I notice a lot of the vlt owners talk about a noise that sounds like (try my best) 'chi chi chrrrrrrr'. A lot of you seem to relate it back to it being the 'intercooler noise'. To me this sounds like a bit of a joke really - every performance magazine I have ever read refers to it as the noise when the pressurised air from a turbo has nowhere to go (when the throttle is suddenly closed during gear changes) and flows back against the turbo compressor wheel. Another word for it is 'cavitation'. Read some issues of Zoom and you'll see what I mean! In relation to your 'intercooler' noise: *Fit a pod filter and it gets a lot louder - because the compressor wheel is now carving up the air and the sound goes straight out the compressor inlet and back through the pod filter (with little sound deadening properties compared to stock inlet) *Fit a correctly working BOV and it immediately goes, simple as that. The air continues to be pumped through the turbo and is fed out the BOV fitted between the turbo outlet and the throttle body. Hence no reversal of flow. If you don't set up the BOV right you'll get a mix of both noises, too tight and you'll just get the same old noise. *It happens on turbo cars without intercoolers (my mates Vl is a classic example) - its not an intercooler noise - its a turbo compressor spinning one way and the pressurised air going the other way *It is not good for your turbo. Everytime you change gears its fighting against air flowing the other direction, and hence not only slows turbine speed, but also places increased stress on the turbo shaft Listen to a stock r32 or r33 car, no 'chi chi chrrrr' noise - why? They come with BOV's standard. I just thought I'd clarify this issue - this is the only performance thread that I have ever seen which refers to 'intercooler noise'!! Why would a different intercooler make a different sound? Probably because its flows differently at different pressures and changes the rate at which the air flows against the compressor wheel during changes - hence different noise. Is this a commodore 'bogan' thing or what? I have a silvia and a v8 commodore 'bogan mobile' and have a high respect for vl turbo's - but you need to know what your talking about if your going to post! Correct me if I'm wrong, but I'll be happy to send anyone the scans of the magazines I've got to back me up Some original photos have not been recovered yet.

it is called intercooler flutter and it is the air equalizing from the turbo and hits throttle body and reverses into the forward moving air . this noise does not happen to cars without a cooler . i know this because i have 2 vlt s one with cooler and one without , you need to listen more closely if you think this noise happens without cooler . maybe get ya head out of magazine and go and check it out on a real car as for not knowing what you are talking about before posting you should take your own advice and not post till you know what you are talking about as for bov it,s a preference thing both my cars have done over 200000 klm with no bov , but i can see the merit in fitting one . i,m not interested in bov as they don,t make more hp so i don,t need to spend money on them .

i second that exactly, my vl "fluttered' a lot more after cooler went on, it is just reversion as you say but it has to go out through the intercooler as well and this is what makes the noise. instead of sounding like a heavy breathing pervert my car now sounds like a helicopter when I back off the trottle. short of running massive amounts of boost, BOVs are not necessary. I am not saying this because i cant afford or dont have one. I took mine off. in my opinion BOVs create more problems, ie they can leak, and they stuff up the airflow meter causing a bucketload of black fuel smoke to drop out of the back of your car if you have an airflow meter ps. the original turbo in my car did well over 250 000 no probs without BOV at 11+ psi

im in the same boat as luke. i had a BOV with out a cooler and just b4 i got my cooler i took my BOV off... only sound was like a "spooling down" of the turbo with a "puff" sortta noise. i then put my cooler and a K&N pod and makes a really loud "flutter". i have never heard a vlt with out a cooler make that "flutter". and if ur mates does it then by all means post pics of his cross over pipe and a sound file with the noise it makes.

can i suggest, rockysilvia, that you reread your post before you submit and try to avoid sounding like a know-all ****? i have no cooler and a pod and it does make a loud noise on backoff from the turbo but it sounds nothing like intercooler flutter.

"Intercooler Noise" is the best way to describe the good flutter sound everyone loves as its the air resonating inside the metal cooler piping and cooler. You wont get it without one as theres not enough metal intake piping and too much flexi rubber ****e that absorbs the flutter sound. Aswell its almost impossible to backspin a turbo thats been spinning at 50,000rpm and higher so BOV's are useless apart from lowering emissions on AFM equipped cars!

not trying to sound like a know it all, just amazed that people truly believe that it is 'intercooler' flutter! If anyone can convince me otherwise, then fine, I'll accept - it is a discussion forum and it sounds like something worth discussing... Consider this: You have an engine boosting, with throttle open. Air is flowing very fast through the pipework, intercooler or not. Boost is controlled by the actuator to a certain pressure. When the throttle is snapped shut, you suddenly have a volume of pressured air with nowhere to go. At the turbo end of the pipe you have a compressor spinning at 100,000 odd rpm and on the other side of this wheel is atmospheric pressure (0 psi). Just like a balloon, or like a gas bottle, a volume of air will always try to equalize pressure, so the air forces its way through the turbo in the opposite direction against the compressore wheel, to atmospheric pressure on the inlet side of the turbo. The noise you here is pressurised air 'slapping' against the compressor blades doing 100,000 rpm in the opposite direction. This quickly slows the speed of the compressor. If you have an intercooler the noise is louder and longer because within the piping and IC there is a much larger volume of pressurised air which has nowhere to go and hence gets fed back through the turbo. Much like a larger volume balloon takes a longer time to deflate than a smaller one if you open the end up. That's my opinion - for those who say 'intercooler flutter' from air hitting the throttle body and turning around only to hit air travelling in the other direction. I ask you this: 1. are you saying that 'no' air travels back through the turbo when the throttle is closed? if this is the case, then while the throttle is closed the turbo keeps pumping air into a confined space, and you should get a pressure 'spike' on your boost gauge when you close the throttle to change gear - i am yet to see this happen on mine or any of my friends turbo cars. 2. on any turbo car i have been in this 'noise' only happens when the boost gauge starts reading positive pressure (and therefore a positive difference when the throttle is closed). why doesn't is happen at anywhere less than positive pressure? even when the car does not have positive pressure there is still air flowing fast through the intercooler and piping. shouldn't this make the same noise when you snap the throttle shut? It doesn't. Try it. Some original photos have not been recovered yet.

