VP37: Questions on Dynamic Start Settings

Hi,

According to a technical article, the engine should be warm during adjustment, and since I have to do this on the road , I came up with the following idea:

Loosen the two nuts on the console and the screw on the side of the fuel injectors, warm up the engine, and then adjust it. Does the third screw in the console withstand the vibrations during driving? If I only start adjusting after warming up the engine, too much time passes (getting the ESP wheel into the correct position, reaching the fourth screw), and then the fuel temperature is too low... or am I being overly meticulous ?

In VAG-COM channel 4, the start of injection can be adjusted via software. To have the entire control range available during operation, shouldn't the average value between the highest and lowest values be set here beforehand, or am I mistaken ?

Thank you in advance.

Best regards, Christian.

Hello,

Quote:

In VAG-COM channel 4, the fuel injection start can be adjusted via software. To have the entire control range available during operation, shouldn't the average of the highest and lowest values be set here beforehand, or am I mistaken

.
Yes, you have a misunderstanding. The values for the start of injection that are regulated during operation are independent of the mechanical zero position of the pump. Of course, this is only true if the mechanical position is not so incorrect that the adjustment in the ESP reaches its mechanical limits.
Normally, you don't need to adjust anything on channel 4. If you want slightly lower fuel consumption and more responsiveness in the higher RPM range, you can set it 1° BTDC (Before Top Dead Center) earlier.
Regarding the starting behavior, I doubt that adjusting it via channel 4 will make much difference, because the pump needs a minimum amount of internal pressure to be adjusted. To what extent is this pressure built up during the "organizing" process...?
If you ever have to "organize" something, then something is probably going wrong.

Best regards, Rainer.

Rainer K. wrote:

Yes, you have a misunderstanding. The values for the start of injection that are engaged during operation are independent of the mechanical zero position of the pump.

Hi Rainer,

That means the values in section 000 don't change when the pump is running? That can't be right!

Rainer K. wrote:

Of course, this is only true if the mechanical position isn't so far off that the adjustment in the ESP reaches your mechanical limits.

The static start-up value is correct, but the dynamic value in 000 is slightly below the yellow line!

Rainer K. wrote:

Regarding the starting behavior, I doubt that adjusting it via channel 4 will make much difference, because the pump needs a minimum amount of internal pressure to adjust. To what extent is this pressure built up during "organ playing"...? If one absolutely *must* "organize" something, then something is probably going wrong.

So, if a diesel engine starts immediately at minus 15 degrees Celsius, then there cannot be a significant pressure loss .

A forum member was able to reproduce the same effects (starting problems within a specific temperature range) by rotating the pump timing later.

Therefore, I would like to adjust the pump in such a way that I am slightly above the yellow line in the diagram .

Best regards, Christian.

Quote:

You loosen the two nuts on the console and the screw on the side of the fuel injectors, warm up the engine, and then adjust it. Does the third screw in the console withstand the vibrations during driving? If I only start warming up the engine and then loosen something, too much time passes (getting the ESP wheel into the correct position, reaching the fourth screw), and then the fuel temperature is too low... or am I being overly meticulous again?

Okay, I wouldn't drive around with a loose fuel injection pump; those screws can be loosened in 5 minutes. Do you want to wait until summer, when the fuel is probably even warmer?

Greetings Albrecht[/quote]

So...
- the dynamic injection start does not need to be adjusted.
- The static backscatter (SB) is configured as described in the technical article.

The static SB determines when the NBF (Needle Body Fuel) in the ESP (Electronic Spray Pump) registers the start of the injection process, meaning fuel is injected, with respect to the continuously actuated injector adjuster.
The static SB (likely referring to "static site building" or a similar concept) is important in the following cases:

- Cold start.
- Warmstart

The diagram only applies to the static SB.

The static SB (slip-boost) value can only be determined using a diagnostic device if you enter the default settings mode. Otherwise, you will read dynamic SB values.

The dynamic injection start is regulated to the correct value for the respective operating condition based on characteristic curves in the EDC, within the closed-loop control system of the NBF-EDC injection adjuster.
The dynamic fuel injection start affects engine operation but hardly the starting behavior. Reason: see the last post.

Therefore, my question to you is: What do you want to achieve with your settings?

Best regards, Rainer.

haehnlein wrote:

If I have to warm it up first, and then loosen it, too much time passes (getting the ESP wheel into the correct position, reaching the fourth screw), and then the fuel temperature is too low... or am I being overly meticulous again

.

Hi Christian,

Yes, in my opinion, you're being too meticulous again.

I can only repeatedly suggest moving away from abstract chart analysis and instead observing the actual operating parameters during driving using a multimeter or VAGCOM device --> expert article.

If the regulation only operates at the lowest load range during late injection (approximately 0-5%) and never exceeds 90-95% at full throttle for any engine speed, then, based on my experience, the pump is optimally adjusted. That's it, end of discussion .

Okay, this refers to the AFN, but the basic principle is the same .

Hi Christian,

In the cold start discussion thread, people are currently focusing on the pump settings again.

Here's another conspiracy theory about that:

Since a previous owner may have already tampered with the settings, it's possible that the fuel injection timing is incorrect. This could be due to someone using VAGCOM to alter the target value (adaptation channel 4) and then adjusting the pump so that it perfectly "obeys" this false setting – for example, always injecting fuel 3° too early.

With the AFN, the desired injection start can be adjusted by approximately 5 degrees forward and backward compared to the factory setting. A range of 10 degrees is quite significant and, in my opinion, can definitely have a noticeable impact on the starting behavior.

The factory-set value for my car was exactly in the middle of the range of values that could be stored.

Check it out on yours too:
Log in as "12233", select channel 4, record the current value, and then determine the minimum and maximum acceptable input values.
Then store the midpoint between the maximum values and observe how the system behaves.
Adjust the pump accordingly, based on this adaptation, or perhaps set it a fraction of a second earlier.

Here's something else about the starting behavior.

At the beginning, the initial spray pattern from the EDC (Electronic Discharge Coil) plays absolutely no role.

During the initial pressure build-up phase, the pressure inside the housing needs to be established first. This then sets the injection timing to its maximum early setting. Only then does the EDC (Engine Control Unit) have a chance to intervene. However, the engine should already have started by this point...

if the engine is difficult to start and the pump is correctly adjusted, then the fuel filter or a too-low starter motor speed could also be the cause .
or the pump is worn out (initial flow rate too low).

@haehnlein

My ALH doesn't cool down that quickly either, and after 10 minutes of idling, it's back up to its normal 90°C (real temperature, I mean). You just have to turn off the heater, and if necessary, turn on everything electrical. Or set the air conditioning system to its coldest setting.

CU Gremlin.