Bora AJM: Extend VTG Rod - Need Help

Hello forum community,

Since my boost pressure logs indicate overly sensitive regulation, I checked the vacuum adjustment (according to the instructions in the technical article) using a syringe, and it seems to be working perfectly and smoothly.

So, this morning I wanted to turn my VTG bar for a longer length in order to better control the over- and underswing.

Despite all the excellent explanations in various posts, I still haven't managed to do it.
The box is so awkwardly placed that I can't even see the frame – I know, that probably doesn't surprise you.

Anyway, I'm not clear on what needs to be dismantled in a reasonable way to get there, and from where is the best approach (it seems like it can only be accessed from the top, front, and right).

At least I was able to take pictures of the frame and the length adjustment screw with the digital camera.
http://members.aon.at/835935/050115/CIMG0670_s.jpg
http://members.aon.at/835935/050115/CIMG0671_s.jpg

Since the casing and mechanics appear to be in order, the question now is whether I can proceed without...
It can be disassembled further, and the length of the rod can be adjusted, which would be nice and easy if I don't get it right the first time.
I also feel confident enough to tighten the screws 'blindly' or using only a shaving mirror, but:

Do you think the vacuum chamber can withstand it if you turn the motherboard on the stand using a wrench?

What is the function of the knurled piece (see the image above)? Is it a locking nut?

Sure, here's the translation:

'Thank you in advance.'
Herwig.

Hi.
The knurled part is the adjustment nut. By loosening the lock nut (which is the lighter nut on the threaded rod), you can adjust the length using this nut.

Unfortunately, I can't tell you if the can will withstand it; I'm also curious about that. It's incredibly tight there, right next to the injection molding wall.

herwigw wrote:

Hello forum community, Since my boost pressure logs indicate overly sensitive regulation, I checked the vacuum adjustment (according to the instructions in the technical article) using a syringe, and it seems to be working perfectly and smoothly. So, this morning I wanted to turn my VTG rod for a longer length in order to better control the over- and underswing. Despite all the excellent explanations in various posts, I still haven't managed to do it. The box is so awkwardly placed that I can't even see the frame – I know that probably doesn't surprise you. Anyway, I'm not clear on what needs to be dismantled in order to properly access that area, and from where the best approach is (it seems like it can only be accessed from the top, front, and right). At least I was able to take pictures of the frame and the length adjustment screw with the digital camera. Since the casing and mechanics appear to be in order, the question now is whether I can proceed without... It can be disassembled with the can still attached, allowing you to adjust the length of the rod – which would be really convenient if I don't get it right the first time. I also feel confident enough to tighten the screws "blindly" or using only a shaving mirror, but: Do you think the vacuum chamber can withstand it if you turn the motherboard on the stand using a wrench? What is the function of the knurled piece (see the image above)? Is it a locking nut? Sure, here's the translation: "Thank you in advance." Herwig

I would advise against messing with the basic settings of the turbocharger. You won't solve your problem by making any adjustments. Instead, check the basic settings themselves. There are specified values from VW/Garrett: at a certain vacuum pressure at the sensor, the variable geometry turbo (VTG) should be just before its upper limit. This can be determined with a 0.1mm feeler gauge. However, you'll need a vacuum pump, and the specialists in the forum probably know the specific vacuum pressure value.
By the way, equally sized upswing and downswing usually don't indicate a fundamental setup issue; this is typically only the case when you have very pronounced upswings or downswings.

I would advise against messing with the basic settings of the turbocharger. You won't solve your problem by making any adjustments. Instead, check the basic settings themselves. There are specified values from VW/Garrett: at a certain vacuum pressure at the sensor, the variable geometry turbo (VTG) should be just before its upper limit. This can be determined with a 0.1mm feeler gauge. However, you'll need a vacuum pump, and the specialists in the forum probably know the specific vacuum pressure value.
By the way, equally sized underswing and overswing usually do not indicate a misaligned basic setup; this is usually the case when you have pronounced underswing or overswing.

hello bavarian,

Thank you for your assessment, it was correct! After I was finally able to loosen the lock nut, I extended the rod by one full turn of the adjustment screw (original position marked).

The result is unsatisfactory and, based on my current knowledge, also unexpected: A significant turbo lag has occurred, but the over- and undershoot values have hardly decreased.

Of course, there's another MWB 011 log available, although yesterday I wasn't able to use my usual route and had to test it on a rather steep uphill section, which slightly distorts the graph.
However, this shows all the more clearly that even with 'all the time in the world,' my approach has only improved marginally.

