A4 2.5 V6 TDI: Loud Exhaust Sound (B5 Quattro)

Hi experts,

After finding so many good tips and tricks here in the forum, I have to bother you all with a problem!

The following is a description of the situation:
I have the Audi mentioned above! It has approximately 36,000 km, so it's practically brand new!

'The acceleration is actually okay! But overall, the engine is quite loud (it's hard to describe)! When it's cold, it sounds like a truck; I expected more from a V6! I already took it to the workshop, and they adjusted the fuel injection timing (it's not chipped yet). I'll get it back tomorrow. Would it be possible to send you an MP3 of the engine sound so you can tell me if that's normal? (Of course, only if it hasn't been fixed by then).'

Best regards and thank you.

Merlin.

Sure, go ahead and try it. It would be interesting to see if it produces a usable audio file. However, volume assessment won't work like that. Unusual types of sounds should be detectable.
You can include links (URLs) in your posts.

Best regards, Rainer.

hi rainer,

Thank you for the quick response. Tomorrow evening, I'll set up the laptop and microphone in the car and give it a try!
I'll try to provide some reference, like a piece of music, so that a comparison based on volume is possible.

See you then, and thank you.

M.

Hello,

You can skip the reference.

Best regards, Rainer.

Okay, I have the file now!

The engine was already warm! I clipped the Micro device to the air filter housing cover (facing the rear of the vehicle). I drove around our block once and then restarted the engine again at the end.

Okay, so I was surprised by the sound... I think that roaring noise is coming from the turbocharger, but it doesn't sound too bad (if it is)! I only hear it whistling when the windows are open, and it's not that loud.

Here's the MP3 file: www.markus-merk.de/audi/audi.mp3

Thank you all!

Markus.

'Just so you know: I don't really know much about this!'

Ugh, that sounds weird.
When idling, it sounds relatively normal. However, when you accelerate, it makes some strange, creaking noises that sound like the turbo.

Sure, I'd be happy to help. Please provide the text you would like me to translate from German to English.


arne

How does the original file sound, i.e., with a high bitrate? Is it the same as what you uploaded, or different? (If the original has a different bitrate).

I can imagine that some of the noise artifacts are due to the *extremely* low 32 kbps bitrate of your MP3 encoding. It's often "risky" to encode with a high sampling rate (22 kHz) but a low bitrate.

Compare it to see if it sounds the same at high quality (meaning the original, not a file that has been upscaled!), or if there's a difference.

Otherwise, the engine noise is recorded from the engine compartment, which is something new .

Best regards,

Jan.

'I've never noticed that loud noise from the T-loader before! It was a clicking sound when accelerating that bothered me. You can't hear that creaking noise from the outside! You can hear the turbo whistling a bit with the window open, but it's not necessarily unpleasant. I first tried recording outside the engine compartment, but I had too much wind noise. I might try again tonight. Ideally, someone with the same engine would make a similar recording.'

M.

Serpentine belt / ribbed belt slipping, tensioner pulley defective?
"It certainly doesn't sound like a turbocharger. If it were the turbocharger, and if, for example, the compressor or impeller were rubbing against the housing, it would have already been throwing debris everywhere... That would also be accompanied by very poor engine performance, but you haven't mentioned that, so I assume the performance is okay."

Best regards, Rainer.

Here is a log from my car dealership, regarding the start of spraying, and I think it might also be related to the boost pressure, or????? Please take a look. If there's something wrong with the turbocharger, it should be visible there, right? http://www.markus-merk.de/audi/protokoll.jpg


I also have VAG-COM available. Which measuring blocks should I check?


You guys are awesome, THANK YOU!

M.

Hello,

Measurement block 10: The boost pressure reading is correct for you. This allows you to rule out the turbocharger.
Please check all belts and belt tensioners/pulleys.

Best regards, Rainer.

Okay, I'd rather not get involved. I didn't want to make a wrong prediction. But now 'we' know that the loader is working properly.

Have a nice weekend.
Arne.

I can only guess, but to me, it clearly sounds like a belt.

Hello,

As far as I understand the noise, and if you're referring to the sound that occurs when you release the accelerator, I'm familiar with it from my own car as well. I hadn't noticed it before, but it's only been happening for about a year. I haven't been able to find the cause of this noise that started recently, but I believe it's normal.
The noise usually occurs during acceleration. When you suddenly release the accelerator, the rapidly increasing boost pressure needs to dissipate quickly, and this happens by adjusting the guide vanes inside the turbocharger. This allows the exhaust gases to bypass the turbine wheel and flow directly into the exhaust system, creating the noise.

Okay, your answers were helpful! Unfortunately, there wasn't a loose belt or any defect. I spent the entire Friday under my Audi, and the result was nothing found, totally scratched hands, and a huge amount of frustration with the car... well, not really! The actual 'noise that's worrying me' wasn't really audible in the sound file. I'll record another one. I'm just not sure where I can position the microphone outside the vehicle so that I don't have wind noise in the recording. I'll give it a try!

Okay, see you later.
merlin

The acceleration and things like that are actually okay! But overall, the engine is quite loud (it's hard to describe)! When it's cold, it sounds like a truck; I expected more from a V6!

I have the same vehicle... I also had problems with excessive noise while driving... but my workshop also said, 'no, that's normal.'

Whether or not this has anything to do with my major engine failure... who knows...

Regards,
Felix.