LL Speed: Is Lastmanagment Overdriving?

Hello,

My Polo already benefits from the advantages of the CAN bus era and electronic load management. The latter means monitoring the on-board voltage and taking measures to prevent the battery from being discharged.

According to the SSP (Service Information), if the on-board voltage drops below 12.7 volts, the idle speed should be increased. Furthermore, if the voltage drops below 12.2 volts, various power-consuming components should be switched off sequentially (rear window heater, seat heaters, mirror heaters, air conditioning).
As the voltage increases, the loads are reconnected, and finally, the LL speed is reduced to its normal value.

This morning, for the second time, I noticed an increased LL (low-level) speed (~1000 rpm), which is particularly noticeable compared to the adapted normal value of 840 rpm.
While I could achieve almost the same level of initial acceleration without gas as I could with a VP-TDI, a glance at my analog voltage gauge showed a full voltage of almost 15 volts (which is normal after a cold start).
After approximately 45 seconds, the system was returned to its normal low-speed rotation.

The first time I noticed the increased LL (likely referring to a specific engine component) speed was about a week ago, right after I reactivated the glow plug system (I usually disconnect the fuse during the summer).
"At that point, I just thought that must be the reason, because the low alternator speed might not have been sufficient to maintain the 12.7 volts, even after the initial charging and afterglow after starting."

"However, since then, I've had several cold starts in similar or even lower temperatures, without any increased engine speed. This morning, it was even warmer, and yet the engine still revved up."

The battery was not more discharged than usual (or discharged since the last time it was turned off using the radio or something similar).

Can anyone come up with a rhyme? Could my car's body control module (BCM) possibly have a sporadic glitch?

Can someone come up with a rhyme? Does my car's body control module (BCM) possibly have a sporadic glitch? }

Take a look at the lighting equipment utilization. If it's hovering around 100%, the behavior is normal.

CU Gremlin.

Gremlin wrote:

Take a look at the lighting equipment utilization during that time.

If it's hovering around 100%, that's normal behavior.
Hm, then I would probably run the Lappi test x times for free, because the outcome is (still) not predictable or reproducible for me.

If it depends on the utilization rate, that would imply that load management...
a) receives information about the breast pump usage (presumably via CAN).
and
b) that the LL speed is also "preventively" increased, even though the on-board voltage has not yet decreased, and that the SSP is therefore incomplete (-> see above "below 12.7 volts" ) }

Can you confirm that?

Does my AWX still function, but only up to approximately 1000 RPM and at outdoor temperatures below 5°C?

At the time, my Lima's utilization rate was just under 40%, and the voltage was around 14.14V. I believe it's simply a result of an idle speed adjustment related to the catalytic converter warm-up and the Euro3 standard.
Once it starts and the engine has been running for a bit, the sputtering stops after a few seconds. If it were a collapsing board voltage, those few seconds of operation wouldn't make much difference.

However, there's a significant difference here compared to the ALH (D3) that I used to drive. When it was really cold (-15°C, and the engine was cold too), it would rev up to 1300 RPM at idle, while the AWX never really went above 1000 RPM.

I observed the same thing with my AWX last winter. The maximum speed was around 1000 RPM at -15 degrees Celsius, and that was only for a short period.

Julian wrote:

If it were a collapsing board voltage, those few seconds of increase wouldn't help much.

It's possible that the system checks whether the normal speed is sufficient again.
For example, the battery draws a significant charging current immediately after starting, which decreases noticeably within a few seconds.

Quote:

However, there's also a significant difference here compared to the ALH (D3) that I drove before. When it was really cold (-15°C, and the engine was cold too), it would rev up to 1300 RPM at idle, while the AWX never really went above 1000 RPM.

For our cars (ASZ / ALH), it's essentially the same thing.
"So far, I haven't been able to identify a clear pattern for when the upper link is raised... well, I'll keep observing."

Hi,

Quote:

Immediately after I reactivated the glow plug system (I usually remove the fuse during the summer).

