Jump to content
SAU Community

Recommended Posts

Hey all,

Wsa just thinking bout it the other day after i heard a VL with some crazy ass sounding BOV flutter was real loud, and was wondeirng why mine doesn't do it? I have a huge bar and plate cooler, big turbo, BOV, filter etc and i get flutter but not like other skylines i have heard...? I don't get that hollow sound or slow sounding flutter, mine is quick. SO i took my BOV off and went back to standard one to see if it was my BOV and now i got absolutely none... but i have heard heaps of other skylines with just a cooler and the stock BOV that flutter mad... just wondering why mine don't do it? Or if there is a BOV that has a better sounding noise... i.e. I heard the A`Pexi BOV makes this sound.

(P.s. please don't all right its compressor surge cos i kno it)

Link to comment
https://www.sau.com.au/forums/topic/20645-bov-flutter-cooler-flutter/
Share on other sites

Guest RedLineGTR

usally with pods your can hear the flutter. Have my stock bov on now...when i get between 2000-2800 i get flutter effect might just be the bov or something, but when over those rpms i get a proper sound pppssshh like sound cos of the pod and no stock airbox..i dont beleive the flutter at around 2000-2800 does any damage since there is a low amount of boost coming on, it could just be the bov since there is not enough pressure to open it up fully it opens abit at a time, not enough to fully keep it open. Hope it helps somewhat *shurgz*

Yeah if i run no BOV i get flutter but thats jus compressor surge routing my turbine shaft and thrust bearing... so i'd rather not, but i heard skylines all the time with no aftermarket BOV that flutter awesome, so the only thing i could bring it down to was that its cos i have a bar and plate core as aposed to tube and fin... i dunno got me stumped.

Yeah i have a filter also and yeah that does amplify the flutter sound as its coming directly off the turbo, and that is in fact where the sound comes from, but i jus can't work out why after those rev's also that it doesn't flutter... i think i might go for BOV number 4 and get an A`Pexi dual chamber and see, cos my mate has one of them and it flutters unreal, real slow distinct sound... and if it don't work then i'll chuck it out the window ont he freeway ha ha

Yeah i had a Type 3 Supersonic on, it had huge flutter but it sounds like the BOV opening and closing continuously (the piston actually jitters if you watch it) but doesn't sound like the normal flutter. Sounds alright but not great. Pretty loud tho. I just went for a drive then with no BOV at all and it sounded sick, i just want it so stay like that without doing damage to the turbo. I know it can be done cos i heard it on heapsa other cars so i'm gunna find out how.

dude.

the skylines you hear making a fluttering with the stock bov means that the bovs are blocked of either under the bov or in the return pipe where you can't see it.

and so the sound you hear is just compressor surge as air goes back through the turbo.

VL Turbo's DON'T have bovs as standard and as soon as you put a pod filter on them, you can hear them fluttering away on gear changes or throttle off...

the sound all depends on the turbo blade and type of piping from the turbo to the filter..

if the turbo blades a more further apart, you will get like a slow flutter.. like ch ch ch ch ch

if the blade design is different, the flutter will be more of a ft t t t t t t...

you get me?

and the loudness of the sound depends on the piping from the turbo to the filter... because this is what makes it louder or quieter depending on the material it is made of..

like if it is the standard rubber item, it won't be as loud as if it were made from a LARGER diameter stainless steel pipe..

You will be dissapointed when you waste your money on the APEXI bov as the flutter sound will not change at all.

the bov should simply make a psshhh sound of some sort..

not a fluttering sound.

