Boost Overrun: Causes & Solutions

Hello,

Dear admins, could you please check my thread?
'Delete 'boost pressure overshoot' data (from measurement run - log file)?'

Now I've logged correctly, and I'm getting the same question again.

Here's the log for my Ibiza AFN, manufactured in 1998, with 141,000 km on the odometer, and a mass airflow sensor (MAF) with 20,000 km.
AGR closed, no tuning.

- Is this turbocharger pressure buildup normal?

- Why does the soot limit reach a relatively low value specifically at the highest boost pressure (at 2300 1/min), and then increase again when the boost pressure decreases? Shouldn't the smoke limit become active at low boost pressure?

- Is it normal for the torque limit to be active all the time?

Oops, I just realized that I should be comparing the injection amounts to the air mass, not the boost pressure. That makes the smoke limits look much more reasonable now!

But even now, I don't understand why I have a massive increase in boost pressure between timestamps 4.54 and 5.74, while simultaneously experiencing a significant decrease in air mass. Is this due to the 'air pocket effect' (-> delay) in my intercooler system? Or is there another problem?

Thank you very much!

Attached again is the file with the MAF - Inject. quantity comparison.


Thank you, Martin.

Hello Martin!

It's likely that your VTG (Variable Turbine Geometry) is a bit stiff, which can lead to more pronounced pressure surges in both directions.
Generally, all values are within the normal range. Notably, the pressure drop is particularly pronounced, which is likely caused by a faulty VTG (vacuum train valve).

Okay, try doing the following: Perform data logging from (only) the MWB11 (due to the sampling rate).
After that, I drove a few kilometers on the highway, pushing the car to its limits, to clear the VTG (vehicle tracking device) data.
Then immediately log the MWB11 data again and compare it. If the behavior improves after the highway drive, then you'll know why .

You can also use a 100ml syringe to examine the VTG for proper movement and locking points.

Good luck.

Regards,
Alex.

Sure .

You can usually get a quick sense of it.

I agree with Alex.

To understand VTG, this is perfect:
http://www.technologie-entwicklung.de/Gasturbines/VNT15-Turbo/vnt15-turbo.html

(Oops, I just saw the private message now, so I'll leave the link in for others

m;

Hello Martin,

I can also confirm and understand the behavior of your turbo.
Also, Alex and Dieselmartin's tips as well.

I recently specifically installed an LDA.

In the second gear, the pressure is extremely high, at 1.35 bar compared to 0.65 bar, at 2300 rpm.
In the third one, it's barely noticeable, and mine isn't quite as stiff.
(But take another reading and -'575 intake manifold pressure - control difference', etc.)

After a week of navigating city traffic, the experience leaves a lasting impression as described above.
and is almost gone again after the BAB. Subjectively, I sometimes feel like the car is going into a limp mode ->575, but it's not really the case.

Here's a question for Golf owners: How the Hell do you access your charger, not from below, right?
I can only reach the pressure gauge with my arm. How do you adjust your VTG (Variable Turbine Geometry) etc.?

Quote:

How do you adjust your VTG, etc.

Not at all, didn't you?

I have to use a wastegate turbocharger.

m;

Martin L. wrote:

- Why does the soot limit reach a relatively low value specifically at the highest boost pressure (at 2300 1/min), and then increase again when the boost pressure decreases? Shouldn't the smoke limit become active at low boost pressure? - Is it normal for the Nm limit to be active all the time?

Here's the translation:

"Regarding point 1: Please look at the timestamps. The measurement blocks are retrieved sequentially, even though the values are displayed in a row, they still don't represent the same operating state. This is because the sampling rate is too low compared to the frequency of the overshoots."

2: Yes, unless, for example, the mass airflow sensor is faulty.

Thank you everyone for your feedback on my files.
After a long weekend trip, the overbite has actually decreased in size.
I'll see if I can fit a larger vacuum chamber onto the charger.

Hello everyone,

Here's a brief explanation regarding the deleted thread:

My first thread (which has since been deleted) regarding boost pressure overshoots showed my very first measurement run. Several forum members responded that I should log data using channel numbers 003-008-011 and that my visualizations didn't provide any meaningful information.
Of course, there were constructive suggestions. However, after I had logged the correct data, I asked the administrators to delete my old thread containing the incorrect measurements. I also sent a private message to a 'professional mechanic' with the same request.

I requested that the thread be deleted, not because of the quality of the answers, but because of my poorly worded question in the forum. I thought it would be better to create a new thread and include the relevant log information there, rather than attaching it as an afterthought to an existing thread. To prevent duplicate posts, I asked for the thread to be deleted, as I believed that future users would appreciate it if search results included posts with properly formatted logs.

This will not happen again at my request.

Best regards, and please excuse any inconvenience.
Martin.

Thank you for the clarification, Martin.