Engine Performance Issues: Low RPM Problems

Hello,

Currently, I'm experiencing problems with a loss of power in the lower RPM range. Above approximately 2700-2900 RPM, it runs normally.

The AGR valve is defective, the mass airflow sensor (MAF) is new and showing excellent readings. The error code in the fault memory indicates 'control limit exceeded.'
The control valve for the VTG (Variable Geometry Turbine) was temporarily replaced with a new part, but this did not have a positive effect.
The VTG (vertical travel gauge) is easy to operate, and I was able to reach and maintain specific positions using the syringe test.
Clicking the link will take you to the current log file. Notably, the boost pressure curve shows a pattern within the engine's power loss range.

http://home.tiscali.de/husqvarnatreiber/

Best regards and thank you.

For me, this log doesn't really look like a functioning VTG (Variable Transmission Gear).

The nearly linear increase in readings from point 40 to 55 looks like what I would expect from a rigid, completely unregulated turbocharger (i.e., not even with a wastegate, or with fixed-geometry turbine vanes).

Then everything "clicks" into place, and the system works perfectly.

But a leak in the vacuum hose should not allow any boost pressure to build up... (Fail-safe principle of VTG).

Something must be wrong with the VTG (variable turbo geometry), or the pressure sensor is faulty.

Do you have a mechanical LDA (Laser Doppler Anemometer) to verify the values?

m;

Your turbocharger boost control is working perfectly. You've already identified the problem. The log looks like it's related to the EGR (Exhaust Gas Recirculation) system.

Regards!

@Diesel_Rudi:

... by 'defective,' I mean it's meant to be deactivated (using a metal gasket), sorry.

@Dieselmartin:
Unfortunately, there is no analog LDA available. I haven't installed one so far because of the fixed mounting location. However, I will try to find a temporary solution.

Okay, let's log the values with the VTG disconnected. If the result is the same, then check these possibilities: vacuum sensor is faulty, there's a leak in the vacuum line, the LR valve is faulty, or the turbine (guide vane ring) is clogged.


Best regards!