Boost Control for VW/Audi AFN Engine

hi,
I was wondering if it's possible to adjust the turbo boost pressure in an AFN engine while it's running, for example, using a potentiometer, or if that might lead to unwanted error messages?
"I can definitely adjust the resistance at the pump connector using a potentiometer or something similar, even while driving (which I have to do anyway, otherwise it would go into emergency mode when starting!)."

"If I increase the turbo boost, wouldn't it logically be possible to also increase the amount of diesel injected, without the engine starting to make excessive noise? (More oxygen means I can inject more diesel, right?)"

3. Is it better to delay the injection time using a 100nF capacitor or a 1µF capacitor? (When should a 100nF capacitor be used, and when should a 1µF capacitor be used?)

4: How far can you push the boost pressure (temporarily??)

Hello,

Depending on where your boost pressure sensor is located (either in the control unit or in the intake manifold), it may be easier or more difficult to adjust the set boost pressure using a potentiometer.
The control unit monitors the boost pressure, and if it detects implausible values, it switches to limp-home mode and stores an error code. However, since the normal atmospheric pressure is also subject to relatively large fluctuations, the control unit is relatively insensitive to this. Therefore, the potentiometer may already be set during startup.
You should only adjust the boost pressure while the pressure gauge is connected! The turbocharger can fail very quickly if you attempt such a modification.
For a short period (approximately 2-3 seconds), pressures of 1.3-1.4 bar are not a problem in the engine speed range around 2000 rpm. However, the situation changes when the turbocharger needs to deliver more air at higher engine speeds.
You should keep the pressure set to a maximum of 1.15 - 1.2 bar.

If you increase the turbocharger boost pressure, you can inject more diesel fuel without the engine producing more soot.

3. No idea. Without a diagnostic tool and an oscilloscope to determine the actual injection start time, I wouldn't adjust anything here.
It might also be possible to adjust the injection pump to an "early" setting and then fine-tune/check the injection timing using a diagnostic device. I plan to try this, but haven't done it yet.

Best regards, Rainer.

First of all, thank you for the quick help!
I was thinking about increasing the 10k ohm resistor in the control unit (using a potentiometer for variable adjustment) to control the boost pressure, and also adding a potentiometer to the pump. I plan to "fix" the injection timing using a 100nF capacitor, hoping that it will work reasonably well across the entire range of variable injection and boost pressure.
I already have a pressure gauge installed.
During the drive (as I thought), I can adjust the injection timing and boost pressure to 1. achieve a good combustion, and 2. really increase the power (even for short bursts).

My only concern is about the timing of the injection; it would be better if it were more flexible. With Trimmkos available, it wouldn't really be a problem.

Hi.

Quote:

The only concern I have about this is the injection time; I wonder if it could be more flexible.

Since there are Trimmkos available, it wouldn't really be a problem!! }


I've also experimented with larger values.
With a 1µF capacitor, the 2000-4000 time significantly worsens (approximately 0.3 seconds, if I recall correctly), while it's not quite as bad with a 470 nF capacitor.
So, I would stick with a fixed value of 100 or a maximum of 220 nF.

It would likely be difficult to obtain trimmers or varactor diodes in that size range.