Boost Pressure Curve

I'd like to get your opinion on the following measured mass airflow (LMM) and boost pressure values. The boost pressure drops significantly after a brief overboost (at 2000 rpm) to approximately 1750 mbar. The measured mass airflow follows a similar pattern (high, then a drop). Here are the measured values:
(approx. 90,000 km)

gemessen im 3. Gang.

Boost pressure:

Zeit Drehz. Should
Is

301.04 1386 1010 1040
301.86 1449 1183 1112
302.68 1617 1795 1418
303.52 1890 1928 1928
304.34 2142 1948 2213
305.1 2373 1948 1846
305.98 2646 1948 1734
306.8 2898 1948 1836
307.62 3150 1948 1928
308.38 3339 1948 1979
309.14 3549 1948 1969
309.9 3759 1948 1969
310.64 3927 1948 1958
311.4 4116 1928 1948
312.14 4263 1907 1938
312.92 4431 1836 1856


LMM:

Zeit Drehz. Should
Is

301.47 1407 575 550
302.29 1512 850 705
303.11 1764 850 960
303.89 1995 850 1125
304.71 2268 850 1150
305.53 2520 850 875
306.41 2772 850 915
307.19 3024 850 940
307.99 3255 850 960
308.75 3465 850 940
309.51 3654 850 930
310.25 3843 850 910
311.01 4032 850 885
311.77 4200 850 855
312.53 4347 850 805

Hello denis79!

Please take a look at my post from today (regarding the air-fuel ratio and the wastegate control valve).

I find your specifications excellent compared to mine. However, I have an AGR engine, while you have an AFN engine. Does the AFN engine have 81 kW or 66 kW? Is your engine chipped or stock?

"My LMM (mass airflow) readings are nowhere near your measurements. For me, the maximum value is around 920 mg/H at low 2000 RPM, then the value steadily decreases to about 800 mg/H at 3000 1/min, and then drops significantly. Above 4000 RPM, my value is already below 700 mg/H."

"However, I also find the pronounced boost pressure oscillation between 2000 and 2900 RPM to be strange. Normally, the control system should ensure that the boost pressure approaches a steady state asymptotically after a brief overshoot (the best compromise between control dynamics and damping). In your case, the control system seems to be only marginally stable, which usually indicates an excessively high gain factor in the control loop. Since the characteristic curves usually don't change (unless there's chip tuning or a power box), there must be a disturbance in your control loop that is causing this poorly damped control behavior."
The adjustment mechanism (VTG or wastegate) may be stiff or difficult to move. This means the controller has to generate larger setpoint jumps when controlling the solenoid valve in order to overcome the increased friction. When the adjustment mechanism breaks free from friction, it overshoots the desired point (a so-called "stick-slip" effect). The controller then has to counteract this and release the mechanism from friction again at the reversal point.
I think this might explain how your fluctuating boost pressure is occurring.

Regards,
Alex.

Hello.

The values seem good to me, except for the 0.7 bar at 2600.
I agree with Doalexo. It's likely that the VTG is slightly light and oscillates past the target point. That's probably why we're seeing those fluctuations. Otherwise, it looks good.

Please check the search function for 'VTG adjustment cleaning.'
How to do that has been explained many times before.
That's the most likely possibility.

Best regards, Golfmann.

Problem still not resolved .


I've noticed a slight hissing sound, especially at around 2200 rpm (full throttle).
This hissing sound doesn't get louder even at higher speeds.

'I can't find any leaks in the boost pressure system, but my boost pressure control valve is making quite a loud noise (ticking).'
I think this ticking sound from the wastegate valve turns into the whistling sound mentioned above when you're at full throttle.

The duty cycle of the boost pressure control valve does not exceed 70%, even at full throttle .
Is that normal ?

I installed a new boost control valve, but the problem is still not fixed .


I checked my VTG using a syringe, and I noticed that it is difficult to move and makes a squeaking noise .

Now my question: Can someone explain to me how to make these (step-by-step)?

Try searching! Enter 'VTG' and 'smooth-running' and search within the 'technical articles.'

Then you will get exactly two results, one of which will answer your question 100%.

