Disassembling and assembling VTG loaders?

hi,
Can a VTG turbocharger, for example, one from a Lupo 3L, be disassembled and reassembled to be functional again?
or at least remove the exhaust side to take a look after adjusting it?
'I'm having shifting and clutch problems with my 3L.'
they probably originate from a turbo model, despite having had various transmission parts replaced.
When accelerating, the actual charge pressure value follows the target value relatively slowly.
'It's likely that the EDC (Electronic Diesel Control) system is reducing the gas flow because the charging pressure isn't correct yet.'
This can cause the transmission to no longer engage the correct clutch position, resulting in improper clutch engagement, essentially releasing the gas too late after the clutch is engaged.
The 3L features a hydraulically actuated gear shifter that operates a standard 5-speed manual transmission, and a hydraulically actuated dry clutch, which is controlled by the transmission control unit.
Every 30,000 km (or as needed), each vehicle receives a complete transmission adjustment.
which automatically searches for and saves the optimal grinding point.
This friction point then becomes almost as fixed as a characteristic curve.
Over the lifespan (e.g., 30,000 km or according to the inspection intervals), the wear threshold is dynamically adjusted.
However, this adjustment is only very slight and is intended for the long term, to counteract the wear of the clutch, so that this dynamic adjustment of the engagement point cannot cause large fluctuations.
Furthermore, the transmission control unit is connected to the engine control unit via the CAN bus.
However, the engine control unit has a higher level of authorization.
When shifting gears in the 3L model, you keep your foot on the accelerator pedal as you would with any automatic transmission. The transmission control unit then uses the CAN bus to reduce the throttle and, after the shift, to reapply the throttle.
If, when engaging the clutch, the transmission control unit suddenly increases the throttle again...
The engine control unit (ECU) detects that there is insufficient boost pressure (or air volume).
This, of course, removes the natural gas.
Apparently, the transmission control unit doesn't receive this information and continues to follow its clutch control map, which then leads to incorrect clutch engagement.
It's like when you release the clutch too quickly, or simply take your foot off the accelerator while keeping your foot on the clutch.

I once looked at and removed the VTG control panel.
The adjustment on the turbo is very easy.
I have a feeling that maybe something is loose, or perhaps something is coming loose on the shovel.

The Turbo now has 78,000 km on the odometer.
The charging pressure of (absolute) 2 bar is reached and regulated (with an overshoot of up to 2.3 bar).
however, in my opinion, the build-up of boost pressure takes a very long time, which I initially attributed to the control system of the 3L, since it's not a racing car .
Now that several transmission parts have been replaced, I obviously need to explore a different theory.

Can the exhaust side of the turbo be disassembled and reassembled without causing any further issues? (Assuming nothing is initially found to be wrong).

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greetingshttp://pics.m-eit.de/ladedruck.JPG{MARKER}

Hi,
Apparently, it's supposed to work; I've at least seen it done before with photos on a website.
Did you also log any values for the air mass? If the air mass sensor (LMM) reports too little air, as unfortunately often happens, then less diesel will be injected. This results in a lower exhaust gas temperature, and the turbocharger doesn't spool up as effectively.

Hi,
The LMM values are okay.
The oil consumption is almost zero (approximately 0.5 liters per 10,000 km).
Yesterday, I had the lower air intake hose off.
There's just a single, tiny drop of oil leaking out.

Could it be that a turbo seems okay overall, but builds up boost too slowly at low RPMs?
If, for example, I'm at 3000 RPM and I suddenly increase the throttle from 0% to 100%, the boost pressure will increase quite quickly.
but for example, at 2000 RPM, it already starts to become noticeable.
I was wondering if, for example, a misaligned window pane might not start to rotate properly until a certain exhaust pressure is reached?
'Or, if the intake side were blocked by the EGR system, the turbo would essentially start to spool up slowly as well, because it's a closed loop (little intake air => little exhaust gases).'
I can't imagine that the problem is caused by deposits from the EGR system, because the issues started at 40,000 km and have remained constant up to 78,000 km, without any worsening or improvement.
greetings

hi!
Could a leak in the turbocharger pressure system also be the cause, requiring higher engine speeds to build up pressure? This should be relatively easy to determine by logging the control signals of the turbocharger pressure control valve. Furthermore, I could also imagine a faulty wastegate control valve... So, before I start disassembling the turbo, I would take another look at that (if I haven't already:-)).
It might also be worth considering an EGR valve that doesn't close immediately, although this would likely result in significant smoke emissions and lower mass airflow sensor (MAF) values.

