FehlerCode Saugrohrdruck - Regeldifferenz ? Was nun? | Posts 16+

Here is Carsten's log:

http://www.luxus-wg.de/~martin/auto_bilder/log_mit_unterdruck.jpg

Regarding the topic of vacuum pressure, let's talk about boost pressure.

If someone says that negative pressure REDUCES boost pressure, they are wrong.

Imagine the vacuum hose has a hole; then the turbo will immediately start boosting at full pressure.

If the hose bursts at 4000 RPM, your turbo will fail faster than the EDC can cut off the gas!

Furthermore, everyone else says that he's using a vacuum pressure system to achieve boost pressure.

The mechanism operates in such a way that an "increasing vacuum" (a decrease in absolute control pressure) results in an increase in charge air pressure. Therefore, this system is fail-safe; if a hose breaks, the turbocharger will still provide a minimum level of charge air pressure.

here:
http://www.technologie-entwicklung.de/Gasturbines/VNT15-Turbo/vnt15-turbo.html

Hi,

In addition to Martin's post:

If excessive boost pressure is being generated at higher engine speeds despite the vacuum hose being disconnected from the turbocharger, the problem clearly lies within the variable turbine geometry (VTG) mechanism, which should ideally be in the "zero boost" position without vacuum.
This condition corresponds to the EDC system's "minimum boost pressure" fail-safe setting. This explains why the emergency mode is always activated, both with and without the vacuum hose connected to the turbocharger.

In practice, although boost pressure is usually not used, a slight amount of intake manifold pressure is often generated when the engine is run at full throttle and reaches an RPM range of 4000 - but in this case, the pressure must never exceed the target value .

If so, the possible causes could be:
1) Membrane dose clogged due to internal defect (partially) -> Replace the dose.
2) Movement of the steering vanes in the loader is partially blocked due to Russian sediment buildup -> clear the blockage.
3) The diverter mechanism is jammed due to overheating (excessive tuning) -> save up for a new charger.
4) VTG rod set too short -> extend in increments of half turns.

It's actually a relatively straightforward story about error reduction. I'll incorporate it into the section for technical articles...

Here is the second one.

http://www.luxus-wg.de/~martin/auto_bilder/log_mit_unterdruck.jpg
http://www.luxus-wg.de/~martin/auto_bilder/log_ohne_unterdruck.jpg

More data:

Attached are the corresponding logs.

There are several images associated with the tags "*ohneturbo1" and "*mitturbo1".

"otoarg" simply means without the turbo hose and without the ARG hose.
"almmoturbo" means with an old mass airflow sensor and without the turbocharger hose.

http://www.luxus-wg.de/~martin/auto_bilder/csv.zip

"@martin: The last link doesn't seem to be working?"


Okay, I just checked again. When the vacuum sensor activates, it seems like the turbocharger is taking on load; the faint whining sound gets louder, and the engine speed drops slightly. So, it's true that the turbocharger remains in its minimum position without vacuum.

Okay, so something must be wrong with the charger, because as you can see from the log message "without turb1", the pressure is still quite good. Unless someone knows that this is normal when running without a hose...
Or perhaps a slightly leaky expansion joint in the exhaust manifold isn't generating enough back pressure. But I've been told repeatedly that it doesn't matter at all. (Well, VW does state in the manual that the exhaust pipe shouldn't have any leaks for the correct turbocharger boost pressure setting?)

"But why use a loader if the lever, when disengaged, moves the normal distance of about 12 mm, and that distance is also within the limits allowed by the can? There's actually nothing wrong with that."

Do I need to remove the charger now because it's apparently charging too well?
In any case, none of the four logical points made by Ulf seem to apply here.
Does anyone else besides Dieter remember what the effect is in a functioning system when the hose is disconnected? It seems to me that this is the criterion for determining if it's loose .

I can already see the value of a charger being debited from my account.
Where can you buy something like that cheaply, if not from Volkswagen?

Regards,
Carsten.

The link is working now - you should also type in the password .

It would be fantastic if a driver with an Audi A4/A5/Q5 (AFN engine) and a working system could share a log file (including Group 11 data, and possibly mass airflow sensor values), while having the turbocharger hose disconnected!

