FLUTTER sound as BOV

[assyrian4evaa]

trying not to keep this convo going because i think every things has pretty much been covered but ppl that block of their BOV make sure u block of the vacuum hole thingy otha wise ur motor will not run proply...

i have experimented with this whole BOV n FLUTTER thing n i think that nissan engineers r pretty smart so we just have to trust them n keep our factory BOV as theres no power gain in an aftermarket one, u get sum kind of lag if u block it of and ask ur self this IS THE FLUTTER WORTH THE DEFECT STICKER???

[Jago]

*sigh* this topic keeps running in circles, i've just re-read all 7 pages of it. As previously mentioned, i think it would screw with air flow metered cars not to have a BOV. Also noticed that allot of the cars mentioned that didn't use a BOV would have had to have aftermarket ECU's (GAS-747 as an example, running 10's, can't be stock ECU), and other "TOP STREET DRAG cars".

Anywho, i think allot of you actually need to go back, re-read it all, and have a think. The air flow meter is there for a reason. Air coming back out the other way will still register, it's not meant to measure it in a certain direction, it's just a damn wire thing. I think in the end of the day, it couldn't be the turbo to worry about, but engine management etc.

Bleah, im exhausted, can't think propperly otherwise i'd write something more intelligent. I might come back later and add to it once i get a few hours of sleep

[sloe-32]

bleh, don't even waste your time with this crap. turbo becomes very lazy on boost. responsivness goes out the window. Can't run over 13psi as it begins to surge thereafter on mine.

[discopotato03]

I think a few things need to be remembered about std VL Turbo Commode Doors .

Firstly they were deliberatly designed to be in cheap to produce low state of tune , even for a mid 80's production engine . Can you imagine the uproar if the then new VLT with the shudders Jap hair dryer motor was equal to or better than the cast iron V8 boat anchor "batmobile" ? I have visions of the boo sham like after Bathurst 92 from the " if you haven't got a V8 you haven't got a life" brigade .

RB30ET's had very low static CR , no intercooler , a dinosaur dinky bush/plate bearing T3 turbo , had to live on a farts worth of boost (4-5 lbs from memory) and had to run on the then low octane ULP which wasen't much better than power kerosene !

So picture low boost so low speed turbo rotating group and prehistoric bush and plate core which has lots of oil shear drag and loves to slow down when the exhaust gas energy falls away . I know what this flutter noise sounds like because standard DR30 turbo engines do the same thing . The one I used to have was a little louder with this because some mug cut most of the upper half off the airbox away and ditched the snorkel probably to enhance the flutter noise . It used a very similar T3 to VLT's as well .

Jump forward from 1986 to the first half of the 90's and turbos amongst other things changed . More modern BB cartridges tend to spin up at lower engine speeds and load so on off throttle will make them flutter more easily . They run higher boost pressure so the turbine/comp speed is higher as well . One thing I noticed with the old DR30 was sudden feathering of the throttle (but not completly closed) caused weird engine characteristics . One was this flutter noise and the other was a slight power surge sort of back off onto over run and a slight power surge before it was all engine braking - well as far as the idle solenoid allowed . The std RB and SR powered cars I've driven don't do any of this and are pretty smooth and refined . I figure that I don't need to advertise to the world that I've backed off or changed gears so the after market "BOV's" have no useful function for me . I can see value in the std compressor bypass valves because they DO reduce the silly sound/power characteristics and the way the MAF sensor senses air coming into the engine . From Nissans point of view the benefits would have been that Mr/Mrs/Miss don't want the silly sound in their brand new Skyline and the engineers problems with over run enrichment with tightening emissions laws .

I hear people say that these valves leak when they "boost" their engines so I have to assume Nissan designed it to be this way to attempt to save an expensive engine and turbo if the waste gate failed to open . I also hear people say that they have great success with the dual GTR/RB26 bypass valves and its no surprise that they work because they are native to the highest performance variant available and originally a Grp A homologation special as well . I understand none of the std GTR's make silly sound effects and their performance is recognised everywhere .

At the end of the day I guess it comes down to how many of the positive benefits of factory engineering the individual wants to take advantage of . Performance cars are more obvious to the cops/RTA than ever so being incognito is way to go in my book . The less attention I attract on the road the better .

Cheers A .

