Boost Control Valve Airflow Ratio

Hello.
As the title indicates, this is about whether the duty cycle of the wastegate valve can be adjusted. Here's a brief explanation.
According to the logs, the ECU reduces the duty cycle to a minimum of 24.7%. Considering the vacuum pressure of 600 mbar, this means the turbocharger never reaches its target boost pressure in the lower RPM range, which is why the engine feels sluggish and produces soot.
Here's the translation:

'However, in the default settings mode, the duty cycle is essentially set to 0% (measured at 790 mbar) - and interestingly, the turbocharger still achieves its target boost pressure even at lower engine speeds. (There's no sticking in the variable geometry turbine, and the valve is working correctly).'
'I actually didn't want to adjust the VGT (Variable Geometry Turbocharger) because everything seems to be working fine in the default setting – the delta P is 170 mbar. That's why I'm asking if it's possible to adjust the ECU (Engine Control Unit) so that it can operate even further down in the range, beyond the well-known 24.7%. That value is already the minimum at idle speed. When the engine speed increases at idle, this value already increases, even though the boost pressure hasn't increased yet. Consequently, it becomes even harder to build up the boost. Then, suddenly, the turbocharger gets enough airflow, and it suddenly revs up and overshoots the target.'

I hope this is understandable. Does anyone have any tips? Can anyone help me? THANK YOU.

Hi,

Sure, you can adjust the duty cycle in the ECU. But: why isn't your VTG reaching the mechanical stop at 24.x%?
But what if something is difficult to operate, or if a vacuum sensor, solenoid valve, etc. don't fit together properly?
Is this a modified vehicle? It's probably not in its original condition.

Best regards, Rainer.

So, should it already hit the mechanical stop at around 25% (600 mbar)? Why not design it so that the duty cycle can initially be set to 0%, which would correspond to the mechanical stop?
Unfortunately, nothing is stuck otherwise I would have fixed it a long time ago. Also, the solenoid valve fits (the vacuum booster should also fit) because it's not a conversion - it's just typical VAG series junk .

edit: and most importantly, the question - how can I customize it?
'Please provide the text you would like me to translate from German to English.'

So, I guess I have to ask again - how can I change it?

Hi,

Only a reputable chip tuner can modify it. Furthermore, they must possess in-depth knowledge of the structure of the turbocharger control system, as simply adjusting the basic pre-injection map will not be sufficient, as additional maximum value limits, plausibility checks, and linearization processes also apply (depending on your software).

"But anyway, if the VTG (variable geometry turbine) doesn't fully adjust at 600 mbar pressure at the nozzle, then you either have an incorrect initial setting or a defect in the adjustment mechanism (nozzle/linkage/control system). However, Rainer has already explained everything, as mentioned above."

Best regards.

You're welcome, Bavarian.
I thought that there was probably no simple way to adjust that using VCDS.
'Since the defect in the adjustment mechanism isn't actually there, but rather the stop is being reached due to a higher-than-normal vacuum (and this has been the case from the factory), I probably need to shorten the rod and observe what happens. What do you think? - The warranty is probably already expired anyway (the workshop doesn't know what's causing the problem either).'

Devilseye503 wrote:

Since the defect in the adjustment mechanism is definitely not due to a problem with the mechanism itself, but rather because a higher vacuum pressure is causing the stop to be reached (and this has been the case from the factory), I probably need to shorten the rod and observe the results?

What do you think?
Hi,

The approach might work, as long as the VTG can still fully open -> A technical article on adjusting VTG chargers }.

Hi,

'Yes, it needs to transition to the open state even without vacuum pressure. I don't see a problem with the duty cycle itself; it's currently at a maximum of 70%.'

but why actually mess with the mechanics? you can systematically extend the pulse by inserting a little bit of electronics in between, which modifies the pulse width modulation - the regulator works the same way as before - it just has a systematic error .