Intercooler noises

[jhevo]

Hi everyone,

I am just wandering how to get that intercooler noise on a VL turbo. I have a cooler on mine and through gear changes you get a cooler noise, you know which one, its hard to describe. Goes something like kou kou kou kou kou :) However, I have heard other VL's that are so much louder, they sound like trumpets. Sounds awesome. Is this because of a bigger turbo or a bigger wastegate or external wastegate??
Thanks.

[everlast]

umm i dont think its intercooler noise....
usually its more prodominate on a car with no BOV (either atmo or plumb back) and the sound is the air going back through the compressor blades and out through the air filter (i think). The louder ones i think you will find it is louder because they are running a pod filter as opposed to the standard air box that has resonators to quieten that noise from the factory. Id assume more boost + pod would make it pretty loud.

It can also happen on cars with a BOV that is done up tight, the air doesnt vent it goes back through the pipes and through the compressor.

Im pretty sure thats what the go is, but if anyone has corrections or stuff to add, go ahead.

Cheers.

[180sx]

What everlast said.

Definitely not a good thing. I'm sure it lead to my standard turbo's death (ran without bov for 12 months)

[MAZMAN]

the noise can also change with different intercoolers as i have found out.
i had a series 4 cooler and it hardly made that kou kou noise,then i put a BIG front mount and it made the loud KOU KOU noise.
this is all with no BOV,so the air goes through the cooler(and thats why i think it makes different noise).

as soon as you put a BOV,it will make another noise(whistle type)

[QABB]

I know of one which has very loud compressor flutter with the stock airbox, the secret being the T04...
More boost = more flutter too...

[darkstar]

According to 21st centuary performance by Julian Edgar, he states that BOVs do not have a performance aspect to them, and are employed into cars so that the high pitched (kou kou) noise does not come apparrent, and ot keep the car with in noise limits.

Those that drive a vl turob, with no cooler or bov, just stock will know what i mean.


Also the idea that 'compressor stall' lessens the life of your turbo sounds a little vauge.

When the air comes back, the turbo is compressing in a rotating fashion, and therefore the air comming back is also compressing in that same rotational direction, though in the opposite (ie, clockwise compress, anticlockwise - 'back pressure')

Therefore, since the turbo is designed to rotate, i dont see what a little restriction will do by the air rushing back throughthe compressor.

I have tried to measure if i could actually feel the air come out of the turbo inlet, where the afm and all that are, and i havent found it has. But the tests were at idle, playing with the throttle cable to generate some boost. The sound does come from the airbox/filter, but that could be due to a soundwave being formed when air is displaced. It can be modeled loosely as a wind column with 1 closed end. The air gets displaced, a pressure is generated, sound is formed, and the fluttering noise is the result of the sound dispersing or traveling through the veins of the intercooler.

Thats why sounds from a non-intercooled turbo sound like a bov.

the wastegate flutter is wrong, as the wastegate has nothing to do with the noise, and it can be proven by having no wastegate on your turbo (disconnect acuator even), and the noise will be apparent.


A lot of things reflect the quality and pitch of the noise as well as the duration.

Intercooler sizes are one. A small cooler wont produce a loud or long noise, but a larger one will, perhaps due to the more sound distortion?

Also piping diameter is one, as it can be modeled as a wind pipe in loose terms.

Piping and system restriction are other factors.

Filters play a huge role in the noise. with the stock airbox on the vl turbo, it was high pitched and rather short in duration and rather quiet.

When i put a K&N filter on, it was loud as, and the echo was very long. The noise was deep and more spaced out and took longer to die down.

[LJ03L]

I can get my car to flutter. Even with the plumback BOV. it isn't done up tight, its just a bosch one. It is only apparent during full boost. The BOV is situated bettween the cooler and the compressor outlet. If i un-plumb back the bov, i can't hear the flutter - probaly because of the noise from the bov.

[cadet]

[QUOTE]Originally posted by darkstar
[B]According to 21st centuary performance by Julian Edgar, he states that BOVs do not have a performance aspect to them, and are employed into cars so that the high pitched (kou kou) noise does not come apparrent, and ot keep the car with in noise limits.


i have noticed a small performance increase from fitting a BOV


Also the idea that 'compressor stall' lessens the life of your turbo sounds a little vauge.

When the air comes back, the turbo is compressing in a rotating fashion, and therefore the air comming back is also compressing in that same rotational direction, though in the opposite (ie, clockwise compress, anticlockwise - 'back pressure')

Therefore, since the turbo is designed to rotate, i dont see what a little restriction will do by the air rushing back through the compressor.


my CA18 ran fine for years with no BOV and when i pulled the turbo off it seemed OK. however a wheel and shaft spinning at say 100 000rpm has a fair bit of inertia. if you try to suddenly reverse or stop one wheel while still spinning the other wheel in the original direction it has to experience some torsional and lateral (thrust) loads which can't be good for it. i believe a BOV will help reduce this stress.

