back pressure creates shaft play - but if you can turn it on n off than it shouldn't effect it so bad

[rathies]

if you're gonna leave the bov disconnected just be sure your car wont stall mid corner due to the air going the wrong way through the maf, theres nothing scarier then losing your steering and brakes mid corner, at least in manual you just drop the clutch  says something eh jello (get manual)

[Luke]

Ive been told its not bad for the turbo, and you get better performance because the pressure is held in so when you grab the next gear theres still pressure. And it's not bad for the turbo because it 'cavitates' inside the turbo. I don't understand but it comes from an extremely credible source.

More importantly, did anyone else see this, made me laugh.

http://youtube.com/watch?v=amrFdUay24M&mode=related&search=

aah ha ha

[eurisko]

Disabling a bov is very very bad for a turbo.

The TB is closed, not allowing the pressurised gas to go anywhere.... the turbo is still spooling, but now there is a massive positive pressure on the outlet, causing a huge resistance on the compressor wheel. This increases the stress on all the components of the turbo, increasing temperature, increasing wear etc.

In the old days cars didnt have bov's... but they werent expected to last long.

Expect problems to develop quick with that.

[Jono]

You'll get pretty evenly divided answers where ever you ask this question. I've heard someone argue that when a BOV opens shaft speed of the turbo goes through the roof because there's no resistance on the compressor and still heaps of pressure in the exhaust manifold.

Oh and this ad made me laugh:
http://youtube.com/watch?v=KA06Rw-7Y2k

[Budgie]

In the old days cars didnt have bov's... but they werent expected to last long.

Expect problems to develop quick with that.

My bluebird has been without a BOV for 130,000km... it had a GFB atmosphere venting BOV fitted for a few months, which made the car run like shit (atmo not good for nissan AFM's! freaks them out).

My cars T25 is pretty damn good, minimal shaft play and still boosts just fine .  Granted it had been on an auto car for 120,000km and before that, only run @ 7psi all its life (now running 10psi).

However, the main argument has always been.  Why do nissan/subaru/toyota... etc etc... all fit re-circulating BOV's to their modern turbo cars from the factory?  To increase the life span of the turbo I reckon!

[Luke]

The TB is closed, not allowing the pressurised gas to go anywhere.... the turbo is still spooling, but now there is a massive positive pressure on the outlet, causing a huge resistance on the compressor wheel. This increases the stress on all the components of the turbo, increasing temperature, increasing wear etc.

Yes I agree that there is a positive pressure on the outlet of the turbo, but not on the fins. I don't fully understand it but from what Ive been told, the rise in pressure and resistance on the fins is almost non existant.

[LUP15]

i wouldnt be running a car without a bov with boost greater than 14psi or 1bar. i mean its there from factory and im sure they wouldve thought about it as it would cost money to put it on there...

[DannyS12]

lol
im gonna be one of the guys that disagrees with havin no bov will kill ur turbo..
my car has never had a bov on it. 180 xxx ish kms..
never had one from factory.
alot of turbos dont have bovs from factory...
and its not coz they werent around then.. the early saab turbos sum had bovs..

the reason for puttin a bov on is to stop compressor surge wen u take ur foot of the accel..
the only proven draw back of compressor surge is slight lag on gear change.
which is not even noticeable.
im runnin 10 psi ive only had the car for bout 7 months but b4 i got it the previous owner was runnin 13psi.
with out a cooler or anythin... not even a side mount.

there will never be a definitive answer for this question.. until some one some how proves that compressor surge (flutter) can cause premature wear.

just my .2c

[eurisko]

That is true, compressor surge does only effectivley increase lag (a little)... but the fact it is increasing pressure and introducing flow in the reverse direction is not desireable at all. Increased stress on parts that are already aged is not something u want to do... so i wouldnt add to the possiblility of failure.

Throttle bodies as well are also put under tremendous strain when no bov is present. Thats something u dont want to break either. :S

[DannyS12]

yeah that is also true..


this debate is the same as the debate on the r31 forum between rb30et and rb20det.
sum people like torque sum like revs. it will never be solves.

same as the flutter v bov debate..
admittedly its alot better discussion on here then on the 31 club. the 31club just bitch bout it and dont have anythin decent to say.
just my brothers best friends uncles dad told me so.
haha

[DTM]

However, the main argument has always been.  Why do nissan/subaru/toyota... etc etc... all fit re-circulating BOV's to their modern turbo cars from the factory?  To increase the life span of the turbo I reckon!

Older Nissans (pre 87) weren't fitted wit BOV's. They only were factory fitted to help with emissions... because flutter is unmeasured air going out past the afm, it fucks with the fuel mixtures and can cause it to richen up.

i've had my 31 with no bov for nearly 2 years now, not an issue. the only thing is like rathies said, it can cause it to stall on rapid rpm drop and it also gives you a slight delay on boost coming back on after changing gears