Ladedruckaufbau AFN träge, Istwert zu niedrig | Posts 48+

When it comes to evaluating the performance of a fuel pump during operation, simply observing its behavior doesn't provide enough information. To determine whether the pump is injecting the correct amount of fuel, it's necessary to assess the fuel quantity at a controlled engine speed and under defined load conditions.

So, the easiest way is to do it at idle, and there are also target values from VW for the fuel injection amount in that situation.

Hello.

"I've been dealing with turbocharger issues for a while now, and I had a similar problem with my own AFN Passat. I even experimented with a diode and directly manipulating the VNT (Variable Nozzle Turbine) to try and get it working. I only reached the target boost pressure around 4000 RPM. The VNT was very free-moving, like butter, and the entire boost system was tight (I even removed the catalytic converter) but I couldn't find anything wrong! Then, I rebuilt a used turbocharger, making sure the VNT was free-moving, and installed it. After that, the car ran like it was brand new!"

Hi,
I'm having trouble resolving the issue with the VTG turbocharger. No matter what measures I take, the turbocharger doesn't seem to respond to the engine control unit's (ECU) request for increased boost pressure.
I have decided to end this project here. The VTG turbo will be scrapped , and I will switch to the water-cooled wastegate turbo from RA/SB. I have one lying around that I haven't been using, and now it will be put to use.
For me, the fact that the VW T3 Syncro has VTG (Variable Turbine Geometry) is a dealbreaker, and I will never want to own one again.
This clearly shows me again that...
What works well in a passenger car doesn't necessarily work in the demanding everyday use of a van, and adding off-road capabilities on top of that doesn't guarantee it will function properly.
High-tech is great and looks good in typical Central European road conditions, but under challenging circumstances, the failure rate increases significantly.
The engine itself (AFN) seems to handle the stress quite well; it has never given me any problems.
I've been driving this [vehicle/model] for 140,000 km in my T3 Syncro.
And those aren't the same kilometers as you'd find in a Golf or a Passat!
My T3 Syncro always consumes at least 10 liters of diesel per 100 km, meaning the load on the engine is approximately 80 to 100% higher than that of a normal passenger car. This makes sense, considering that it has to move four driven wheels with very large tires, two axle drives, a curb weight of 2500 kg, and a vehicle height of 2.8 meters.
While it might not be possible to simply double the mileage rating compared to a car, it's definitely important to give it a higher rating.
Let's see how the detuned 1Z (which the AFN is now becoming) performs.

Regards,
Jens.

"To complement this:"

The AFN is no longer called AFN; it is now called 1Z.

I initially suspected the VTG turbo, but it turns out it wasn't the problem after all.
The described behavior is observed with both the VTG turbocharger and the AFN engine control unit, as well as with the wastegate turbocharger and the 1Z engine control unit.

With the 1Z engine, I can remove the electric valve from the control system because the 1Z control system is only an addition, and the turbocharger is self-stabilizing. It must, at least, maintain the boost pressure defined by the wastegate spring, without any influence from the engine control unit (ECU). In my case, that should be 0.8 bar. The boost pressure behavior is always the same, whether with or without ECU control.

I removed the turbo from a perfectly functioning Golf and installed it in the bus. Based on my current assessment, I would rule out the turbo as the cause of the problem.

Since the Mass Air Flow sensor has also been replaced with a diode (the Exhaust Gas Recirculation system doesn't exist anyway), the Mass Air Flow sensor no longer has any factors that could negatively affect the boost pressure. Therefore, the Mass Air Flow sensor cannot be the cause (especially since the same effect is observed with two completely different Mass Air Flow sensors).

The VAG-COM recording shows the following:

Vollgasversuch im 2. bis 4. Gang.


Vollgasversuch nur im 4. Gang.


the temperatures for that.


Turquoise (blue) line: Target charging pressure.
yellow line: actual boost pressure.

The actual boost pressure always lags behind the target pressure. After a certain point, the boost pressure starts to decrease. As you can see, it doesn't happen abruptly (like it should if there were a sudden leak), but rather relatively slowly.
The amount of fuel being injected is still high, which results in a massive cloud of soot coming out the back.
The absolute pressure values vary depending on the gear; the higher the gear, the higher the boost pressure (and this is reproducible).
If you don't accelerate fully but instead ease off the accelerator in 4th gear, the boost pressure is maintained at approximately 0.75 bar (1750 mbar absolute), even for an extended period. This also doesn't suggest any leaks in the charge air system.

