What's this noise? Popped DV?

C

cooni

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Since chipping (GIAC), I occasionally get this noise on acceleration. I just notice it, it hangs around for a bit and before I know it, its gone...

http://au.youtube.com/watch?v=1_CSecpYrcA

5mins later, its gone:
http://au.youtube.com/watch?v=wO20hSR21cA

Power wasn't noticibly lacking, but looking at the videos it looks like it was? I can't say really...


Can anyone shed any light on it? Popped DV would give that noise all the time, no?... is it possible for something to be jamming it open or something?
 
dc240969 said:
sounds fine to me.
Click to expand...
same stretch of road, same speed, same incline (flat)... just 5 mins apart...
different noises. very different in real life, maybe you just couldnt hear it too well in the video with your speakers...
 
audi upgrades
Sounds fine to me too.... Can hear the turbo spooling, revs increasing.... that's it.
 
same direction? which way was the wind blowing? grasping a straws here but could be more air passing through.
 
does it sounds like air escaping kind of noise? Like a whooshing noise?
 
I would be more worried about the latter video, sounds like a distinct lack of turbo!
 
Right now Andy has said that i know what ya problem is. My car is doing the same.

It is the wastegate on your turbo and the noise is being amplified out your exhaust. Mine has started doing it since i changed my exhaust (CAT back). Your GIAC map has (obviously) altered settings with regards to airflow/ fueling etc and for whatever reason your wastegate is feeling the need to open. My good freind who has just bluefin'd his car now has the same on occassion.

It drove me crazy for weeks and i eventually took the exhaust off! I then went back to exhausts UK who had a listen and told me the problem. Does it only do it above 4k rpm under heavy acceleration? No loss of power though. If so it is exactly the same as mine.

They have modified my exhaust which has made it quieter but its still there above about 5k rpm. I just need to map my car and balance the system again. Going to get an EVOMS intake which might help prior to mapping.

Anyone going the RR Day at Prosport on Sat will hear it on mine.

Rambled on a bit there i know but if you want more information pm me and i'll give you my number. I've been having this for months and i know it inside out now!

Paul :)
 
Listening to the video's again and it is definately the same thing!
 
Interesting - Eagle - what are the implications of what you're saying then - lost boost???
 
Jamie,

No not really. Basically the wastegate only opens when there is sufficient pressure on the turbo, i:e your pulling the 1 bar of pressure it needs. So it diverts gasses around the turbo so not to put too much strain on it, like an over boost situation.

I'm a electrical engineer and the way cars with turbos have been explained to me by a knowledgable friend is that the system has to be balanced like a mechaincal air system in a building. Not only does the air/ gasses have to flow through the system but there needs to be certain amounts of back pressure etc to balance it all out and make the turbo perform.

In my case i have released some of that back pressure with the exhaust. Now its flowing more freely out of the rear end. This has meant a change in the standard set up and in turn meant my wastegate has started opening. I bought my exhaust off jonny which was made by exhausts uk. As you may or may not know there was not a lot to it! Virtually just a straight through pipe! This meant that the gasses that passed the turbo through the wastegate bounced down the exhaust, echoed in the back box and came out like a screaming witch! Horrible noise and only realised it when i let my mate drive my car one day whilst i stood at the side of the road. Until then i thought it was some sort of induction noise!

Had a centre section box put in now which has made it quieter but it still does it mainly in 1st & 2nd gears when flooring it. Only about 4K revs as well.

Really hard to explain and i baffled many an 'expert' trying to expalin the noise etc. You there sat? If so you'll find out what i mean. I don't really like it but i'm hoping The EVOMS kit and maybe a re-map will sort things out!

Paul
 
Hey Paul,

Yep I'm heading over on sat - coming from the North East though, so will no doubt be a late arrival! Be interesting to see what you're saying!

J
 
HA HA

It will have you scratching your head mate, trust me. Everyone i wwas trying to tell thought i was losing it!

Even i started to believe I was hearing things!
 
lm no expert, l will stand up to that, and since l dont know how the waste gate works coz lve never had one apart lm thinking along the lines that once a spring has reached its limit it compresses. That is if the waste gate has a spring or similar. So wouldnt increasing that resistance stop this. just venting my 2 cents. Pardon the pun.
 
No its the amount of gasses in the turbo chamber that open the wastegate if i'm understanding what you are saying! so if the turbo is spooling to high and trying to move more gas through than it can the wastegate opens due to volume of gas in the space to relieve the pressure on the turbo. It is a protective device in one form or another basically. A standard car has a balanced system so the wastegate should never open

I googled 'How does a wastegate work on a turbo car'. There are some good explanations on there. The guy at exhaust uk said they have this problem with Scoobies and Evo's hence how he knew what it was.

I'm hoping he's right and what he's said does make sense although i'm no expert!
 
thanks for the replies guys...
im running stock intake and stock exhaust.

the second clip actually is what the car shouldn normally sound like... the first clip sounds "better", but its worrying.

re: wastegate opening, it happens as soon as i jump on the throttle, i don't have a boost gauge but will it spool instantaneously?
you can hear (maybe not in the video) the pitch of the noise changing, which means the wastegate is open whilst still spooling...
and surely if the wastegate is opening, im losing boost... same rpm, same gear, same speed... but two different noises
 
pm me your email address mate and i'll send you a video of mine doing it.
 
Right i've just had a chat with Steve from stattler to get his views on what it could be and in my case he thinks its just the increased boost of my turbo plus the fact i might not have enough silencer, say like a milltek.

He then said you'll get a noise like a jet which is right as the whole system then acts like a mini turbine system.

so i'm now officially driving the first S3 Jet! woo hoo

Goes off to get on his Tom Cruise Top gun outfit :undwech:
 
The waste gate is used to control the amount of exhaust gas passing the impeller in the Turbo. If you are off boost the gate will be open so that the exhaust gas by-passes the impeller and you don't produce any boost.

Modern Turbos also have variable vanes so that the amount of boost generated can be finer controlled by ajusting the angle of the blades on the impeller.

A DV (recirc or dump) bleeds off any unrequired charged air when you lift off.

Paul
 
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