The more mysterious it is to me what this now means.

Do I have a VTG with a difficult or stiff mechanism?
During testing with the 60ml syringe, the VTG mechanism seemed to function correctly, although I recall a faint squeaking sound.
With the engine running (before my adjustment), I was able to achieve a change by disconnecting and reconnecting the vacuum hose.
Move the VTG (Variable Turbine Geometry) back and forth on the charge pressure control valve. The movement appeared smooth.

Can a variable torque generator (VTG) only engage under load and disengage cleanly when idling?

Why does the boost pressure suddenly drop at its highest point in my diagrams?
Is it because the engine control unit is reducing the fuel injection amount to limit damage, or is it because the variable turbine geometry (VTG) is actually moving?

Anyway, I want to restore the original state today; it was better before.

Quickly, let's update the spooky log.
http://members.aon.at/835935/050116/011.gif
http://members.aon.at/835935/LOG-01-011-xxx-xxx.CSV

Best regards,
herwig

herwigw wrote:

Can a variable torque generator (VTG) only engage under load and disengage cleanly when idling? Why does the boost pressure suddenly drop at its highest point in my diagrams? Because the engine control unit reduces the fuel injection amount to limit damage, or because the VTG then actually moves?

A stuck VTG (variable torque generator) is conceivable due to the different temperatures during assembly and operation.

I observed a similar behavior on the AFN golf sensor when connected to the LDA, while the original Mini-membrane sensor was still installed:
The higher the overshoot, the more the system is counter-regulated via the duty cycle, until the desired result is achieved "abruptly."

Hi,

Nice log, but: How long was the 'full power pulse'? Take a look at the latter quarter of the pulse: it looks wonderful!
It's clear that the sluggish mechanical system consisting of a can, linkage, and turbocharger cannot regulate to the target value 99% of the time. I believe VW didn't use its own digital signal processor (DSP) to adjust the bearing shims.
Regarding the squeaking: Teflon grease should help.

Regards,
Sure, here is the translation of the text from German to English:

'Micha'

... please hold the rod securely with pliers when loosening and tightening the lock nut.

Best regards, Rainer.

You have some nice diagrams, which is something to be envious of. All that's missing is the time axis. How long does each box represent? One second? What is your sampling rate? 10Hz?

This is a perfect example of a beautiful LD (Load Dump) protection circuit, and you shouldn't have any problems with it. Of course, there are chargers with a more favorable charging behavior, that's undeniable. The manufacturer's calibration is performed with average-quality components, but due to tolerances in mass production, there will be variations in behavior, just like with all other components. And your circuit is fully within the tolerance range.
Another question, and this one is much more important: Do you feel any "over-torque" or "under-torque" sensations while driving, and if so, how?
You shouldn't have any problems with this aircraft, at least not in level flight. If you do, please let us know and we'll ground it.

'I'm also chiming in here. I'm seeing overpressure readings up to 1.5 bar. I don't notice anything while driving, and there have been no error messages or limp mode activations so far. How 'dangerous' is this really for the turbocharger? Above 2,500 RPM, the overpressure readings are much lower. It's most pronounced around 1,900-2,000 RPM. I've already lubricated the control rod with copper grease, but it hasn't made any difference...'

DocSnydor wrote:

I'm also adding my comment here. I'm seeing overboost up to 1.5 bar. I don't notice anything while driving. Also, there have been no error messages or limp mode activations so far. How "dangerous" is this really for the turbocharger? Above 2,500 RPM, the overboost values are much smaller. ...

Hi Doc,

I would like to expand the question about the risk to the charger to include the cylinder head gasket (ZKD), because, as far as I know, the highest working pressures in the cylinder are also reached in the area of the maximum torque (Nm).
If the initial pressure is increased by 50% above the target value, it could significantly stretch the ZK screws...

For the loader, I consider a pressure of 1.5 bar to be less critical than the same pressure within the Pmax range.
Because at approximately 50% of the maximum volumetric flow rate, the speed lines in the compressor characteristic curve are still almost horizontal, so that a pressure increase will not cause the turbocharger to overspin to the same extent as it would if the same pressure increase occurred in the engine's maximum power (Pmax) range, where the turbocharger speed lines have a steeper slope.


Even if Bavarian people now make a face :
In my car, carefully rotating the VTG rod (in several steps) slightly reduced the oversteer.
While the regulated pressure is currently about 50 mbar below the target value, I haven't experienced any problems with it so far.

