Kniffelaufgabe: Ursachen für unrunden PD-BUK-Kaltstart? | Posts 32+

ulf wrote:

If it's washed away, then even with that gone, air pockets could still linger further down in the area around the pump piston and nozzle seat, delaying the injection until they are completely expelled.

Ulf... I'm sorry, but do you really believe that the developers didn't think much about this very important ventilation issue?
If that is the case, then there is no need for me to continue this discussion.
Because even this air (since it delays the injection process – i.e., the needle stroke) is recorded in the diagnostic data.
I can assure you that your "air pocket" theory cannot be correct. The chambers are flushed too quickly and thoroughly for that to happen. Furthermore, the geometry simply doesn't allow for it.

Bertil wrote:

Sorry, but do you really believe that the developers didn't think much about this very important venting issue?

I don't know what the developers were thinking about it, nor do I have any data on the venting speed of a PDE.

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Even this air (since it delays the injection - thus the needle stroke) is recorded in the diagnostic data.

That's incorrect, because a PDE essentially has 2 needles. The MWB23 only provides the closing time of the solenoid valve needle.
The injection process only begins when the injector nozzle opens, after the high pressure generated after closing the solenoid valve has spread to the injector seat and the nozzle needle lifts. To accurately capture the actual start of injection, one would need an NHG (High-Pressure Sensor) for each PDE (Pump Nozzle Injector), similar to what is used with the VP37.
"But that's not available here. Therefore, the actual subject being studied doesn't appear anywhere in the diagnostic data."

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I can assure you that your "air pocket" theory cannot be correct. The chambers are flushed too quickly and thoroughly for that to happen. Also, the geometry simply doesn't allow it.

Do you perhaps know of a PDE diagram (from "non-confidential" documents) that could be posted here online?
I would show you where I see potential possibilities for air pockets to last longer than what the MWB23 standard indicates.

ulf wrote:

...I am not aware of the developers' thoughts on this matter, nor do I have any data regarding the ventilation speed of a PDE.

At least the latter I am familiar with. Without further ado.

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Incorrect, because a PDE essentially has 2 needles. The MWB23 only provides the closing time of the solenoid valve needle. The injection process only begins when the injector nozzle opens, after the high pressure generated after closing the solenoid valve has spread to the injector seat and the nozzle lifts. To accurately capture the actual start of injection, one would need an NHG (High-Pressure Sensor) for each PDE (Pump Nozzle Injector), similar to what is used with the VP37. "But that's not available here. Therefore, the actual subject being studied doesn't appear anywhere in the diagnostic data."

"So, you don't have the hydraulic coupling between the two systems?"

Okay Ulf... I'm logging off now.
Delve into the yellow Bosch manual on Positive Displacement (PD) blowers, and you'll understand how these systems work and why there are no air pockets that would be affected by a coolant temperature of up to 60°C.

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Do you perhaps know of a PDE cross-section?

Yes, I have it.

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(from "non-confidential" documents) that can be made available online here?

It depends on that.
And I certainly don't want to create any trouble for myself today.

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At that point, I would show you where I see potential possibilities for air pockets to last longer than what the MWB23 standard indicates.

Forget it, Ulf... you're looking for things that don't exist.

I've been taking your problem seriously up until now, but I'm going to declare you crazy... Sorry, but you can't be that stubborn.


:opt-out:

Bertil wrote:

ulf wrote: The MWB23 only provides the closing time of the solenoid valve needle. The injection process only begins when the injector nozzle opens, after the high pressure generated after closing the solenoid valve has spread to the injector seat and the nozzle lifts. To accurately capture the actual start of injection, one would need an NHG (High-Pressure Sensor) for each PDE (Pump Nozzle Injector), similar to what is used with the VP37. That one isn't available here, so the actual SB doesn't appear anywhere in the diagnostic data. Do you not have the hydraulic coupling between the two systems?

Yes, as long as there is no air in between.

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Take a closer look at the yellow Bosch book on Positive Displacement Elements (PDEs), and you'll understand how everything works and why there are no air pockets in PDEs.

I don't find anything detailed about venting PDEs in that book. Can you tell me which page you're referring to?
Regarding venting, the SSP 209 from IMO is more informative, but even there, I can't see any way for air to escape from the high-pressure pump (HPP) between the piston and the nozzle seat without passing through the nozzle holes.
The Bosch manual describes the tandem pump as a gear-type variant, while the SSP 209 refers to it as a vane-type.