Regards,
Carsten.

carstenAFN wrote:

It would be fantastic if a driver of an Audi,フォルクスワーゲン,またはSkoda vehicle with a functioning system could provide a log file (Group 11 and possibly also mass airflow sensor values) while the turbocharger hose is disconnected.

Hi Carsten,

I didn't have time to use VAGCOM right now.

I once drove a round with the VTG hose disconnected -> full throttle in 3rd gear from 1500 to about 4200 rpm. (I don't think the air mass values are relevant here; boost pressure is, in my opinion, the main thing.)

Result: At approximately 2500 rpm, the pressure is about 0.4 bar, increasing further to around 0.8 - 0.9 bar at 4000 rpm. Naturally, the engine only started producing significant power well above 3000 rpm.

Then, the engine control unit even kindly switched into emergency mode. It still managed to reach approximately 0.2 bar of boost pressure at 4000 rpm *yawn... snore*.
By the way, all of this happened without a single blink signal from the light bulb .

Finally, I briefly turned off the engine and reattached the hose -> wow, what a suit!

Editor's note .

Ulf has a mechanical boost pressure gauge in the cockpit, which is why the values are not from VAGCOM.

Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

Great, thanks for your effort.

Result: at approximately 2500 rpm, the pressure is about 0.4 bar, and it continues to increase to around 0.8 - 0.9 bar at 400 rpm.
Normally, the engine wouldn't produce its full power until well above 3000 rpm.

Am I understanding this correctly: Does a reading of 0.4 bar on your gauge correspond to 1400 mbar when using VAGCOM (assuming an air pressure of 1000 mbar)?

Well, at 3000 RPM, it performed quite well, which also corresponds to my experience. It starts to come alive around 2000 RPM, and later on, it's not so bad after all.

You're probably thinking that the emergency stop is now being triggered due to pressure values that are too low...
I'm starting to get unsure about what criteria the engine control unit (ECU) uses, or in which map it performs its comparisons.

I just can't figure out where the problem is with the charger...

Regards,
Carsten.

Okay, here's some news...

I once wondered what could cause excessively high pressure in the charging system of a (presumably) functioning charger when the hose is disconnected.

1. The control unit is measuring incorrectly.
2. EGR valve open (the exhaust pressure is normally higher than the boost pressure; otherwise, the exhaust gas recirculation system cannot function).
A little bit of everything.

Hopefully, I'll be able to borrow a pressure gauge soon.

"I quickly sealed the EGR bridge pipe with a piece of metal, and lo and behold, when the hose is disconnected, there's hardly any pressure anymore, and you can clearly see in the log how vacuum develops when you accelerate. And the engine noise seemed quieter. Or is it normal for some pressure to always leak through even with a functioning EGR system?"

However, even with the turbo hose attached, the pressure during idle is still significantly above the target value, so it seems there might be more to investigate. (I haven't done a test drive yet). In any case, the turbocharger appears to be okay.

Initially, the error code stored today was 0519, indicating a short circuit to positive voltage for the intake manifold pressure sensor (G71).
"However, it hasn't reappeared, and I read that this can also occur in conjunction with VAGCOM? (Control unit number: 028 906 021 CK)"
Otherwise, it would smell like a faulty control unit (STG), right? That part is located inside the STG, so there couldn't be any bad wiring... Is it possible to replace individual components?

Is it possible to remove the AGR valve from the intake manifold and replace it, even though Volkswagen doesn't recommend doing so for the AFN engine?

My engine seems to be a case of many small problems accumulating. It's worth noting that it came from a car involved in an accident where the driver had to be extracted, but it only has 94,000 km (approximately 58,000 miles).

Regards,
Carsten.

carstenAFN wrote:

I quickly sealed the EGR bridge pipe with a piece of metal, and lo and behold, when the hose is disconnected, there's hardly any pressure anymore, and you can clearly see in the log how vacuum is created when you press the accelerator. But with the turbo hose attached, the pressure during idle is still significantly above the target value, so it seems like there's still something to be checked. (I haven't done a test drive yet). In any case, the turbocharger seems to be okay.

Hi Carsten,

The AGR story seems to me to be a new, potentially causative aspect -> good instinct on your part .
I consider the fact that the loader runs above the target value when experiencing gas surges while stationary to be (by itself) not critical.
In any case, a proper logging run should still be performed, both with and without the loader control hose attached .

