Bora AJM: VTG-Stange länger drehen - Bitte um Hilfe | Posts 16+

@DocSyndor: It's really tedious for me to piece together the timeline from the data. Could you tell me how long a 'full-throttle' pulse lasts in the first diagram?
To me, this looks like a perfectly normal process, not a 'mysterious problem.'

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

'Micha'

Hello Herwigw,

Submerging in smoke from the catalytic converter is definitely not a pleasant experience and shouldn't happen at these outside temperatures. However, it seems like everything is in perfect order with your vehicle. The mass airflow sensor (MAF) and the electronic power module (EPM) are also working correctly.
I can definitely relate to that disharmonious feeling of acceleration based on this diagram. However, the disharmonious acoustic impression usually dominates, which is, of course, subjectively influenced, and is often not measurable.
A possible solution could be replacing the pressure sensor, but it's not necessarily required, as you have a relatively large hysteresis in the control loop (although still within the acceptable tolerance). This hysteresis is influenced by the pressure sensor, the play in the adjustment linkage, but also by the axial play of the guide vanes – and there's nothing you can do about that except replace the turbine.
I personally would hesitate to put in that much effort.

Hello,

Since I spent half of the weekend 'tuning' my VTG (variable geometry turbocharger), I'd like to share my experiences and opinions on the matter.

After some initial problems,
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/viewtopic.php?t=8011&highlight=rust+vtg
I managed to install a larger vacuum sensor. Despite its higher actuation force, it regulated the load dynamically too gently and sluggishly with the original length of the small sensor. The duty cycle at > 3900 rpm was only around 59%.

After that, I gradually shortened the shaft piece by piece, logging data during each test run, and then analyzing the results.
Now, in the test, I achieved an air-fuel ratio of 69%, but the response from idle has noticeably improved. The turbo's response time has become much shorter (which is very clearly visible on the LDA ). I do have some overshoot up to about 200 mbar above the target value, and slight undershoot, but the lambda sensor then regulates the mixture cleanly afterwards.

As the connecting rod gets shorter and shorter, the over-swing (logically) becomes more pronounced. I thought that this would also cause the under-swing to be more pronounced, as the engine control unit (ECU) would have to/should/must react more strongly. However, surprisingly, this is not the case. With the current setting, the under-swing is smaller than with a less 'aggressive' connecting rod length . In any case, the response has improved significantly, and the acceleration seems better too, although the latter may be purely subjective, as it is a bit colder outside right now.

Is the faster acceleration of the engine actually harmful to the ATL or to the engine } In my opinion, the torque curve should now kick in earlier than the soot reduction system, but to clarify this, I would first need to log MWB 8.

Hello!

@ampac:

Since I've already significantly shortened the connecting rods in my AFN engine, I'm interested in...
How many rotations did you need to achieve the described effect?

Greetings, Klaus.

Hello Herwigw,

Submerging in smoke from the catalytic converter is definitely not a pleasant experience and shouldn't happen at these outside temperatures. However, it seems like everything is in perfect order with your vehicle. The mass airflow sensor (MAF) and the electronic power module (EPM) are also working correctly.
I can definitely relate to that disharmonious feeling of acceleration, as shown in this diagram. However, the disharmonious acoustic impression usually dominates, which is, of course, subjectively influenced, and is often not measurable.
A possible solution could be to replace the pressure sensor, but it's not necessarily required, as you have a relatively large hysteresis in the control loop (although still within the acceptable tolerance). This is influenced by the pressure sensor, the play in the adjustment linkage, but also by the axial play of the guide vanes - and there's nothing you can do about that except replace the turbine.
I personally would avoid that much effort.

I've checked the target values for the mass airflow sensor (MAF) again - the MAF is operating closer to the lower end of its possible range. I might replace it. Unfortunately, I didn't have a VAG-COM diagnostic tool when this MAF was new, so I can't tell if it's already aged or if it's always been like this.
When it was replaced, the difference from the previously defective item (error entry) was already significant.

The issue with the non-harmonic acceleration is a tricky one. In recent logs taken on my usual test track on Sunday evening, the paradox I mentioned earlier in the thread – namely, a shorter VTG and a smaller overshoot – did not reappear.

I'm experiencing significant overboost (up to 1.5 bar) and underboost, but otherwise, the overall control behavior is quite decent. The acceleration spikes, likely caused by the turbo boost, are still noticeable at 3000 and 4000 RPM, and you can also see them in terms of acceleration when you're accelerating alongside a car of roughly the same power, but it feels like it's accelerating slightly less than before (probably just my imagination).
For now, I'm going to leave the issue alone and just occasionally check to see if it gets worse. Replacing the charger isn't worth it to me.

Thank you for your comments!
Best regards,
herwig

Hello.

@ Clause:

Good question.

I measured the distance from the bottom of the can to the lock nut and transferred that measurement to the other can. However, the performance (subjectively) was slightly worse with the larger can. So, I then continued to shorten the rod in increments of 1/2 revolution, tested, etc.
I'm now about 3.5 turns away from the original setting. However, in the idle state, the can no longer presses the VTG (Variable Turbine Geometry) against the stop, but is already slightly raised, meaning the guide vanes are already slightly angled in the idle state.

@ Bee

Sorry, I don't understand what you want from me. This diagram is not mine. I only experienced overboost up to 1.5 bar during spontaneous acceleration, nothing else. You probably mean 'herwigw,' who is actually the person this is about!

@DocSnydor: Sorry for my inappropriate assumption. You are right: My question is directed at 'herwigw,' who, unlike you, is being very hesitant to respond.

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

'Micha'

@DocSnydor: Sorry for my impudent assumption. You are right: My question is directed at 'herwigw,' who, unlike you, is being very reserved in his response.

Regards,
Micha

hello bee,

I didn't feel like it was directed at me - sorry.
I'm not entirely sure if I understood your question correctly, but I'll try to give an answer anyway.

The diagram is a Screenshot of a VAG-COM plugin (a common Windows program for a diagnostic adapter by Rainer) that visually and clearly presents recorded VAG-COM data logs. If there's an option to display a time axis, I'm not aware of it. However, it's not a major issue because the logs are standard CSV files, where a group of values with a timestamp is typically recorded 2-3 times per second.

I'm including the screenshots because they show certain behaviors 'at a glance.'
In addition, there are links to the original log files, and there is enough web space available to store them for a period of time.

Now, to the question: how long does a gas surge last?
The leftmost column of a log (let's take the '008' from above as an example).
http://members.aon.at/835935/050116/2/LOG-01-008-xxx-xxx.CSV
It always has a timestamp - counted from the beginning of the log.
You can tell when the gas surge starts because that's when I, if I want to record something.
At just over 1000 RPM (second column), it behaves like an ox stepping on the gas, or conversely, abruptly releases the gas at speeds above 4000 RPM, which is clearly visible in the third column, representing the driver's request. The duration of the first attempt was approximately 16 seconds.

Best regards,
herwig

Best regards,
herwig