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At least not one that would affect the LLR (Low-Level Relay) up to a cooling water temperature of 60°C.

It's possible that other factors are at play.

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Forget it, Ulf... you're looking for "empty promises" that don't exist. So far, I've taken your problem seriously, but now I'm declaring you crazy... Sorry, but you can't actually be that stubborn.

It's a shame that it ends up like this again...

I think I'll chime in now...



It's a shame that it ends like this again.

Well, Ulf... That's just the way it is when you want to know everything, but don't want to put any effort into using your own brain.
Sorry for the somewhat personal attack.


Think carefully about what you're saying.
Does the pre-combustion chamber contain air for a certain amount of time to cause delayed combustion?
What do you think the volume of air would have to be for that to be a problem?
Not enough air can actually fit into the fuel system of the PDEs. Even if I were to extend it all the way to the diesel filter, it still wouldn't work. The venting mechanisms are simply too complex for that.
Precisely because efforts are made to prevent steam bubbles from forming and to remove them from the system (should they occur), your scenario will not come to pass.

Here's another thought on that...
Surely you're not suggesting that air could remain trapped in the common rail system for minutes, especially considering the developers are making extreme efforts within the low-pressure system to remove any air. This includes components like the direct fuel injection system (including the variable flow pump), the tandem pump, and the common rail itself, which has corresponding cross-drilled holes in the cylinder head.
Your idea would therefore be completely counterproductive to the other efforts being made.

You must understand that diesel fuel located in the high-pressure area of the pump plunger only has one way to go: towards the injector needle. Even if there's an air bubble present that delays the movement of the injector needle, that air in this extremely small space will be completely gone after a maximum of two needle strokes. The remaining air is then expelled through the return flow. Just believe someone who understands the technology.


I will not be providing any construction drawings myself. While I don't possess them, I wouldn't want to compromise the trust I have with my clients, and I certainly wouldn't share them if I did.

Regarding the topic of venting, SSP 209 from IMO is more informative, but even there, I cannot see any way for air to escape from the common rail injection system (PDE) between the pump piston and the nozzle seat without passing through the nozzle holes.

And what about the return flow? You completely ignore that... There are special valves there that accelerate the venting of the pressure-equalizing diaphragms (PDEs).

I see that you're only focusing on the letters in this specific software specification document. So, do you believe that every developer will simply hand you the data on a silver platter? You won't find that to be the case, and some independent thought is still required.
That's ultimately what Bertil (and others too) are accusing you of.
You constantly try, but unfortunately, you can't let go of an idea once it's formed, and that ends up hindering your progress. Often, your observations are very incomplete. And even when someone tries to help you with new ideas, they are completely ignored. I think this is one reason why I rarely respond to you.

Let's say you were to install a heater or a Calix system (I know you probably think that's unnecessary extra equipment, but just for the sake of argument) and you preheated it, then the BUK (presumably referring to an engine component) would start up smoothly, just like in summer. No rumbling, no misfires, nothing like that. I know this because our Sharan behaves exactly the same way.
However, preheating won't remove any air that might be present in the fuel lines or injectors. And even with air, the engine would still start and run smoothly. Therefore, the problem cannot be caused by air in the high-pressure diesel system.

Once again, a warm "hello" from the world of wheat beer!

ulf wrote:

... It's a shame that it ends like this again.

I had intended not to post anything here anymore because of the ignorance of other *no one-cares* people, but my avatar picture is mandatory!

Ulf got it RIGHT!!! ...I mean, I really need it...
Not everyone necessarily has to be rude or dismissive for the message to get across.

The sound from the football loudspeaker is booming.
"Goettmann! Again and again, Goettmann!! Rarely seen, but when he has the ball, he scores every time, and no goalkeeper can stop him, and it's always a spectacle!"
...copy my avatar image, I think we two are really (mentally) related - however, with different (age-related? *lol*) focuses here...

Ulf doesn't have a heated seat in his car because... it weighs [EDIT: ...and could break *sorry*].

And so that my contribution at least adds something to the discussion: My AXC in the T5 has a heater (water heater!), and it starts up when pre-warmed like a young goat... *shivers*

Best regards from Munich!

To avoid getting too personal, I will only respond to the technical arguments here.

goettmann wrote:

Think carefully about what you're saying. Minutes of air in the PDE that is supposed to cause combustion delay? Please provide the text you would like me to translate from German to English. I will then give you only the translation. It surely can't be your serious intention to think that air could hide in the PDE for minutes. I already understood that from what you wrote above:

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At least, not any that would affect the LLR up to a cooling water temperature of 60°C. Quote: It's possible that other factors are at play.

