Boost Pressure Difference at 1400 RPM (VTG On/Off)

Hi.

Today, I tested the basic settings on my AXR engine using VAGCOM in channel 11. This involves keeping the engine at 1400 RPM and repeatedly actuating the VTG (Variable Turbine Geometry). The value I measured was 960 mbar (without actuation) and 1020 mbar (with actuation). The vacuum actuator was functioning correctly; the actuation rod moved smoothly up and down.
In the thread by cetano /viewtopic.php?t=7254&highlight=, there was talk of a pressure difference of 100 to 200 mbar, which should be achieved in the aforementioned test. Since I am experiencing almost the same symptoms (lack of power in the lower RPM range), a faulty turbocharger could also be the cause in my case. The mass airflow sensor (MAF) was replaced under warranty 2 days ago. However, since cetano drives an ASZ, I would like to know the pressure difference from a functioning AXR (perhaps bertil ?).

I have ADHD, but maybe this information will still be helpful to you...
For me, it went up to 1150 mbar. However, I've experienced overpressure during driving, reaching up to 1.5 bar. I suspect my VTG (Variable Turbine Geometry) is sticking. That's why I did a test today and fiddled around with some copper paste. It's still unclear whether it will be better after a test drive... In my case, the VTG linkage also moves 'up and down' nicely, but it seemed to me that the last 2-3 mm of the downward movement were slower! It's just really difficult to access sometimes.

Please find the log file attached.

Sure, no problem.
'Yours is already above the tolerance limit, with a difference of sometimes over 200 mbar. Mine is definitely too low, at around 60 mbar. Thanks to the warranty, it will probably result in a replacement charger next week.'
Let's see (or hear) what VW has to say about it...

VW has commented on the matter.
After my workshop tried to obtain authorization from the VAG dealership that provided the warranty to replace the turbocharger, the dealership wanted to take the car to perform the repair themselves.
Okay. It's only 70 km... , at least there's a free rental polo...
Today, I received a call: 'The car is ready, but the charger is still the same.' They replaced the charge pressure control valve.
I put it in gear and started driving. After the first 400 meters, I immediately noticed that the car still doesn't really start running properly until around 1800 RPM. Before that, there's nothing; you can clearly see this on the fuel consumption display, which stays at around 6 liters per 100 kilometers and then suddenly jumps to around 13 liters per 100 kilometers above 1800 RPM.
So, they went straight back and complained.
The mechanic came in and then gave me a quote. When I pointed out that the problem wasn't at 3000 RPM ('I don't understand what you want. It pulls really well at that speed'), he just said that you can't really measure the boost pressure at low RPM anyway, and that a 'guided troubleshooting' process almost always results in a faulty turbocharger. The VAG 1552 scanner that was then connected showed reasonable pressure readings even under load (after the car had been modified) starting at 1400 RPM.
However, the pressure difference without load, both with and without the activated VTG, is still only 60 mbar.

What bothers me the most is the statement that guided troubleshooting is essentially garbage.

Could it perhaps be my fault? Should the boat perhaps only be operated above 1800 RPM when the engine has reached its operating temperature? Is there perhaps a protective function that prevents excessive pressure buildup in an engine that is not yet warm (and thus prevents overloading)?

Hati wrote:

Can the engine perhaps only be loaded above 1800 RPM when it has reached its operating temperature? Is there perhaps a protective function that prevents excessive pressure build-up when the engine is not yet warm (which could lead to overload)?

Based on my experience with 3 of my own TDIs and a few others: 2 times, no.
However, there was no AXR among them...

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

'S.'
'I went to VW today. The diagnostic tests revealed a faulty turbocharger, after the mass airflow sensor and the turbocharger pressure control valve had already been replaced under warranty. The measured pressure difference (VTG open/VTG closed) at 1400 rpm was only 30 mBar. The target value is 100 - 200 mBar.'

The error has been found. It was a crack in the membrane of the vacuum sensor for the exhaust cooling throttle valve.
The mechanic initially concluded that the loader was faulty, and he looked at me with a sympathetic expression. As I smiled, he then noticed that the loader was new. He then smiled back, quite embarrassed. I told him that the problem must be a defect in the vacuum supply, as the VTG (Variable Turbine Geometry) wasn't fully engaged. He then checked again and found the defect in the membrane.
'For now, the hose to the canister is sealed until the replacement part arrives. The EGR system is already 'defective' anyway. But now, I have the usual performance again.'

Great, thanks for the feedback!