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Thread: Cold Air Induction Kit Noise

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    Ginger Prince's Avatar
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    Cold Air Induction Kit Noise

    Hi all,

    Im hoping someone can help/offer some reassurance....

    I have my S3 (8P) with a Milltek cat-back exhaust and Cold Air Induction Kit installed in June.

    As soon as the induction kit was installed the car now makes a loud squeal/squeak in-between gear changes (when putting your foot down).
    Prior to the induction kit being installed, it used to make a good noise (sort of like a subtle dump valve type of noise) in place of what is now an irritable noise. Im guessing this is because the original noise was due to the panel filter which is now obviously not fitted any more due to the induction kit now being installed.

    I much prefer the original noise rather than the now high pitch screech (sounds like a belt slip or wheel spin sort of thing) in-between gear changes/taking your foot off the gas, but, as long as I know its normal I will live with it as I bought it and had it installed to improve performance , etc.

    As I have never heard this noise before Im concerned it's not right but I have been told by the company who sold/fitted it that it's a characteristic of the induction kit I've purchased, like an engine, they all have their own quirks...!
    Im told the sound Im hearing at high load / revs is due to the overrun of the engine, when I lift off the throttle, air coming through the induction system is re-circulated out and this is the noise I'm are hearing. They said I'm not hearing the noise at lower revs as the air will only recirculate on overrun of the engine.

    I also asked Awesome GTI in Manchester (over the phone) and they too said that this noise was normal on the S3 with a cold air induction kit fitted.

    Sorry to post an essay but it's doing my head in and just want to know others experience this too.IMG_1394.jpg

    Thanks very much,
    Mike
    Last edited by jojo; 12th April 2013 at 00:05.

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  3. #2
    S3Alex's Avatar
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    The squeal is due to compressor stall on the turbo as the throttle closes between gear changes.....it is as your tuner has said,normal,but some people find it irritating.

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    Ginger Prince's Avatar
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    Quote Originally Posted by S3Alex View Post
    The squeal is due to compressor stall on the turbo as the throttle closes between gear changes.....it is as your tuner has said,normal,but some people find it irritating.
    Nice one Alex, thanks for that.
    Cant be good for the turbo that can it, sounds like its screaming for help...?!

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    that's actually good for turbo
    s3 Ibis White ... Build Thread

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    Ginger Prince, im sure you can overcome this by installing a dump valve. This releases the boost pressure when u come off the throttle so you wouldn't get any stall or surge from the turbo

    Quote Originally Posted by S. View Post
    that's actually good for turbo
    How is compressor stall good for a turbo?

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    Quote Originally Posted by Sidhu88 View Post
    Ginger Prince, im sure you can overcome this by installing a dump valve. This releases the boost pressure when u come off the throttle so you wouldn't get any stall or surge from the turbo



    How is compressor stall good for a turbo?
    The S3 recirculates gas measured by the MAF and thus you cannot use a dump valve.
    The diverter valve switches gas back into the inlet tract below the MAF.

    The reason for all the squealing is that when you wind the boost up,the poor old K04 is run to the edge of its map and turbine speed is pretty much maxed out.

    The squealing is the result when the throttle closes and the compressor stalls.

    The 3071 on mine is much quieter but dump valves won't work ... The air/fuel calculations made by the ECU will be thrown out.

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    Quote Originally Posted by Sidhu88 View Post
    Ginger Prince, im sure you can overcome this by installing a dump valve. This releases the boost pressure when u come off the throttle so you wouldn't get any stall or surge from the turbo



    How is compressor stall good for a turbo?
    didn't ment for that actually at all.
    s3 has a DV and the sound that it makes when he comes off throttle is the air recirculating back to the CAI, and i thought he is talking about that sound.
    s3 Ibis White ... Build Thread

    / Black Grill / FbMfSw / Sunroof / Hill Hold / Armrest / Black Leather-Alcantara interior / Rear Parking Sensors / Heated Seats / Folding Mirrors / Cruise / Rns-e mk2 // ttrs-Brembo Brakes / 12mm spacers / Forge Short + Side Shift / 42dd's / ITG CAI / GfB DV+ / Forge Catch Can / Milltek TBE / Forge Twin IC/ Autotech HpFp / H&R ARB's / WALK / KW v3's / RS4 fpr / Loba&Sachs clutch / Revo Stage 2+ / ...


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    Quote Originally Posted by S. View Post
    didn't ment for that actually at all, but thanks.
    2nd thing is that s3 has a DV and the sound that it makes when he comes off throttle is the air recirculating back to the CAI.
    The sound is compressor stall and is the result of the compressor still turning at maximum speed against a closed throttle.

