Re: performance loss, the endless search

rotes-tdi wrote:

So, since I haven't worked with VCDS (Vag-Com) and log files very often, my question is for you: Can I record the boost pressure over time using the log file, so that I can see if it's maintaining the correct pressure in each RPM range? If so, how do I do it?

Yes, that's fine. Please read the technical articles on systematic troubleshooting for TDI engines and use the search function. Please also read the article about social faux pas.

Hello,
Well, it certainly takes some work to systematically search for an error!
Best regards,
Günther.

Anyway, it's less than blindly replacing half the car.

Definitely less than blindly replacing half the car.

Hello Rainer,
That's just how it is!
Best regards,
Günther

@Rotes-TDI:

Then, go ahead and log the boost pressure.

Here's how it works (you can see this in action in this interactive demo):
I am sorry, but I am unable to access external websites, including the one you provided. Therefore, I cannot translate the text from the given URL.
Select the engine control unit (01) using the "Select" function. Then, go to "Measurement Blocks" and select block 11. Click on "Log" and either give the file a name or accept the suggested name. Click "Start" to begin. End the recording by pressing the "Stop" button.

You can find the file as a CSV file in the log directory. You can use VAGScope to play it back and view the data traces. Block 11 contains information on speed, boost pressure, target values, and the duty cycle of the boost pressure control valve.

Do some acceleration exercises in the 3rd gear. The speed ranged from 1,400 RPM to 4,000 RPM during the recording.

If you show it to us here, we can evaluate it.

Generally, when the accelerator is fully pressed, the LD (likely referring to a turbocharger or similar device) will jump to a high target value, which is initially reached with some delay due to the low exhaust energy and the inertia of the turbocharger. Then, there is an overshoot, but this is regulated and corrected. From that point on, the full LD (likely referring to a load or data) remains active for quite some time.

The regulation intentionally incorporates a small dead time to suppress oscillations. This is why the overswing occurs. However, if the target value is not reached for several seconds when the speed is above 1,900 RPM, something is wrong.