Regards,
Private.

I noticed today that the car pulls almost as well when it's cold as it does when it's warm .

The exhaust smells a bit more than with other TDI (injection nozzles) .

The car has 111,000 kilometers on the odometer.

Hello,

Okay, I generally have the same symptoms. However, I have a 1Z engine.

I can't measure boost pressure or mass airflow.

I've already replaced the pressure control valve, but it's still rattling. And does it even have a VTG (Variable Turbine Geometry) system?

Despite this, it sometimes doesn't work correctly (e.g., it might display 'sdi' instead of 'TDI'). It also occasionally displays the error message 'boost pressure difference implausible.'

Greetings.

@ Road

How do you know about the error, but can't log it?

I would proceed as follows:
- delete all errors.
- drive around until I feel that "SDI" sensation again (possibly logging data in the process).
- Read the error codes as quickly as possible after the fault occurs.

If he has a "rule difference" with you, a hose and I will be there.
Most likely one of the colorful, thin wires (and it's important to check it all the way to the control unit, so *inside* the water tank).

m;

(Oops, you have a Passat - the valve is located above the brake booster in that model).
http://people.freenet.de/golf-schrauber/Magnetventil.jpg

I replaced this hose that connects to the engine control unit because it was completely rotten.
http://people.freenet.de/golf-schrauber/LDAnschluss.jpg

Hello,

Okay, I know what the problem is because I've already taken it to the workshop four times to have it diagnosed.

'The first thing I did when I bought it, just to be safe, was check the storage. It was completely full of all sorts of things. Even though the car had a complete service history from a dealership.'

(I'll just say that I recently had to replace the needle lifter, the dome supports, and an ABS sensor. What exactly did this workshop do besides write invoices? Well, never mind, it's a familiar story.)

Okay, then after another month, we'll check again to find any remaining errors.

Then there was still some speed signal remaining, and a pressure difference.

Then I replaced the items I described above (the fuel injector due to misfires on the highway).

'It's still showing the same errors, and it's not running properly. Plus, the battery gave out, so I replaced it, along with the glow plugs.'

I just replaced the solenoid valve.

But no changes to the errors.

What happens if you remove the battery? Does it go into a kind of emergency mode or something?

Okay, I'm going to check the pipes again, even though I didn't notice anything unusual when I replaced the valve.

Greetings.

Yesterday, I re-coded my control unit from 00002 to 00001 in measurement block 7.
I made this change because my engine was having trouble starting when it was warm.


The effects are that the car pulls noticeably better, especially above 2000 rpm .
DZR improved from 6.3 to 5.8 .

The subjective warm-start behavior has not improved .

What exactly did I change by recoding, and is it chronically harmful to the engine ?

After installing the LDA, I noticed the following: even when I only apply 50% throttle, the boost pressure is reduced from 0.7 to 0.5 after approximately 1 second.


Is that a sign of a jammed VTG ?

Hello Dennis,

Isn't that normal? The target boost pressure is adjusted based on the load.
You should also be able to see this in measurement block 11. The important thing is that the actual value matches the LDA value in the VAG-COM system.


What happened to your recoding? Did your friend inquire about it? Was the measurement block correct?


Greetings, Rainer.

What happened to your recoding? Did your friend already ask about it? Was the measurement block correct?

'Measurement block' is not correct; it should be 'Function 7' or the 'Coding' menu option in VAG-Com. I would also like to test this, but I have a chip installed and I'm not sure if I should do it. The following questions arise:

- What exactly is being changed when switching from a manual switch to an automatic setting?
- Will the tuning software be deactivated, or will it remain active?

Dennis has impressively demonstrated that it provides a performance benefit (improving lap times by 0.5 seconds).

I have now installed a VNT 17 turbocharger, and I have noticed the following: there are no more overboosts, but the boost pressure drops to 0.8 bar at full load after it has been holding at the target level for about 2 seconds, and then it slowly increases again.

What exactly is wrong with my boost system ?
I really don't know what to do anymore.

Is anyone in the 06295 Eisleben area willing to help me increase my charging pressure using a resistor?
(AFN)