You must understand that the diesel fuel located in the high-pressure area of the pump plunger only has one way to go -> towards the injector needle.

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Even if there is an air pocket present which delays the injector needle stroke, the air in this extremely small space will be completely gone after a maximum of two needle strokes. The rest of the air is expelled through the return flow. Just believe someone who knows the technology. OK, this goes much more specifically into my considerations than Bertil's answers - and incidentally confirms the thoughts about injection delay, even though the MWB23 simultaneously reports "no air in the system." Here's a possible explanation for the short bursts of blue-white smoke and misfires seen in the video: it's likely that air is passing through at least one faulty spark plug (PE).

And what about the return flow? You completely ignore that... There are special valves there that accelerate the venting of the PDEs.

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I've seen them.

A few of my own thoughts are still relevant.

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It was with those thoughts that I tried to imagine what happens to air portions that don't reach the venting throttles (if the PDE is momentarily supplied with more air than diesel), but instead manage to sneak into the high-pressure chamber: injection delay and quantity loss, which you apparently don't contradict?

You try again and again, but unfortunately, you then find it impossible to let go of a thought once it has formed, and this ends up hindering your own progress. Often, your observations are very incomplete. And even when someone tries to help you with new ideas, that is completely ignored.

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Okay, I could have brought this up earlier: The approach of attributing compression loss to hydraulic lifter issues bothers me significantly because the most noticeable misfires and blue smoke only appear after many engine revolutions, long after the hydraulic lifter noise in older engines has largely subsided, or when the compression should already be back within the normal range. Because the compression will never be worse than it is during the initial engine rotation (after reaching the low-speed RPM), especially with empty hydraulic lifters after a cold start. Therefore, if misfires and blue/white smoke are caused by compression issues, shouldn't they occur immediately after starting the engine, rather than later? Air in the system, depending on its origin (e.g., from the differential pressure sensor, supply line, etc.), can indeed take a considerable amount of time to reach a primary drain valve (PDV), as evidenced by the delay between the initial noise and the distinct interruptions heard in the video. Based on these considerations, it has so far been my favorite explanation for the rough, smoky cold start – after Bertil dismissed the coolant theory based on the need for topping up.

To avoid delving further into personal opinions, I will only respond to the technical arguments here.


I promise to improve .


I tried to imagine what happens to the air portions that don't make it to the venting throttles (if the PDE is momentarily supplied with more air than diesel), but instead manage to sneak into the high-pressure chamber: injection delay and quantity loss, which you apparently don't contradict?


It might be, but your error message looks quite different.


The approach of attributing compression loss to hydraulic lifters that have run dry bothers me significantly because the most noticeable misfires and the blue-white smoke only appear after several engine revolutions, when the hydraulic clatter in older engines has already largely subsided, or when the compression should long since be back within the normal range.


Two notes on that:
Air will only be noticeable during the first two or three strokes; after that, all air should be purged from the system. There's no such thing as 'hidden' air (unless the system is completely empty).
According to that, your theory about the air isn't convincing either, because the effect of your statement comes later (which I can't see or hear in the video).

Hydraulic systems not only lose pressure overnight but can also be depressurized when the system is started. This can lead to delayed start-up problems. However, I would actually rule out this as the cause. Then the engine oil would be a real disaster.


Air in the system, depending on its origin (e.g., from the differential pressure sensor, supply line, etc.), can indeed take a considerable amount of time to reach a primary drain valve (PDV), as evidenced by the delay between the initial noise and the distinct interruptions heard in the video.


You seriously believe that at the same time, regularly, and over a long period of time all ventilation measures between the DiFi and PDE fail? Then you have a miracle car.



Okay, let's switch gears and talk about something for the sewing box now.
In some tests conducted in cold climates, we also encountered vehicles that exhibited a peculiar and stubborn starting behavior (both gasoline and diesel engines). However, the initial analyses led to a dead end. It wasn't until someone damaged the oil pan on one of these vehicles that the problem was eventually identified. After the repair, the issue disappeared.
What does the oil pan have to do with this?
Okay, so we figured out that a different type of oil was used during the repair compared to what our local workshop uses. So, as a test, we changed the oil in another vehicle and sure enough – the problem disappeared.
Both oils met the manufacturer's specifications 100%. Therefore, the wrong type of oil was not used. Nevertheless, these issues occurred.
Okay, now it's your turn to use your imagination and come up with reasons why that might be the case.
Elsewhere, I had already told you something about the engine oil that you are using.
It's hard to say whether this applies to you.


