VTG Rods: How to Rotate Them Properly

Hello.

I'm having a problem with an AJM engine, manufactured in 01/2001. When I accelerate fully, the pressure goes up to approximately 1.4-1.5 bar. It immediately drops to about 0.8 bar and then slowly increases (within about 3 seconds) to 1.1 bar.

Otherwise, the engine runs normally. The mass airflow sensor (MAF) is new. I was advised to have the VTG linkage lengthened (I haven't done that yet).

'Last week, I drove my car to Prague. On the way, four times the pressure went up to 1.8 bar while accelerating on the highway, and then dropped to 0 bar (presumably due to the system shutting off). Turning the ignition off and then on would get it running again, but it would happen again when I accelerated to full throttle.'

Could it really be related to the antenna being set to too short a length? Otherwise, it would always exhibit the same problem.

'Today, I removed the pressure sensor. It filled up normally and didn't get stuck. The VTG (variable turbine geometry) was working smoothly and could be easily moved up and down with a finger. When you wiggle it, you can hear a metallic rattling sound. Is that normal? My ALH turbocharger also makes that noise.'

'However, if I push the rod all the way down, it gets stuck. You have to wiggle it back and forth to pull it back up. Applying force doesn't help. You have to wiggle it gently to release something. Then it comes back up very easily.'

I then drove around once without the vacuum pump. It shook again, and then it stopped. I then installed the vacuum pump from my other car (ALH) as a precaution, but it didn't really help. The pressure rises to 1.5 bar when I give it full throttle, drops to 0.8 bar, and then slowly climbs back up to 1.1 bar.

What is the pressure behavior like in an engine that is running properly? Does it immediately drop to the correct value (in this case, 1.1) after reaching its peak? In the 2nd and 3rd gears, the drop to 0.8 bar is very noticeable. The car feels sluggish and doesn't accelerate as it should. My previous car (ALH) didn't exhibit this behavior; after reaching its peak, the power delivery was smooth.

Regards,

Paul.

Replace the magnetic valve for turbocharger pressure regulation. If the problem persists after that, it could unfortunately still be due to the turbocharger or the vacuum actuator (e.g., sticking membranes or a jammed adjustment mechanism when hot).

Best regards, Rainer.

The valve was replaced three weeks ago. I put the old one back in for testing, and nothing has changed.

How would you proceed in this case? Would you get a new container somewhere, or would you first disassemble the exhaust side?

Make sure that a kinked or blocked vacuum hose isn't the cause, check the vacuum system's ventilation, and then install a new turbocharger.

Reasons: The vacuum sensor is not sold separately. Cleaning the VTG (Variable Turbine Geometry) is a tedious and time-consuming task, and it's not faster than simply replacing the entire turbocharger. If you have a lot of time, you can disassemble and clean the VTG.

Best regards, Rainer.

Hi.

"search for 'ASV inspection'. I spent a few days working on a Leon ASV (including some initial incorrect assumptions about how to disassemble the linkage)."

He also had some overdriving, but not as extreme as yours (no limp mode).

For that, there are diagrams available, one showing the original length, another showing a length that is 2 rotations longer, and a third showing a length that is 1 rotation longer.

m;

Okay, I still haven't done anything. I've just been driving around and seeing what happens.

I'm ruling out a faulty vacuum sensor and N75 valve because swapping them doesn't change anything. I've completely replaced all the vacuum hoses and checked them according to the ELSA documentation.

I've noticed that the higher the engine temperature, the greater the pressure spikes.

Can I be 100% certain about VTG here, or is there anything else I should check? Also, should I log MWB (?), if it helps with troubleshooting?

polo2f wrote:

I've noticed that the higher the engine temperature, the higher the pressure spikes. Can we be 100% sure about VTG here

?
I would say it's more like 95%...

Quote:

or is there anything else I should check?

Or should I log the MWB(?) if it helps with troubleshooting? }
MWB 11, aiming to provoke as many "beautiful" overreactions as possible.

Ideally, include the difference between a warm and a hot engine, but avoid logging a second measurement block (MWB) because the overshoot can be lost with a coarser sampling rate! Instead, simply add a few notes about the engine temperature to the log.

