VTG: How to Set Up & Configure

Hello fellow DIY enthusiasts,

A brief question: How does an 'overly aggressive' VTG (Variable Transmission Geometry) manifest itself?

Is the pole adjusted to be too short?

Shouldn't the vehicle go into limp mode in every gear at high RPM?

And what error code will then be stored in the error memory?

Thank you for your responses.

Greetings from Lake Constance.

Tobias.

Hi Tobias,

"On my Passat (AFN), it only happens in fourth and fifth gear."
Emergency mode, also known as the state when the rod is in its maximum position.
"it was jammed, meaning it was pulled as far as possible into the pressure chamber."
was.

Best regards,
Ralph.

Hi,

Tobias wrote:

a quick question: how does an VTG that is set "too sharp" manifest itself?

- High overshoot during turbocharger pressure adjustment.
- The duty cycle of the solenoid valve controlling the VTG adjustment has been shifted upwards.

Quote:

Shouldn't the vehicle then go into limp mode in every gear at high RPM?

It's a bit of both. Yes, under high load for several seconds (the mechanical linkage is no longer sufficient to limit boost pressure).

Quote:

And what error code will then be stored in the error memory?

"My invoice states 'Pressure difference in the intake manifold' as the reason for the charge."

Best regards, Rainer.

Hi Rainer K.

Thank you for your quick response.

I have an ASV (Adaptive Speed Limiting system), and if there's a fault, the same error code should be stored in the error memory.

It only occurs in the 4th and 5th gears... it's easiest to reproduce in 5th gear, under full load, on a flat or uphill road, after about 10 minutes.

I have already visually inspected all the U-tubes... now it's time to check the N75.

The VTG adjustment seems to be easily adjustable.

Thank you... Tobias.

Oh yes: the effect is more pronounced in cold weather, as it creates lower boost pressure, which requires the VTG (Variable Turbine Geometry) to adjust more frequently.

Best regards, Rainer.

Hi Rainer...

Okay, one more quick question... maybe it's a silly one... but anyway.

I have the following error:

Error: 17965 P1557 035
Boost pressure control.
Limit exceeded.

According to the error database, this indicates that the hoses are leaking, or that something is reversed/swapped.

According to AUDI, the following components should be checked: N75 valve, hoses, Mass Air Flow Sensor (MAF), and turbocharger.

I think it might be the turbocharger or the mass airflow sensor. Could it be something else?

Probably near the N75?

Thank you very much for your help!!

Tobias.

Hi,

Tobias wrote:

I think it might be the turbo and the mass airflow sensor (MAF)? Could it not be related to those??

It could be related to the turbocharger, specifically if either the vacuum sensor is faulty or the VTG (Variable Turbine Geometry) adjustment is mechanically stiff. I'm less likely to think it's a problem with the mass airflow sensor.

Quote:

More likely near the N75??

It might also be possible to swap the solenoid valves for the AGR (Abgasrückführung) system with the ones for the VTG (Variable Turbine Geometry) system, but only after you've ruled out all other potential causes (hoses, vacuum actuator, etc.).

Best regards, Rainer.

Hi Rainer,

Thanks for the quick reply... that's really great!!

So, I have visually inspected all the hoses and tested them using a vacuum pump.

The VTG (variable geometry turbine) is easily adjustable; I can freely adjust it by positioning my mouth near the U-shaped tube.

Thanks for the tip about the AGR solenoid valve... are they the same?

'I also found that part about the LMM strange, but my contact at AUDI NSU said, 'The LMM is a key component in the actuator chain of the turbocharger control and engine management system. (I believe that too.) It's quite possible that a fault in the LMM could have such an effect.'

Hmm......

Thank you for your help!

Greetings, Tobi.

Hi,

Tobias wrote:

The VTG is easily adjustable... I can loosen it and adjust it with my mouth on the U-shaped tube...

It also shouldn't be too loose, because the spring in the vacuum chamber must be able to shift the VTG (Variable Turbine Geometry) to its "minimum pressure" stop.

Quote:

Thank you for the tip about the AGR solenoid valve... are they the same??

Let's say it's at least similar. If the problem with the swapped solenoid valve is resolved, then it's worth investing in a new one.

Best regards, Rainer.

Okay, okay... it was way too easy... I had to work like crazy!

And that thing about my smoker's lungs, haha...

Okay, so the two are similar... meaning their functionality and connections are the same... of course, otherwise they wouldn't work!

I will definitely test it!

What's still bothering me is that the problems only started with the cold weather... and as you mentioned, the turbocharger boost is likely building up more easily here... hmm... maybe I should reduce the VTG (variable turbine geometry) setting a bit... since I didn't have any problems in the summer, and I set it myself (in the summer).

But first, I'm going to test the solenoid valve replacement!!

Thank you and greetings from Lake Constance.

Tobi.