[jhevo]

Thanks everyone for the replies, I think I have a better understanding now.

My car doesn't have a BOV but I do probably want to put one on. I have one at home but its not a plumback one, its an atmosphere one. What is a better BOV to put on a VL, I heard an atmosphere one might create some idle issues due to the AFM and its better to go for the plumback style Is this true?

[GTSBoy]

A plumb back type is better, but you can set up and atmosphere venting one so that it won't open at idle (or cruise!!!). This is just a spring pressure adjustment so that they take a lot of vacuum in the manifold to open. This reduces the effectiveness of it as a BOV...but then people like the noise.

My solution is to use a plumb back one (standard on my RB20DET) and modify the turbo inlet piping (steel mandrels instead of convoluted rubber) and the airbox (4" cold air inlet).

I wasn't after the BOV noise, but you get excellent aural feedback on what the turbo is doing (read that as you can hear everything it does) through a big system like that, including the BOV venting back into the turbo inlet.

cheers

[Ustasa]

Those sounds like the kou kou isnt necessarily air coming back, but the associaated pressure waves in the system resonating. A mass of air travelling in a restricted system has both flow and pressure waves and in some cases they become disassociated with one another. It's the rapid fluctuations in pressure that would damage a turbo compressor wheel if anything.

[jhevo]

How would I put the plumback one on.

On my cooler pipe going to the throttle body has a welded bit for a blow off valve (which I have blocked now as I dont have one on). However I can put an atmospheric one quite easily as I just need to T off a vacuum line to the BOV.
As for the plumback one, do I plum it back to the rubber pipe that goes from the AFM to the turbo? That means I would have to cut a hole in the rubber so I could plum it back. Is this correct? Any other way of doing this?

[THE ASH]

Originally posted by jhevo
On my cooler pipe going to the throttle body has a welded bit for a blow off valve (which I have blocked now as I dont have one on). However I can put an atmospheric one quite easily as I just need to T off a vacuum line to the BOV.

Correct :)

Originally posted by jhevo
As for the plumback one, do I plum it back to the rubber pipe that goes from the AFM to the turbo? That means I would have to cut a hole in the rubber so I could plum it back. Is this correct? Any other way of doing this?

2 for 2. I'd make a larger steel inlet pipe instead of the rubber one like GTSboy described because you don't want unmetered/unfiltered air getting in there. I have this kinda setup too & it works well for me also.

[HDTvlt]

i have seem turbos break compressor blades as there was too much back pressure on the turbine

[bugle]

I have a turbo with a snapped shaft could have been caused by no bov maybe?

[darkstar]

WHat kind of boost was the turbo running to chip/snap the blades?

when you say performance increase, what kind of perofrmance increase are you talking about specifically?

Ive tried to look at the movment of my boost gauge to and from 12psi, and it seems that the bov might give an effect in terms of needle swing, but im still a little unsure if it does much aside from making the noise.

Also, if you ever were to race in a manual car, youll find that its more the way you drive and change gears that will ensure a good run, not how good the bov works.

Again on boost gauge swing, it appeared that the needle went a little faster to the boost settting with the bov on, but that could be the 'placebo' style effect, where you think its faster, but its really the same :)

I suppose if your running excessive boost pressures, then a back pressure system could develop, and back pressure is something that you might not in a high HP appication. therefore, the bov will reduce the back pressure in the system, and increase spool up time.

Then again its also how you would like to enjoy the car as well. I quite like the intercooler noise, as it is unique to every car, and has quite a nice sound to it all.

Im not sure if i should sell mine, or keep it, or what ! :)

[JiMiH]

I've been looking into that fluttering noise heaps, and I spoke to a guy with a 200sx (intercooled obviously). He said that he gets the flutter noise from his BOV ... which is an HKS super sequential.

Maybe this helps?

P.s. I love that flutter noise :D

[cadet]

Originally posted by darkstar

when you say performance increase, what kind of perofrmance increase are you talking about specifically?



i noticed more power immediately after changing up, the bov was doing its job and letting the turbo freewheel so i got boost again sooner. it made a small difference but enough to notice.

[Doctor]

I beleive that there are 2 types of noises. The first is turbo flutter or compresser stall, making a hard edge choo choo choo noise

The other is when you have a intercooler fitted and all intake pipes are welded together. It makes a more rounded doo doo doo doo noise. Pipe chatter occurs and vibrates/resonating through the pipes as there are no rubber connectors to take away the vibration.

Doc