Snorkeling / "Kaudern": known. TDI AWX error?

Hello.

'On my A4 Avant 1.9 TDI (10/02, 96 kW, engine code AWX), a noticeable gurgling or rattling sound occurs when releasing the load (whether with or without the clutch), especially in the RPM range of 1300-1600/min. This sound stops after 1-2 seconds. It is not reproducible when the car is stationary (or without load), and it also does not occur above approximately 2000/min. This strongly suggests that the problem originates from the turbocharger. Various workshops have so far been unhelpful or dismissive, but one workshop showed me a technical bulletin stating that this noise (which is called 'kaudern' and there's even a VAG example sound file) is known to occur in 1.9 TDI PD and 2.0 TDI engines, and is caused by the interaction of unfavorable tolerances.'This results in resonances throughout the entire intake and exhaust system, which in turn cause further resonances. There is no solution, and the production model will not be changed. My questions:
1. Are there any other people affected, and is this really that common?
2. Is there a solution? If resonance is created by the interaction of various components, shouldn't it be possible to eliminate it by modifying a single component?

I hope someone has some advice.

Regards,
0588.778

If it doesn't affect the engine in any way, hopefully it won't be too bad.
I haven't heard anything about that before, maybe it's also something that happens very rarely.
and is sometimes even ignored.

My engine also exhibits a resonance vibration at 3000 RPM, decreasing to 2000 RPM.
But it only became this loud recently, after I adjusted my timing a little bit, and that's when I noticed it.

It would be great if you could check the valve timing.

0588.778 wrote:

On my A4 Avant 1.9 TDI (10/02, 96 kW, engine code AWX), a clearly audible "whooshing" or rattling sound occurs when releasing the load (whether with or without depressing the clutch), especially in the RPM range of 1300 - 1600/min. This sound stops after 1-2 seconds. It is not reproducible when the car is stationary (or without a load), and it also does not occur above approximately 2000/min. It actually quite clearly indicates that it's, in the broadest sense, related to the turbocharger.

Your description of the circumstances reminds me somewhat of a previous phenomenon on my AFN.

I would describe the sound more as a single "scratch-scrape-scrub" noise, with an approximate total duration of 1.5 seconds.
It typically occurred around 1300-1400 rpm, when abruptly releasing the accelerator pedal after rapid acceleration from low engine speeds.
During the LDA measurement, I observed that the pressure gradually decreased in sync with the sound.

I then adjusted the VTG (Variable Turbine Geometry) rod to be slightly longer, which reduced the pressure buildup at low engine speeds – and since then, everything has been quiet.

I therefore suspect that the noise came from some kind of pumping effect in the turbocharger (too much pressure at a low mass flow rate).

You could also try adjusting your VTG settings -> it doesn't cost anything .

Thank you for the quick responses. I doubt it's related to adjustable valve timing, but the possibility of lower pressure buildup sounds plausible. Here are two more questions about that:
Ultimately, this also reduces the torque (and potentially the power in that specific RPM range). If the loader later applies more force, will this primarily result in a shift in the Nm (Newton-meter) diagram, or will it generally flatten the torque curve?
'I'm a bit of a DIY enthusiast, but with this car, I'm more of a theorist (it still has a manufacturer's warranty).' How complicated is it to adjust the VTG (vehicle traction control)? Do I need any special tools, and can I access it relatively easily?

Regards,
0588.778

0588.778 wrote:

"I'm a bit of a DIY enthusiast, but with this car, I'm more of a theorist (it still has a manufacturer's warranty)." How complicated is it to adjust the VTG (vehicle traction control)? Do I need any special tools, and can I access it relatively easily? Regards, 0588.778

That should only take about 15 minutes, assuming the threads aren't too corroded.
Remove the airbox and connect the intake hose to the turbo.
Then a 10-gram fork will work well.

0588.778 wrote:

Ultimately, this also reduces the torque (and possibly the power in that specific RPM range). If the loader later applies more torque, does this primarily lead to a shift in the Nm diagram, or does it generally "flatten" the torque curve?

The Nm (Newton-meter) reading at low RPM depends on the speed-dependent behavior of your torque limitation, the soot limitation (both software-based), the actual boost pressure, the condition/age of your mass airflow sensor, and ultimately, even the weather.

Overall, the boost pressure should build up a bit later.
You might experience a slight loss of power in the lower RPM range, but the engine should pull just as strongly as before starting around ~1700 RPM.

Hi!


1. Are there any other people affected, is this really so common?

I've noticed the exact same phenomenon in my AXR engine (05/04). There's a slight, short-lived rattling/whooshing sound in the lower RPM range when releasing the accelerator abruptly. It's hard to describe the sound...

