Boost Pressure, VTG, Check Valve: I Don't Get It

Hello and good evening.

I still have (see also https://community.dieselschrauber.org/en/viewtopic.php?t=17411) the problem that my Golf IV (110 HP TDI, manufactured in 7/9 goes into limp mode. The reason for this is a constantly too-high boost pressure.
After checking the system with VCDS and having already inspected the vacuum hoses several times, I decided to buy completely new hoses.
I installed it today and I'm off to drive. Everything is actually working perfectly, except that above 3800 RPM, the boost pressure gets a little too high (about 0.3 bar).
I then wanted to check if the VTG (variable turbine geometry) was still functioning correctly (in its default setting), but nothing changed. The reason for this was that there was no vacuum reaching the turbo.
Okay, so I reversed the check valve, and I was right back to the same problem. Even at 1500 RPM, there's way too much boost pressure, and it doesn't regulate itself after releasing the throttle (or it regulates very, very slowly).
However, VTG had adjusted its basic position in the meantime.

Why is it that my boost pressure is building up perfectly (target pressure equals actual pressure), even though I don't see any adjustments and don't feel any vacuum?
Actually, it should behave as if it's in a degraded mode, even though it's accelerating perfectly.
I am now completely confused and hope someone can help me.

Thank you in advance, and have a pleasant evening.

Sven.

"Hi, I had something similar once. There's a vacuum hose that runs behind the diesel filter to the turbocharger. Check it to see if it's been pinched by the diesel filter. I had a service done, and after that, the engine was only producing 50 horsepower! Then we checked the hoses, and the variable geometry turbo (VTG) couldn't move anymore (due to the vacuum). After we pulled the filter out a bit and rerouted the hose, everything worked as it should again."

As I understand it, you're referring to the hose that runs directly from the boost pressure control valve to the pressure sensor on the turbo. I replaced that hose, among other things, yesterday. And as I said, what's strange is that I haven't experienced any noticeable loss of power, despite everything. I'll try driving without the hose later. There was a topic where someone had similar symptoms, which turned out to be caused by a turbocharger that was incorrectly assembled.

Is it conceivable that a detached VTG impeller could generate enough boost pressure to allow the turbocharger to operate without regulation, but that the pressure would be excessively high if the other impeller blades were also engaged?

There appears to be enough space in the turbocharger for a control arm to disengage.


m;

Yes, that's certainly possible. As I said, I found a similar post. I'll link to it later (I have it at home).
It seems that the adjustment ring was installed incorrectly, which caused it to lock up. Unfortunately, I don't have a lift or a garage, which makes removing the turbo quite complicated.
However, I've been looking for a used turbocharger for a while now.
The turbocharger is currently in a maintained condition, which is something you generally wouldn't expect.

Here's the link: /viewtopic.php?t=4969&postdays=0&postorder=asc&highlight=rückschlagventil&start=24

Unfortunately, the images and logs are no longer available. It would certainly be helpful to have them.

Regards,

Sven.

Hello,

Yes, there were actually some ATL models with the shovel arms attached from the factory. Some were delivered that way, but it's a rare occurrence and falls within the PPM (parts per million) range.

This error can only occur during assembly. Once the impeller is correctly installed, the impeller blades will no longer come out of the pockets of the adjustment ring. If your engine was running properly before, it's unlikely that an impeller blade that was incorrectly installed from the beginning will now cause problems.

Why can the maintenance technician do it better? After all, they're just people too.

Greetings.

Andreas.