MKB AFB: Solldaten & Data

Hello,

Here's the measurement log for an Audi A6 2.5 TDI V6 with engine code AFB. The mechanic says the mass airflow sensor (MAF) was replaced because it was showing a low reading. The error database indicates 'minimum 750 mg per stroke.' I want to know if the measurement block is working correctly.

376,969,958 0.0%
730 969 2131 100.0%
765 969 2131 100.0%
733 969 2111 100.0%
753,969,2142, 100.0%
796,969,2182, 100.0%
682,969 2080 100.0%

Are the measurements correct? Or should they always be significantly above 750? The boost pressure seems to be okay to me.

Hello,

Was die Drehzahl betrifft, lag sie auch innerhalb des vorgeschriebenen Bereichs, wenn die Werte unter 750 waren?
Otherwise, the values look quite good.

Unfortunately, I wasn't there myself; that's my brother's A6. Is it possible to fully depress the accelerator pedal and not have the engine speed reach that range (presumably up to the point where it's limited)?

So, values 'around 750' are fine, then. I was just wondering if they're normally supposed to be significantly higher.

Hello,

That's where most measurement campaigns go wrong.

Sure, here is the translation of the text from German to English:

"Specifications:"

- Coolant temperature must not be below 80°C.
- Full throttle
- Drehzahl bei 3000 U/Min (am besten im 3. Gang)

If these parameters are not met, the values are not usable.

That's exactly why I'm asking, because I've often heard in this forum that it's not being done correctly.

Unfortunately, I wasn't there myself. When you say 'full throttle and 3rd gear' -> 3000 RPM, I can imagine that's really difficult. And speaking of gears, you really have to drive the car, not just let it sit somewhere, but I already suspected that; I just wasn't 100% sure.

How do I achieve full throttle while maintaining 3000 RPM? Or does the system only record the value when it's 'around' 3000 RPM? Why didn't Audi include the RPM value in the measurement block if it's relevant? Now I have this beautiful measurement report, but I still don't understand anything.

Well, this is a good opportunity for me to expand my basic knowledge of TDI engines, in case I ever drive something with one.

Hello,

VAG-Com, for example, also offers the possibility of recording data from various channels. This allows you to determine the exact values at precisely 3000 RPM.

So, then thank you for your answers.

1.9 TDI 66kW ALH

speed of 1800 - 3500.

675,969,1285,100
965,969,1826,100
955, 969, 2183, 100
850,969,1836,100
855,969,1836,100
860,969,1877,100
870,969,1918,100
860,969,1928,100
865,969,1938,100
860,969,1948,100
855,969,1948,100
835,969,1948,100
840,969,1938,100
825,969,1928,100
810,969,1918,100
800,969,1907,100
795,969,1897,100
785,969,1887,100

corresponds to http://www.ralfhandel.de/ladedruck2.jpg as well.


See you, Ralf.

I don't think you can directly compare them like that. The AFB is a 6-cylinder engine with a 2.5-liter displacement, which means approximately 417 cubic centimeters per cylinder. And the air mass is specified in mg per stroke, which is the amount of air filling each cylinder, or am I mistaken?

While the engine boasts 4 cylinders with a displacement of 475 cubic centimeters, you should also expect a higher value per stroke. Even considering the difference in boost pressure, which is approximately 0.9 bar compared to the 1.1 bar of the AFB.

Or am I completely on the wrong track now? Even though I had never thought about it before, I would come to this conclusion.

Wow, this is getting more and more complicated.

Or am I completely on the wrong track? Although I had never thought about it before, I would come to this conclusion.


No, that's already .

It was only meant for comparison.
Based on your (completely correct) thoughts, the values for the AFB should roughly be around 750-800.

Your list is rather short... in my case, you can clearly see the pressure surge in the boost pressure.


CU Gremlin.

That's a relief, but unfortunately, my brother didn't bring any more copies of the protocol.

I only have a mechanical LDA.
Here are some data points; perhaps someone can tell me if they are okay. I unfortunately don't have any target values; these were obtained with the engine running at full throttle in 3rd gear. Several measurement series were performed, and the average was calculated.

Engine speed Turbocharger pressure
1000 1100 mbara
1500 1250 mbara
1600 1375 mbara
1800 1625 mbara
2000 1750 mbara
2200 2000 mbara
2400 2100 mbara
2600 2200 mbara
2800 2250 mbara
2800 2250 mbara

Lowest measured charging pressure: over 2800 1/min, 2200 mbar. Highest measured charging pressure: 2300 mbar.


It seems like the turbocharger is a bit hesitant at the lower RPMs. I don't have anything to compare it to, just this graph.

Best regards, Johannes.

Sorry, I posted my information in the wrong thread.