Diode Trick: Low LMM, Why? (SEO)

Hello forum,
I have a G3 variant with an AFN engine. Is it normal that when I install a diode as a replacement for the mass airflow sensor (MAF), the MAF value also decreases? Something must be wrong! The MAF value remains constant at approximately 1275mg/h up to about 3500 RPM, and then it starts to decrease to around 1000mg/h. I don't understand this. Does this mean that the supply voltage is decreasing?
Maybe I'm just having a brief moment of weakness? Or what could the problem be?

Greetings.
Reuselkopp.

Hi,

no, that's correct, the diode doesn't know your motor's speed .
She's just pretending that the same amount of air is being drawn in every unit of time.
With increasing speed, the amount produced per piston stroke naturally decreases.

Best regards, Rainer.

no, that's correct, the diode doesn't know your motor's speed icon_smile.gif.
She's just pretending that the same amount of air is being drawn in every unit of time.
With increasing speed, that is naturally always less per piston stroke.

That's confusing me now. Isn't the diode just setting the supply voltage that's needed for the flow meter?
intended to be the negative voltage drop across the diode (0.7V for silicon, 0.3V for germanium), at the...
Mass airflow sensor input to the control unit. The control unit is receiving a high mass airflow value.
simulated, but which is lower than the supply voltage, in order to avoid...
To induce a short circuit and supply voltage. How will the voltage change now?
In my opinion, it should always be the same, unless the control unit is malfunctioning.

Or have I made a mistake in my thinking?

Hi,

The voltage remains constant. This constant voltage corresponds to a constant mass flow of air being drawn into the motor.
The control unit, however, provides a measurement value in mg/stroke, not mg/s. And the number of strokes per second, of course, increases with increasing speed .

Best regards, Rainer.

Rainer K. wrote:

The voltage, of course, does not change. The constant voltage corresponds to a constant mass flow of air being drawn into the motor. The control unit, however, provides a measurement value in mg/stroke, not mg/s. And the number of strokes per second, of course, increases with increasing speed

.
... that is, the MSG divides the LMM voltage by the speed.

At low speeds, the measured value exceeds the internal scale of the MSG, resulting in a constant display of 1275 mg/stroke.

However, above a certain speed, the result drops below 1275, and then the "correct" result is displayed.

Hi.

1. I asked the same question after my attempts last December.
/viewtopic.php?t=7962&highlight=lmm+diode

... and it was answered in the same way, and therefore completely.

2. How does your AFN (Air Fuel Nitrogen) value reach 1275 mg? What is the LMM (Lambda Measuring Module) and STG (Steuergerät - Control Unit) being used?
I always thought that all G3 TDI engines only had the Pierburg injector and a maximum fuel injection amount of 850 mg. ?!?!

http://www.luxus-wg.de/~martin/auto_bilder/LMM_pierburg.jpg

http://www.luxus-wg.de/~martin/auto_bilder/LMM/Version1.0.jpg

dieselmartin wrote:

and it was answered in the same way, and therefore completely

.
Alzheimer, I hear you knocking... but that's why I'm not deleting my answer.

Quote:

2. How does your AFN (Air Fuel Needle) achieve 1275 mg ??? Which LMM (Lambda Measuring Module) and which ECU (Engine Control Unit) are being used? I always thought that all G3 TDI engines only had the Pierburg system and a maximum of 850 mg.

850 as a max. value should be in the AGR-related memory blocks.
But with my previous AFN (from 1997), I also logged over 1000 mg.

NE ulf,

You shouldn't delete anything; I was more focused on identifying duplicate and already answered questions .

Over 1000 logged entries? Using the Pierburg 074 906 461?

Okay, in the 1Z (with MSA 12, 028 906 021 AF), it outputs a maximum flow of exactly 847.9 mg/H.

And that's precisely the value that Block 003 is designed to display when it's stepped on (as the maximum target value).

m

Okay, guys, guys, guys. You're comparing apples and oranges here. The displayed LMM value depends on the resolution of the diagnostic interface and the software version of the control unit. Generally speaking, for the MSA12, a value of 850mg/R is typical, while for the MSA15, the higher value is usually indicative of a diagnostic issue.

lappen wrote:

In general, it can be said that for the MSA12, a value of 850mg/R is indicative of a diagnosis, and for the MSA15, the higher value is indicative of a diagnosis.

It's probably like that... In my Golf, the part number 028 906 021 GH was/is installed.

@ lappen

That AHU, with the 021 GG model, should also be able to deliver 1200 mg.

He doesn't, though; it then has a value of 850.0 or so, which is minimally different from the value of the MSA12.

I really should finally start up my MSA15 .

m;

martin,

As I mentioned before, it's quite possible that an MSA15 with the 66kW software for the AHU engine only produces 850 mg/R. As I said, the software version also plays a role. I had an MSA15 as a replacement for a 1Z engine, and it also only produced 850 mg/R.
The message should be that it's not solely due to the mass airflow sensor (MAF). I have a vehicle here in the workshop that also has the older Pierburg MAF sensor installed (thankfully), and the actual values are above 1200. If I replace the MAF sensor with a 1Z model, I only get 850 mg/stroke.

Okay.

I probably had too much on my mind to fully grasp it the first time.

Greetings.
m;