Search for values for full load boost pressure at 1200 - 1800 RPM

While on vacation, I again noticed the relatively weak acceleration of the AXR engine at low RPM (particularly noticeable in 5th gear) up to approximately 1800 RPM. I then logged the boost pressure values. Slightly uphill in 5th gear, under full load, starting from around 1200 RPM. According to VAG-COM, the actual value (2nd column) is always below the target value (3rd column) up to 1800 RPM. Above that, it always matches the target value. Could it be related to the VTG (Variable Turbine Geometry), or can someone else verify or confirm these values on their AXR engine? If the values are 'out of range,' I would be in a fortunate position to still have VAG warranty, as I only purchased the car from the dealership two months ago. That's also one of the reasons why I don't want to work on it myself. Unfortunately, the charger is quite difficult to access.
The error memory is empty. The maximum speed is also easily achieved. Current mileage: 95,000 km.

u/min Target pressure (mbar) Actual pressure (mbar) % Actuation of load control valve
1155 1560.6 1132.2 23.1
1176 1570.8 1132.2 23.1
1218 1581.0 1132.2 19.9
1260 1591.2 1132.2 19.9
1281 1611.6 1132.2 19.9
1323 1632.0 1132.2 19.9
1344 1642.2 1142.4 19.9
1365 1662.6 1162.8 19.9
1407 1693.2 1162.8 19.9
1428 1693.2 1173.0 19.9
1449 1723.8 1193.4 19.9
1491 1744.2 1203.6 19.9
1512 1764.6 1224.0 19.9
1554 1774.8 1244.4 19.9
1575 1795.2 1264.8 19.9
1617 1815.6 1305.6 19.9
1638 1836.0 1366.8 23.1
1680 1856.4 1428.0 30.7
1722 1876.8 1509.6 25.1
1764 1897.2 1642.2 34.7
1827 1917.6 1734.0 37.9
1890 1938.0 1805.4 37.1
1932 1948.2 1866.6 37.9

Hi Hati,

I might be able to provide you with comparative data sometime during the week.
Currently, I'm working on another project that requires a lot of time, which makes it impossible for me to work on the computer at home. Unfortunately, I also can't say where my laptop is buried...

Thank you, Bertil.

While I believe that the long drive of approximately 900 km back from vacation, driven at full speed, may have already improved the issue, my subjective impression might be misleading. Comparison values would definitely be the best option in that case.

Thank you in advance.

Hati wrote:

According to VAG-COM, the actual value (2nd column) is always below the target value (3rd column) up to 1800 RPM. Furthermore, it is always equal to the target value above that. "Does this relate to the VTG (vertical travel gauge), or can someone verify or confirm these values on their own AXR (machine)?" u/min Target pressure (mbar) Actual pressure (mbar) % Actuation of load control valve 1512 1764.6 1224.0 19.9 1554 1774.8 1244.4 19.9 1575 1795.2 1264.8 19.9 1617 1815.6 1305.6 19.9

While I don't drive an AXR, even my ASZ engine reaches the target value significantly faster than yours, despite the claim that the 74kW engines have better low-end performance.

It's unacceptable to me that the pressure is still 0.5 bar below the target value at 1500 rpm.
-> IMO, there's definitely something wrong with your charging system, for example. VTG is stuck in the upward position, or the limit switch is misaligned, or there are pneumatic problems.

First, I would check if the VTG adjustment moves the usual amount during engine start.

Thank you, Ulf.

I'll wait to see the values from Bertil (assuming he's found his notebook and a little bit of time ).

Do the 'friendly' technicians also have a similar tester (perhaps integrated into the 1551/1152 system) to compare the target values with the actual values? Or are they reliant on a working popmeter? I can't just drive to the 'friendly' technician and claim that the VTG is stuck. And whether they would believe in the values that were logged.

Hi Hati,

Yes, the VW employees can also take a look at the values.

But try to prevent them from logging your air mass values, because then they will see your faulty EGR valve and use that as an excuse for everything.

You should be able to see the VTG container, so check it first. You can also drive in a basic mode in Block 011, which will cause it to be repeatedly accessed.

Alternatively, you can go to a pharmacy and buy a 60 ml syringe and try drawing some fluid from your own VTG (ventriculocisternal shunt).

From a values perspective, this looks suspicious because it's operating at 19% power, yet there's no pressure buildup.

Perhaps "getting your hands dirty" and actively working on the VTG system might help solve the problem.

m;

Hi,

Yesterday, I was able to quickly generate a log for MWBl 11.

5th gear, nearly flat road.

