Loader Piping After Cold Start

Hello everyone!
Here are some observations I've made about my G3 AHU:
When I start the engine from a cold state and then release the accelerator, I can hear the turbocharger whistling (or rather, a quiet but distinct whistling sound) from approximately 1900 RPM down to around 1400 RPM engine speed.
When the engine has reached its operating temperature (the coolant temperature gauge is in the middle), you can't hear the turbocharger anymore.
A friend suggested that it might be due to play in the bearing shaft or a problem with the lubrication of the turbocharger. I find that odd, considering I've only driven 75,000 km. Or could it also be due to the wrong oil (0W40)?
Or am I just panicking right now?

I couldn't find anything about it through searching, thank you very much for your answers.


Greetings.

Is your EGR valve functional or deactivated?

Okay, yes, sorry, I forgot to post that...
Unfortunately, the AGR (Active Grill Roller) is defective... however, the noise level hasn't changed; it sounded the same before.

Greetings.

Hi,

I drive an A4 AFN.
I also hear the fuel pump more clearly during a cold start than when the engine is warm.
Especially when the window is open and I accelerate, you can hear the turbo whistling (quietly) shortly after the idle speed.
I've noticed this in many (including almost new) TDI models.
I actually like the sound, but your post has made me a little unsure now...
Is something wrong?

best regards
mortl

Ah, yes, sorry, I forgot to post that...
Unfortunately, the AGR (Active Grill Roller) is defective... however, the noise level hasn't changed; it sounded the same before.

Greetings

Yes. Especially when the engine is cold, the EGR system is responsible for reducing noise. Also, no exhaust gases are being diverted, and the turbocharger is forced to spin a bit faster. This is normal; I've observed the same thing on my ALH and AWX engines.

Hello,

"I'm also experiencing the same issue under the described conditions. I'm on my third turbocharger (the first one was replaced due to a stuck variable geometry turbocharger, the second one failed after 500 meters of full throttle, and the third one has been running for 60,000 km)."
The only loader that didn't whistle was, incidentally, number #2.
That's why I can sleep soundly at night, as long as there are no damages to the charger's wheels and it doesn't require any oil.

Best regards, Rainer.

Hi,

I drive an A4 AFN.
I also hear the fuel pump more clearly during a cold start than when the engine is warm.
Especially when the window is open and I accelerate, you can hear the turbocharger whistling (quietly) shortly after the idle speed.
I've noticed this in many (including almost new) TDI models.
I actually like the sound, but your post has made me a little unsure now...
Is something wrong?

best regards
mortl

Hello?
I didn't post my comment a second time... I don't know why it's showing up again!! (Maybe it's because of a 'back' function in the browser...?)
Sorry anyway.

best regards
mortl

Hello!

I find it strange that it only whistles when it's cold... I think I remember my old car behaving the same way (although I didn't pay much attention to those noises back then).
The noise doesn't bother me at all, quite the opposite, it sounds good.
Your posts all refer to engines with VTG turbochargers, but I have an engine with a wastegate turbocharger. My mother has a G4 with a 90 hp TDI engine; I don't know the exact engine code right now (but I think it also has a VTG), but in any case, the turbo whistles on that car too, even when the engine is warm and you let off the gas.

But to get back to the main question: Why does it only whistle when it's cold, and not when it's warm?
That must have something to do with the lubrication, right? The flow, the injection nozzle, etc., shouldn't behave the same way, right?

Best regards,

Read! It's already written there!

Hi,

"My turbo also whistles when it's cold (Golf 2, engine code SB, water-cooled wastegate turbo), but not when it's warm. It doesn't have an EGR valve, so it's not related to that."
Due to the recurring expressions of anxiety regarding the fluctuating patterns, here's a quote from the linked page:

"Das Radial- wie auch das Axiallagerspiel ist in Ordnung, wenn die Laufräder die Gehäuse nicht berühren". AlDon't panic!

Turbo-Tips: http://www.motair.de/seiten/tip1.html

Best regards, Uli.

Deleted upon request.

Hello everyone,
My AFN (air filter noise) also whistles, and as long as it does that, it's okay. If you want to know what a charger looks like when it dies, watch Formula 1 - it's like that!
The loader is failing; the oil pressure is forcing oil into the cylinders. If you're lucky, it's only enough oil that the engine still takes in air and isn't just compressing oil.

'Anyone behind you will immediately notice that the turbocharger is failing. Shortly after, the engine will follow suit if you continue driving, either due to oil compression or a lack of oil.'

In short: When the turbocharger fails, it's usually the bearing that's gone, and the turbo starts leaking oil, either into the exhaust or the intake manifold. In either case, you'll have an exhaust problem, but don't worry, no one will be able to read your license plate anyway...

Why does it whistle more when it's cold? I suspect that the lower exhaust gas temperature in the cold exhaust system results in less back pressure, and therefore less damping. It stops relatively quickly, long before the engine warms up. This suggests that only the exhaust system needs to heat up.
And it's even louder with an empty cat.

The question isn't why he whistles so coldly, but:

What is needed to make it sound warm like that? Does anyone have a VSD dummy?

What is needed for it to sound warm like that? Does anyone have a VSD simulator?

Yes, I have. However, the loader only whistles when it's cold. When it's warm, the entire exhaust sounds a bit more muffled, and at full load, there's a bit more hissing coming from the back – although it could also be ice formation. I don't think that provides much information.

If you drive without an air filter, the engine sounds good. You should try it sometime!

Hi,

Do you want to know how a charger behaves when it dies? Watch Formula 1 - it looks like that!

Formula 1 cars do not have turbochargers.
But the appearance would likely be quite similar (if a charger fails).

best regards
mortl

Good day!

Okay, here's a brief summary:

So far, we have identified two fundamental theoretical approaches and understand how they work.
If an imaginary Formula 1 turbocharger looked like it was escaping through the exhaust.

@julian: I repaired my EGR system again yesterday, just to be absolutely sure that...
What I wrote is correct; there's no change in the sounds, whether the EGR system is active or deactivated.

2. Theory:
The exhaust system isn't warm enough yet.
It makes sense that the resonant behavior of a heated metal is different from that of a cold metal.
'But the noise is actually generated before the exhaust system, which you can clearly hear.'



By the way: Does anyone know a good link that explains how a wastegate turbocharger works? I'm still quite a beginner, but I'm very interested in learning about it.

Greetings[/quote]