Okay, I finally got a laptop today and created two log files.

Cold, approximately 30°C oil temperature.

Warm, approximately 90°C oil temperature.

http://www.polo2f.privat.t-online.de/kalt.CSV
http://www.polo2f.privat.t-online.de/warm.CSV

I removed the pressure sensor again. The rod moves easily. It rattles when moved. You can move it back and forth with just a finger, without any effort.

polo2f wrote:

I unscrewed the pressure can again. The rod is loose. It rattles when moved. You can move it back and forth with just one finger, without any effort

.
Without having studied the logs:
Something's wrong -> broken feather??
Standard push tubes extend the rod to its limit using a spring mechanism. When pushing it back in (without any rattling!), you can feel the increasing spring force that you need to overcome.

I'll join Ulf for now.

Regarding your logs: I would have liked to take a look, but sorting through a bunch of numbers really isn't my thing.

Please note: The more informative the information, the more well-founded the answer. In other words, if you provide us with a graph showing the trends clearly, you will help us and yourself, because problems will become more apparent. If you are not sure what I mean, please search the forum; there are instructions on how to create a good log.
Consider this as a suggestion, and we'll quickly get to the bottom of the problem.

I can at least see the numbers in the columns, but there are too few of them!

Please create a 003-008-011 log (as always).
Because what good is the RPM information to me if I don't know whether you're accelerating or not? And that's crucial for the turbo boost pressure.

Up to the log I mentioned.

m;

Sure, here's the translation:

"One more sentence:"

You probably never kept your foot on the accelerator for long enough; I suspect you kept lifting your foot. That's a wild ride, not a test drive .

m;

@Ulf: I meant that the linkage on the VTG is loose. The pressure sensor is fine.

Here's what I've noticed. When the engine is cold, everything seems normal. The boost pressure doesn't go as high. The warmer the turbo gets, the worse it becomes. If I drive for a while at 160-180 km/h and then give it full throttle, the pressure spikes up (according to the LDA, about 1.7-1.8 bar) and stays high until the engine control unit completely shuts it off. Then I drive without any boost until I turn off the ignition. It's possible that the VTG linkage is sticking when it's hot. Would opening the turbo help in that case?


Regarding the test drives: Ulf suggested that I should try to achieve the highest possible overshoots, and that's only possible if you play with the accelerator. Please let me know how to do it better. Which gear, from what RPM, and how long should I keep my foot on the accelerator?

Regards,

Paul.

polo2f wrote:

The warmer the turbocharger gets, the worse it becomes. If I drive on the highway for a while at 160-180 km/h and then give it full throttle, the pressure increases (according to the LDA, about 1.7-1.8 bar) and remains high until the engine control unit completely shuts it off. Then I drive without any pressure until I turn off the ignition. It's possible that the VTG linkage is sticking when it's hot?

Yes, it's called a "VTG hot clamp".

Quote:

Does opening the charger actually help in that case?

It's hard to say. If you can manage to restore a heat-warped VTG mechanism so that it operates smoothly at all temperatures, then it might work. However, I have no personal experience with that kind of thing.

Quote:

Regarding the test drives. Ulf suggested that I should try to produce the highest possible overshoots, and that's only possible if you play with the accelerator. Please write to me and tell me how it's better. Which gear, from what RPM, and how long should I stay on the accelerator?

That's perfectly fine for those who are overly enthusiastic.

The VTG (Variable Turbine Geometry) basic function can be observed with constant full throttle from approximately 1300 to 4500 rpm in 3rd gear or higher, as indicated by a logged MWB (Mass Air Flow) value of 11.
The full throttle setting can be determined with sufficient accuracy based on the desired load curve, so other measuring devices are not initially necessary.

I still have one loader available. VTG didn't clamp properly on it, but it's leaking oil into the intake manifold. Do you know if it's possible to install the VTG linkage from this loader into mine?

Regards,

Paul.

If it's the same one: Yes.

In the search results, you'll find a link to instructions on how to disassemble the loader. The VTG (Variable Transmission Gear) is simply a ring to which the buckets are attached. It's secured to the housing with three screws. If you already have a faulty loader, take it apart and examine it. It's very straightforward.