[benro2]

Well, personally I believe you should use a bypass valve or BOV, as according to a couple of books I've read (one being Turbocharged by Corky Bell, can't remember the name of the other one but it was first published this year), compressor surge will eventually cause damage to the turbo. I believe they said it could damage the bearings, not sure about the compressor wheel itself.

Although, having said that, there are two factory cars that I've seen videos of that have a flutter sound when the throttle is closed. The first one was the Porsche GT1, driven by Tiff Needel in 5th Gear (the show). That's a full on road car for the race track, I assume with a warranty and everything, ie: not just for the one racing season or whatever. The second one was a turbo diesel 4wd, an Audi something on an Aussie car review website. It wasn't very loud, but it was definitely a fluttering sound. I was quite surprised to hear a diesel 4wd making that sound!

I personally have a GTS-T with an Apexi pod filter which I scored off Ebay brand new for $105 shipped. Really good price for what seems like a nice filter, and on stock boost I thought it was pretty loud (if that's what you want). Not as loud as an atmospheric BOV, but I reckon much louder and the cops would be all over you. Now that I'm running higher than stock boost, it is quite loud. There is no flutter sound, but for me, that's good I like the fluttering sound, but now that I know what it is, I think I'll avoid it...

One more thing, slightly OT, there is a guy around Penrith who has a dark blue S14 with an atmospheric BOV that sounds like a low whistle. Like the kind of pitch you could whistle normally with your mouth, gradually decreasing in pitch. Not like the HKS SSQ which is a really high pitched sound. Anyone happen to know what BOV it is? There is no flutter in his sound either.

My 2.2c

[MR 33]

Geez touchy topic here. It's a shame no one has HARD CORE evidence to support their arguements. I had mine blocked off, just coz i was bored and wanted to see what it would sound like. I didn't keep like that for long. For those that want to know an easy way, go to REPCO or similar and ask for the rubber bungs they stock. Then just take off the rubber hose connecting the bov to the return line and bung up both ends. I'd like to think that having 'the flutter' would not cause any damage the the turbo (considering it sounds pretty cool lol) but it's hard to imagine why so many cars come equipped from factory with bovs. But alot of peoples posts make alot of sense. A couple mates have had their bovs blocked while running 16+psi for quite a while with no damaging affects. Each to their own i suppose, i mean even the chance of ruining your turbo sounds pretty scary.

My 2c

[AlexCim]

just to try it, just remove the vacuum line going into your stock block off valve and if you have a pod filter it should flutter.

Actually, this is probably the most incorrect peice of advice anyone has ever given, unless you didnt explain what you ment fully, that it needs to be covered and cant be left atmo venting.

First of all, lets explain how a BOV works. Its basically a spring loaded valve which "releases" when a pressure difference is felt. The vac line you suggested to remove is what causes pressure on one side of the valve. The vac line goes to the plenum, and the other side of the bov is before the throttle body.

Hence, when the body closes, the pressure is greater on the inside, then the valve "blows off" venting back to before the turbo.

By removing the vac line, you are essentially always making one side 1 bar (atmospheric) so at ANY boost the BOV will just open and vent air.

Removing the vac hose will result in

- Stalling

- Running MEGA rich

- Annoying the ecu for a little while as it goes into limp home mode

To get flutter, REMOVE the stock bov and cover the hose that goes to pre-turbo and also cover the hole on the intake pipe where the BOV mounts. Or, instead of removing the bov, get a rubber cap for the hose size and attach it on with a hose clamp. Then, remove the vac hose and it wont matter that the BOV is always open if its clamped up ok.

You will then get sick flutter.

No idea why, but my stag fluttered with the stock BOV, GCG highflow and 1 bar (with pod), but when I put it back to the stock turbo at 10psi it went back to the stock "pffffff" venting noise.

[Captain Drift]

Foznice is right the air forcing its way back past the compressor wheel makes the noise as it comes out the filter.