I've been meaning to consult a doctor about it, but I haven't gotten around to it yet due to a lack of motivation and energy. He's still running...

Regards,
Curtis.

PS: You have a great forum here! *Thumbs up*

Hi,

Where can I get the sound file?
I have an AXR model year 2005, and I'm experiencing a noise between 1800 and 2000 RPM during partial load operation. It sounds like a metal edge is vibrating and hitting something.
The workshop suggested that I should wait and see if the noise gets worse. Then the error would be easier to find.

@Curtis: Where are you from? Randomly in the Stuttgart metropolitan area?

Regards,
Sure, here is the translation of the text from German to English:

'Micha'

Bee wrote:

I have an AXR model year 2005, and I have a noise between 1800 and 2000 RPM in partial load operation. It sounds like a metal edge is vibrating and hitting something somewhere.

That will probably be something different. Here, we're (so far) talking about noises during the gas removal.

@Ulf:
That will probably be something else. Here, we're (so far) talking about noises when releasing the gas pedal.
Here's my question: Is it definitely a different sound, or just possibly?
Therefore, I would like to listen to the sound file from VAG and/or hear Curtis's car.

Regards,
Sure, here is the translation of the text from German to English:

'Micha'

Hi,

Unfortunately, I don't have the sound file. It was just the friendly person's statement that one exists. He showed me the workshop information as a printout for viewing, but he wouldn't give it to me. But it's pretty much the same for me, just like Curtis described.

After the Audi service in IN was so helpful in suggesting I look for a different workshop, I did so. They came to the same conclusion; we also removed the air filter housing, and it was clearly audible that it was likely resonances. 'State of the art, unavoidable due to boost pressures up to 2 bar , it happens occasionally due to different tolerances .'

I'm going to try using the VTG bar for now. I can also imagine that an air intake pipe with a different design between the air filter and the turbocharger might help (perhaps with an integrated 'backflow prevention' mechanism?).

Regards,
0588.778

@Bee,

Unfortunately, I'm not from the Stuttgart area. I am only available for assignments in Cologne or, alternatively, with companies located in the Saarland region.

The noise I'm hearing only occurs when I release the accelerator pedal in the lower RPM range, and it sounds – however strange it may sound – similar to a horse exhaling (that 'brrr' sound), but much more metallic (duration: about 0.5 seconds). However, it really always works, and it's also quite noticeable. My AXR had it from the very beginning (no tuning or modifications).

Unfortunately, I don't have any experience comparing it to other PD-TDIs (although this isn't my first TD(I), it's my first PD-TDI), and I assumed that this might be normal behavior for this model range.

Performance, incidentally... Could it be that the AXR values are showing a significant degree of variation?

Mine has 114 horsepower according to the DZR... (This is also one of the reasons why I'm 'hesitant' to go to the dealership with this noise... ).

Regards,
Curtis.

Curtis Newton wrote:

By the way, performance... Could it be that the AXR values are showing a significant degree of variation? My car, according to the vehicle registration document, has 114 horsepower... (Also a reason why I'm "hesitant" to go to the dealership with this noise... )

Sure, generally speaking, PDs with 100 horsepower and 110 or fewer horsepower are fundamentally defective...

Since, as far as I know, hardly anyone knows where the excessive horsepower comes from, your friendly dealer certainly won't be able to steal any from you .

@Curtis,

Based on how you're describing the sound, I'm experiencing the exact same sound! Good analogy with the horse!
My AXR has only 2700 km on it (so it's new and untuned).
What worries me is that, in most cases, resonances are not a good thing. Let's see what long-term experiences reveal.

Regards,
Sure, here is the translation of the text from German to English:

'Micha'

Bee wrote:

@Curtis, Based on how you're describing the sound, I'm experiencing the exact same sound! Good comparison with the horse!!!!

Hm, I would still like to know if it also only happens when reducing gas at low RPM "horseshoes," and how long the noise lasts approximately... ?

Can you also trigger it in other situations?

Hi,

Sorry for the late reply.

I haven't heard that noise when releasing the accelerator pedal before.
Yes, I can reproduce the noise: There's a suitable, consistent slope near the exit of our town. There, at approximately 1900 RPM, it climbs the hill, and it 'powers' its way up the entire incline (over 5 seconds).
The noise only occurs when BOTH conditions are met:
1.) Speed approximately between 1800 and 2000 RPM.
2.) Accelerator pedal position set to a specific point (for me, it's somewhere around half-throttle).

I once got into a fight with a former workshop foreman. Perhaps I will meet with him next Friday at a service center to listen to the VAG sound file.

Does anyone know if it's possible to save the VAG sound file from the VAG system somehow? Or can you only listen to it there?

Regards,
Sure, here is the translation of the text from German to English:

'Micha'