Boost pressure not maintained + severe overboost

Hello everyone,

Sure, here's the translation:

"Here's a little background:"
I bought a Seat Leon Cupra TDI (engine code: ARL).
Mileage slightly above 250,000 km.

There was a large folder of invoices included, but the only issue is that the engine is misfiring.

The cause was quickly identified: the camshaft was missing the lobes for the first cylinder. The cylinders, including the hydraulic ones, were extremely worn, and one of them even had a "hole in the head."

After that, the car ran great again.

Shortly after, a control arm on the rear axle broke.
According to one of the invoices, it was replaced less than 9,000 km / 11 months ago.
The cause of the breakage has been found (the metal bearings were stuck) and fixed. All bearings have been replaced with rubber bearings, a new control arm has been installed, and the job is complete.

Then, there's "rattling" when taking right-hand turns with approximately 45 degrees of steering angle and a slight acceleration; it's quiet when in acceleration.
Following that, I replaced the engine mounts and transmission mounts, but the same problem persisted.
In addition, "surging" or "jolting" when there is a sudden change in gas flow, either a decrease or an increase.
Torque strut replaced -> error still present.

Another issue: A squeaking noise occurs depending on the load when engaging the clutch.
Here as well, an invoice confirmed that the gearbox was refurbished, and a clutch kit from LUK was installed at the same time - the invoice was for well over 1500 euros.

After a long period of deliberation, the gearbox finally came out.
I had Hanno (from Northern Hesse) inspect the transmission. After 3 weeks, Hanno said, "Everything is fine, and I can confirm that the transmission has already been disassembled."

During this process, the clutch was replaced with a Sachs ZF Performance clutch, including... ZMS and clutch release bearing replaced.

That's the background story...

In the invoices, I also found a record of the turbocharger being replaced. The invoice for just the turbocharger itself is just over €900.

Upon my inquiry as to whether the loader was refurbished or new, the response was, "It's new; they simply cannot be refurbished."
I was hoping to hear that statement, as I personally have had bad experiences twice with reconditioned chargers – being cheap can backfire.


I'm now experiencing a problem where the turbocharger is exhibiting excessive surging and is unable to maintain boost pressure above approximately 3500 RPM.


I have attached 2 log files and I'm asking: in which direction should I look?

My hypothesis: if I had leaks in the intake manifold pressure system, wouldn't the air mass be significantly higher?

The logs include one driving session from my Cupra and one from a friend's front-wheel-drive ARL, both of which are chipped, and the engine maps are completely identical except for the torque limiter.

As you can see, the turbocharger provides excellent control and also matches the N75 characteristic curve.

Mine, on the other hand, is even trying to close the VTG (Variable Transmission Gear) to increase the pressure, but it's not working.

LG
André.

"Update: Both Leons have had the AGR (Abgasrückführung) deactivated. The soot level is now regulated based on boost pressure in both cars, not on air mass."

Hi,

The log for "Meine" is messed up. Please don't use the CSVConv for this, as it produces garbage in some cases and is, frankly, pointless. Does the original log also indicate a jump from 44 seconds to 78 seconds?

Open the original log file with KDataScope - as a customer, you have access to that - and then you won't need to "convert" anything or similar.

If you only look at the last part of "Meiner," you'll notice that the target pressure reading is stuck at 2601 mbar. It's possible that this is how it's programmed, or it's possible that something else is programmed and that the conversion factors for the diagnostic values in the engine control unit were missed: In that case, you would only see the maximum value that can be displayed with the corresponding factor.
-> Check which boost pressure curve is desired here (values).

Assuming the target value for the boost pressure is indeed 2601 mbar, the overshoots could be caused by the following:
- Incorrect programming of the smoke limitation (other characteristic curves are used because the torque limitation is implemented differently).
- Incorrect VTG (Variable Turbine Geometry) pre-tax characteristic curve (other characteristic areas are used because the torque limitation is different).
- electrical problems with the turbocharger pressure sensor and its wiring.
- Is there a jump in the log, is the diagnostic connection stable, and is the engine control unit not rebooting occasionally?
- The usual suspects when it comes to boost pressure regulator differences: sticking variable turbine geometry (VTG) (turbocharger overheated or carbonized due to improper tuning), stuck magnetic valve for boost pressure regulation, faulty vacuum system venting...

Overall, I believe it's best to have the tuning file with the respective tuner, because only they can see what has been programmed, as the diagnostic values in the file may not be informative, and only they can know whether the displayed values are actually programmed that way or not.

Best regards, Rainer.

Hey Rainer,

Thank you for the feedback.

The values are actually programmed as shown in the log. The jump occurs because I paused the recording after the acceleration, rotated the device, and then restarted the recording.

I will flash the original dump and log it again.

"Also, tomorrow I will be replacing the charge air hoses along with the O-rings. I noticed that on one of the hoses, the edges appear to have been reshaped using a chisel."

I will use KDataScope for this and will no longer convert the logs in the future.

Kind regards,
André.