Anfänglicher Drehmomentschwund beim Gasgeben | Posts 16+

I have now come to the conclusion that the VTG is being over-controlled.

The optimal point is a delicate balance. If not enough boost is applied, the pressure build-up takes unnecessarily long. If too much boost is applied, the backpressure is too high, and the turbocharger pressure also builds up sluggishly.

Since the engine noticeably drops in power when accelerating below 1800 RPM and then slowly recovers, that could be the effect.
If I completely release the accelerator and then press it again, it pulls properly.

You can notice it when driving up a steep hill in second gear. If you accelerate so that the engine speed reaches 1800-2000 RPM, there's a point on the way to the target RPM where the "fuel mixture" is optimal, and you experience a sudden surge of acceleration even though you're not changing your foot position on the accelerator pedal.

It's the same thing when I slowly release the accelerator while accelerating; there's still a noticeable jolt of acceleration.


My turbo has electric adjustment. It is also linked to the control unit, or vice versa.

Could the problem be solved by adjusting the end-of-travel switch (VTG side) by a few percent?
Then, instead of being capped at 80%, the VTG might only be reduced to 75%, but the overall control behavior will be lowered.

Okay, I'm not familiar with the specific details.
However, when looking at the VCDS data, you can see that when accelerating, the VTG (Variable Turbine Geometry) closes significantly for a brief moment and then gradually reopens.
She thinks it might be too tight, and that reducing everything by a few percentage points could solve the problem.

What do the experts say?

Ski_Andi wrote:

You can notice it when you drive up a steep hill in second gear. If you give it enough gas so that the engine speed reaches 1800-2000 RPM, there's a point on the way to the target RPM where the "fuel mixture" is optimal, and there's a sudden acceleration, even though I'm not changing my foot on the accelerator pedal. The same thing happens when I slowly release the accelerator while accelerating; there's still a noticeable acceleration jolt.

Gut feeling/Intuition:
The variable turbine geometry (VTG) is closing too aggressively (restricting the exhaust flow), and the acceleration jerk occurs each time the VTG opens slightly from its closed position – at the very moment when it's passing through the optimal setting for that closed position.