Good luck.

dirk

hi kamil,

Okay, I also think your charge air system is leaking! You might not notice it because there's apparently no oil in the system, and that's why you're not seeing the 'blow-out' points. I'm not familiar with the Lupo and don't know exactly what's installed, but it was similar in my AWX. There are profiles installed that end as pipes at both ends. A rubber hose with a vulcanized pipe and a round ring is inserted into them. Due to vibrations, etc., the round ring eventually stops sealing, and some pressure escapes. This means that the target charge pressure is reached later/slower. The overboost was quite significant in my case. I cleaned the charge air path with soapy water and only then did I see...It's probably just leaking. I've re-sealed it, and everything seems to be fine now. Maybe you should check that first, before you take the turbo apart and potentially ruin it.

Hello Jörg,

There was already a discussion here about "small" leaks in the intercooler system and their effects. It turned out that people usually don't notice it very much.

Quote:

The overshoot has been relatively severe in my case

.
What I would be interested in knowing is how you explain the increased overshoot caused by a leak.
IMO, the VTG operates at speeds below 1800-2000 RPM, and always runs at maximum charging pressure under full load.
In the case of a leak, the over-travel would likely decrease because the air would be escaping.

@LUPO3L

Quote:

I was wondering, for example, if a misaligned guide vane

wouldn't start rotating properly until there's a high exhaust gas pressure?

All the guide vanes are mechanically linked. So, either they are all crooked, or none of them are.
Generally, I don't see the problem with your car being related to the turbocharger, especially if you say you can easily move the control rod.

Best regards,
Albrecht.

Hello Jörg,

There was already a discussion here about 'small' leaks in the intercooler system and their effects. It turned out that people usually don't notice it very much.
The overshoot has been relatively severe in my case.
What I would be interested in knowing is how you explain the increased overshoot caused by a leak.
IMO, the VTG operates at speeds below 1800-2000 RPM, and always runs at maximum charging pressure under full load.
In the case of a leak, the over-travel would likely decrease because the air would be escaping.



hello albrecht,

Here's the translation:

'Simply put, the VGT (Variable Geometry Turbine) blades are positioned more aggressively in the airflow because the target boost pressure isn't being reached, as it's being blown away. From approximately 2500 RPM, the exhaust flow and blade position are such that excessive boost pressure is generated, and the boost pressure increases dramatically until the after-regulation system kicks in. I've observed momentary overshoots up to 2800 mbar! At that point, the boost pressure is fully established and remains so due to a blade position that is more aggressive than the normal setting. This can also be observed by a higher duty cycle of the VGT adjustment compared to the normal setting.'

Oops, hopefully you understand what I mean!

I understand what you mean. We need to clearly distinguish between the different RPM ranges here. Above approximately 2000 RPM, you might be right.
However, in my vehicle, I can experience the largest boost pressure overshoots when accelerating heavily in the lower gears, starting from around 1500 RPM.
That goes up to 1.5 bar, which is quite a lot.
I'm concerned about this issue because I suspect there are small leaks that aren't affecting performance, but are likely impacting fuel consumption due to the constantly unnecessary high exhaust backpressure caused by the variable turbine geometry (VTG).
However, excessive over-travel could also be caused by a VTG (variable travel gear) that is worn out and therefore not as smooth in its operation. I've only been driving in the city lately.
Unfortunately, I don't have any reference values right now, such as what the key press rate should be when everything is working correctly (above 2000/min).

Sorry if we're not talking about the main topic anymore.

Best regards,