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    Quote Originally Posted by S3Alex View Post
    The sound is compressor stall and is the result of the compressor still turning at maximum speed against a closed throttle.
    Ive also read:

    the noise I am hearing is from the turbo and due to the remap causing 'cavitation', not that of the cold air intake.


    Apparently, its common on K04 turbo'd cars as remapping takes them near to the limit of their airflow capabilities.

    If true, this is the point at which the turbo runs out of puff basically and cannot push air any faster. The noise itself (I'm told) is turbulence in the intake caused by the compresser wheel, it can be fixed by turning the boost down a couple of settings... however this will make less power!! Any glitches that are felt along with this noise are most likely down to intake pulses caused by cavitation.


    Because I don't want to damage the turbo i'll have to go back up to Preston from Manchester to where I had the remap etc and have things adjusted which is bad really as the software should have been designed to/for the Audi S3 (8P)

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    Mine flutters during the top end of spool up while accelrating, no power loss or anything. Then on the gear change it sounds quite normal with just a little hiss.
    Running stage 1 with a Forge twintake, does this sound OK or a bit concerning?

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    Quote Originally Posted by CornRattle View Post
    Mine flutters during the top end of spool up while accelrating, no power loss or anything. Then on the gear change it sounds quite normal with just a little hiss.
    Running stage 1 with a Forge twintake, does this sound OK or a bit concerning?
    Prior to fitting a Milltek cat-back & cold air induction kit being installed (on the same day) it used to make a nice little hiss similiar to a subtle dump valve type of noise in-between gear changes & coming off the throttle.

    Now in place of that I get a type of belt slip squeal/screech type of noise which to me (who isnt an expert) sound irritating but more importantly, a concern?!
    Last edited by jojo; 12th April 2013 at 00:07.

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    Quote Originally Posted by Ginger Prince View Post
    Ive also read:

    the noise I am hearing is from the turbo and due to the remap causing 'cavitation', not that of the cold air intake.


    Apparently, its common on K04 turbo'd cars as remapping takes them near to the limit of their airflow capabilities.

    If true, this is the point at which the turbo runs out of puff basically and cannot push air any faster. The noise itself (I'm told) is turbulence in the intake caused by the compresser wheel, it can be fixed by turning the boost down a couple of settings... however this will make less power!! Any glitches that are felt along with this noise are most likely down to intake pulses caused by cavitation.


    Because I don't want to damage the turbo i'll have to go back up to Preston from Manchester to where I had the remap etc and have things adjusted which is bad really as the software should have been designed to/for the Audi S3 (8P)
    This is basically what I've already said.

    The K04 is run at the limits of its compressor flow map at 360-380bhp and certainly at the maximum turbine speeds which accounts for the screeching due to the turbine blades meeting air with nowhere to go.

    Put simply,the sound is cavitation or compressor stall and the origin is the same.

    There are conflicting views on whether or not this is harmful but a lot of us(myself included) have run K04 turbo at this level over many tens of thousands of miles.

    It is not a software fault as much as a limitation of the K04 or indeed any turbo run to its limits.

    There appear to be very few of us reporting failures but it depends on how far you want to go with the car.

    I replaced the turbo on mine with something a bit bigger as the stock one was at its limits.

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    Quote Originally Posted by Ginger Prince View Post
    Prior to the Revo remap, Milltek cat-back & cold air induction kit being installed (on the same day) it used to make a nice little hiss similiar to a subtle dump valve type of noise in-between gear changes & coming off the throttle.

    Now in place of that I get a type of belt slip squeal/screech type of noise which to me (who isnt an expert) sound irritating but more importantly, a concern?!
    The hiss there was the sound of air being diverted back via the diverter valve to the intake distal to the MAF.

    That ensures that air which had already been metered and fuel calculated against that is not lost or dumped hence no dump valves on an S3.

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    I ran my last S3 8P for nearly 60,000miles (from 198 miles on day 2 of ownership) with remap, and my car was fine. No turbo issues at all.

    If its not a sound you like then I'd suggest backing off the boost a setting or two or reverting to std airbox which can manage to 340bhp'ish.

    Most of these sounds are 'engineered' out by Audi to give a perception of quality, constraint and respectability. When you start pushing 20-30% more power and put free flowing exhaust and intakes the running characteristics have to change, but there are many mapped S3's and I've yet to read of a story that is backed up with evidence that says the noise you mention does damage. It might reduce operating life, but as to what extent????