RPM should be %

0987 1040 0969 22.3
1008 1510 1071 23.9
1113 1550 1346 23.9
1239 1591 1612 30.7
1323 1632 1775 49.4
1407 1683 1724 56.6
1512 1754 1612 45.8
1617 1816 1867 56.6
1701 1867 1877 57.0
1827 1918 1897 56.6
1932 1948 1938 58.6
2016: 1958, 1958, 61.4
2121 1979 1907 59.8
2205 1989 1897 59.0
2310 1999 1938 57.8
2415 2020 1979 57.0
2499 2040 2040 59.4
2604 2040 2081 61.4
2730 2040 2060 62.6
2814 2040 2050 63.0
2898 2040 2050 63.8


As far as I can tell, the turbocharger boost comes on much earlier for me.

The graph shows a "dip" in the boost pressure curve. Where it comes from... I have no idea. Anyway, the boost pressure is being regulated precisely as it should be.

Yesterday, I also noticed that my mass airflow sensor is starting to weaken. It no longer delivers the values as originally specified, but it is still within the acceptable tolerance range.

And here is the desired comparison:

@Bertil

Thank you very much.
Okay, I guess I'll have to log in again, and then maybe I'll need to contact support. I'm curious to see how they'll react. The (temporarily deactivated) EGR valve, which was previously disabled via a closed hose, will then naturally be temporarily reactivated.

Hati wrote:

try to be friendly. I'm curious to see his reaction.

Hopefully, he won't make it too easy for himself by following test rule "3". "Full throttle from around 1500 rpm, and read the boost pressure at 3000 rpm."

Then, your engine would probably still be "within tolerance" .

If I were in your position, I would already start mentally preparing for something like that and formulating appropriate answers...

Or are there different testing requirements for the AXR or PDs?

Hi,

Here are the two measurement series presented graphically (see image). The rule of thumb is that the percentage value is multiplied by 100 (for better representation).
It's clear that HATI's regulation aims to make the turbine blades steeper (i.e., increase exhaust flow through the turbine), but the turbocharger doesn't seem to be responding to it.
In my case, the design clearly shows that as the exhaust flow increases, the impeller blades are angled more horizontally to prevent the pressure from becoming too high.
When the back pressure drops due to VTG (variable turbine geometry) blades being set too flat, the control system immediately compensates by briefly opening the VTG again.

At HATI, I have the impression that the variable transmission gearbox (VTG) is not working or being activated at all. I've experienced something similar before, where a squirrel had chewed through the pressure line for the control pneumatics on the VTG. The car ran completely normally from approximately 2000 RPM onwards.
The maximum boost pressure was achieved exactly as Ulf described, but the boost pressure curve was completely wrong.

@ Bertil

Did you not mix up the terms "steep" and "flat"?

If you position the VTG (Variable Geometry Turbine) blades flat, you create a smaller cross-section between them, which results in higher pressure on the turbine and, consequently, more revolutions of the turbine.

If you angle them steeply, they create a large cross-section through which the exhaust gases flow more slowly towards the turbine, resulting in less boost pressure.

Steep = large opening cross-section = low flow velocity = low boost pressure.



Flat = small opening cross-section = high flow velocity = high boost pressure.


m;

Okay, so, after driving approximately 900 km on the way back from vacation (of which about 650 km were on the highway at full speed), I just logged the boost pressure values again. It's interesting how the variable turbocharger (VTG) can be cleaned again without disassembly. Anyway, the values are now more or less where they should be.


Speed | Target LD | Actual LD | Deviation
1050.0 1530.0 1071.0 24.7
1113.0 1540.2 1193.4 24.7
1155.0 1560.6 1315.8 24.7
1197.0 1570.8 1428.0 19.9
1260.0 1601.4 1540.2 29.5
1323.0 1642.2 1662.6 38.6
1386.0 1672.8 1795.2 51.0
1449.0 1713.6 1693.2 48.2
1512.0 1754.4 1642.2 41.8
1575.0 1795.2 1693.2 45.0
1638.0 1836.0 1774.8 45.8
1701.0 1876.8 1866.6 48.2
1785.0 1907.4 1917.6 50.2
1869.0 1927.8 1948.2 54.2
1932.0 1948.2 1968.6 54.6
1995.0 1958.4 1978.8 57.8

I hope this continues. As far as I know, this car, with its current mileage of 90,000 km, was likely never driven aggressively during its time in driving school. The return journey seems to have done him good.
To everyone who put in the effort with graphics and other visuals, thank you very much!

dieselmartin wrote:

@ Bertil Did you not mix up the terms "steep" and "flat"?

Exactly as you described, that's what I meant.