Despite this, my engine still gets enough air because the long-term temperature (under load) after the modification of the cooling system is about 20 degrees Celsius lower than the standard value.

Hi Doc!

My wife's ALH also produces overboosts up to 1.5 bar of overpressure in the area of maximum torque (between 1800 and 2200 1/min). However, this is followed by a smaller undershoot that drops the boost pressure to approximately 0.7-0.75 bar. I don't notice the overboost, but I do notice the undershoot .

I've also checked the valve timing gear (VTG), but it seems to be working smoothly and is in good condition.
The driving profile also argues against permanently fixing the moving parts: Almost 200 km every day, of which approximately 120 km are on the highway with a high load and RPM ratio. In this case, everything should always be properly ventilated .
The car drives in a completely unremarkable way, meaning it has good acceleration even at the lowest RPMs and a smooth power delivery all the way up past 4000 RPM. You only notice the effect of the underbody diffuser if you have the on-board computer displaying the boost pressure and are monitoring it.

Regards,
Alex.

You have some nice diagrams, which is something to be envious of. All that's missing is the time axis; how long is each box? 1 second? What is your sampling rate? 10 Hz?

This is a perfect example of a beautiful LD (Load Dump) protection circuit, and you shouldn't have any problems with it. Of course, there are chargers with a more favorable charging behavior, that's undeniable. The manufacturer's calibration is performed with average-quality components, but due to tolerances in mass production, there will be variations in behavior, just like with all other components. And your circuit is fully within the tolerance range.
Another question, and this one is much more important: Do you feel any 'dip' or 'rise' during driving, and if so, how?
You shouldn't have any problems with this ATL, at least not on the ground; if you do, please let us know, and we'll shut it down.

@Rainer: Thanks, I did that to avoid stressing the can and the rod as much as possible.

@bavarian
In the log file ( *.csv), each group of values (i.e., each row) has a timestamp associated with it.

The old control behavior wasn't very exciting because the mass airflow (MAF) value would drop so drastically during the overrun that the fuel cut-off limit was reached, and the engine noticeably lost power. Additionally, the acceleration was somewhat uneven, always following the boost pressure.

Since this issue doesn't always occur, it makes driving 'unsafe' because you can't fully rely on the acceleration.

I've now tried to restore the original state. While reverting to the old setting has somewhat reduced the subjective 'dip,' the pressure build-up is still a bit too late, and the curve doesn't really recover after the undershoot. I'm also going to try shortening it by half a rotation. (Right now, the actual pressure curve still looks a lot like my second post on the 011 forum.)

Here's the translation:

'Even though I risk annoying you with my constant speculations: I've noticed that, in all the settings so far, the behavior of the system is perfect starting at 4000 RPM. Could this indicate a gradual defect in the vacuum system that is less noticeable at higher RPMs?'

Is it sensible to have the vacuum pressure measured either at idle or under load?

Best regards,
herwig

Hi,

Ulf is (almost) completely right.
For the ATL, this is not a critical issue for the reasons mentioned above.
However, the maximum cylinder pressure does not occur at the engine speed where the maximum torque is achieved, nor is it at the limit, at least in VAG TDI designs. Therefore, overshoots in the range up to 2500 rpm are not critical, but of course they are not beneficial for the cylinder head gasket (Gasket), which is thereby subjected to higher stress, and any increased stress...
However, pressure fluctuations of 500 millibars are not normal; it usually indicates a defect or a completely incorrect setting of the control rod (basic setting). I would need to see some measurement data to investigate further.

The realization that Ulf gained from his changed perspective is completely understandable. I can only confirm that. However, this also shows the danger of a changed attitude:
The primary focus should always be on setting the target value correctly, which is important because only deviations from the target value that last for a longer period are dangerous and need to be monitored or can have negative effects. Target values are certainly justified for things like acoustics, consumption, and performance. However, if overshoots occur in a critical range, or if they lead to noticeable changes in driving behavior, adjusting the settings can often help. However, you can only improve in one direction, and that always has consequences for the overall tuning behavior. For example, smaller overshoots often mean that the settling time to the steady-state value becomes longer, or that the steady-state value is no longer reached. It's important to understand the trade-offs involved.

