Electro Pneumatic Converter: Details & Info

Good day!

Since I'm new here, I'd like to start by expressing my respect for the forum!
I haven't found this level of expertise anywhere else, WOW!

Now, however, let's get to my problem:
I've been having a lot of trouble with my Passat lately.
Da Ich leider (noch) nicht über VAGcom verfügen kann, bin ich leider auf die 'Oldscool' Fehlersuche angewiesen. Ich weiss, dass der Fehler (keine Leistung, ständig Notlauf) im Bereich des Ladesystems liegen muss. Ein freundlicher KFZ_Meister hat aus meinem Steuergerät den Fehler 'Saugrohrdruck Regelgrenze unterschritten' ausgelesen, und hat nach einigem geprüfe vorgeschlagen, einen neuen Lader einzubauen. Das fand ich nicht ganz so witzig, ´da ich das Auto erst 2 Monate habe, und auch die Einspritzpumpe schon kaputt war. Darauf hab Ich den Turbo selbst ausgebaut, und zu der Firma XY gebracht (dazu später mehr) . Die haben mir gesagt: Bubb; den kannste wieder einbauen, der ist in Ordnung. Ich den wieder eingebaut, und erstma ne ganze weile dieses Forum durchwühlt. Dann hab ich die Vakuumsteuerung vom Turbo mal unter die Lupe genommen. Wie Ich hier bereits gelernt habe, soll ja die Unterdruckdose der VTG nach dem Start des Motors im leerlauf bis anschlag anziehen. Tut sie aber nicht. (ach ja: Die Mechanik an sich ist Leichtgängig). Daraufhin habe ich alle Unterdruckschläuche kontrolliert, und nichts gefunden. Dann habe ich mit einem Unterdruckmanometer festgestellt. dass -0,4bar notwendig sind, um die Dose an den Anschlag zu ziehen. Im Leerlauf kommen im Steuerschlauch zur Dose jedoch nur max -0,2bar an. Auch während der Fahrt bleibt dieser Unterdruck die meiste Zeit konstant, wenn sich was ändert (max-0,3bar), dann stossweise. Ist das nicht eigentlich stufenlos? muss ja, oder? IIn emergency mode, the pressure remains constant at -0.05 bar.
Then I measured the vacuum pressure at the 'vacuum supply,' which is the hose system leading to the vacuum pump. And there it was: -0.8 bar.
Then I disconnected the breather hose from the 'valve' (while the engine was idling) and held my thumb over the connection. The result: it sucks in air like crazy, and now the canister is also pulled all the way open.
That probably brings me to my actual question:
Should the valve, when idling, not fully connect the vacuum line to the control unit to ensure it is fully actuated, without mixing in any atmospheric air?
And how is the valve controlled? By varying the voltage or the frequency? What voltage, or frequency should be applied to the valve when it's idle (assuming it's actually designed to fully open at that point)?

Now, a few words about company XY: (turbochargers)

I've read that it's not possible to adjust the VTG (Variable Turbine Geometry) mechanism on the turbocharger without a special test bench, so I've conscientiously avoided doing so.
The employee of that company, however, disassembled the connecting rod of the vacuum sensor right before my horrified eyes, claiming he was doing it 'for safety reasons' to readjust it. When I asked him how he had done that, and he reassembled it (with an adjustment that was approximately 5mm longer), he said: 'Just add about half a millimeter of preload to the lever, and it will be fine!' Is that really true??? The stop screw on the housing remained untouched. What do you experts think about this? Is it really possible to say that (I don't think so), or did he just tell me a complete fabrication?

Later today, I will test what happens when I apply 12V to the valve using a 'normal' configuration, and I will let you know the results.

Okay, just so you know, my Passat is a 3B AFB TipTronic, with approximately 125,000 km on the odometer, and it was manufactured in 1999.

Okay, and finally, I hope that with this post, I don't come across as a complete idiot. Please remember that just 2 months ago, I was driving a 32B, which also ran without an engine control unit (somehow) .

PS: Since I just came from the night shift, I unfortunately can only be partially responsible for my wording and spelling .

Looking forward to your help: Good night!

Hi,

Try searching for an older post by Ulf; he once disassembled a pressure transducer.

In short, it works like this: Inside, there's a kind of iron core that can be moved vertically. One end directs fresh air, while the other creates a vacuum. The control unit controls this component with a PULSED voltage (alternating between 0 and 12V) and regulates it by varying the pulse ratio. This keeps the metal core "suspended," allowing it to partially open both paths and thereby regulate the vacuum for the container.

So, with 12V or anything between 12 and 0, you can't achieve anything; it really needs to be pulsed.

You could try measuring the voltage with an analog voltmeter to see what's arriving (a digital one would just fluctuate). Depending on the control signal, you should be able to see 0-12V, because the needle's inertia averages it out. If that's okay, I would replace the valve (around 100 euros); it probably wouldn't be worth repairing. Or, look for Ulf's old post and try taking it apart, maybe there's dirt inside. (If you do that, some photos of the insides would be great, because there aren't any pictures of the internals of this thing in the forum yet).

Best regards,

Jan.

Hi,

Before you disassemble it, you could try to see if you can get it free again (in case it's just dirt stuck in there).
I once experienced this (of course, while on vacation) because I had cut corners during my car's modification and left the breather hose for the atmospheric air open in the engine compartment. I then performed an actuator test, and it worked again afterwards.
During the actuator test, the valve is switched back and forth between its minimum and maximum positions. You can also turn it on and off with 12V.
You can also try using the AGR valve for the turbo, but make sure to connect both valves, otherwise it will generate an error message.

Greetings,
dieter