TDI Boost Problem: Passat 81 kW (AFN)

hello everyone,

Some time ago, while checking the clutch, I noticed the following:
established.
(The boost pressure was measured with a pressure gauge while the vehicle was in motion.)
I have attached a connection here.

The maximum boost pressure of 0.98 bar is not reached until 2800 RPM.
At approximately 2000 RPM, the charging pressure is about 0.96 bar.

Auf dem Leistungsprüfstand wurde dies durch das max. Torque.
Approximately 2800 revolutions per minute confirmed.
There was no overshoot in the boost pressure during the measurement.

Between 2000 and 3000 RPM, the boost pressure actually drops to 0.9 bar.
Sure, here is the translation of the text from German to English:

'ab.'
The test was repeated multiple times.
Bei VW hat man mir gesagt, dass Sie nichts machen können. I was supposed to...
zu einem Tuner gehen. They could do that.

Does anyone know how to adjust the turbocharger boost pressure?
According to my knowledge, a boost pressure of 1 bar should be reached, starting at approximately 4000 RPM.
something sinks.
Is there also an electronic solution?

Thank you in advance.
Hturbo01

hturborbo01 wrote:

The maximum charging pressure of 0.98 bar is not reached until 2800 RPM. At approximately 2000 RPM, the charging pressure is about 0.96 bar.

Hi,

I would consider a difference of as much as 20 mbar to be normal variation.

Quote:

Auf dem Leistungsprüfstand wurde dies durch das max. Torque. Approximately 2800 revolutions per minute confirmed.

LMM - old / dirty / defective?

Quote:

Between 2000 and 3000 rpm, the boost pressure even drops to 0.9 bar. Sure, here is the translation of the text from German to English: "ab." The test was repeated multiple times. Bei VW hat man mir gesagt, dass Sie nichts machen können. I was supposed to... Go to a tuner. They could do that.

0.9 is a bit tight.
I'd say it's probably one of the usual suspects: the VTG (variable geometry turbine) is stuck, the control rod is misaligned, the solenoid valve is faulty, or the diaphragm is damaged.

Quote:

Is there also an electronic solution?

Yes -> 10c-technical article, section on increasing charging pressure. However, this would probably bypass the actual root cause of the problem...

Hello Ulf,

Thank you for your reply.

The LMM is approximately 5 months old.
The VTG shaft is fine. I already have one.
checked.
The membrane dose is also acceptable.
I checked the can with a syringe.

How can a faulty solenoid valve be repaired?
determine.
During a diagnosis at VW, everything was fine.
There, it was also checked whether the solenoid valve...
VTG also controls it.
According to VW, everything is fine.

According to Volkswagen's technical specifications, the maximum...
The torque is already available at around 1900 rpm.

Could the error possibly be corrected by adjusting something?
How can the alignment of the VTG rod be corrected?

Regarding the 10-cent tuning:
I've been looking for a clean solution.
However, the solution would already be usable for testing purposes.

Regards,
Hturbo01

By the way, here's another question:

Where does one actually get...?
For example, connectors.
Connector with 8 or 10 pins.

Or the connectors on the boost pressure sensor.

The 10cent-Tuning article includes an example.
with photos.
I would also like to know from whom.
Got plugged in.
Otherwise, you would always have to work on the wiring harness.
See a doctor.

Regards,
Hturbo01

hturborbo01 wrote:

How can you fix a defective solenoid valve? to determine.

Hi,

Replace the AGR valve with the VTG valve and check if the boost pressure behaves differently.
Or VAGCOM diagnostic drive cycle.

Quote:

During a diagnosis at VW, everything was fine. There, it was also checked whether the solenoid valve... VTG also controls it. According to VW, the result is: Everything is fine.

That contradicts your own observation...

Quote:

According to VW's technical specifications, the maximum... Torque is already available at approximately 1900 rpm.

And what values did the dynamometer actually produce? (Because it often measures more things than people usually want to acknowledge...)

Quote:

Could the error possibly be fixed by adjusting something? How can the alignment of the VTG linkage be corrected?

Yes, possibly -> rotate in steps of approximately half a revolution less each time.
Has anyone ever messed with these things before? Most of the time, they are properly calibrated from the factory.

Hi Ulf,

For clarification:
When the VTG rod is shortened, the overswing would...
Let the 'undershoot' of the boost pressure not be any more pronounced!
Because the standard route is shorter.
And would the boost pressure perhaps build up a little later?

Regarding the electronic control system:
Could a capacitor be connected to the boost pressure sensor?
which is charged via a potentiometer.
And thus, the initial voltage of the boost pressure sensor is sent to the control unit.
Sure, here is the translation of the text from German to English:

'I have corrected the text.'
And once the capacitor is charged, then the...
Restore the standard boost pressure.
Something like a voltage divider (with a timing element).

And as a safety measure, the entire system should also have galvanic isolation.
to avoid damaging the control unit.

