Chiptuning AVF: Performance Issues & Solutions

Hello there!

I'm actually more of an avid reader in this forum than someone who can offer much advice.
But this time, I need your expert opinion. I'm really stuck and don't want to be led around by someone who might not have my best interests at heart. While I have some knowledge about cars myself, as I used to be a car mechanic, I haven't had much experience with TDI engines because I haven't been able to practice my profession for some time now due to being paralyzed from the waist down after an accident.
Therefore, I am also hoping for your help.
My problem is that I can do everything with VAG-COM, but unfortunately, due to my paralysis, I can't physically inspect or test anything mechanically.
Let me just explain my problem.

Okay, let's start with the starting issue. When I start the car in the morning, it cranks a bit harder when the temperature is around 15°C or higher. And regardless of the temperature, the exhaust fumes smell very strong for the first few moments; they really sting your nose.
The next thing is that I feel like the car isn't performing at its full potential, and it sometimes feels sluggish. Also, when accelerating or driving at higher speeds in the higher RPM range, the car occasionally emits smoke, but not always.
Meanwhile, I have the feeling that the consumption is quite high, or has increased somewhat.
By the way, the AGR valve makes a squeaking noise shortly after starting, especially at higher engine speeds. However, it is not responsible for the smoking; I have already disconnected it.

Regarding the vehicle:
Passat Variant TDI Highline.
Year of manufacture: 01/2003; Mileage: 141,000 km.
96 kW, 310 Nm.
Tiptronic EYF
Chip tuning to 121 kW and 380 Nm.

I'm attaching some logs and I hope you can provide me with some insights about them.

Sure, no problem. Here's the translation:

"Thank you in advance."

Regards,
Tobias.

Title edited by moderator (ulf).

I've made some additions and sometimes included a diagram showing the boost pressure.

Please take a look and let me know if you notice anything unusual.

A thousand thanks.

Regards,

Tobi.

Okay, I can tell you what I've noticed, but unfortunately, I don't know if it has anything to do with your chip tuning.

Your boost pressure is too low (below the target value). That's why the soot reduction system is active up to approximately 2400 rpm (and the mass airflow sensor is also automatically set low). I suspect a stuck variable geometry turbocharger (VTG) or a clogged catalytic converter.

Hopefully, someone can confirm (or contradict) my assumptions.

I had also suspected a jammed VTG (Variable Transmission Gear), but I wasn't sure if the control rod was moving properly within the measurement block 11 for basic adjustment.
Have you ever had to deal with a cat constipation issue?

Thank you for your help!

Best regards, Tobi.

The tuning is quite impressive, especially the fuel injection amounts, which are already quite high.
Otherwise, I don't see any errors. The air mass readings look very good, and the boost pressure is also fine. There seems to be a slight lack of power at lower RPMs, but that could also be due to the tuning. The magnetic valve isn't engaging the turbo as aggressively as it could to accelerate boost build-up, which it should. I think the relevant maps need to be adjusted again.
In the higher engine speed range, the boost pressure decreases slightly, and it's particularly noticeable that the target value also drops. Ulf once suspected that this might be due to excessively high intake air temperatures, causing the engine control unit (ECU) to reduce the boost pressure to avoid thermal problems and prevent the turbocharger's rotational speed from increasing further.
I think this might be the case for you, especially due to any tuning modifications. To check this with VAG Com, you should create a log of measuring blocks 03/07/10; this will show whether it's related to excessively high load limit torque (LLT).
In my opinion, the cat should be ruled out as a cause for your problem, and I would also exclude a sagging VTG (Variable Transmission Gear) at this point.

Zak1976 wrote:

In the upper speed range, the boost pressure decreases slightly, and it's particularly noticeable that the target value also decreases. Ulf once suspected that this could be due to excessively high intake air temperatures, and that the engine control unit (ECU) therefore reduces the boost pressure to avoid thermal problems and to prevent the turbocharger's speed from increasing further.

Hi,

That's how it is with serial software.
However, it seems that tuning can shift the protective functions (possibly unintentionally).
Furthermore, it's unknown what the tuner programmed into the load control system (LD-KF): perhaps, considering the loader, the desired load (LD-Soll) was already reduced from the top end, without triggering the overspeed protection (LLT).

