Lastmanagenemt: unnötig erhöhte LL-Drehzahl? | Posts 32+

Perhaps it's because you don't have glow plugs?
'Should I quickly charge the battery to its maximum voltage so that the heating system doesn't have to be turned off again due to the charging demand?'


My ALH engine also only increased its RPM at arctic temperatures (below -5°C). I think, Ulf, that you are mistaken here, because the RPM increase is related to the exhaust behavior, not the turbocharger's performance.

Julian wrote:

I think, Ulf, that you are basing your understanding on a misconception here, because the increase in RPM is related to the exhaust behavior, not the charging behavior.

It's possible that I don't know the true "primary" reason for this programming.

However, in case of doubt, the result will also benefit the (fast) battery charging.

Hi,

However, the ALH and ASV engines have the same emission standard, namely Euro3. Therefore, according to your theory, Julian, the ASV should also exhibit the same behavior, but I don't recall seeing that in previous winters.

Let's see what he does this winter when it gets really freezing cold – I'll pay attention.

Best regards,

Jan.

Jan6K wrote:

Let's see what he does this winter when it gets really, really cold - I'll pay attention.

So, anyone who is somewhat familiar with their TDI "by ear" and is technically inclined will probably notice, even without looking at the tachometer, that it's behaving differently.

When searching for the explanation, you can see what's happening on the tachometer - and you should remember the deviation from the normally (without load) very stable idle speed of a VP-TDI engine.

Hi Ulf,

"Of course, you'll notice that... but I didn't really experience it from last winter, because there were only a few days in Berlin that were actually that cold, and my TDI probably experienced even fewer of those days, since it's parked right next to a house wall at night."

Best regards,

Jan.

@Ulf:

You could try verifying the "exhaust emissions" issue by temporarily reactivating the EGR system and resetting the mass airflow sensor for a few days.
My automotive service center has never encountered such idle speed increases before, even with the EGR system deactivated, but with the default air mass flow sensor setting.

It's possible that the diesel OBD device will trigger an error again for you.

Roger wrote:

You could try verifying the "exhaust emissions" issue by temporarily reactivating the EGR and resetting the mass airflow sensor value for a few days.

IMO not necessary... I'm slowly getting closer to understanding the load manager, and I can now reliably trigger or predict the LL (Load Limit) increase based on the voltmeter and by connecting appropriate loads .

Let's see if he ever surprises me with a behavior that doesn't fit the pattern.

Julian wrote:

So, yesterday I was tinkering with my friend's Golf4 (1J, ALH, 44,000km, 5/00) a little bit... When the rear window/mirror heaters, all lights, seat heating, etc. are turned on, the voltage drops briefly (~13.1V), but then rises again to 14.36V.

I've also started to notice this myself, although the charging system otherwise seems to be functioning normally.

In conventional control engineering, this would indicate an error, as voltage deviations in the range of 1/10 of a second need to be corrected.

However, with today's high-tech controllers (my controller looks completely different from the "known" models), a sluggish power-up response might be "not a bug, but a feature," to avoid causing drops in engine speed and potential speed oscillation of the low-load engine speed due to a sudden surge in alternator power demand.
Because decreasing rotational speeds must be compensated for by an even greater driving force, since power equals torque multiplied by rotational speed.

Okay, in VP-TDIs with the very aggressive torque boost under load, it's likely that nothing would start to vibrate.
"In older PD models, this might not be the case, but with today's small, rotary-valve gasoline engines, I fear that the load regulation (LL) is not very 'self-stabilizing.' Therefore, a gentle increase in load by the alternator (even if it involves brief voltage dips, which are considered a lesser evil) is necessary to maintain the usual running characteristics and avoid load regulation fluctuations."

But with today's high-tech controllers (my controller looks completely different from the 'known' models), a sluggish power-up could be 'not a bug, but a feature'.

is it also...

It's called a load-response function, and it's designed to dampen hard impacts on the belt drive. Everyone knows this feature: 'the lights flicker at 2500 rpm' .

CU Gremlin.

Julian wrote:

@Ulf: Are you sure that everything is okay with the power supply of your 9Ns? I don't think 13V is high for such low-power devices; perhaps your line regulator is faulty?

Here's another update after a few measurements.

In the µCarge thread, I described how I measured the resistance of my B+ line using the 5A power supply.
Computationally, this resulted in a line resistance of approximately 1.6 mΩ (including a 175A fuse with 0.4 mΩ), which is roughly plausible for a 1-meter length of 16mm² copper cable.

I just measured the voltage drop in the wiring after the engine start, while the voltage is still rising towards 14V, meaning that the alternator, under full load, is primarily supplying power to the glow plugs and the battery's charging demand.

There were measurements of up to 110 mV, which, even at 840 motor rpm, suggests a current output of the alternator of around 70 A (nominal current = 90 A).

Gremlin's hypothesis that the screw fuse might exhibit increased resistance under load (due to potential contact problems or heating) has not been confirmed: A voltage of 25 mV across the fuse corresponds quite accurately to its share of approximately 25% of the total cold resistance.

Even a rough calculation of the acceptable load until the onboard voltage drops with a warm engine (LL = 840 rpm) doesn't reveal anything fundamentally different:

-> Rear window defroster = 17 A (just measured).
-> Heater fan at full power = 16A.
-> Total current consumption for low beam, high beam, and parking light: approximately 19 A.
-> Pre-charge pump = 4 A
-> Power steering with pump in the left-hand side = approximately 2 A.
They have been together for 58 years.

In addition, there's the difficult-to-estimate power consumption of the engine (PDE, solenoid valves, TCU), as well as minor consumers like the instrument cluster, ABS, and likely some current draw for charging the battery, which probably never fully charges given my mostly short trips.

The result is trending towards 70A, which my small 90A LiMa already achieves in reduced idle speed -> Respect .

If I then have the brake (6 A) and NSL (2 A) activated, as well as the prohibited NSW (8 A), the battery would definitely be discharged in the LL (low-level) mode, so the load manager would urgently need to increase the speed - even without afterglow or active electric heating.

It's good and also entertaining to have a voltmeter on board so that I can additionally monitor the whole thing.