T4 2,5 Tdi , ACV Baujahr 2001 mal wieder Leistungsverlust! | Posts 32+

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.

You could also temporarily connect a simple mechanical boost pressure gauge to see if it shows the same readings as the display in the instrument cluster.

Werde ich morgen Mal angehen. Heute hier Dauerregen und keine Garage.
Best regards.
Thomas.

Wastegate without pressure!
The full boost pressure is being applied.
The N75 valve controls the boost pressure (the hose runs from the pressurized side of the turbocharger to the N75). The valve often fails because it's constantly exposed to high boost pressure. This is why many turbochargers have been incorrectly declared defective, as the valve failure can cause them to stop producing boost.
But not in this case!
The boost pressure sensor in the intercooler might be oily.

Beim ACV ( nicht Wald und Wiesen verbastelt) ist eine Diagnose eigendlich ganz einfach.

The engine electronics aren't exactly that smart yet.

What bothers me is the exceeding and falling short of established limits.
Let's assume there is no squealing or rattling to be heard.

Please take a look at the basic settings of the VPE.

You have the MSG 15 .

I finally found some time to look into the logs.

Please urgently check the TDI timing.

The charger control is not synchronized .

Check and adjust the wastegate linkage.

Basically, there's an attempt to establish a regulation, but it's happening very slowly.
So, either the torque limit or the maximum power output (VPE) will kick in and regulate things.


It should be noted that the charger can reach a maximum pressure of approximately 0.85 bar without any additives.
"It's important to have some slight oversteering tendencies, as the handling is generally quite sluggish."

Good morning everyone.
I installed the old pressure sensor again today.
Die Druckdose am Turbo lässt sich per Hand und mit Druck bewegen. Ein testen mit dem Motor im Stand ist nicht möglich, da er da ja keine Last aufbauen kann. Hoffe ich habe mich verständlich ausgedrückt. Ich bin der Ansicht, dass die Druckwerte nach Austausch viel höher liegen als zuvor. Das heißt er ist nun oft im Überdruckbereich wenn ich die Anzeigen richtig verstehe. Deswegen kommt dann ja auch der Notlauf wieder. Könnte das am Laderegeldruckventil liegen? VielIs it broken again?

The start of injection seems to be okay as well. I tried taking a Screenshot.

Best regards,
Thomas

by the way

Check this out: Database, everything's here!
Idle and full-load data for ACV.

Jeeper-Thomas wrote:

Good morning everyone, I installed the old pressure sensor again today. Die Druckdose am Turbo lässt sich per Hand und mit Druck bewegen.

Please answer the questions...

@Dawinchie: Which question are you referring to?
Didn't I take a Screenshot of the distributor injection pump?

Am I missing something?

Best regards,
Thomas.