Ladedruckaufbau AFN träge, Istwert zu niedrig | Posts 32+

Hi Jochen and Roger,

We don't agree on that, and I think you need to look more closely at the diagrams.


Sorry, Jens, but don't fall into the same trap that I did a few days ago.
You can read all about it at the following link, although I think the second page is particularly interesting, as it shows how the VTG is controlled, especially in extreme conditions (low exhaust volume, high LD request).

/viewtopic.php?t=15983&start=24

Here, I was ultimately able to convince myself that my perspective, which aligns with yours, was wrong.

Regarding the duty cycle:
Take a look at Dieter's diagram; he has the same engine, the same vehicle, and the same software. The only difference is: his AFN is working as it should.

Dieter's vehicle works exactly like mine.
With a high LD demand, low PWM values are used, which allows the VTG to build up the LD.
High engine speed > high exhaust gas volume, the PWM values increase, the VTG opens to allow the LD to be regulated.

If the target LD value is not reached, the PWM values will continue to increase, further reducing the LD.

This is exactly the behavior that Roger and I described.

Folge: hohe %-Zahl = hoher Ladedruck = Ventil N75 auf !!!
The VTG opens, allowing exhaust gas to flow (relatively) unimpeded through the turbocharger, which reduces the engine speed and, consequently, the boost pressure. This is similar to how the bypass valve opens in other types of turbochargers.

The 92% reading from the emergency mode should be treated with great caution; who knows what signals the control unit is outputting in emergency mode and how the VAG-Tool interprets them. The 92% in emergency mode may have nothing to do with the actual duty cycle. I wish I hadn't written anything at all.

'92% PWM means the VTG (wastegate) is open very wide, which results in very little boost pressure. The behavior is similar to having the connector unplugged.'

In 'slide' mode, no boost pressure is required, and both Dieter and I experience a duty cycle of 25% = valve N75 to
In push-pull operation, the VTG (Variable Turbine Geometry) charger brakes. The 25% PWM (Pulse Width Modulation) is set after the speed has decreased sufficiently and the VTG enters braking mode.

This has also been discussed in detail in the aforementioned article.

Regarding the N75 itself:
I bought it just a few days ago.
Then take a closer look at the wiring harness.

Best regards, Jochen.

Interestingly, the attempt ended in failure.
Here, the MSG is desperately trying to build up LD:

Nein, genau das macht es eben nicht !


Please provide the text you would like me to translate from German to English. I will provide only the translation, without any explanations.


But, look again, carefully:

It builds up boost pressure as desired for a few seconds
To achieve this, the system briefly reduces the duty cycle (using a small PWM), the LD (load current) increases, and the VTG (voltage throttling gate) is reopened to prevent the LD from 'exploding.' To accomplish this, the duty cycle is increased.
danach wird aber wieder runtergeregelt obwohl die Maximal-Forderung nach Ladedruck bleibt.
no, is already being fought against the missing LD, VTG is closing, the duty cycle is decreasing again.


Strictly speaking, the STG is working against itself!
On the one hand, there's a demand for maximum boost pressure, but on the other hand, the duty cycle is reduced, which causes the boost pressure to decrease.
This is a contradiction in itself

No, if you change your mindset, not at all.
That should be addressed in the thread I mentioned earlier, if you read it carefully.
He has it too.

Best regards, Jochen.

Okay, I understand. Please provide the text you would like me to translate from German to English. I will only provide the translation.

Hello Jens,

a not entirely optimal example:

Consider the area when the target LD (blue) starts to increase towards the maximum value.

Here, the PWM value is decreasing. The VTG (variable turbine geometry) closes, allowing for boost pressure build-up. Simultaneously, the actual boost pressure is increasing.
In this example, it's minimal, but noticeable. A better example would be one where the vehicle was driven for a long time at a constant, low speed, and then suddenly accelerated to full throttle.

As the exhaust volume increases with increasing engine speed, the LD (likely referring to a pressure or temperature value) would increase very sharply if the VTG (Variable Turbine Geometry) were not simultaneously opened again. Therefore, the PWM (Pulse Width Modulation) ratio increases.

At the end of the designated area, the target LD value decreases to zero. The duty cycle is further increased to allow the VTG to open further and prevent the buildup of any additional LD.

Take another look at the examples in the other thread, especially the last graphic, as it clearly shows the behavior.

Best regards, Jochen.

Jochen_145 wrote:

Sorry Jens, aber renn nicht in die gleiche Falle, wie ich es vor ein paar Tagen gemacht habe.

JEHOVA !

*chips and beer run*

No, without me .