Since this does not result in an increase in performance, one should also...
Will it pass the technical inspection without any issues?
I'm going to discuss this with the TÜV (German technical inspection authority).

What do you think about it?


Regards,
hturbo

hturborbo01 wrote:

For clarification: When the VTG rod is shortened, the overswing would... Let the "undershoot" of the boost pressure not be even more pronounced! Because the standard route is shorter. And the boost pressure would perhaps build up a little later?

Yes and no... The general rule is: Shorter struts tend to increase pressure and amplify oversteer. This is probably because the adjustment in practice doesn't have ideal-theoretical properties, and the "offset" is not completely compensated for by the changed length.

Quote:

Regarding the electronic control system: Could a capacitor be connected to the boost pressure sensor? which is charged via a potentiometer. And thus, the initial voltage of the boost pressure sensor is sent to the control unit. Sure, here is the translation of the text from German to English: "I have corrected the text." And once the capacitor is charged, then the... Restore the standard boost pressure. Something like a voltage divider (with a timing element)

.
I can't really picture what you're talking about. It would be helpful if you could somehow record it.

Quote:

And as a safety measure, the entire system should also have galvanic isolation. have, in order to avoid damaging the control unit.

Quote:

Since this does not achieve an increase in performance, one should also... Will it pass the technical inspection without any issues? I'm going to talk to the TÜV about this.

Okay, go ahead and tell us the answers. Although, I can pretty much guess what they'll be: "Such modifications to the engine management system are not covered by the type approval, blah blah blah..."

Hi Ulf,

First, let's talk about the electronic control system.
The controls are more complex than I initially thought.
That's how I found my chip tuner.

The catch:
Actually, the additional electronics are offered as part of the chip tuning package.
because there is a TÜV inspection (report) for the combination.

If needed, additional electronics can also be used for the...
Request turbocharger pressure correction separately.

TÜV inspection for additional electronic components:
The TÜV expert (from TÜV Essen) was not entirely sure whether...
A modification to the electronics to achieve a default state.
(Boost pressure correction) is required during a TüV inspection if...
Korrektur keine Leistungssteigerung statt findet. To be continued...
He wondered if the exhaust emissions would be affected and if that would lead to something else.
Whether the insurance company might cause problems in the event of a claim.
He also said: 'This whole thing is a gray area and should be addressed accordingly.'
Don't take any risks.

Regarding galvanic separation:

Transformer that completely isolates two circuits from each other. There is no direct connection via a conductive material such as iron or copper. The transfer of electrical power, audio, or video signals occurs through induction. Applications include isolation transformers.
Conclusion: In the event of damage to the additional electronics, the control unit would be protected.

I'll think about whether it's worth the effort.
It's not worth correcting at all.

Regards,
Hturbo01

hturborbo01 wrote:

If needed, additional electronics can also be used for the... Request turbocharger pressure correction separately.

Hi,

That, in my opinion, would be addressing the symptoms rather than the (still unknown?) root cause.

Quote:

Regarding galvanic separation: Transformer that completely isolates two circuits from each other. There is no direct connection via a conductive material such as iron or copper. The transfer of electrical power, audio, or video signals occurs through induction. Applications include isolation transformers. Conclusion: In the event of damage to the additional electronics, the control unit would be protected.

...and constant charging pressures = direct currents are neither transmitted by transformers nor by capacitors!
That is, in my opinion, that the regulation, due to constantly drifting measurement values, might not be working correctly}.

Hi Ulf and everyone else.
Today, galvanic isolation is more commonly achieved using optocouplers or modulated inductive couplers. (In the latter case, the useful signal is superimposed onto a carrier signal via modulation and then transmitted inductively.)

Both can transmit any kind of signal.

Hello everyone,

Problem identified and problem solved.
After extensive test drives with a boost pressure gauge.
Finally found the source of the error.

The main cause was a vacuum hose connecting to the solenoid valve.
The vacuum sensor is working.
'This one wasn't broken or leaking, but after...'
Exchanged for a new one, the turbocharger's boost behavior.
significantly improved.
Furthermore, I also applied Never-Seize to the VTG linkage.
(-180°C to 1100°C), bolded even though there's no checkmark or...
I was able to identify a problem with the VTG's clamping mechanism.

Since then, the boost pressure has been regulated very precisely.
Thank you very much for your tips and help.


Regards,
hturbo01

hturborbo01 wrote:

The main cause was a vacuum hose connecting to the solenoid valve. The vacuum sensor is working. "This one wasn't broken or leaking, but after..." Exchanged for a new one, the turbocharger's boost behavior. significantly improved.

Hi,

And what was the problem with the hose? Was it kinked, or did it have a weak spot that collapsed under vacuum, blocking the hose?

Hi Ulf,

Based on how the hose looks, I would say that...
He felt dejected.

Regards,
Hturbo01