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    Well put ,Warren.

    The lifespan of a turbo is a variable in any case and includes things like regular servicing,oil changes and driving style.

    If you run the turbo to its limits then you should expect a shorter life but changing the oil every 5000 or so miles will help prolong that.

    Audis service schedule is aimed at unmodified cars and should not be applied to any modified ones.

    I had no problems with my K04 but in the end it couldn't provide what I wanted but it has to be said that getting reliability and a power increase of 30% is a good result.

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    .IMG_1394.jpg

    Lovin the enclosure. Definitely something different. What did you use to make it and does it work ?

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    Cold Air Induction Kit Noise

    Quote Originally Posted by Dan Hobley View Post
    .IMG_1394.jpg

    Lovin the enclosure. Definitely something different. What did you use to make it and does it work ?
    Looks like the BSH Truseal intake.

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    Alex / Warren - Cheers boys, the high pitch screech was worrying me but I'll chill out now since its nothing to worry about.

    Dan - It does seem to be something different that not many have seen, pretty cool as its supposed to try and eliminate the heat from the engine bay etc. I've checked my invoice though and it doesn't have the brand name listed but if you wanna know what it is then I'll ask the guy I bought it from once he's back off holiday next week.

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    I love the little chirrup you get on some changes, but my CAI usually only makes a psssshhh as the air dumps back into the intake/exhaust (whichever one it is... never remember).
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    Cold Air Induction Kit Noise

    Deffinetly not s pssssst, thats what it used to sound like prior to fitting a cai kit and cat-back exhaust but now it screeches instead in-between gear changes when putting your foot down....
    Last edited by jojo; 12th April 2013 at 00:07.

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    I think your all wrong lol, big power gain = more boost (when putting foot down) at gear change usually peak boost = lots more pressure on original boost pipes at peak = small boost leak. Think of a baloon full of air then stretching the neck for a fraction of a second to let some air out, it squeels.

    Compressor stall is a flutter not a squeal and compressor stall is bad not good in fact anything that stalls thats not designed to is bad usually means theres a problem somewhere if your engine stalled every day/hour would you just leave it or think mmmmm there's a problem? Over time the stalls will cause other component problems.

    And who mentioned installing a dump valve to overcome the problem, all turbo cars have dump valves as standard anyway and even though i'm an 8L boy I know the standard valve on the 8P is actually quite a good valve untill silly power levels are reached. The 8L dv's are pants thats why we all go for the 007p (now the newer 008p).

    Now a note on sounds.

    Manufactures pour millions in to designing quiet and high flowing intake systems as they do exhausts so that noise polloution is kept to a minimum. so when you mess with thease components you will get noises such as air been dumped, turbo spool and a roar. The more of the original you take away the louder the noises will usually get.

    Like I say i'm an 8L boy 8p's are different so you could be right but above is what I think lol.

    Please feel free to shoot me down at any time lol.
    Ill try stuff out! If you never try and never fail, you will never know and never learn.

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    Quote Originally Posted by cjsuk View Post
    I think your all wrong lol, big power gain = more boost (when putting foot down) at gear change usually peak boost = lots more pressure on original boost pipes at peak = small boost leak. Think of a baloon full of air then stretching the neck for a fraction of a second to let some air out, it squeels.Compressor stall is a flutter not a squeal and compressor stall is bad not good in fact anything that stalls thats not designed to is bad usually means theres a problem somewhere if your engine stalled every day/hour would you just leave it or think mmmmm there's a problem? Over time the stalls will cause other component problems.And who mentioned installing a dump valve to overcome the problem, all turbo cars have dump valves as standard anyway and even though i'm an 8L boy I know the standard valve on the 8P is actually quite a good valve untill silly power levels are reached. The 8L dv's are pants thats why we all go for the 007p (now the newer 008p).Now a note on sounds.Manufactures pour millions in to designing quiet and high flowing intake systems as they do exhausts so that noise polloution is kept to a minimum. so when you mess with thease components you will get noises such as air been dumped, turbo spool and a roar. The more of the original you take away the louder the noises will usually get.Like I say i'm an 8L boy 8p's are different so you could be right but above is what I think lol.Please feel free to shoot me down at any time lol.
    Firstly......go and check how air mass is metered on the 8P,and then you'll see why a diverter instead of a dump valve is used.
    Here's something simple on chatter/flutter etc etc....whatever people want to call it.... Wastegate - Wikipedia, the free encyclopedia

 

 

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