For me, your car seems to be in perfect condition.

goettmann wrote:

Air will only be noticeable during the first two or three strokes; after that, all air should have been purged from the system. There's no such thing as "hidden" air (unless the system is completely empty). According to this, your theory about the air is also not conclusive, because the effect of your statement comes later (which I cannot see or hear in the video)

. At approximately 7 seconds in the video, there are two interruptions, even though the motor had already been running "for a while" before that.
http://www.youtube.com/watch?v=gTcb2zKzsSM
What other explanations are there, besides airflow through the PDE (e.g., air pumped in a loop using a device like Knackfrosch and not completely returned to the return flow in the tandem pump)?

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Hydros not only drain overnight, but can also be pressed empty when starting. This then leads to delayed start problems. However, this is an error that I would actually rule out. Then the engine oil would be a real disaster.

You mean: thin like water? That would at least guarantee ultra-fast lubrication during cold starts .

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In some tests in cold climates, we also had vehicles that exhibited a strangely stubborn starting behavior (both gasoline and diesel engines). Bitte gib mir den deutschen Text, den du übersetzt haben möchtest. So, we also tested it by changing the oil in another vehicle, and sure enough, the error message disappeared. Both oils met the manufacturer's specifications 100%. Therefore, no incorrect oil was used. Nevertheless, these issues occurred. So now, let your imagination run wild and speculate why this might be the case.

Did all the oils have the same viscosity (on paper)?

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For me, your car is definitely in good condition.

...with a bit of asthma during cold starts...but well, it runs great once it's warmed up.

What other explanations are there, besides airflow through the PDE (e.g., air pumped in a loop using a device like Knackfrosch and not completely returned to the return flow in the tandem pump)?


'Because, as he concludes with sharp precision, what cannot be, simply cannot be.'

For you, there are no other causes because you don't want to allow any other causes in your thoughts.
There are thousands of parameters that influence the combustion process in your printer.

What I hear in the 7sec clip sounds like a diesel engine that's misfiring.
I can't say without knowing more specific values. However, you won't be able to obtain these values using a standard diagnostic interface. You need real-time data that hasn't been manipulated or altered through the diagnostic interface.
The smoking is definitely mostly over by this point (allow about 2-3 seconds for the exhaust gases to pass through the muffler).

The 'ignition timing' in a diesel engine is not only influenced by the engine itself, but also by the fuel quality. If the fuel quality is poor, the engine may momentarily misfire. By excluding this possibility (through analysis to ensure compliance with EN590 standards), you can further rule out potential control errors within the EDC system (for whatever reason).
and thousands of other factors. Of course, there could also be air in the system. However, I wouldn't rely on that as the sole explanation .


You mean: thin like water? That would at least guarantee an ultra-fast lubrication during cold starts .


Or exactly the opposite, depending on the design of the components involved.

Do you still believe that the oil recommendations from manufacturers are completely arbitrary decisions made by people at desks? Then my job would certainly be completely unnecessary .
No, these recommendations are very important and should be followed, even if they seem completely nonsensical from the outside.


Did all the oils have the same viscosity (on paper)?


Yes... Not only that. They also met the same specifications (oil standard). At least on paper.

goettmann wrote:

Yes... Not only that. They also met the same specifications (oil standard). At least on paper.

I apologize, but I'm retracting my previous statement about "incorrect motor oil." However, this raises the question of what constitutes the "correct oil."

goettmann wrote:

For you, there are no other causes because you don't want to allow other causes in your thoughts.

It's understandable that people prefer explanations that fit within their own understanding.

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There are thousands of parameters that influence the combustion process in your PD engine.

. . . most of which probably don't change so quickly (with a constant RPM and [zero] load demand!) that sudden, sharp misfires could occur in an otherwise smooth-running engine.

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What I hear at 7 seconds is a diesel engine that's misfiring. I cannot say without further values. However, you will not be able to obtain these values with a standard diagnostic interface. You need real-time data that has not been "manipulated" through the diagnostic interface.

Too bad...

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Of course, there could also be air in the system. However, I wouldn't rely on that explanation alone

See above: the most plausible explanation within one's own understanding...
Anyway, I'm going to install clear tubing sections between the engine and the fuel injection system soon, and then check for air bubbles there after a cold start.

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Do you still believe that the oil recommendations from manufacturers are completely arbitrary decisions made by people at desks? Then my job would certainly be entirely unnecessary.

