So to my understanding the rattling noise is created by the wastegate rod which is affected by air flow and vibrations caused by exhaust gases coming out of the turbo.
A bigger downpipe increases the volume and speed in which the exhaust gases can be channelled out of the turbo/engine.
In theory it would decrease the amount of influences the air flow has on the wastegate and maybe even reduce the vibrations.
So couldn't a aftermarket downpipe "fix" the rattling noise by relieving the wastegate-rods?
@Dandanfings - Are you saying that since you've installed a new downpipe you no longer have the rattle?
I have booked my car in for service and asked them to look into the rattle. They basically told me there and then they won't do anything about it but they will report it anyway and i am to basically put up with the "characteristic". I went down the "how can it be a characteristic if not every engine has it" he couldn't answer and made his excuses and left..
To me it sounds more like the wastegate rattling rather than the turbo blade catching. I've been youtubeing for wastegate videos and I've found one where you can hear the wastegate 'ring' as he opens and closes the wastegate. If you imagine this 'ring' speeded up to, say, ten times, and a metre away then I think it would sound like what I'm hearing on mine:
Since it happens at lowish revs, and not under any real load, there will be no demand for turbo boost: so could the engine management just be opening the wastegate slightly to let any boost out (its not needed under those conditions) and the peak of a standing wave within the pipe just happens to unfortunately resonate with the wastegate and rattle/jiggle it? Maybe this would explain why fitting a different downpipe (and changing the resonanace of any standing wave) would remove the rattle?
I don't know enough about wastegate actuators to know how much force they apply to the wastegate to hold it open / closed / mid-position.
There's just something about the noise that brings to mind the rattling of the lid of a boiling coffee pot on a stove in some old western film I've seen... But speeded up a bit.
The characteristics of a standing wave will change with pressure (so change the engine load and it will go away). Also the characteristics would change if the exhaust back pressure was different (say on a 1.4TFsi rather than S3) and it may be sufficient to add a little extra mass onto the wastegate to hold it - which is why it can be eliminated on a 1.4 by adding a small amount of weight, but not on a S3. Although apparently on an S3 changing the actual downpipe can cure it.
Maybe I'm overthinking this?
So where from here? Downpipe aftermarket? Continue to pursue with Audi even without a warranty fix? Would appreciate you suggestions Dave to help me on what to do next even though it sounds faint in my S3.Sounds extremely logical to me !!! and that little metal cap he showed us tapping on a metal surface sounds like the exact noise I am hearing!!!!
Well ive had a call from Audi today and mine and Andys cars are going in to be measured on Friday 15th. I cant really advise on your own situation as each of see the issue maybe slightly differently. For me its Audi's issue and they need to sort it out. others might accept it .....some may not even mind it. Just do what you think is right for you
Apologies- What's the RTR thread?Check the RTR thread for updates. There has been a few.
Got it - cheers. I have my call with 'customer relations manager' tomorrow - won't hold my breath!Report The Rattle ...... just search the forum for "RTR"
Would you know where to start with that sort of thing? Or what to do? I don't I'm afraid, but would be happy to record vehice details.I wonder if its worth knocking up a website that can record VIN numbers etc to present to Audi/VW UK and share this on the various VAG forums. At the moment the biggest battle seems to be collecting a list of affected cars in one place to log a complaint they will have to do something about.
Would you know where to start with that sort of thing? Or what to do? I don't I'm afraid, but would be happy to record vehice details.
Not that strange as the 1.8 and 2.0 in the S3 are both EA888 Gen 3 and so pretty similar and both have electronically actuated wastegates. Both also have 8 fuel injectors (in EU spec); 4 direct and 4 indirect. The 2.0 has uprated parts and fancier electronics.