LMM: Too much air?

Hi.

I did some test drives today using VAG-COM.
(The test vehicle was a Golf 3 TDI with a 1Z engine, manufactured in December 1995, with 150,000 km on the odometer. At the time of the measurement, the engine had been running for half an hour, and the coolant temperature was consistently 82 degrees Celsius, according to measurement group 7.)

I'm a bit confused about the LM value:
http://people.freenet.de/golf-schrauber/LMM.gif

Higher values on the mass airflow meter (MAF) could potentially be caused by a clogged EGR valve, because if the EGR valve is blocked, the engine might be drawing air from the fresh air intake instead of the EGR system (did you find an answer to this?).
Here https://community.dieselschrauber.org/en/viewtopic.php?t=4459&highlight=lmm+werte, a similar question was asked, but not yet definitively answered.

There are no error entries.


Why does it have so much more air than the EDC wants?

"I think turbo pressure seems more sensible (even though I never really had the time to let it adjust properly because of the traffic...)"
http://people.freenet.de/golf-schrauber/LDD.gif

Please read this:

/viewtopic.php?t=2126&highlight=

Rainer explained it to me very well back then.

That doesn't quite apply to my situation.

I have a Series 1Z (so, one that hasn't been "tampered with" regarding the EGR system).

Why are the values deviating then? Or is my EGR valve unintentionally broken (that's my only explanation).

"Furthermore, during a 1.5-hour test drive yesterday, I noticed that at full throttle, the mass airflow sensor (MAF) value DECREASES above a certain RPM. Up to approximately 3000 RPM, it provides the desired value of 841 mg (with the EGR system already activated, resulting in 4.7% EGR). However, when the engine is revved higher, the MAF value decreases."

Okay, it rained, which could have caused the paper air filter to become clogged... but 740 instead of 840 mg/H at 3300 RPM seems suspicious, right???

m;

I would be happy to upload the measurement data online this evening, if it can be helpful to anyone.

Hello,

I'm experiencing the same phenomenon with a decreasing mass airflow (MAF) value at higher engine speeds in my Golf IV PD AJM 115PS. During a VW test at full throttle in third gear at 3000 RPM, I measured a value of 911 mg/H. During extended full-throttle driving, the value drops to as low as 800 mg/H at around 3800 RPM.

I'm also not sure whether the mass airflow sensor is malfunctioning or if this behavior is normal.

theory1:

The flow losses increase more significantly at high speeds than the (already constant) boost pressure can compensate for.

theory2:

The fresh air mass sinks due to increasing intake air temperatures (because the intake pressure remains constant in this case).

CU Gremlin.