No, these recommendations are very important and should be followed, even if they seem completely nonsensical from the outside.} Even though this is off-topic:
According to the documents, the engines from ARL (150 hp G4 platform EU3) and BPX (160 hp Ibiza EU3) are completely identical in design. On paper, the BPX has 10 Nm and 10 hp more, and a different turbocharger, which [speculation] may slightly reduce exhaust backpressure in the maximum power range [/speculation].
The ARL engine can use either 505.01 or long-life oil, while the BPX (and the BUK, which is identical to the BPX except for the particulate filter) is specified in the documentation to exclusively use long-life oil, even with fixed service intervals.
As someone who is not an insider, I find it extremely difficult to believe that this comparison is based on objective technical necessities.

It's understandable, after all, that people tend to seek explanations that fit within their own frame of reference.


No!
Otherwise, you're using completely incorrect lines of reasoning.


...of which the vast majority probably won't change that quickly...


In my opinion...


...
(at a constant speed and

You want to hear glitches there.
'I hear an engine running irregularly. And if you listen carefully to the video, you can hear that it's running with a fixed timing advance. This advance causes an immediate counter-regulation. At 7 seconds, the engine even briefly runs faster (pay attention to the ignition timing). Are you trying to explain this with air? If so, it should be slowing down instead.'


Anyway, I'm going to install clear tubing sections between the engine and the fuel injection system soon, and then check for air bubbles there after a cold start.


Do it...
However, even with that, you still can't tell if the air actually reaches the PDE (Pressure Drop Element).
On the way from the DiFi (presumably a specific location), there are plenty of built-in 'air traps.'


According to the documents, the engines from ARL (150 hp G4 platform EU3) and BPX (160 hp Ibiza EU3) are completely identical in design. On paper, the BPX has 10 Nm and 10 hp more, and a different turbocharger, which

If your engines only consist of the block itself, then your observation is correct.
Unfortunately, many components within and around the engine have been changed and are designed to function with motor oil, which means that the oil recommendation is tailored to these specific components. Also, the particulate filters (DPFs) operate using this type of oil.
According to my records, the hydraulic components are also different in both engines, at least for the standard equipment. However, replacement parts are the same. And these components are also lubricated by oil.
And finally, the other turbocharger might also use a completely different type of oil. Or does yours not receive any engine oil?

Ulf, you're not thinking long-term enough.


Okay, I need to finish my time here for the year... I'll be living outside of this place until next year.
Happy holidays... Wishing you a happy New Year.

goettmann wrote:

... So, I have to finish my year here now... I will be living outside of this place until next year. Happy holidays... Have a good start to the new year.

Wishing you peaceful holidays as well, and may you recharge your energy for the next "football game" commented by the DBär .

goettmann wrote:

Quote: According to the documents, the engines from ARL (150 hp G4 platform EU3) and BPX (160 hp Ibiza EU3) are completely identical in design. On paper, the BPX has 10 Nm and 10 hp more, and a different turbocharger, which [speculation] may slightly reduce exhaust back pressure in the maximum power range [/speculation]. The ARL can use either 505.01 or long-life oil, while the BPX (and the BUK, which is identical to the BPX except for the PDE) is, according to the documentation, fixed to using long-life oil even with fixed maintenance intervals. As someone who is not an insider, I find it extremely difficult to believe that this comparison is based on objective technical necessities. If your engines only consist of the block itself, then your observation is correct. Unfortunately, many components inside and around the engine block have been changed, and they are supposed to function with motor oil

. Then this is probably a more recent information status than what I gathered during lengthy meetings on the case a few years ago... I will need to re-examine everything.

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By the way, the PDEs also work in this oil...

. . . which are the same for both ARL and BPX. Therefore, I don't think there is a reason to mandate the use of BPX 506.01.

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And finally, the other turbocharger might also use a completely different type of oil. Or does yours not receive any engine oil?

What it has already achieved for me would probably not have been possible without lubrication...
However, after a cold start until approximately 20°C water temperature, the charger actually provides very little charging power from the bottom end; there's a huge difference between cold and warm conditions, which is very noticeable compared to the ARL charger.
Das wäre wohl mit einem 506.01 / 0W30 Öl besser, aber die freigegebene 507.00 Alternative ist ja auch wieder ein 5W... Öl

Can you briefly explain how 506.01 and 507.00 are better suited for a GT1749VB compared to 505.01?

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Happy holidays... Wishing you a good start to the new year.

Thank you as well (if you check back later).