Boost Sensor: Internal (AFN) vs. External (AHF)

Hello,

Does anyone know if the boost pressure sensors in the engine control unit (e.g., for the AFN engine) and those located outside (e.g., for the AHF engine) are the same, or if they have the same characteristic curves/voltages? I would also like to know if there are any lists available with BOSCH part numbers and/or pin assignments .
It would be great if someone could write something about this, thank you very much!

Hi,

"They are definitely not the same types of sensors; for example, the sensor in the MSG 021GH looks completely different from the intake manifold sensor in the ALH Ibiza or the ASZ Polo."

The latter ones are already 4-pin, as they also include an NTC thermistor as a temperature sensor.

I can't say anything definitive about distinguishing features or differences.

"With the newer models, I was almost certain, but is this really always the case with the older engines that were also used in the Golf 3? I mean, is it really impossible for there to be internal and external sensors that are the same from a sensor perspective? (Let's put aside the aspect of combination sensors for pressure and temperature for now)."

PS: By the way, until when were actuators actually equipped with sensors and pressure connections? Was it 1998?

Deus Violentia wrote:

I mean, is it really possible to exclude the possibility that there are internal and external sensors that are the same?

Yes: because internal sensors have solder pins on the circuit board, while external sensors have connectors.

That a platinum sensor X may have the same LD characteristic curve as the external sensor Y is another question that, regarding certain types, can probably only be answered by Bosch insiders.
It probably goes faster to record the characteristic curve of the specific types yourself, or to search for them in the MSG software...

I know for sure that the AFN engine in the A4 had an internal pressure sensor until the very end of its production. However, in the G3 AFN engine, that sensor was outsourced much earlier.

Nope, the G3 AFN also had an internal one.

I believe the last "internal" model was the ALE (90 horsepower, EURO 3, in the G3 variant), and it was likely produced sometime in 1999.

The AFN engine in the 3B model was, in some cases, a rather odd mix of parts typically found in Golf 3 and Golf 4 models.

m;

I know of a G3 AFN with an external sensor. (GTI TDI) Apparently, they also used mixed fuels here.

And Passat owners often had them installed externally (I know of four such cases from vehicles manufactured between 1998 and 2000).
The A4, on the other hand, had [something], and I'm not aware of any other cases like this in the STG.

I am referring to AFN engines in this case.

First of all, thank you for the extensive feedback so far! Again, we're dealing with these mixed-use aspects where no one really knows (can know) why, who, and why.
Even though it might be frowned upon, I'd like to try something out in this context. I have this (I'll cautiously call it a) auxiliary control unit from WENDLAND lying around. This thing is intended for a 110PS TDI engine with a VP37 injection pump and an external boost pressure sensor, as there's a pin there that's supposed to be connected to that sensor. The rest is the usual injection pump stuff . My idea is to test whether this thing also works if I simply connect a piece of pipe with an external sensor into the intake air path of the AFN engine, which has an internal sensor, and then simply power that sensor. It would then provide evaluable and plausible signals.
Since I don't have an internal versus external comparison regarding the characteristic maps, it would be wise to try an experiment to see if something like that is possible. Although the usefulness or lack thereof is something that is known to be debatable .
I'm just curious to see how this works and whether we can draw any conclusions from it. Is the GTI TDI just a matter of trim levels, or why would VW simply move the sensor? That would mean having another control unit in the lineup, which seems illogical at first glance. What do you think?

cksIT wrote:

I know of a G3 AFN with an external sensor. (GTI TDI) Apparently, they also used mixtures here...

. . and I know of a GTI TDI with an old-school internal sensor.
Was there a possible switch to a new MSG generation during the production period of the G3? As far as I know, newer vehicles no longer have an internal LD sensor anywhere.

It would be quite puzzling, however, that my 1997 G3 AFN, being one of the last models of its kind produced (when the G4 was already available for order), still had the internal sensor .

Deus wrote:

Since I don't have an internal versus external comparison regarding the characteristic curves, it would be wise to try an experiment to see if something like that is possible.

Somehow, it will probably work, because all LD sensors deliver a maximum signal just below 5V, and the box probably becomes active in the range of 3 - 4V.
If the LD sensor connector (KL) doesn't fit the box properly, it will activate at unexpectedly low or high pressures, which shifts the transition range between the standard and tuned settings, and that's all there is to it.

@ cksIT

Do you have any photos?
Ideally, from the two large intercooler pipes and the intake manifold.

Greetings.
m;

I can obtain parts from a 1999 and a 1996 A4 (both are in the junkyard).

I also need to get something for the Passat 3B (I'm unfortunately not sure of the year of manufacture).

It's becoming more difficult with the G3 because I don't have one anymore, and the other two are 200km away. But maybe I'll drive over there for Christmas, and if I do, I'll definitely make some then.

I don't really understand the system either... It seems like they were always just randomly deciding things.