Assess the Air Mass Meter Diagram

Hallo, ich habe bereits viel über Probleme des LMM beim Golf IV in den Foren gelesen, ich habe bei meinem TDI 85KW auch das Problem, dass die Leistung nachgelassen hat. Ich habe versucht, mit VAG Com ein Diagramm zu erstellen, bin aber nicht vom Fach. Kann mir jemand sagen, ob das Diagramm so ok ist oder kann man daraus Fehler erkennen, z.B. Luftmasse zu gering? Second question is it "normal" for these PD diesels to barely pull/perform at only 2000 RPM? (Golf IV 85KW PD, 2000, 1JZ1)
For information, I would be grateful.
Best regards, Pit

Hi pitdahl,
You can find out if your LMM is still in good condition here: http://www.dieselschrauber.de/Solldaten_Main.html I think this should be fine (Article 850-1050) - however, it is known that LMMs tend to report fewer cases, so there may also be a few more cases reported in your area.

Quote:

is it "normal" that these PD diesels barely pull at only 2000 RPM? As you can see in your diagram, he can build up full boost pressure from around 1600 RPM - from that point on, you'll feel that he's pulling. At 1900 RPM, that's the max.

Torque - you should feel it
With chip tuning, you can extract more power over the entire RPM range - even at 1600 1/min, however, this comes at the cost of torque. Limitation, the charging geometry (pressure buildup) and, above all, simply due to the low speed (power = torque x speed), which you cannot overcome.

What surprises me about your diagram is the extreme variations in boost pressure (and therefore also the LMM variations). I believe this is not normal, although I don't know your engine. Search the forum for it - you might be able to improve it by adjusting the VTG gate (Do you have a VTG loader??)

Otherwise, everything looks OK to me...

Hi Beany,
Thank you for the quick response. The fluctuations also surprised me; I would have expected the curves to be "smoother." I need to familiarize myself with the loading process first, as I still lack sufficient knowledge about diesel engines. But I'll take some time to explore the forums and try to find some information.
It would be interesting to see a comparison curve of the same engine. Maybe someone could post one sometime.
See you later.
Best regards, Pit

Hi,

There's not much to say about the diagram, except to use the search function
One can clearly see that the LMM actual value is below the target value -> LMM is measuring too little.

The adjustment of the boost pressure is still okay.

Hello, Rainer

Hi Rainer,

Thank you for the assessment. So, you also believe that the air mass is lagging behind? It would probably be best to simply get a new LMM. After 80,000 km, it could already be worn out, and cleaning has certainly not brought any noticeable improvement. Or try the diode trick.
Thank you.
Best regards, Pit

@Rainer (off-topic)

Quote:

to ensure that the measured value of the air mass is at least equal to the target value.

I don't understand why it should be like that. I've only read about this in the forum, but I don't understand why...

How should the control unit know what air mass it expects? Due to loading pressure, LLK temperature & flow velocity?
Or simply experience values? --> He can only say what the minimum air volume he needs to burn the amount of liquid he wants to inject, while maintaining a smoke-free condition. And I also thought that the target LM is determined in this way. Does anyone know how the target LM is determined?

I thought LMM was only used for controlling the AGR. And so, the MSG would actually have to open the AGR even if the actual value (Ist) is greater than the target value (Soll LM)?
..yes, I know that AGR is always off when the system is fully loaded. But nevertheless, it seems that this with the target LM is quite arbitrary...

Please provide information

Quote:

--> He can at most say what minimum amount of air he needs to burn the amount of smoking mixture he wants to inject in a way that produces smoke-free combustion.

Correct. Otherwise, less is injected. The necessary air volumes are specified for each operating condition in the STG.

Hello, Rainer

I want to say: Comparing LMM-Target and LMM-Actual seems dangerous to me because I lack the necessary context.
And that's why my question is: could someone explain this to me...?

PS: Why did this mark me down with a negative point?

The only way to test the LMM:
- Compare values with log data.
- And the safest decision for non-chipped vehicles: Record driver preference / torque limitation / blurring limitation:

- If the engine is being braked by the restriction limit (lowest value), it's time to replace the MAF sensor.
- Even the lowest torque limit results in a complete LMM failure, requiring a full replacement.

Beany wrote:

The only way to test the LMM: - Compare values with log data. - And the safest decision for non-chipped vehicles: Record driver preference / torque limitation / blurring limitation: - If the engine is being braked by the restriction limit (lowest value), it's time to replace the MAF sensor.

Correct - as long as the rest is OK (boost pressure, cat normally permeable, etc.)

Quote:

- The lowest torque limit results in everything. Changing the LMM has no effect!

This is always correct.

The same information is now also included in the FAQ about the TDI principle.

Hi Ulf,

which MWB do I need to log in to
"Driver preference / Torque limitation / Turbidity limitation" "
assessing a golf game?

Thank you for the information.
Best regards, Pit

pitdahl wrote:

What MWB do I need to log in to? "Driver preference / Torque limitation / Turbidity limitation" " assessing golf

In my ASZ: MWB 8.

I think it's probably the 8er for you too.

Hello Ulf,
I logged again on the highway today, MWB 3.8, 11, and created diagrams. I have a question regarding the "Russ" limit. As the diagram shows, the "Russ" limit seems to be the limiting factor. Is this "normal" during acceleration, or does it indicate an error? Can this be seen from the diagrams? Maybe you could take another look at it.
Thank you.
Best regards, Pit

If the Russian border is the smallest value, something is wrong!

"You can" have a certain value, but yours will always be the smallest.

So, a new LMM... Or Diode, or clean...

Everything here in the forum has already been described.

m;
The night before yesterday, I managed to revive an ASV (Automatic Voltage Stabilizer) using a diode.

Hi Dieselmartin,
That was a great response, wow. So, I'll try disabling the AGR experimentally on the weekend and see if the diode trick works. That's when I'll definitely see a difference in
must be aware of the acceleration. According to what I read, the 2000 AJM should not have any errors in the fault memory.

Thank you for the response,
Best regards, Pit

YES, it _should_ go without errors.

After examining the diagram values, you should also "detect a wave-like acceleration".

That's what happened with the ASV last time. There's also an article about "wave-like", check it out.

m;

Hi Martin,

Indeed, wave-like acceleration also often occurs. Sometimes, the vehicle also performs better if I briefly reduce the throttle and then carefully reapply it. Okay, I'll wait until the weekend and see what the diode does, and also disable the AGR.
Best regards, Pit
P.S. I also took a look at the articles about wave-like acceleration, thanks.