Regarding. | Posts 24+

Hello Herbert,
Thank you very much for your patience!

Attached are the new data from today.

Best regards,
Thomas.

Okay.
Is the error memory now empty?
Okay, the next test drive will be with the same vehicle configurations. And please, no sudden acceleration!
Simply drive step by step – accelerate gently in the first to third gears, then in fourth gear, start with full throttle around 1500 rpm and accelerate to 3500 rpm. If the engine doesn't go into limp mode, hold the RPM for 10-20 seconds, then continue in fifth gear at a constant speed for several tens of seconds.
Once the measurement is complete, stop any attempts and switch to idle mode. That's it.
Then check the error memory again.
Hopefully, this gives us a profile of the boost pressure build-up.
hg
Herbert.

Unfortunately, I cannot provide any data today.
My computer crashed and didn't save the files. Unfortunately, because I live in a rural area, I can only repeat the test tomorrow.

Previously, the emergency brake would activate when the vehicle needed to drive uphill on a slope.

Best regards and see you tomorrow.
Thomas.

Okay, it worked this time!
I started two recording sessions because someone drove in front of my car during the testing, which disrupted things. Hopefully, at least one of them can still be used.
In the first test, the error memory was cleared, but in the second test, the error reappeared. I have also attached the diagnostic report.

Best regards.
Thomas.

I suspect the log was created during the emergency program of the engine control unit, so it's meaningless.

Are the engine control unit (ECU) and turbocharger pressure sensor original parts?

The turbocharger isn't even able to achieve a boost pressure of 0.6 bar.

Relevant for you (if you have a wastegate turbocharger and not a variable geometry turbine):
I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.

Creating logs:
Ich kann den Inhalt dieser URL nicht abrufen und übersetzen. Bitte gib mir den Text, den du übersetzt haben möchtest.

Good luck, Rainer.

Good morning.
As previously mentioned, all errors were cleared before the first test. Please refer to the initial error log. During the second test, the emergency mode was activated (which was clearly noticeable). After that, the system was read again, and the error was present (see the second error log), so it wasn't pointless after all.

The engine control unit is original, but the turbocharger pressure sensor has been replaced before. The old one is still available.

In den von Dir weiter geleiteten Beschreibungen wird ja immer von einem Fehler im Unterdrucksystem gesprochen. Wie schon zum Anfang beschrieben hat mein Unterdrucksystem nur ca. 0,3bar Unterdruck obwohl im Handbuch beschrieben steht, dass dieser min. 0,6Bar betragen sollte. Und dass obwohl alle Unterdruckschläuche erneuert und auf Druckdichte überprüft wurden. Nur die Verbindung zum Steuergerät konnte ich bisher nicht lokalisieren. Meine jedoch gelesen zu haben das diese ab Modell 2000 nicht mehr vorhanden sein soll. WeiDo you want more of that?

Today, I will replace the boost pressure sensor with the original one and test it. If that doesn't work, I will disconnect the hose from the pressure sensor to the turbocharger and see if the boost pressure increases.

Best regards.
Thomas.

Caution: Without the hose connected to the pressure sensor, the wastegate control will be completely disabled, and boost pressure will not be limited.
The machine doesn't actually go into a proper emergency stop mode (if I understand the recorded torque limitation correctly).
The LD is responding slowly or not at all to the control signals. You could almost say that it's temporarily freezing.

Let's start by discussing this:
You could now disable the control of the N75 and observe how the boost pressure behaves (by unplugging the connector). However, before doing that, I would first check the observed target/actual values.
- Proper operation of the wastegate valve;
- the pressure vessel;
- the length of the regulating rod;
- the pressure lines connecting the discharge outlet, N75, and the pressure sensor.

hg
Herbert.

"Edit: Someone was faster; my post overlaps with the previous one. The topic of vacuum pressure doesn't belong here unless it has been modified to use a VTG turbocharger. The engine originally comes with a wastegate turbocharger."

The vacuum principle only applies to the heating system, Syncro unit, and shut-off valve in the ACV system.

If the bypass valve is functioning correctly (no influence on boost pressure).

Perhaps the catalytic converter is clogged (back pressure on the exhaust side).

Wastegate linkage misadjusted.

And again .
Please check the default settings of the VPE (dynamic).

You can already find instructions for that .

I won't be able to review the log files and compare them with mine (T4 ACV) until next week.

Best regards,

Dawinchie wrote:

I can only review the log files next week and compare them to mine (T4 ACV)

.
You can skip that; the readings are meaningless due to the faulty engine control unit/turbocharger pressure sensor.

Quote:

The controlled wastegate turbocharger (e.g., in the 1Z, AHU, AAT, AEL engines) has a conventional diaphragm chamber with a spring that opens the wastegate at approximately 0.6 bar of boost pressure and prevents further increases in boost pressure. Der hierbei entstehende Abgasdruck drückt also ab ca. 0,6 bar Ladedruck das Wastegate auf, womit der Ladedruck nicht mehr weiter ansteigen kann.

It is the boost pressure that acts against the spring through the membrane. The exhaust pressure plays no role in this process.

Herbert.

@Herbert:
"Quote:"
So, it's not original, and that would also explain the strange boost pressure values. I suspect that the values shown as "0.5 bar" in the last log (viewed with KDataScope), along with the "limp home" mode, actually correspond to 0.6 bar, which is what the turbocharger can produce without a connected pressure sensor.
Did I miss something, or did it really take that long to figure out the problem with the messed-up engine control unit?

The fact that the sensor was replaced is stated in the first post at the beginning of this thread! Therefore, I don't understand why I am being accused of withholding information .

And as far as I understand, no one has ever tampered with the engine control unit. Therefore, I don't understand your statement about a "modified" or "tampered-with" engine control unit. Perhaps you could explain that to me more simply?

Since the vacuum system, as I understand it, is supposed to regulate the "pressure below 0.6 bar," I still don't understand why no one has commented on the low vacuum level present in my vehicle?
Or is it generated by the control unit?

Best regards.
Thomas.

The LD (boost pressure) is tapped off at the turbocharger's outlet and fed to the control valve (N75), which then directs it to the diaphragm chamber. If the LD is high enough, it pushes against the spring force of the diaphragm, actuating the wastegate. The N75 can then "override" this by switching to ambient air using PWM (Pulse Width Modulation), effectively reducing the boost pressure.
"In older diesel engines (like my late Passat), there was no N75 valve; instead, boost pressure and membrane dosage were controlled via a simpler system. Additionally, the Passat TD had an overboost valve."
And – think about it – what is the exhaust pressure (like in modern TDI engines with a DPF)?

@ Thomas - Where is the pressure sensor located on your machine? There are two versions: one inside the control unit (STG), and another in the engine compartment.

hg
Herbert.

You can see if the boost pressure sensor is working within the MSG by checking the measurement blocks; it should have almost identical values to the altitude sensor.

At atmospheric pressure: yes. At higher pressures, it depends on the characteristic curve. However, a sensor from the parts catalog should have the correct characteristic curve.

Here's the question again for Thomas: Where is the sensor located (from model year 2000 onwards, it should be housed together with the intake air temperature sensor in a housing on the intake manifold)?

hg
Herbert.

Hello Herbert,
He's in the low loader truck next to my bus.

Best regards,
Thomas

Update: The boost pressure sensor with part number 074906018AM is an external component.

Please check if the actual boost pressure is equal to the ambient air pressure when the engine is running.