Yeah know all bout the compressor surge and the piping differences as to pitch and sound of BOV, but then why do cars with say GReddy Type S/R or A`Pexi BOV still flutter... must be because the BOV spring is tight and hence not opening? I am running all alloy piping for cooler and am changing the pipe from the inlet of the turbo to the filter to alloy aswell once i get the computer in and can remove the plum back lines for the standard BOV. So if i change this to alloy it will amplify the sound eh? But obviously not as much as it is softer than steel which would resonate a lot more... stupid really that i am even bothering with all this but its a mad sound lol

Ads for changing from the Turbosmart BOV i have found that it doesn't go well with my turbo... not sure why but when i am on the throttle say in a constant gear (i.e. 5th gear on fwy) then i back off even the slightest to control speed the BOV piston starts fluttering and wont stop until i change my throttle position, so it is shit to drive... like i am talking ti can keep the BOV doing this for km's, its plain stupid and jerky to drive. So iunless i can cure thios i want a different BOV that will more suit my turbo, hence something based on say a pull type design like the HKS SSQ.

i can hear flutter AND my BOV venting at the same time at lower revs....at higer rpms it vents alrite though...no flutter.

one of the bad points of the HKS SSQV is that you can't adjust the tension of the smaller valve, the screw only affects the larger valve...no matter how much you loosen the screw it won't affect the smaller valve's tension :)

yea my mates s15 sileighty had no flutter/very little flutter with stock BOV, when an adjustable racepro BOV was put on, any less than 5-6psi you can hear a prolonged FLUTTER LIKE CRAZY... but with higher boost it would do the normal BOV thing. I put this down to the harder spring setup.

From what I understand (and I hope we're on the same wavelength) .... Running NO BOV, ie. replacing the stock/aftermarket one with a metal plate blocking the opening off, will cause all pressure to flow out tru the turbo, making the fluttering noise...

From what I understand running under about 14 psi, this is fairly safe to to on a street car, anything higher and the causees damage to your turbo.. Plus an advantage from this setup is that You can get a boost spike which throws the power down..

Ask R31Nismoid about his setup as he has an R31 GTS-R , and it runs no BOV from the factory, and he can explain a bit better...

But when ever I watch my HPI DVD's .. and Listen to the track cars over there, it sounds as tho they are not running a BOV from the flutter I hear after their burnout... which they may do to get that boost spike I meantioned.. BUT they run High boost AND replace turbo's often.. Hence the 14psi+ Rule in regards to damaging the turbo..

This is what I gather from talking to various people.. I may be wrong or mislead.. but it's just my 2 cents worth...

I found out recentyl that running an external wastegate has a large deal to do with the flutter. The flutter you would hear on your vid's from ripped jap cars is because the large majority of them run bigger turbos which need external wastegates and is the reason alot of them flutter on the burnout cos they are reving high enough for it to bypass gasses and flutter as the turbo constantyl produces pressure after each time it releases air... makes sense cos its running of exhaust gases. However i still can't manage to work out why mine sounds so different to other skylines out there... i think like someone mentioned earlier the fin shape on turbos has a lot to do with it, and as i have an after market bigger turbo then thats probably the reason, but i'll keep searching for the answer to end this discussion once and for all lol.

  • 9 months later...

ok.. i had an afta market BOV (HKS), with cooler and standard air box.. i got no flutter what so ever.. Recently i bought a afta market pod, and the flutter is amazingly LOUDD! at 1500rpm u hear the flutter go.. im only rnning 7psi with all these mods.. is it bad for my turbo? I also have 3" exhaust from turbo back and a s-afc.. there has been so much talk about this topic that itts confusing me.. Flutter does sound way better.. btw, is there a way to check if ur standard BOV is blocked off, and this may seem really dumb, but where is the standard BOV located? lol

i once had a series 2 rx7 in which i put a series 5 turbo motor with a pod filter screwed directly onto the turbo and no BOV, i had the loudest flutter i ever heard in my life, i hated it so i changed the setup. btw i ran a 12.7 1/4 with a motor and a turbo that needed rebuilding.

Recirc bovs also help reduce emissions, similar to your egr valve, an recirc bov constantly recircs your compressed air, as most oem ones open up even in vacuum.

