VCDS: Check Turbocharger Boost Pressure

Hello to all the professional thieves.
I just cleaned the VTG turbocharger on a 1998 Skoda Octavia and I'm wondering which parameters, besides the values in measuring block 11, are needed in VCDS to check the adjustment of the VTG control rod.
VTG adjustment is functioning correctly.
The valve for adjusting the boost pressure is new.
Acceleration rate during driving, at a maximum of 94.4%.
Boost pressure varies between 980 and 2500 mbar depending on the accelerator pedal position.
I know that the boost pressure for the 110 hp AHF engine should not exceed 1.0 bar.
Just how and where to properly check and adjust.
The percentages for the timing seem to be almost correct, but the 2500 mbar reading is concerning.
The error memory only contains an old entry related to "intake manifold control difference" or something similar, but I assume it's from when the VTG (variable turbine geometry) adjustment was not working properly, and also when the adjustment of the VTG push rod was incorrect.
Perhaps you could give me some advice on what I should look out for.
Sincerely, Franz.

Hello,

The expected range for the AHF (setpoint/actual value) in measurement block 11 is a maximum of 1950 mbar.
A common issue with AHF loaders is that the VTG (Variable Torque Geometry) adjustment doesn't fully retract the last 3mm, making it appear as if it's at the "open" limit, but it's not actually at the limit.

Tip: Unscrew the VTG adjustment container from the loader (DO NOT turn it on the adjustment rod!).
The VTG (Vertical Travel Gauge) is at its 'open' position when the can is fully extended and then can just be pressed into the 'tightening position'. The rod inside the can should be pressed in by a maximum of 1mm, ideally just not at all. This is also the 'default setting' here.

It is also important to ensure proper ventilation of the vacuum system. In the case of the AHF system, a (vacuum) hose is directly connected to the air filter housing for this purpose.

Relevant for charger testing are measurement block 10 (ambient pressure) and measurement block 11.

Best regards, Rainer.

Hello Rainer,
Thank you for your quick response.
The problem is that I already adjusted the VTG adjustment rod during a disassembly a few months ago, so I can no longer determine its original position.
If I can restore the baseline position using your suggestion, that would be great. Presumably, the maximum charging pressure should then be around 1950 mbar.
"settling time". Are there specified rotational speeds at which the 1950 mbar pressure can be reached?
Should I check the boost pressure while the engine is idling or under load while driving? What would the comparison of measurement block 10 (ambient pressure) and 11 look like?
What should the optimal values look like there?
I've installed a new mass airflow sensor, but what should the measured airflow be at each engine speed? I want to make sure everything is working correctly here.
I'll try out your suggestion tonight.
Thank you again.
Best regards, Franz.

Hello Franz,

Quote:

Are there specified engine speeds at which the 1950 mbar pressure needs to be reached?

Yes, everywhere where the engine control unit requires a target value of 1950 mbar. You can see it directly in the log, see the picture.
"A 10% overshoot in the default state is acceptable; anything above that is not ideal. If the overshoot is below 5%, the settling behavior will tend to be sluggish."

Quote:

Should I check the boost pressure at idle while the engine is stationary, or under load while driving?

You will hopefully realize that this cannot be done standing up.

Quote:

What would the comparison between measurement block 10 (ambient pressure) and 11 look like. What should the optimal values look like there?

What reason would there be for the ambient pressure to change while driving?
In the MWB11 system: The actual value is always equal to the target value, as described above, except under low load conditions, where the desired boost pressure may not always be achievable.

Quote:

One more thing: I installed a new mass airflow sensor, but what should the measured airflow be at which engine speed? That way, I can be sure that everything is okay here too.

The measured value block 8 shows that at full load, the airflow limitation is greater than the torque limitation. In idle mode without EGR, your engine sucks in between 440mg/stroke and 480mg/stroke, and the mass airflow sensor (MAF) should measure this value. If it doesn't, the MAF is defective, there's a problem with the EGR or intercooler piping, or the wrong MAF was purchased. Always buy an original MAF sensor, as there's a lot of low-quality junk on the market.

Best regards, Rainer.