In such a case, I will only link to the most recent thread.

But at least, for me, it 'clicked' .


Best regards, Jochen.

Hello Jochen,

Okay, I'll be convinced.
The secret probably lies simply in understanding the principle of how it works.
Voller Unterdruck auf der Dose heißt wirklich hoher Ladedruck, da volle Anströmung der Turbine. Das N75 regelt den Unterdruck, indem Luft aus der Umgebung (dem Luftfiltergehäuse) zugegeben wird. Je höher also das Tastverhältnis umso mehr Luft strömt zu, umso niedriger der Unterdruck. Du haYou are absolutely right.
High duty cycle = VTG open = less airflow to the turbine = less compressor capacity.

Yesterday, I connected an analog vacuum gauge (manometer) to the line between the N75 valve and the turbocharger vacuum sensor using a T-connector.

Idle speed = high vacuum -0.64 bar.
High boost pressure = low vacuum -0.20 bar.

The turbo is therefore more likely to be open at high boost pressures.

Unfortunately, the faulty behavior of the turbocharger's boost pressure can also be read on the analog pressure gauge.

Full guest test:
* Vacuum pressure: -0.2 bar, boost pressure: 0.9 bar, read from the analog LDA sensor.
* After approximately 3 seconds (still full throttle): Boost pressure drops to about 0.5 bar, while vacuum increases to -0.4 bar.
* So, the MSG is actually trying to increase the boost pressure.
* It doesn't care about the boost pressure; it stays where it is.

Now, the questions are flooding my mind again:

Why is the boost pressure dropping even when the engine is running at full throttle?
Why isn't the turbocharger responding to the increased vacuum pressure at the vacuum sensor of the VTG (Variable Turbine Geometry) adjustment?

Mechanically, I can only explain this with a stuck VTG (Variable Turbine Geometry). If it were stuck (which wouldn't be noticeable in a cold state by manually moving it), why does it never get stuck in a state of "high boost pressure"?
During the full-throttle test, the boost pressure always increases, then decreases, but never increases again.

Does anyone have a control unit left over from a 1Z?

Regards,
Jens.

You can also look for errors in other places besides the VTG (Verfahrensweise und technische Gültigkeit).

- Electrical wiring to the N75 valve (intermittent shorts/ground faults).
- Can the VTG (variable turbine geometry) also only get stuck when the engine is hot?
- The vacuum sensor may leak, sometimes exhibit fluctuations in its reading, but for example, may not maintain the pressure.
- The vacuum hoses from the N75 valve to the "ambient pressure" sensor are kinked (a common issue when the load dump is too high - in this case, you can't relieve the vacuum by mixing it with ambient pressure).
- You don't have enough vacuum (the vacuum pump/reservoir may be leaking, etc.) => insufficient laser-induced breakdown.

Yesterday, I connected an analog vacuum gauge (manometer) to the line between the N75 valve and the turbo vacuum actuator using a T-connector.

Idle speed = high vacuum -0.64 bar.
High boost pressure = low vacuum -0.20 bar.

The turbo is therefore more likely to be open at high boost pressures.


Hello Jens, now you have it .

The VTG (Variable Turbine Geometry) is open at high boost pressures and high engine speeds .
At low engine speeds and high boost pressures, it is largely closed.

The reason for this is the increasing exhaust volume as the speed increases.


* So, the MSG is really trying to build up more boost pressure.
* It doesn't care about the boost pressure; it stays where it is.
(..)
Now, the questions are flooding my mind again:

Wieso fällt der Ladedruck trotz Vollgas zusammen ?

Since this behavior doesn't always occur, I would look for a crack in the charge air cooler that opens up under prolonged high stress.
Activate the LLM again; you should be able to measure a leak like that.


So rein mechanisch kann ich mir das nur mit einer klemmenden VTG erklären.

No, I don't think so. He can definitely build up LD (load demand) even at low speeds, so he can close the VTG (variable torque generator).
He can completely disassemble the LD (likely referring to a specific component), which would allow him to fully open the VTG (likely referring to a specific assembly). Therefore, the VTG IMA (likely referring to a specific mechanism or part) should not be jammed.

Best regards, Jochen.

Quote:

Da dies Verhalten aber nicht immer auftritt, würde ich nach einem Riss, der sich bei längerer hoher Belastung öffnet, im der Ladeluftstrecke suchen.

I would also suspect that, so please double-check for any possible turbocharger intercooler leaks before you start twisting the VTG rod or anything like that.

Alternatively, I could imagine that, for example, the return spring of the AGR valve is defective and that it opens or leaks at full load.