Quote:

Otherwise, it would smell like a faulty control unit (ECU), right? The part is located inside the ECU, so you can't have any bad wiring...Can individual components be replaced there?

I wouldn't assume a faulty STG (Steuergerät) just yet.
The internal pressure sensor should, in my opinion, be easily replaceable (3 wire solder joints and some kind of mechanical fixing on the circuit board) - if you can find a suitable replacement part -> the Bosch number is printed on the plastic housing of the sensor.

Quote:

Is it possible to remove the EGR valve from the intake manifold on an AFN engine, even though VW doesn't recommend it, and replace it?

I'm afraid not likely. In any case, I would first try loosening it (with persistent effort).

'Hello, please check the air mass readings at idle and then apply vacuum to the VTG (Variable Turbine Geometry) control unit. If everything is okay, the air mass should increase slightly at idle. If the readings remain the same, even though the linkage is free, it means that the guide vanes are stuck in an aggressive position (possibly due to a defect in the swivel shaft or the connection to the guide vanes).'
To be absolutely sure, disconnect the charger and take a closer look at it.

Hello,
Okay, first of all, thank you everyone for your strong interest in this issue!

Unfortunately, I didn't get a pressure gauge today, but I did manage to test drive the vehicle and review the manual.
Now it reaches 140 km/h for the first time (without the attached charger hose!!!), but then it still goes into emergency mode. And it's not reproducible; on the second attempt, it stopped again at 120 km/h, but with a suspiciously high amount of boost. Maybe the turbocharger impellers are doing whatever they want... Without the charger hose, the boost pressure is beautifully linked to the engine speed in the log .
With the loader, everything depends on how much you press the accelerator, but it tends to go into limp mode sooner.

It's incredibly frustrating. A log under the same conditions cannot necessarily be reproduced... However, the readings from the control unit are actually plausible, so I will unscrew the loader tomorrow and take a look. It's always annoying the first time because you have nothing to compare it to.

I was just reading about the relationship between the AGR (Abgasrückführung - Exhaust Gas Recirculation) and LMM (Luftmassenmesser - Mass Air Flow sensor), and I'll try testing that. The LMM values are always significantly higher than they should be. And it's the only part where I extended the original wiring harness, maybe there's a problem somewhere in that connection...

"If the loader isn't displaying anything, I guess I'll have to find a way to get a testing device. Adapting it to WFS seems straightforward..."

It's also annoying that I can't determine the reason for the emergency stop from the logs; either the sampling rate isn't fast enough, or perhaps an unacceptable pressure difference is dependent on another parameter (a characteristic curve).

Sure, here's the translation:

"See you."
Carsten.

Hello everyone,
Okay, the cause of the discrepancy in the settings has been identified and resolved, so dance and be happy...

The turbocharger was assembled incorrectly, unbelievable, right???

What delights the tuner is a lesson for those who believe they should get good work for their money: You can assemble the VTG turbocharger in a normal way, or you can adjust the guide vanes slightly more. All you need to do is rotate the adjustment ring, as the adjustment notch is positioned asymmetrically.

I created a PDF with an image and emailed it to Martin; he's probably very kind and will definitely post it .

"Now there's no more blue smoke when accelerating with a cold engine, the pressure readings are stable and differ by less than 20 mbar, and there's no more limp mode – that's great!"
The old mass airflow sensor shows slightly too much at lower RPMs and significantly too little at higher RPMs, but I still have the new one to test .

The downside: The top speed is now noticeably lower than before (before the emergency mode came on). But my T3 transmission will probably thank me for it . However, I need to rethink that long gear ratio I was aiming for...

"As a test, I removed the turbo hose again, and it's as Ulf said: there's normal boost only above 3000 RPM, but then it quickly goes into limp mode. However, I can't confirm what Dieter once wrote about it being limited to only 40 (presumably referring to a pressure reading)."

Okay, so once again, a heartfelt thank you to everyone who contributed their ideas. Now, I will send an email to the turbo mechanic! If I can secure some compensation, say in the value of a small spare part (after all, it took 1 week of searching and half a tank of fuel for test drives ), I will pass on that amount accordingly!

Best regards,

Carsten.