Not directly related to the topic... but... why are you doing that? You're mainly preventing the "afterglow" effect, which also happens in the summer. Are you trying to save the candles, or is your primary concern the fuel consumption in the first few minutes?

Best regards,

Jan, whose car has now passed the TÜV and ASU inspections and is valid for the next two years.

Hi there,

The alternator load is monitored even in the older TDi engines without CAN, via the alternator's DF connection. The duty cycle on the DF signal indicates the load (a high "ON" time corresponds to a high load). In my AFN, a low-voltage boost (LL) may occasionally occur, but more likely, large consumers controlled by the MSTG, such as the coolant pre-heater, are simply switched off.

Greetings.
dieter

Not directly related to the topic... but... why are you doing that? You're mainly preventing the 'afterglow' effect, which is also done in the summer. Are you trying to conserve the candles, or is your primary concern the fuel consumption in the first few minutes?



to save weight??!!!!! *quickly move away*

joergs wrote:

Jan6K wrote: By doing that, you are primarily preventing the "afterglow," which is also done in the summer. Are you trying to conserve the candles, or is your primary concern the fuel consumption in the first few minutes? to save weight??!!!!! *quickly move away*

I hadn't even thought of that . The fuse is also "permanently" attached to the boat, even in the summer.

@Jan: Both answers are correct .

A friend with a Leon (81 kW) has been experiencing rough cold starts after only 2 1/2 years -> likely the first spark plug is broken.
When I look at the excessively long afterglow times of our Ibi (even after warm starts ), and I extrapolate that to the Leon, I'm not really surprised...
Oh yes: The Ibi candles, of course, also always have a summer break .

Of course, Ibi candles also always have a summer break .

And the results?

Think about the PDEs; they also draw enough power, and an air conditioning system will certainly run even with only 2 or 3 functional PDEs.

Which brand of spark plugs does your car have installed from the factory?

Julian wrote:

ulf wrote: Of course, the Ibi candles also always take a summer break And what about the results?

3 1/2 years, almost 40,000 km, no broken spark plugs yet, and according to the onboard computer, there's a difference of about 0.1 - 0.2 liters in fuel consumption (this difference is quite noticeable immediately after deactivating or activating it, even without a sudden change in the average outside temperature) .
And there are no noticeable drawbacks (which was the same with the G3).

Quote:

Think about the PDEs; they also draw enough power, and an ASZ (Air Source Heat Pump) will certainly run even with only 2 or 3 functional PDEs.

But if I turn it off, I always get those annoying error messages.

Quote:

Which brand of spark plugs does your car have installed from the factory?

*pondering* I believe all three are Beru, if I recall correctly.

Okay, I took a closer look again this morning:

Immediately after starting, my 90A alternator, even at the reduced low-speed setting, is unable to raise the onboard voltage to 14 volts to power the consumers (afterglow, battery charging, engine, and headlights) - it only manages to creep up from 12.5 towards 13 volts.
In this scenario, the utilization of the liquid ammonia (LiMa) system will inevitably be 100%.

So, after a few seconds, it appears that the load manager kicks in and increases performance based on the LL (low-level) speed – at least that's how it seemed to me this morning.

The question is, why doesn't this happen every cold morning since my glow plug system was "repaired"...

In this scenario, the utilization of the liquid milk production line will inevitably be 100%.


Were you unable to read the percentages in any of the MWB documents within the MSG?

Julian wrote:

ulf wrote: In this case, the LiMa utilization will inevitably be 100%. Were you unable to read the percentages in any of the MWB (Multi-Waveform Burst) within the MSG (Meteorological Satellite)?

No. The value can be accessed via the MSG, but I only carry the Lappi device in exceptional cases.

Since the Lima hasn't been causing any problems so far, I assume it's functioning normally.
This means that the regulator provides full power (100%) when the voltage is below the target voltage (approximately 14.5 V, depending on the temperature).

'Hmm, that's strange. My battery voltage has never been much above 14.2V, and even during a proper cold start, the generator load has never exceeded 45%, which would be approximately 63A.'
And I have more consumers 'in the system' than you do... fascinating!

What is the capacity of your battery?