Quote:

- The vacuum sensor may leak, sometimes exhibit fluctuations in its reading, but for example, may not maintain the pressure. - You don't have enough vacuum (the vacuum pump/reservoir is leaking, etc.) => insufficient laser-induced breakdown.

This could also very well be contributing to your symptoms. The vacuum pressure might be enough to activate the VTG (variable turbine geometry) and build up LD (load demand), but when the vacuum disappears, the VTG opens again. Consequently, the MSG (motor control system) reduces the TV (torque value), but the VTG no longer responds, until the MSG has to switch to emergency mode.

Edit: To test this, you could try applying 12V to the N75 sensor and see if the VTG remains fully engaged, while also using the brakes to create vacuum.

Brief update on the status of the investigation:

- Please no more suggestions related to the EGR valve; the engine hasn't had one for over 140,000 km.

- Vacuum pressure is present, measuring -0.90 bar before the N75 valve.

- After the N75, I also measured the vacuum (using an analog pressure gauge) while the engine was running and compared it to the duty cycle. It matches well; the duty cycle and the actual vacuum pressure are in good agreement. Therefore, the vacuum is reaching the vacuum sensor as desired by the control module. I'm stopping my troubleshooting efforts and focusing on the N75 and vacuum lines. I haven't found anything wrong there anyway.

- I removed the vacuum actuator and tested it with a large syringe. I can move the control rod (the threaded rod that comes out of the actuator) to any position, and the actuator holds that position for minutes. So, it's functioning as it should.

- I've re-examined the boost pressure line, and it's sealed.

The symptoms don't really match a leak in the intercooler system; it only seems like they might.

Sure, I'm ready. Please provide the text you want me to translate from German to English.
In the lower RPM ranges, I never exceed 0.6 bar of boost pressure, and as the engine reaches higher RPMs, the boost pressure drops.

In 3rd gear (I only have four gears), the boost pressure sometimes reaches 0.7 bar. After a few seconds of full throttle, it slowly and continuously drops back to zero.

In 4th gear, boost pressure can reach up to 0.9 bar at low RPMs. Full throttle results in a drop in boost pressure. If I maintain around half throttle in 4th gear, the boost pressure of 0.8 to 0.9 bar remains stable for a while. If there were a leak in the charge air system, the pressure would escape. If you then give it more gas, the boost pressure drops back to 0.5 bar or less.

I'm starting to think the turbo itself is the problem (even though it's brand new from a repair shop, which doesn't necessarily guarantee it's working correctly), although I haven't yet figured out exactly what the defect might be.

Regards,
Jens.

Jens 16syncro wrote:

I'm slowly starting to believe that the turbo itself is the problem (even though it's brand new from a repair shop, but that doesn't necessarily guarantee it's working correctly), although I haven't yet understood exactly what the defect might be. Regards, Jens

Do you recognize this? It was already linked in the forum back in February.
http://www.turbolader.com/STL/Bilder/Tech042-Deutsch.pdf

Roger wrote:

Do you recognize this? It was already linked in the forum back in February. http://www.turbolader.com/STL/Bilder/Tech042-Deutsch.pdf

Hello Roger,

I wasn't aware of that, thank you.
It probably won't be of much use to me, as I can't observe the described irregularities on my turbo.
I also did some research to see if my problem could be explained by a faulty turbocharger (even a damaged one), but so far, all the turbocharger experts I've consulted have said no.
How much credence one should give to those statements is debatable.

Regards,
Jens.

Can the behavior of the turbocharger pressure be explained by properly seated fuel injectors?
I took them out, and they look pretty bad.

The amount of fuel injected is only controlled, not regulated. The engine control unit (ECU) doesn't know exactly how many milligrams of diesel are actually being injected. If the injectors are clogged, the control slider in the electronic fuel pump (ESP) may be in the correct position, but the corresponding amount of fuel doesn't reach the combustion chamber.

And insufficient fuel leads to low exhaust emissions, which in turn results in reduced turbine power.

Does anyone know about the behavior of TDI engines with stuck injector nozzles?

Regards,
Jens.

What is the fuel injection amount you are getting with a warm engine at idle (MWB 1, field 2), and what does MWB 13 indicate?

Malte1408 wrote:

Was hast Du denn für eine Einspritzmenge bei warmen Motor im Leerlauf (MWB 1 Feld 2) und was sagt MWB 13 ?

Hi,
I don't know .
Since the nozzles are currently outside, I can't log any data.

Here.


I once logged the fuel injection amount.

turquoise = IST quantity
green/yellow: Limit values for soot and torque limitation.