herwigw wrote:

bafische wrote: You have some beautiful diagrams, one could almost be envious. All that's missing is the time axis; how long is each box? 1 second? What is your sampling rate? 10 Hz? This is a perfect example of a beautiful LD (Load Dump) protection circuit, and you shouldn't have any problems with it. Of course, there are chargers with a more desirable charging profile, that's undeniable. The manufacturer's calibration is performed with average-quality components, but due to tolerances in mass production, there will be variations in behavior, just like with all other components. And your circuit is well within the acceptable tolerance range. Another question, and this one is much more important: Do you feel any "dip" or "rise" during driving, and if so, how? You shouldn't have any problems with this ATL, at least not on the ground; if you do, please let us know, and we'll shut it down. @Rainer: Thanks, I did that to avoid stressing the can and the rod as much as possible. @bavarian In the log file ( *.csv), each group of values (i.e., each row) has a timestamp associated with it. The old control behavior wasn't very exciting because the mass airflow (MAF) value would drop so drastically during the underswing that the exhaust backpressure limit would be reached, and the exhaust flow would noticeably stop. Additionally, the acceleration is somewhat uneven, always following the boost pressure. Since this issue doesn't always occur, it makes driving "unsafe" when you can't fully rely on the acceleration. I've now tried to restore the original state. While reverting to the old setting has somewhat reduced the subjective "dip," the pressure build-up is still a bit too late, and the curve doesn't really recover after the undershoot. I'm also going to try shortening it by half a rotation. (Right now, the actual pressure curve still looks a lot like my second post about the 011.) Here's the translation: "Even though I risk annoying you with my constant speculations: I've noticed that, in all the settings so far, the behavior of the system is perfect starting at 4000 RPM. Could this indicate a gradual defect in the vacuum system that is less noticeable at higher RPMs?" Is it sensible to have the vacuum pressure measured either at idle or under load? Best regards, herwig

No - The vacuum system is working properly for you.
I'm glad your boost pressure control is working properly, especially where it matters most, which is within the rated power range. That way, you can be confident in its performance.
Regarding your other issue – the wavy acceleration – I need a bit more information. By how much (in mg) is the amount being reduced? It would be helpful to have a log of the transition from smoke limitation to torque limitation, the airflow mass, the control value of the boost pressure regulation, and ideally, a recording of a drive where the problem is clearly noticeable.

No - The vacuum system is working properly for you.
I'm glad your boost pressure control is working properly, especially where it matters most, which is within the rated power range. That way, you can be confident in its performance.
Your other problem - with the wave-like acceleration - I need a few more details on that. By how much mg is the amount reduced? It would be important to have a log of the transition from smoke limitation to torque limitation, the airflow mass, the control value of the boost pressure regulation, and ideally, data from a run where the problem is clearly occurring.

hello bavarian.

I'm back, fresh from a measurement run using the new settings: original brand, -1/2 U, direction shorter.

First of all, I'm happy because I've almost completely restored the old behavior.
That confirms your suspicion that the problem isn't related to the vacuum system.
An overshoot, an undershoot, and then it settled nicely around the target value, and it seems like I haven't ruined anything.

What's crazy about this is that now the upper and lower coupling points are smaller than originally and also smaller than with an extended drawbar.

It's possible that I just got lucky and found a good parking spot, or maybe my car is just trying to trick me – whatever the reason.
The point at which the actual boost pressure reaches the target boost pressure is currently about 100 RPM higher than it was before I started adjusting the VTG rod, but I think the response is acceptable. For today, I'll leave everything as it is.

Sure, I'd be happy to provide you with the latest logs. I've completed entries 008 and 011. (Entries 009 and 010 seem to be following the pattern correctly and logically.)
http://members.aon.at/835935/050116/2/LOG-01-008-xxx-xxx.CSV
http://members.aon.at/835935/050116/2/LOG-01-011-xxx-xxx.CSV

The wavy acceleration isn't as severe as, for example, a faulty MAF sensor - which I also had to replace. Nevertheless, a slight difference can be noticed, especially the drop at 2400 RPM in the smoke curve (because the LD also causes the LM value to drop), and the small 'peak' at 4000 RPM is definitely noticeable - I would like to have that everywhere.

as a GIF (just a single loop):

http://members.aon.at/835935/050116/2/008.gif
http://members.aon.at/835935/050116/2/011.gif

Edit: And THANK YOU to everyone who helped me so promptly this weekend.
I would have been lost without you!


Best regards,
herwig

Okay, for now, I'm not going to do anything further. I still have 8 months of used car warranty on the car. But I doubt anything will be done about it. If I hadn't installed the LDA, I wouldn't have even noticed. Let's see how things change in 2-3 months...

@Alex It looks like we're having another 'mysterious' problem again.