Appart from that, theres plenty stock ca18det, e15t, rb30et, fj20t's still running about, and they dont have any oem bovs.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Well, after the full circus this week (new gearbag, 14 psi actuator on, injectors and AFM upgraded, and.....turbo repair) the diagnosis on the wastegate is in. It was broken. It was broken in a really strange way. The weld that holds the lever arm onto the wastegate flapper shaft broke. Broke completely, but broke in such a way that it could go back together in the "correct" position, or it could rearrange itself somewhere else along the fracture plane and sit with the flapper not parallel to the lever. So, who knows how and when exactly what happened? No-one will ever know. Was it broken like this the first time it spat the circlip and wedged itself deep into the dump? Or was it only broken when I tried to pry it back into place? (I didn't try that hard, but who knows?). Or did it break first? Or did it break between the first and second event of wierdness? Meh. It doesn't matter now. It is welded back together. And it is now held closed by a 14 psi actuator, so...the car has been tuned with the supporting mods (and the order of operations there is that the supporting mods and dyno needed to be able to be done first before adding boost, because it was pinging on <<14 psi with the new turbo with only a 6 psi actuator). And then tuned up a bit, and with the boost controller turned off throughout that process. So it was only running WG pressure and so only hit about 15-16 psi. The turbo is still ever so slightly lazier than might be preferred - like it is still a bit on the big side for the engine. I haven't tested it on the road properly in any way - just driven it around in traffic for a half hour or so. But it is like chalk and cheese compared to what it was. Between dyno numbers and driving feedback: It makes 100 kW at 3k rpm, which is OK, could be better. That's stock 2JZ territory, or RB20 with G series 550. It actually starts building boost from 2k, which is certainly better than it did recently (with all the WG flapper bullshit). Although it's hard to remember what it was like prior to all that - it certainly seems much, much better. And that makes sense, given the WG was probably starting to blow open at anything above about 3 psi anyway (with the 6 psi actuator). It doesn't really get to "full boost" (say 16 psi) until >>4k rpm. I am hopeful that this is a feature of the lack of boost controller keeping boost pressure off the actuator, because it was turned off for the dyno and off for the drives afterward. There's more to be found here, I'm sure. It made 230 rwkW at not a lot more than 6k and held it to over 7k, so there seems to be plenty of potential to get it up to 250-260rwkW with 18 psi or so, which would be a decent effort, considering the stock sized turbo inlet pipework and AFM, and the return flow cooler. According to Tao, those things should definitely put a bit of a limit on it by that sort of number. I must stress that I have not opened the throttle 100% on the road yet - well, at least not 100% and allowed it to wind all the way up. It'll have to wait until some reasonable opportunity. I'm quite looking forward to that - it feels massively better than it has in a loooong time. It's back to its old self, plus about 20% extra powers over the best it ever did before. I'm going to get the boost controller set up to maximise spool and settle at no more than ~17 psi (for now) and then go back on the dyno to see what we can squeeze out of it. There is other interesting news too. I put together a replacement tube to fit the R35 AFM in the stock location. This is the first time the tuner has worked with one, because anyone else he has tuned for has gone from Z32 territory to aftermarket ECU. No-one has ever wanted to stay Nistuned and do what I've done. Anyway, his feedback is that the R35 AFM is super super super responsive. Tiny little changes in throttle position or load turn up immediately as a cell change on the maps. Way, way more responsive than any of the old skool AFMs. Makes it quite diffifult to tune as you have to stay right on top of that so you don't wander off the cell you wanted to tune. But it certainly seems to help with real world throttle response. That's hard to separate from all the other things that changed, but the "pedal feel" is certainly crisp.
    • I'm a bit confused by this post, so I'll address the bit I understand lol.  Use an air compressor and blow away the guide coat sanding residue. All the better if you have a moisture trap for your compressor. You'd want to do this a few times as you sand the area, you wouldn't for example sand the entire area till you think its perfect and then 'confirm' that is it by blowing away the guide coat residue.  Sand the area, blow away the guide coat residue, inspect the panel, back to sanding... rinse and repeat. 
    • The detail level is about right for the money they charge for the full kit... AU$21.00 each issue, 110 issues for a total of $2,300 (I mentioned $2.2K in the first post when the exchange rate was better). $20/week is doable... 馃槓
    • If planning on joining us for the day(s) please indicate by filling in this form. https://forms.gle/Ma8Nn4DzYVA8uDHg7
    • You put the driver's seat on the wrong side! Incredible detail on all of this. It looks like you could learn a lot about the car just from assembling the kit.
  • Create New...