If it's possibly due to the low-temperature coolant temperature, do you know at what temperature the control system intervenes? Is this the same for all TDI engines, or are there differences depending on the engine management system (MBK)? I've seen several logs where the low-temperature coolant temperature reaches 100°C or more (mostly in the 130PS TDI), without the target boost pressure being reduced, which I find quite significant.

The LLT is probably very popular. If the LLKs (presumably referring to some kind of equipment or components) aren't dirty, I can't explain the change in consumption and performance. Then it must have always been like that.

Looking at the logs, I see that the soot limiter is active up to approximately 2500 rpm. If it wasn't like this before, that would explain the change in performance and fuel consumption. However, if it has always been this way, did the tuner overshoot their target?

The boost pressure is adjusting nicely (although it's a bit low, but without overshooting), which suggests a relatively free-running variable turbo geometry (VTG), but does it cover the entire control range? Perhaps there isn't enough vacuum? However, it probably isn't the N75 valve...

Could the exhaust and knocking sounds be caused by compression issues or misaligned valve timing, rather than something else affecting the entire system?

This morning, I checked the temperatures in measurement block 007 for consistency. All values are within acceptable limits, with a maximum deviation of 1.9°C.

What I also noticed during a troubleshooting diagnosis is that the relay for the fuel cooler pump, J445, is not responding.

And also, I have some errors in the error memory that have just appeared. I'm attaching the log again.

You can probably ignore the climate control, navigation system, radio, and memory seat for now. The radio and the air conditioning vents have been working fine for a long time, but the air conditioning has started failing in the last few days. I think the new message mentions a pressure switch as the cause. As for the navigation system, I have no idea what's wrong with it, but it seems to be working! However, there's an error related to the memory seat because I disconnected the connector since it wasn't accepting any new settings. I need to check later if that fixed anything.

I'll also do another LOG run with measurement blocks 003-007-010 later. The tank is almost empty now! Should I do one run with the tank nearly empty and one with it full, or what do you think?

Regarding the turbocharger boost and its lag, it seems to be quite pronounced. The car also exhibits a noticeable lack of power when starting from a standstill, which was already present in the original version. I've already had a new control unit installed. It was previously a 038 906 019 GQ and has been replaced with a 038 997 019 A. According to VW, there is a list specifying which control unit numbers can be exchanged for others or must be replaced in cases of starting problems. However, it hasn't really made much difference.

As you can see, I've already had quite a few experiences with my beautiful Passat.
And by the way, thank you in advance for all your efforts and help.

Best regards, Tobi.

Here's an old log file containing the measurement data blocks 003-008-011, without the chip but with the replaced control unit already installed.

The regulation isn't as precise as it is now (regarding overswing and underswing), but the target pressure is reached much faster.

Here's the error log again. I forgot to attach it earlier.

The "last signal" error on my device was caused by a disconnected mass airflow sensor (MAF).

Zak1976 wrote:

if it is indeed due to a potentially too high coolant temperature, do you know at what temperature the control system intervenes, and is this the same for all TDI engines, or are there differences regarding the engine management systems (MBK),

I've only had a basic understanding of the software's Low-Level Trigger (LLT) protection features so far (specifically, quantity reduction), and there are already differences in the KF (presumably referring to some parameter or setting) between the performance levels (the higher the performance level, the sooner the protection function activates).
I haven't seen any corresponding parts for engines up to 115 horsepower yet, but I haven't specifically looked for them either.

Quote:

I've seen several logs here where the coolant temperature reaches 100°C or more (mostly on the 130hp TDI), without the target boost pressure being reduced, which I find quite a lot.

Oh, I must have missed those – please post the links!

I have the feeling my car is falling apart. Just now, the external display in the dashboard that shows the radio and navigation has also stopped working. Now all I have left is the onboard computer.
I logged the temperatures earlier, and even under full load for an extended period, the intake air temperature remained at around 55°C. However, despite the cooling system being activated, the fuel temperature continued to rise until it reached approximately 90°C, and I'm sure it could have gone even higher. I will refine the logs and post them later.

Hello!
The idle speed control on cylinder 1 isn't very impressive.
Here's the translation:

"Another question: Did you turn off all appliances during the test, especially the air conditioning? Volkswagen requires this, and you might be surprised how much the readings change! Also, was the engine at operating temperature?"