Low turbo pressure, noticeable loss of power

Hello,

My T4 ACV has approximately 0.15 bar less boost pressure than it should.
Target boost pressure not achieved. See log data from test run 1.

Here's the translation:

"What I've noticed are two things. First, I'm essentially working on the entire torque limiting system. Second, the LDA valve doesn't regulate anything when the actual LDA value is lower than the target value, which is correct."

To determine if the LDA valve is faulty, I disconnected the hose from the turbocharger pressure sensor and sealed it, then performed another measurement run. (Of course, I had previously checked with an LDA display to ensure that the pressure did not increase indefinitely.)

Without LDA (Lambda-controlled direct injection) regulation, I'm just barely reaching the target boost pressure (see test run 2 with the boost pressure sensor disconnected), but I'm still experiencing torque limitation with the same fuel injection values as in test run 1.

For me, this means that although the LDA valve, in measurement run 1, is not being activated, it is still allowing pressure to pass through to the boost pressure sensor, which causes the wastegate valve to open, preventing the target boost pressure from being reached.

My questions:

If I'm already operating below the torque limit values with 0.15 bar less boost pressure, can I then avoid replacing the LDA valve? (And incidentally, the turbocharger will be less stressed).


What is the typical coolant temperature for a T4 ACV engine? During some test drives, I noticed that the coolant temperature was only 75°C. The heater was turned off. (Of course, the combination instrument is stuck in the middle thanks to the infamous VW temperature plateau function). Could the thermostat or temperature sensor be defective?

Are other parameters, such as coolant temperature, taken into account in addition to engine speed when determining the torque limit values?

If the torque limit is solely determined by mechanical constraints, where does the power loss originate?

Thank you + Best regards.
Steffen.