LMM Values: Actual / Target

Hi!

Okay, here's a potentially silly question:
I am currently taking care of a VW Transporter, manufactured in 2008.
It doesn't have proper engine power. Approximately 150,000 km. TDI.
I forgot to read the engine identification number, but I'll find out tomorrow.

Well, the error memory is clear, and many authorized workshops "in the West" have already tried.
because the car is mainly used on construction sites in the "western" part of the country.

Many expensive parts have already been replaced, and a lot of money has been wasted, all without success.
We don't know what else to change anymore.

Based on my brief test drive, it strongly suggests a faulty mass airflow sensor (MAF).
Surprisingly, no one has replaced it yet.

Test drive with a laptop.
And there, in the extended measurement data, is the mass flow rate (LMM) value.
and LMM Target.

The values deviate, and the difference becomes more pronounced as the required engine power increases.
Approximately 30% or more.
The engine just barely reaches 3500 RPM, and its power output is increasingly limited as it goes higher.

That IS, is probably the actual LMM value that the LMM generates.
Where does the target value come from?
Does the engine control unit calculate that?
And what's the point?, so that one can easily assess the actual value?

Quote:

And what's the point?, so that one can easily assess the actual value?

Without a target value, there can be no comparison. And if there's nothing to compare it to, you don't need an LLM either.

I would say that the target value is essentially predefined within the characteristic curves.
If the actual value is less than the target value, the injection amount is reduced to prevent soot formation. In general.

Steffen G wrote:

That IS, is probably the actual LMM value that the LMM produces. Where does the target value come from? Does the engine control unit calculate that? And why?, so that one can easily assess the actual value?

Okay, I'm ready. Please provide the German text you want me to translate.

Quote:

"But doesn't MWB 3 provide the desired air mass? If that is achieved, doesn't that automatically mean that the engine doesn't have an air problem!" If the target value is not reached, either the mass airflow sensor (MAF) is defective, or there is insufficient boost pressure! Incorrect! The air mass in the MWB 3 is only relevant for the EGR function and is expelled at 850 mg/stroke @ full throttle in most TDIs. However, this is not enough to eliminate the uncertainty when dealing with engines with high displacement (ASZ, ARL, BPX, etc.), meaning that even when the target air mass is achieved, they may still exhibit a loss of power! Conversely, in the 1.9L 90PS variants, significantly less than 850 mg of air per stroke is often sufficient to achieve full power.

This is true for the engines up to and including... EDC15 written, but I suspect that it's not completely different in the newer ones .

@ Steffen: Do you have the part number for the MSTG?

I have Kat in mind.
The mass of air entering the engine also increases with increasing boost pressure.
And if the turbo is constantly being slowed down, doesn't that also affect...?
Air mass gone?
Correct me if I'm wrong.

Wiesel wrote:

@ Steffen: Do you have the part number for the MSTG?

Hi!
I had someone look into it because the car is currently en route.
Engine code: CAAB
Engine Control Unit: 03L 906 022 CD

Too bad - it's (unfortunately) an EDC17.
I haven't had to deal with that in much detail yet.

Best regards,
Micha

Wiesel wrote:

Too bad - it's (unfortunately) EDC17.

But AFAIK, they also still use the well-known MWB structure of the MSA12 and EDC15?

For those, it definitely applies that MWB1 and 8 log at WOT.
As long as the torque limit in MWB8 is at its lowest setting AND the value in MWB1 matches it, the software recognizes sufficient airflow to allow for full power output, AND no other power limiting factors are engaged (e.g., high LLT).
If the engine still doesn't run properly, it can only be a hardware problem outside of the fuel injection system, including... To be a loader.

If the driver's requested torque or the torque limitation in the MWB8 (Motor Torque Management Block are lower than the torque limit, then the error lies within the known areas that are monitored by the MSG (Motor Control System) via sensors.

ulf wrote:

Wiesel wrote: Too bad - it's (unfortunately) EDC17. But AFAIK, they also still use the well-known MWB structure of the MSA12 and EDC15?

Are you sure? The A6 with EDC17 that I recently had as a loan car no longer recognized the classic MWBs (Module Working Bits). Measurements were "only" available.
about the "Advanced Measurement Blocks" function.
That's not what I was talking about, though. I wanted to check the dataset.
What the LMM is used for.

Wiesel wrote:

ulf wrote: . . . the familiar MWB structure of the MSA12 and EDC15? Are you sure? The A6 with EDC17 that I recently had as a loan car no longer recognized the classic MWBs (Module Working Bits). Measurements were "only" available. Regarding the 'Advanced Measurement Block' function.

Oh dear... if no information similar to Measurement Block 1 + 8 is received, I'm out of the loop on this topic.

Hi!

Thank you for the responses.
I'll see if I can get the car this weekend.
to thoroughly review everything.
and see if I can get some log data...

The new LMM is here, but if it's unused, I can return it.

Hi!
So, the mass airflow sensor is now installed, which was basically pointless.
While the value has increased, from 1000 mg/H to 1150, there seems to be another problem.

Okay, the error memory is clear, the boost pressure is 2 bar, and the exhaust seems to be okay. VTG is no longer available.

Okay, if you can read, you're always at an advantage. (In the FAQ,) I should have checked the fuel filter beforehand because I saw that there was a vibratory plate, an asphalt cutter, and several canisters on the loading platform.
The driver also told me that the car is often refueled using jerrycans.

Okay, so I guess I'll continue working on it next weekend, and I'll change the fuel filter.
Can someone please provide some input on this?
Does it self-prime, or is there a pre-charge pump in the tank that needs to be activated?

"It's a 2.0 TDI CR engine, code CAAB, from 2009, and as suspected, the diagnostic trouble codes cannot be accessed."

Hi!

I took it for a test drive today. I'm now really excited to see if uploading the log file works this time.

Hello,

The logged values don't tell us anything because you didn't log the correct ones.
"The following are meaningful/relevant/useful:"
- Driver torque request (torque setting via accelerator pedal, missing).
- Torque limiting (already implemented).
- Limitation via air mass/boost pressure (missing).
- Actual boost pressure (you have this value).
- Lambda (missing)

Best regards, Rainer.

Hi!

Okay, let's wrap this up.
I spoke to the driver today, and the car is working properly again.

When I created the data log, it was already working correctly.
I had strongly suspected that already, based on my intuition. And the values, according to my feeling, were also good. It was all 100% full throttle. If someone wants to compare, it's like starting and accelerating up to the 4th gear, with constant full throttle.

Okay, so I had someone look into it, and apparently the fuel filter had already been replaced shortly before. I left him in.
I then, as suggested in this forum, read the rail pressure, and it was fluctuating quite a bit, despite the new filter.

Then, as I usually do when I'm stuck, I checked all the cables and vacuum hoses.

The marten seems to particularly like the cable from the rail pressure sensor, which I had already repaired on this car some time ago.
Somewhere along the way, it had already been patched up again. I just unwrapped the electrical tape, and the repair was done really poorly – half-rotted, cold-soldered, and only hanging on by a single wire, which then broke off.

Then I tidied it up nicely again and wrapped it in a weasel-proof pipe.
Since then, everything has been working properly again.
That was probably the problem.

Thank you for your support!

Great, thank you for the feedback!