PDE Expiration Dates: Time to Replace?

Hello,

I explored the switching behavior of my power distribution elements (PDEs) today.
In the MWB 23, the deviation is displayed, which each PDE exhibits from the normal (unavoidable) delay between power-on and the start of injection.

According to a log, the component in cylinder 3 is significantly slower (or faster?) than the others during a period of over 6 minutes of highway driving with acceleration ranging from partial to full throttle.

The average values across the entire log are as follows for cylinders 1 through 4:
16 / 10 / 38 / 9.

The maximum value for cylinder 3 was 62; the specified range according to my ASZ label (from Theresias) is -100 to +100.

By the way, the minimum value of all cylinders was 0, specifically for cylinder 4.

The idle speed control is unobtrusive, and in most cases, it performs better than +/- 0.4 mg per cycle.


Question:
What can be inferred from the significant differences in PDE switching times?

Is my PDE number 3 already headed for the trash, or are these manufacturing tolerances of the solenoid valve that won't change during its remaining lifespan?

Yes, I'm also interested in that. I also have a "high-performance" cylinder (2) that achieved a score of 91 in the log. So far, no one has scored above 100 (at least in the logs), but I never get a score of zero either!
I hope this doesn't indicate an imminent failure, because my company's Passat has similar readings with 132,000 km and is still running perfectly.

I've analyzed the logs a bit.
PDE 3 not only provides the overall highest values, but also reacts approximately 3 times more sensitively to the instantaneous engine power (speed and, above all, fuel injection volume) than the other three.
(The higher the performance, the higher the logged time value.)

According to the error code list, the possible causes are:

Rule limit overstepped.
-> Possible causes:
Time limits are too high.
Transition resistances.

Regulatory limit below steps.
-> Possible causes:
Timings are too tight.
Fuel shortage.
Air in the fuel system.

Now I wonder: are times around 60 heading towards the regulatory limit above steps or below steps ?

"That is, if I start looking for issues and, for the sake of simplicity, ignore manufacturing-related variations in the PDE, should I then look for transition resistances or air leaks (that are currently still within the acceptable error range)?"

Update:

I've looked in both directions.

a) Transition resistances seem unlikely, as I measured constant and almost 100% identical resistances and inductances for each individual PDE at the MSG connector, despite simultaneously wiggling the wiring harness at as many points as possible.

b) I can also practically rule out air in the coolant system. I've replaced the supply and return hoses between the filter and the engine with clear sections, but I don't see any bubbles anywhere when the engine is running.

A theoretical possibility for gas leakage in a PDE (common rail pressure sensor) could be a breach of the combustion pressure through the sensor's mounting hole into the diesel pre-injection circuit. This would require the pressure to overcome one metal gasket and one O-ring.
Something like that, in my opinion, should only be revealed by bubbles only in the return flow.
As I said, I can't see anything.

As a final "external" option, PDE No. 3 could remain in place, and I will check this and, if necessary, adjust it to align with the others.

If that doesn't work either, the only likely explanation would be a tolerance outlier in PDE 3.


By the way, the behavior of the idle speed control (ISC) after a cold start is different from that when the engine is warm.
Average values in the LL (likely referring to a specific measurement or system) for cylinders 1-4 = 42 / 37 / 61 / 38.

Do the higher positive values now indicate shorter exposure times?
It's conceivable that copper (as a likely material for the PDE windings) has a lower resistance when cold compared to when it's warm, and that the starter battery also provides a higher voltage when cold.
But, on the other hand, isn't cold diesel less fluid than warm diesel, and therefore shouldn't it brake the movement of the PDE valve piston more strongly -> resulting in a longer engagement time ?

Where are the PD cracks located?
Hi Bertil and Co...

ulf wrote:

..... If that doesn't work either, the only likely explanation would be a tolerance outlier in PDE 3. ... Where are the PD cracks located? Hi, Bertil + Co. . .

Hi Ulf,

I wanted to verify your measurements first.

"I don't observe any deviations. Since I have a pre-calibrated PD set, I would expect tolerances in the PD elements. The tolerances that apply to the manufacturing of such injection systems are quite significant."

I don't think you need to worry about it.

Hi,

It's due to manufacturing tolerances. My AXR has the same issue, but it's been there since the first kilometer.

Best regards, Christian.

Ah, so you also mean "tolerances"...?

Does anyone actually know what order of magnitude these questions operate on?

The rate of increase of the coil current can be calculated from the time constant 2πRL.
With R = 0.2 Ohms and L = 0.13 mH, this results in approximately 0.16 milliseconds as the time between switching on and reaching 63% of the maximum current, if I recall correctly.

But what is the actual correction range in milliseconds (msec) or microseconds (µsec)?
Or, in what unit are the VAGCOM data measured in control module 23?

Okay, I've adjusted all the PDE settings as precisely as possible.

However, it has practically not changed the boot-up times.

Then I experimented with different battery voltages:
When the alternator excitation line is disconnected, resulting in a lower battery voltage, the values are generally slightly lower.

It can be inferred that high values indicate short switching times, while low or negative values indicate long switching times.

So, it seems my PDE No. 3 is a bit faster than the others.