Couple of sites to have a look at: http://www.skylinesaustralia.com/forums/showthread.php?s=&threadid=2105 http://www.davidrawlinson.org.uk/200SX/200SX_dumpValve.html www.supras.com/sogi/techtips/bov.html Its called 'compressor flutter' or 'compressor stall' Some original photos have not been recovered yet.

you say ta-mah-to, we say ta-may-to

I say who cares!

one word WASTEGATE

atmospheric pressure is not 0psi it is 14.6psi. you said: "If you have an intercooler the noise is louder and longer because within the piping and IC there is a much larger volume of pressurised air which has nowhere to go and hence gets fed back through the turbo. Much like a larger volume balloon takes a longer time to deflate than a smaller one if you open the end up." so there is a different noise if you have an intercooler, you said it yourself. why then should it not be called intercooler flutter if there is a different noise?

A VL Turbo with just a pod let's out that stock sounding backoff, no flutter there. Sound's nothing like it.

i would like to see some pics and hear some sounds off this "mate who's vlt "futters" without a cooler..... :roll:

rockysilvia maybe it is different on your car but without an intercooler on a VL it won't make a fluttering sound, with just a rampod on mine and 12 pounds it used to make a very loud whoosh sound (kinda like a BOV sound except better). Once you add an intercooler on it will start making fluttering noise. This is why people refer to it as intercooler noise, why get technical when describing the sound to someone. I'm sure if I got stopped in the street and asked why it made it, I wouldn't offer a technical explanation that went for ten minutes. The most simple and true thing to say is 'Intercooler noise'. My mate has a R33 skyline and he deliberately blocked off his standard BOV just so he can get the fluttering sound. Is he also a bogan?(It would be the first ever asian bogan)

Quote: Originally Posted by RB3-747 My mate has a R33 skyline and he deliberately blocked off his standard BOV just so he can get the fluttering sound. Is he also a bogan?(It would be the first ever asian bogan) cmon he has to be - he gets cooler flutter so he is a bogan for sure

vlred - I said 0psi being relative pressure to atmosphere - not absolute pressure. A boost gauge reads relative pressure.... rb3-747 - your mate backs me up - with the stock bov he didn't get the noise, because the air flowed through the bov rather than back against the turbo wheel during changes. He blocks off the BOV and suddenly he gets the noise, just like any vlt without a BOV. Your mates not a bogan, he knows exactly what is going on - he didn't have to slap a big IC in the front to get the noise!! I just wanted to clarify that the noise is from the turbo, not the intercooler. Change the intercooler, you change the volume of pipework and therefore make the noise much louder/longer. But you could have your pipework connected to a 20lt jerrycan instead of an IC and it would once again make the noise much louder&longer - no intercooler, same noise. The reason the noise is hard/quiet/short in duration is the very low volume of the stock vlt pipework, but if you listen it is there, louder with increased boost.. Yes, it is a great noise, maybe not good for the turbo, but a broken turbo is always a good excuse for a bigger one. Some original photos have not been recovered yet.

Quote: Originally Posted by rockysilvia not trying to sound like a know it all, Consider this: atmospheric pressure (0 psi). ---Ehhh WRONG. Atmospheric pressure is roughyl 14psi. Boost is manifold pressure above atmospheric pressure, so a car on 6 psi boost is running at Atmospheric pressure (14psi)+ 6 psi = 20 PSI. AS FOR THE CHII CHHHR DOOOO NOISE Although, Silvia guy is right about the source of the noise. The VL guys are more accurate though because the reason you hear the noise is the surface area offered to the air by the intercooler is what amplifies the noise. So let me offer an analogy. You are playing an electric guitar without an amp to a crowd at the Sydney Entertainment Centre, the crowd can not hear the guitar but you are playing your heart out. Then you plug it in to an AVP Stage 2 amplifier and the crowd can hear you. Ask the crowd where the noise is coming from. The answer is THE AMPLIFIER SPEAKERS. Chances are the guitarist can not even hear the sound coming from the guitar. It is completely academic that the noise originates from the turbo blades because its final point of dissipation is at the Intercooler (which anyone serious about turbo cars has.) so therefore it is completely logical to call it intercooler flutter. If you have a comeback to this then I will pre-empt it by saying this: The exhaust note of a car originates in the cylinder chamber with the noise of internal combustion but we still call it exhaust noise. Why? Because we are bogans??? No because we are 100% accurate as to where the noises final point of dissipation is. Same with INTERCOOLER FLUTTER. So take your purely academic logic which someone smarter than you actually came up with and stick it in your ear. Because guess what I and many others on this site are smarter than you too. Some original photos have not been recovered yet.

I think that you are contradicting yourself rockysilvia, we all know a BOV vents excess air into atmosphere thus eliminating flutter. Correct me if I'm wrong though but wasn't your initial argument that intercoolers dont help make the fluttering noise. Also my mate doesn't back you up as R33 skylines have intercoolers as standard.(he actually has a Supra cooler though) Any VL without a BOV won't make a fluttering sound unless an intercooler is added. If you read my post before I was running 12PSI without an intercooler and there was no flutter. My bro runs 15PSI in his ceptor(only because of retarded timing) and same thing again.

good explantion choice bro