LMM Defect Causes Bonanza Acceleration Problem

Hello,

Regarding the issue of "mima," I've once again tried to understand the possible processes involved, and I would like to present my thoughts here for discussion.

Please provide the text you would like me to translate from German to English. I will then give you only the translation, without any explanations.
If the engine power fluctuates or oscillates despite a constant pedal position (e.g., full throttle) and a functioning accelerator pedal sensor, it can likely only mean that the speed limiter is active instead of the torque limiter.
Because only it can significantly influence the amount of fuel injected with minimal changes in engine speed, resulting in noticeable fluctuations in power output.

2.
If the soot limit is active, any changes to the mass airflow rate (MAF) will affect the injection quantity, especially due to changes in boost pressure. This will also make the normal overshoot during full throttle acceleration noticeable.

Normally, even the minimum pressure after the boost pressure overshoot is high enough that the torque limiter is not yet active, meaning the injection quantity remains constant, and the electronic diesel control (EDC) can regulate the pressure without interference.

3.
However, if the fuel injection quantity (via active boost limiting) is linked to the turbocharger pressure, then any adjustment to the turbocharger pressure will be noticeably felt as a change in engine power.
For example, a decreasing fuel injection amount further reinforces any downward correction of boost pressure (due to the reduced power output driving the turbocharger). This can cause the boost pressure to drop significantly below the target value, prompting the boost control system to correct upwards again.
The pressure , including the fuel injection amount and engine power , is increasing again and exceeding the target value.
The regulation reduces the pressure and thus the engine power, etc., etc. The "Bonanza effect" is present.

Overall, an active limitation of Russian influence is, in my opinion, a mandatory prerequisite for the "bonanza effect."

Possible causes include:
a) Defective mass airflow sensor (this is relatively common).
b) The boost pressure is regulated at too low a level (this is rare, e.g., due to a faulty boost pressure sensor).
c) Extreme pressure fluctuations in the intake manifold, for example, caused by very tight clamping mechanisms or stuck solenoid valves, can activate the soot limiter during pressure minima (which is likely a rare occurrence).
d) Blocked intake and/or exhaust passages result in low mass airflow (MAF) values.
e) Ineffective liquid cooling lubricant under unfavorable conditions (e.g., high temperature and altitude) results in low lubrication performance values.

What do you think about it?
Sure, I'm ready when you are. Just paste the text here and I will translate it for you.

Hi Ulf,

'Sounds good and makes sense. For my G4 ALH, solution C applies. However, without the 'Bonaza' effect. But it's very noticeable that the engine loses power when the boost pressure drops from 1.3 bar to below 0.5 bar. This only happens after the boost pressure has risen to about 1.3 bar for 1-2.5 seconds at full throttle. After this sudden drop, it takes a long time, sometimes 10-15 seconds depending on the gear and increase in RPM, for the boost pressure to slowly return to its target level. However, there isn't another significant surge that would trigger the soot limiter.'

Greetings.

Eike.

eike wrote:

Sounds good and makes sense...

Thank you for your approval (this doesn't mean that corrections are not welcome!).

I'm considering putting this somewhere within the section for technical articles.

Another question for the group:

How does it work with turbocharged engines?

The amount of fuel injected must be adjusted according to the boost pressure to maintain the mixture within the intended lambda range - and this constantly puts the system in a condition that is typically associated with "Bonanza" (a situation that only occurs in TDIs under exceptional or defective conditions).

Hi Ulf,

Your explanations seem logical to me.
It would also be important to know exactly what the LMM does in case of an error.
It should behave in a way that the mass airflow sensor's output level drops significantly once a certain threshold is reached, then returns to normal, and drops again when the threshold is reached a second time. This behavior would be clearly visible in a graphical representation of the log files, showing the mass airflow values, the Russgrenze (presumably a reference value), and the boost pressure.

EDIT: Of course, this only applies if the mass airflow sensor (MAF) is causing the error. It should also be possible to reproduce the problem by using a switchable MAF replacement with a 1N4148 diode.

Marco wrote:

It would also be important to know exactly what the LMM does in case of an error. It should be the case that the air mass flow sensor's output level drops significantly once a certain threshold is reached, then returns to normal, and drops again when the threshold is reached a second time.

No:

IMO, it is sufficient if the LMM signal generally drops far enough - meaning a normal amount of wear and tear , without the LMM characteristic curve having to develop a "kink".

I once wrote a technical article in which I described the (likely) processes in more detail.
Okay, I'm ready. Please provide the German text you want me to translate into English. Just paste it here, and I will give you the translation.

Hmm...

And how can the normal acceleration and driving behavior, up to a certain speed, be explained? In my G4, it was also like that – the car only started swaying in 5th gear, around 140 km/h. Is the technical article already online?

Marco wrote:

and how can the normal suit/driving behavior up to a certain speed be explained?

Due to the signal voltage drop of the mass airflow sensor, which initially occurs in the upper measurement range.

If you mean by

Quote:

that the air mass flow rate drops significantly from its initial level once a certain threshold is reached

, then I probably misunderstood something.
massive = sharp bend in the characteristic curve.

I don't think that's necessary; a "smooth transition into the error range" should be sufficient. Once the soot limit drops far enough below the torque threshold, the control oscillations will have enough "room to grow."

I will add to the article (which is already online, see my previous post) that the problems often associated with LMM aging usually start in the Pmax range first.

Hi Ulf,

Now I understand.

ulf wrote:

Another question for everyone: How does it work with turbocharged gasoline engines?

Since the gasoline engine relies on a purely quantitative regulation, it depends on a boost pressure that precisely matches the driver's desired performance.

Therefore, a turbocharger, just like a naturally aspirated engine, has a throttle valve that reacts faster than any boost control system.

Best regards,
Uwe

Uwe wrote:

Therefore, a turbocharger, just like a naturally aspirated engine, also has a throttle valve that reacts faster than any boost control system.

Oops, I completely forgot about the throttle valve .

Although I drove "a few" gasoline cars before the TDI era (including even one turbo with a carburetor), they seem to be just as foreign to me now as diesels were back then.