LDA Damping: Pointers and Overdamping

I have an LDA (Lambda-controlled Diesel Air) sensor from VDO (-1 to 1.5 bar) installed in my ALH engine, and I'm tapping into the boost pressure just before the EGR valve. I'm experiencing the following problem.

To avoid vibrations in the gauge needle, I've tried all sorts of damping methods (sprays, foam, clamps). If I dampen it so that nothing vibrates, the needle doesn't react at all in the lower pressure range (up to about 0.5 bar), and when the pressure increases suddenly, it jumps to about 0.5 bar and then continues to rotate at a normal speed. If I give it gas while it's stationary, nothing happens at first, and then it jumps up abruptly again. If I dampen it less, the needle moves smoothly and without jerks in all ranges, but then it starts to vibrate. So, I had to compromise and couldn't find an ideal solution. By the way, the boost pressure control is fine (I tested it with VAG Com at the same time).

Is this a known issue with LDA engines? A friend of mine has an AFN engine and uses a T-piece to tap into the boost pressure, and everything works fine for him.

Hello,

I assume you've read the technical article on LDA. How close to the LDA did you implement the damping? It also mentions that the damping might consist of multiple components.
Bottlenecks can occur when striving to achieve an optimal result.

Den Artiekl habe ich bereits gelesen. Ich habe derzeit zwei Sprühröhrchen kurz hinter der Anzapfung. Ich habe aber auch schon probiert, eine Engstelle kurz vor der Anzeige einzubauen. Ma guess:

Due to the damping, the air cannot reach the LDA at low pressure. However, if the pressure exceeds a certain value, everything rushes through the narrow opening at once, causing the pointer to jump abruptly upwards. If you didn't know better, you might think that the pointer initially gets stuck and then suddenly shoots forward. With a slow pressure build-up (e.g., accelerating from a low RPM or with a very gentle throttle), the pointer also rises slowly and steadily.

Could it be that my hose, which is approximately 2.80 meters long, is too long (unfortunately, a shorter one is not available)? Does anyone else have any ideas?

Hello.

'I'm experiencing the same problem with my Golf 3 AFN. The LDA is also from VDO. I installed it using a T-piece. It makes a very loud rattling noise under partial load.'
I would also appreciate a suggestion for improvement. I'm also having trouble with the 'bottlenecks' feature.

Hello.

Normally, this should work with the bottlenecks in the line, but finding the correct (minimum) cross-sectional area can sometimes be quite difficult.
Spray nozzles are not a guaranteed solution here, but are only to be understood as an example.

As a possible solution, the volume behind the constriction could be increased, for example, by using a (of course airtight and pressure-resistant) pill container that is fitted with connections for the incoming hose and the hose leading to the LDA.
... or whatever else you can find in the grab bag.

Then, the cross-section of the constricted area, located before the damping volume, can be increased again.

Hi,
There is no minimum cross-sectional area below which air will not flow. At most, there might be a kinked hose that occasionally sticks together, a stubborn oil droplet in the spray nozzle, or, indeed, a hanging instrument that might come loose due to vehicle vibrations when accelerating slowly.
For increasing the volume, I would probably use an old fuel filter or a longer hose.

christians wrote:

Hi, There is no minimum cross-section below which air will not flow. At most, there might be a kinked hose that occasionally sticks together, a stubborn oil droplet in the spray nozzle, or actually a hanging instrument that might come loose due to vehicle vibrations when accelerating slowly.

...or a piece of foam that, when compressed inside the tube, could change its effective cross-sectional area depending on the pressure difference (some pores only open under pressure)?

Quote:

For increasing the volume, I would rather use an old fuel filter or a longer hose.

Exactly that (the filter) didn't immediately come to mind for me in my previous post .

I've also tried using foam, and I've observed exactly the behavior that Ulf described. If you hold your hand in front of the hose, you can clearly feel that with slight gas bursts, little or no air comes through. But with higher pressure, some air does get through.

The idea about the filter sounds good. Let's see if we can find one somewhere.

christians wrote:

Hi, There is no minimum cross-section below which air will not flow. At most, there might be a kinked hose that occasionally sticks together, or a stubborn oil droplet in the spray nozzle.

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

"Addendum:"
Could grease also become so "clogged" that air can only "break through" it with a higher pressure difference, and does the opening in the grease re-seal after the pressure difference has been equalized?
That would then appear on the display as if there were a jammed mechanism...