Seeking expert opinions on boost pressure and lambda (air-fuel ratio) behavior!

Hello,

Today, I logged the actual boost pressure and airflow values of my chipped VW Passat 3B AFN (mileage: 220,000 km) using VAG-COM.

The engine was at operating temperature, and the air conditioning compressor and other power-consuming devices were deactivated. The acceleration test was performed with full throttle in 3rd gear on a level road surface.

http://www.creativepc.de/auto/Diagramm.gif


What is the outlook like? It would be nice if the experts could comment on this!

Thank you in advance!

verdiener wrote:

What is the outlook like? It would be nice if the experts could comment on this! Vielen Dank im Voraus!

The lambda sensor seems to be malfunctioning during the last interval, with almost constant boost pressure -> I suspect a faulty mass airflow sensor (MAF).

Here is another graph with a linearly scaled abscissa and the corresponding target value curves:

http://www.creativepc.de/auto/Diagramm3.gif


I once read in this forum that the actual airflow should always be at least (preferably above) the desired airflow.

Therefore, the dip at the end seems to be okay, but it doesn't look very optimal in the lower RPM range, does it?

Can anyone comment on the boost pressure curve? Do you think it could potentially be better? I'm planning to switch to a VNT17 turbocharger soon and then compare the curves.

Hi there,

In my humble opinion, it's like this:
There are 3 key parameters that control the injection amount.
(1) Driver request (equals accelerator pedal position).
This will be corrected downwards if...
(2) the speed at which it operates determines a lower maximum torque.
or / and
(3) the Russian-style boundary field specifies a lower maximum injection amount.

It's interesting to see that only above 1500 rpm is there enough airflow available for (3) not to engage anymore.
That's probably okay; after all, the boost pressure is still low there, and the airflow is correspondingly small.

"However, as Ulf already mentioned, the final reading of the air mass at almost constant boost pressure around 4000 rpm doesn't look good. To be sure that this isn't an artifact of the measurement interval (it's the last data point!), I would repeat the entire process and this time run it up to 4500 rpm."

The overboost at a boost pressure of 1.5 bar is very high! My ASV (Anti-Slip Valve) with the standard software doesn't do that.
Even with a diode trick and good holding pressure of 1.1 - 1.2 bar, my automatic shut-off valve (ASV) only allows for maximum overpressure up to 1.4 bar.

Is it chip-tuned? Awesome enclosure?

Best regards, Georg.

Very important.

It's not the amount of air, but the mass of air!

These are two different values, and the AFN measures the MASS.

At the beginning of the torque dip, things might still be okay because there are very few measurement points, and the engine needs to rev up first in order to draw in more air. However, the EDC (Electronic Diesel Control) system assumes that more is coming immediately.

It looks the same for all engines in this case.

With more measurement points, it's easier to determine whether there is a problem or if the values are still within the acceptable tolerance range.

Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

Ich hatte sowieso vor, die Messung am Wochenende nochmal zu wiederholen (auch mal im 4. und 5. Sure, here is the translation of the text from German to English:

'Gang.'

After that, the new turbocharger will be installed.

What other metrics (or values) should I log at this time?

Gibt es in VAG-COM eine Möglichkeit, die Messdichte zu erhöhen, sodass in kürzeren Abständen Werte aufgenommen werden?


@dieselmartin

Thank you for the note about 'air mass/air volume'!

Gibt es in VAG-COM eine Möglichkeit, die Messdichte zu erhöhen, sodass in kürzeren Abständen Werte aufgenommen werden?

Yes.


Settings -> Set 'Blk Int' to 25 and 'Char Int' to 0 -> Save, and do not select any options under 'Reduced CPU Usage'.

That should work.
I'm getting intervals of 0.28 seconds with this setting.


Best regards,

Here are the measurements I promised for 3rd and 4th gear, with a wider range of RPMs:

http://www.creativepc.de/auto/003.gif

http://www.creativepc.de/auto/004.gif

verdiener wrote:

Here are the promised measurements in 3rd and 4th gear with a wider RPM range:

Ah, it looks much better in terms of Large Language Model performance.

Only the extreme angles would be too high for me -> Turn the VTG rod longer .

I'm experiencing a problem where the engine goes into limp mode after longer periods of high load (e.g., driving at top speed on highways for an extended time).

Could this be related to overboost situations, i.e., if the turbocharger pressure goes too high? At what boost pressure is the tolerance limit for the engine management system?

Ulf's comment about the oversteering and your emergency maneuver are a perfect match – they have exactly the same effect.

So ran to the pole .

Okay, please provide the German text you would like me to translate into English. I will only provide the translation.