Ladedruckregelung: Regelgrenze überschritten | Posts 32+

Quote:

Where is the exhaust gas temperature measured on the engine?

In the DPF.

Okay, the BRE system has an additional temperature sensor inside the compressor housing, near the turbine inlet.

Best regards, Rainer.

Hello,

"Over Easter, I disassembled the turbochargers from two 3L Lupos because the variable turbine geometry (VTG) was stuck. In one turbocharger, the impeller vanes were likely blocked by small pieces of debris – it wasn't easy to see exactly what was causing it. In the second turbocharger, mainly rust clumps from the exhaust manifold were stuck in the actuator ring for the variable geometry."

I removed the rust from the corresponding areas on the exhaust housing of both turbochargers using a wire brush, cleaned the adjustment and actuation rings, and reassembled everything. One Lupo is running properly again (no more limp mode, better response at low RPMs). The other one is not registered and therefore cannot be properly tested.

"I adjusted the tightness of the blades after cleaning by adjusting the three Torx screws that hold the adjustment ring in place. Even when these screws were tightened correctly, some of the blades were still slightly tight. Loosening them slightly resulted in the blades moving freely. I couldn't feel any significant build-up on the two contact surfaces of the blades, so I tried this method first instead of trying to smooth anything down."

The following questions are still open for me:
"What type of screws (quality and material) should be used for the adjustment ring? The old screws were quite damaged at the threads, and they were so difficult to remove that the heads would eventually detach from the shaft - but lacking alternatives, I reused them. Finding the right material combination seems to be a science in itself, and even if you find the right combination, retailers probably won't stock it (or only in packs of 1000). Torx heads are probably essential due to the torque involved, and so far, I've only found them in stainless steel."
* The same question arises again regarding the screws used to attach the exhaust manifold...
"The description of my ceramic paste states that it is suitable for temperatures up to 1400°C and also provides a seal. So far, I have only used it for the threads of the screws, but I briefly considered whether it would be worthwhile to apply it to the sealing surfaces between the adjustment ring and the exhaust housing, hoping that it would prevent soot from reaching the side with the adjustment levers. Does anyone have any experience with this?"

Bye.
peace

Quote:

I adjusted the tightness of the blades after cleaning by adjusting the three Torx screws that hold the adjustment ring in place. When these were tightened correctly, some of the blades were still slightly tight. Slightly loosening them resulted in the blades moving freely. I couldn't feel any significant build-up on the two contact surfaces of the blades, so I tried this method first and didn't attempt to smooth anything down.

The problem is caused by a warped exhaust manifold. You can easily verify this by using a depth gauge on a flat surface. The difference in height can easily be 3/10 mm or more.
If the guide vanes are already sticking when cold, without any lubrication, I have no idea whether or how long that will be okay.

Unfortunately, I don't have any information about the screws.

Autoservice wrote:

The problem is caused by the warped exhaust manifold

.
You slide the adjustment ring over the spacer sleeves against a plate that is located separately within the exhaust housing. With the first turbocharger, I didn't even notice this plate, but with the second one, it fell out when I was knocking off the dirt. If the exhaust housing isn't so severely deformed that the clearance in the adjustment ring's seat prevents it from being aligned parallel to this lower plate, then it's essentially a separate mechanical unit, independent of the exhaust housing. Because these three Torx screws were so difficult to loosen (and also different in terms of how difficult they were), you couldn't tighten them equally with a torque wrench.

"Where exactly do you think the exhaust manifold runout should be measured? I think it would be better to mount the adjusting ring and counterplate outside the exhaust manifold. There, you could check the distances all the way around. By the way, are there any high-quality replacement parts available for this?"

Autoservice wrote:

I have no idea if and for how long this will work well.

They are both my own cars, so I can, without a guilty conscience, rely on this attempt. For the first 150 km on country roads and a short stretch of highway, it initially worked. The boost pressure values during the test drive were also suitable for acceleration. And after 100 km continuously, the VTG could be moved freely by hand. I could only estimate the actuation force against the pressure sensor - but that seemed normal to me and easier to operate than before. What happens during the next few kilometers, we'll have to wait and see.

Bye.
peace

Quote:

Where exactly do you think the delay of the exhaust manifold should be measured?

Check out page 1, image 5, in this thread. You can still visually see the bulge; it's more shiny where it was sanded down.

Okay, this is the counterplate that I mentioned. It wasn't part of the exhaust housing in the chargers that I disassembled – it simply fell out. I'm not entirely sure right now whether it could have been rotated. Unfortunately, I didn't take any pictures because I was really pressed for time.

I'll probably get another delivery of materials this weekend, which will allow me to take a closer look at everything.

Bye.
peace

Quote:

By the way, I adjusted the tightness of the blades after cleaning using the three Torx screws that hold the adjustment ring in place. When those screws are tightened correctly, some of the blades still have a slight amount of resistance.

Not good...

If everything is properly assembled and functions as it should, the VTG adjustment lever will move freely into all positions due to the weight of the adjustment rod.

Best regards, Rainer.