Allroad AKE V6 2,5TDI keine Leistung unter 2500 u/min | Posts 16+

@dieselschrauber:
Hi,
Okay, so the charger has been replaced... The behavior is the same with different chargers.

Regards,
Al.

Hello everyone, is my assumption correct?
If I remove the catalytic converter from the loader, will the lack of power disappear if it's due to a clogged exhaust? Or will there then be a problem due to the complete lack of back pressure?

Regards,
Al.

altonno wrote:

Hello everyone, is my assumption correct? If I remove the catalytic converter from the loader, will the lack of power disappear if it's due to a clogged exhaust? Or will there then be a problem due to the complete lack of back pressure? Regards, Al

.
No, in that case, the device should start working and begin accelerating sooner.

So, should the almost full power be available then?
I had tried it, and I couldn't really notice any difference.

Okay, so it seems like the troubleshooting should now focus more on the VEP (Visual Evoked Potential) tests?


Regards,
Al.

dieselschrauber wrote:

Hello. It's possible that the VTG (variable turbine geometry) is not properly adjusted on the turbocharger. If the AGR (exhaust gas recirculation), MAF (mass airflow sensor), and vacuum system are all functioning correctly, this should be checked. You can usually see the VTG's duty cycle relatively quickly. Da ich in dem Log was ich ansah keinen Überschwinger fand, evtl. mal die Länge der VTG-Verstellstange markieren (genau! Farbpunkt an Verstellmutter, Stangenlänge messen) und diese eine (!) Umdrehung kürzer machen. DanTest drive. Best regards, Rainer

Hello Rainer, I have already read about the VTG adjustment and I have not ignored it .
The issue was that I had replaced the charger with a "new" refurbished one just last week. And the behavior hadn't improved. So, I came to the conclusion that the problem wasn't the charger. I could always reinstall the old one and "tweak" the settings a bit.

Regards,
Al.

If you don't want to look for the cause, then just keep trying different things...

Hi Rainer,
Sure, I want to find the root cause... that's what I'm aiming for. I'm also very grateful for any input. I just wanted to say that the charger has already been replaced, so the question is whether there's a high probability that there's actually something wrong with the charger itself.

Okay, please don't misunderstand my responses.

I'm going to reinstall the old loader and then try out different settings.

Regards,
Al.

The goal is to determine whether a more precise control of the VTG (Variable Transmission Gear) system alone is sufficient to achieve good driving performance.

Then you know in which direction you need to continue searching, or whether you should just leave it as it is.

Okay, I'll try that now!

Hi,
and also perform the test described in the second link above https://community.dieselschrauber.org/en/viewtopic.php?t=10810 to check for misadjustment of the VTG: "If there is suspicion of a misadjustment of the turbocharger, you can use VCDS in the basic settings mode of the MWB 11 (or the dropdown selection for newer engines) to quickly check whether the VTG is working and whether the setting of the closed position is correct. ..."
In my opinion, the problem clearly lies with the turbocharger, and it would be quite misguided to look for the issue in the fuel injection pump or the mass airflow sensor.
hg
Herbert.

Hello and thank you again... I've read it through again and I think I understand everything so far. Unfortunately, I'll be away for the next few days and won't be able to get to the car. I'll try it out sometime at the end of next week.

Regards,
Al.

Hello everyone,

I finally had some time again and was able to put the tips into practice.

I switched the turbocharger back again. While doing so, I noticed that the pipe between the turbocharger outlet and the EGR valve was broken! I have no idea how I could have missed that last time. I even looked at it specifically. However, it's sealed again now.

I also shortened the connecting rod by exactly one rotation, as suggested. After assembly, the car is now "driveable." Definitely much better. Of course, I don't know for sure whether the improvement was primarily due to the leak being fixed or to the adjustment of the tie rod.

Unfortunately, I didn't have a tester available to log the results. However, there was a noticeable increase in torque that could be felt starting at 2000 RPM.

I then, as a test, shortened the tie rod by another full rotation, but nothing noticeably changed. Attached is the log from the version with the tie rod shortened by two rotations. You can now see a clear overshoot.

I would now turn the rod back one more revolution and test it again.

What the logs now show (and what is also felt in reality) is that not much happens below 2000 RPM.

But, as I said, purely in terms of performance, the vehicle is now significantly more powerful and responsive.

Attached is a Screenshot of the log.

The boost pressure should be significantly higher than 2000, right? Is that correct? Where else could I make adjustments?

Looking at the N75, it seems to operate at around 80% at just under 2000 RPM. Doesn't it open up to 100%? Then, according to my understanding, the EGR adjustment would be somewhat more aggressive, wouldn't it?

Best, Al.

Hello,

Thank you for the feedback. But two negative things at once.

Quote:

I switched the turbocharger back to the original one again.

It was never requested. If you have a new one, then just leave it in.

Quote:

I then, as a test, shortened the tie rod by another full rotation, but nothing noticeably changed.

I said *one* revolution, and I emphasized "one" because if the overspeed is too high, the turbine shaft can break off from the compressor. Boom, broken, engine failure.

"At least you checked how the wastegate looks; as expected, it's too high, and I suspect the old (carbonized) turbocharger has been reinstalled, which seems to be causing the VTG (variable turbine geometry) to jam. The boost pressure drops almost abruptly from 2500 mbar to 2000 mbar. The target boost pressure at 2000 rpm is still not being reached."

Quote:

I noticed that the pipe between the turbocharger connection and the EGR valve was broken! I have no idea how I could have missed that last time.

Yes, I have no idea. Usually, you don't even need to see it, because you can already hear the loud hissing sound when you accelerate.

Best regards, Rainer.