I have also extensively investigated the intercooler system.
Disconnect the hose from the intake manifold and seal the opening with a plug.
Disconnect the hose from the turbo and seal the opening with a plug.
a plug with a tire valve.
Inflated to 1.5 bar using a simple foot pump -> HOLDS AIR!
Above 1.5 bar, the plug always pops out because it doesn't have a lip or flange.
I can leave it at 1.2 bar for minutes without any pressure drop.

Removed the intake manifold and carefully inspected it for cracks, but found nothing.
re-attached with new seals and sealant.

Does anyone have any other ideas?

Regards,
Jens.

Hello Jens,

Have you considered the exhaust system? It probably isn't the original TDI system for the T3. Perhaps it's simply not designed to work properly with the engine.

Malte1408 wrote:

Hello Jens, Have you considered the exhaust system?

It probably isn't the original TDI system for the T3. Perhaps it's simply not designed to be suitable for this application.

Hi Malte,
I hadn't really considered it.
There are two reasons for this:
- Before reaching 100,000 km, it functioned without any issues.
- Since I've already held them in my hand several times, I can confidently say: I have a complete understanding .

The pipes leading to the muffler are all clear; I can see through them.
The muffler itself is clear; I can see through it } (Diesel mufflers have a different operating principle than gasoline mufflers).
Inner diameter of the pipe: continuously 50 mm from the turbocharger.
The length of the pipe leading to the muffler is very short compared to a normal car, namely just a little more than one meter.
Pipe length after the silencer: 10 cm.
Kat: does not exist.

The exhaust pipe is free of corrosion damage because it was custom-built using the appropriate material.

I'm going to drive without an air filter tonight, just for a short while. I'm going to remove a connecting piece from the air filter box. That will also show me if a bird has built a nest somewhere in an inaccessible place or something like that. }

Regards,
Jens.

Jens 16syncro wrote:

I'm going to drive for a short time tonight without an air filter; I'm going to remove a connecting piece from the air filter box. This will also help me determine if a bird has built a nest somewhere in an inaccessible location.

Hi,

Well, what can I say, I found it .
"Eureka" is what an ancient Greek would probably say.

What was it?
It's a bit embarrassing, actually, because this is something I've suspected for a long time, but I just couldn't find it.

The key indicator for me was that the wastegate turbo exhibits the same behavior even without any regulation, and that it doesn't overboost even when the wastegate is completely blocked.
Based on my assessment, there can only be a few possible causes:

- The turbocharger is mechanically faulty (the shaft is seized, and the wastegate is stuck in the open position).
=> That wasn't it; I've held that turbocharger in my hand many times before.

- The turbine is not generating the required power, which means there is insufficient exhaust gas.
=> That wasn't the issue; the fuel injection quantity is consistently high (indicated by soot emissions and the VAG-Tool log). According to the VAG-Tool, the injection timing was okay.
The exhaust pipe was clear; you could see through it everywhere.

- The intake manifold is airtight.
=> that was it

I had already done some test drives and replaced the air filter in the initial phase. The intake path leading to the air filter box was clear.
Yesterday, I finally had enough and removed a hose directly in front of the turbo, allowing the turbo to draw air directly. And sure enough, I got endless boost pressure in every RPM range!
Now, based on the previous finding, I have examined the intake path *before* the air filter housing.
A hose in the D-pillar was damaged at a non-visible location and had partially sucked in a cleaning cloth that was lying there, so the hose was partially blocked. The remaining cross-section was probably too small to allow the required amount of air to pass through at higher speeds.

What does this teach me?
Perform more logical analysis and search more specifically, or conduct appropriate experiments (e.g., disconnect the intake hose directly at the turbocharger).

Now, I'll probably have to make some more adjustments to the engine for the KKK14 turbo, because I'm keeping it. There might be a new thread about that later.

Thank you everyone.

Regards,
Jens.

If the initial pressure is approximately 1 bar, then the example with 2 RPM would represent a very rapid increase in boost pressure, wouldn't it?
http://youtube.com/watch?v=_Mbb8-UwHFI

It hasn't been this fast with the VNT17 in my AFN for a long time.

Best regards.
peter