In the uk all the fords ( fiesta rs and escort rs and cosworths) make that noise with just a filter bolted on the turbo

[Freddy Kruger]

imo just look at the vl turbo boys. the vl is 20 years old and many still run the standard turbo and a bov is not standard. i think nissan put a plumback bov on to make the car more drivable and quieter. i gotta admit i dont get as many looks when i dont get the FLUTT0Rz))r0rzzzz11!!11!one

[r32matt]

Hey,

Blocked off my BOV last night. Was so easy and works well. I don’t feel any lag in between gears and it still drives smooth. I get a lot of flutter when just driving around but when i give it full boost I can barely hear the flutter because of the big Whoosh! that the turbo lets off. Kinda still sounds like a BOV with flutter, lol.

Im using:

K&N Pod

FMIC

To block off your BOV you just need to:

Unplug the small tube going from the Manifold to the BOV and block off the Manifold side. (If the Manifold side isn’t blocked the engine will run very bad.)

Take off the BOV - After taking off the BOV you can replace it with a metal plate that is the same shape as the BOV which blocks off the hole.

Or you can cut out some Aluminium the same shape as the BOV from a Coke can. Then just put the Aluminium over the hole and put the BOV back on. This makes it look standard plus the BOV is blocked.

The only other pipe is the one that goes back into the Air intake. You can leave this on or take it off and block up the hole in the air intake.

And when it comes down to arguments on the BOV there are only a few things you need to know.

The BOV is there for Noise - Stops Flutter and the Big Whoosh noise.

The BOV is there for Turbo Life - Helps the turbo live longer but nothing to worry about.

You do not need another ECU or a aftermarket ECU.

If you want flutter or a different noise instead of the BOV. Just block it off and start driving. It works well and I haven’t noticed any Lag or problems with my engine.

Ive also added a Diagram on how to Block off your BOV

Edited October 5, 2006 by r32matt

[Rissole]

nice docco matty.

could of just bought a HKS SSQBV, holds the boost nice and constant at top boost , and flutters....

but... nice work.

Wanna sell me that 4 door yet?

[123456]

Hmm its odd that my 32 doesnt do it, 34 turbo, fmic, and some other crap. With pod on it gives a good intake sound, but flutters are impossible to hear outside of the car.. I've heard some VL's and a gsr lancer (hehe) do the flutter noises at high rpm, mine seems to do it only at RPM's where the turbo is just coming onto spool, doesnt seem to make any sense to me, would have thought the more RPM u got the louder it would be. Makes no sense to me Maybe my turboes just to small. Lancer has significantly smaller engine capacity to..

Not that i really mind, coz im not a wog, but still find it odd

[readyGO]

I've got a massive amount of flutter.. ill trade with a bov that opens correctly..

[Freddy Kruger]

how to block of bov - BOGAN SPEC

take of bov.

get an empty can of coke/vb or my choice JB Black

cut open can and trace the base of the bov onto the metal.

cut and make holes for the bolts.

put bov back on with the can gasket thingy.

FLuTT0rZZZ0rZ!!!!1!

10mins max.

(pic of mine, still had to cut holes for bolts...)

i might also add i did this for shits and giggles. it worked, but it got too much attention compared to the stock bov...

Edited October 6, 2006 by Freddy Kruger

[r32matt]

Yeah you wont hear the flutter as much on high boost. You will get a big WOOSH sound instead. I get heaps of flutter when my turbo is spooling up and I let go at about 8psi. Im running a R34 turbo on 12psi in my R32.

Yeah running a HKS SSQBV would be sweet, but it costs money, lol.

Coke can is what I used, lol

mmmm gtst I would swap you my standard BOV for one that flutters. It sounds really good and opens at low boost so no fluttering.

Edited October 6, 2006 by r32matt

[Modena]

I had flutter sound at low RPM when I had an apexi pod filter and a GFB hybrid BOV. The car ran like shit so I returned to stock set up.

Also Ive disconnected the snorkel from the air box and it also made some wierd sound...

But yeah while BOV and flutters sound cool I think your making your car run like shit and waste fuel, not to mention police attention.

PS you wont get any chicks driving past even in a Ferrari, if you want the girls, go talk to them!

[assyrian4evaa]

just a quick question guys.. how does an external wastegate affect the flutter when the bov is blocked?

[Rolls]

just a quick question guys.. how does an external wastegate affect the flutter when the bov is blocked?

It doesn't, external wastegates have nothing to do with flutter.

[paulr33]

its doesn't

its just urban myths and retard talk

[assyrian4evaa]

thank you very much..... i've tried telling this muzza but he wont listen