T4 ACV: Zu niedriger Ladedruck | Posts 16+

Both the valve (N75) and its hose have already been replaced.

It would be interesting to see if it actually works.

Use a 50 (or preferably 100) ml syringe with a *short* hose connected to the wastegate and press firmly.
Then the wastegate should also move and then close again.

Hmm, darn it, with the ACV (Audi coil valve), you can't see the wastegate as easily as you can with the 1Z because the pipe bends are fixedly attached to the turbocharger.

It looks something like this:
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Bitte nutze 'Attachment hinzufügen' bzw. das Upload Forum hier.

I'll try the test with the syringe. I still have a 100 in the basement.

I had already examined the external frame. It functions normally, doesn't get stuck, can be moved with the necessary force, and then retracts automatically.

In the resting state, it appears there is no tension on the rod, and the spring of the pressure sensor seems to be at its limit. Would it be worthwhile to adjust the rod a few millimeters towards the "closed" position? This is also how it's described in the T4 wiki.

That could be the reason.

In standby mode, it's not the gate that's active, but the enclosure itself.
Then the gate is always slightly open, and the tractor feels like it's being pulled from behind.

Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

Okay, let's investigate this further. Unfortunately, the adjustment process is quite tedious when it's installed, especially because of this metal piece that surrounds the locknuts, as you can see in the photo here.

http://www.t4-wiki.de/wiki/Datei:Motor_Turbolader_Wastegate_ACV_Muttern_Schubstange.jpg
I might have to take it to a workshop after all. Removing the turbocharger is beyond my mechanical skills. However, I have a good independent mechanic who I trust, and she won't immediately try to sell me a new turbo.

Okay.

Do you know what you're doing?

BECAUSE:
If you shorten the rod too much, the valve gate may not be able to open wide enough.
If you then want to drive with full throttle without any reservations, it could damage the turbocharger.
If you're lucky, the engine control unit (ECU) will activate the limp-home mode before that happens, because the boost pressure will become too high.

Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

Yes, I understand the mechanisms and risks involved. It's not about artificially "forcing" the wastegate. I just want to rule out the possibility that the linkage is jammed, meaning – as you already mentioned – that the pressure sensor is at its limit while the wastegate is still open.

I have found the following procedure for adjusting [something] on various forums:

1. Loosen both nuts.
Tighten the lower nut until the wastegate is fully open.
3. Tighten the lower nut by another 2-3 rotations, or approximately 5 mm.
4. Counter with a top mother.

"Does anyone have an official repair manual, for example from Garrett, for comparison purposes, especially regarding point 3? (VW certainly won't have such a document; they just replace the part immediately.)"

...and Honeywell (Garrett) won't reveal it either.

Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

yps77 wrote:

In the resting state, there appears to be no tension on the rod, and the spring of the pressure chamber seems to be at its limit.

This means that the rod moves even with minimal force or the slightest overpressure applied by a syringe?

This is quite unusual for a wastegate turbocharger, because the gate should only open above a certain boost pressure (even in controlled turbos) .

-> I'm guessing it's a broken membrane spring -> Replace the can .

... or a previous owner may have fiddled with the linkage to adjust it in a way similar to how VTG loaders are adjusted .

ulf wrote:

That means the rod moves even with minimal force or with the slightest pressure applied by a syringe?

Um, no, I meant something else. The pressure capsule is okay, and the membrane spring is working. However, my impression is that the rod isn't applying any pressure at all to the wastegate lever when it's in its resting state. That's why I suspect that while the membrane might be fully extended, the wastegate itself isn't actually opening, or only opening very slightly.

According to the instructions found, the rod should be adjusted so that the membrane has a slight amount of upward play when at rest, meaning only the wastegate is touching its limit. As long as there is sufficient clearance in the opposite direction, the MSG (Motor Steuergerät - Engine Control Unit) will continue to regulate the boost pressure.

yps77 wrote:

From my impression, the rod does not exert any pressure on the wastegate lever in its resting state. Therefore, I suspect that while the membrane may be at its limit, the wastegate itself is not, or only barely so.

Aha: then the gate may not be closing completely: this tends to result in lower LD (load). Rotate the rod a little further until the wastegate clearly reaches its stop; this should not cause any damage, IMO.

I'd like to revive this thread and let you know that the problem has now been resolved. It turns out that adjusting the wastegate slightly more towards the "open" position, about a quarter turn of the locknuts, actually helped.

This is just a service for anyone who might come across this thread in the future. Even though the thread is a few months old and things have dragged on quite a while, it's probably still useful to share how the story ended.

Thank you again to everyone who participated here.

yps77 wrote:

Even though the thread is a few months old and the matter has dragged on for quite some time, it's certainly still useful to share how the story ended.

Yes, because feedback on resolved issues contributes greatly to the overall quality here.

Thank you .