Turbo Comprehension: Questions & Answers

Hello,

I'm still having the problem with my A4 where the load is too high when using the VA loader.
I've already opened and cleaned the loader. The pressure vessel is accessible, and the valve seems to be working properly with each cycle.
However, the pressure reading is heading towards 2 bar when running at full throttle.

Okay, so I disconnected the vacuum hose and now I'm reading a value of 1.5 bar on the gauge when fully accelerating! According to my understanding, the lambda value should be less than 0.5 bar, right??? I also already tried another air filter, but got the same result.

"So, yesterday I reinstalled the vnt15 and now the turbo boost is maintained up to approximately 4000 RPM in 4th gear (at 0.95-1 bar). After that, it goes up to 1.05 bar (possibly even higher in 5th gear, which I haven't tested yet), but it definitely doesn't go into limp mode."

After removing the vacuum hose, the LD (likely referring to a pressure reading) also goes above >1 bar.
"In all these turbochargers, the pressure sensor was standard equipment and would tighten properly even when the engine was stationary. With variable geometry turbos (VTG), the adjustment changes from one position to another."

To be honest, I don't understand anything right now... Maybe I just missed something.

Hmm.

Actually, it seems that the variable geometry (VTG) rod was set too short on *all* of your turbos. This would mean that the "no pressure" stop isn't allowing the guide vanes to open wide enough.

Otherwise, I don't understand any of it either.

Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

cksIT wrote:

I still have the problem with my A4 that the laser level goes too high when using the VA loader... I then disconnected the vacuum hose and read a value of 1.5 bar from the display when fully accelerating! According to my understanding, the LD should be less than 0.5 bar there, right??? Another turbocharger was also installed, but the result was the same. "So, yesterday I reinstalled the vnt15 and now the turbo boost is maintained at approximately 4000 RPM in 4th gear (0.95-1 bar). After that, it goes up to 1.05 bar (possibly even higher in 5th gear, which I haven't tried yet), but it definitely doesn't go into limp mode." After disconnecting the vacuum hose, the LD (likely referring to a pressure reading) also goes above >1 bar. ...

Did you include the cost of any modifications or upgrades in the estimate?
Possibly, the ventilation system has less capacity to maintain the air quality within a reasonably normal range when there is a significantly increased exhaust flow.
It might sound strange compared to the "small" VNT15, but I once heard somewhere that its exhaust turbine is larger. This could potentially help it control the minimal overboost (LD) at maximum pressure (Pmax) and with the variable geometry turbocharger (VTG) open, more effectively than the VA.

A conversion to a VB loader might help you.

Oops, I missed the attachment.

Then I'll join this theory .

Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

No, those values were measured in unchipped mode.
That's funny because I thought that with the modifications, there would be too much exhaust coming out.

With the VNT 15, it's not much different; the only difference is the 216 injectors, and those can't possibly make that big of a difference... especially since there are multiple vehicles using them on the road.

Regarding the VTG rod: they are all originally calibrated... and under original conditions, the value should be correct.
Does anyone have any other ideas?

cksIT wrote:

No, the values were measured in the unchipped mode... That's the funny thing, even with the tuned version, I thought there were simply too many exhaust gases.

Then, without the vacuum pressure affecting the throttle, the load value (LD) should increase significantly with the tuning .

How certain are we that in "unmodified mode," only the standard fuel amounts are injected (plus a nozzle correction factor)?

How reliable are the reported LD data: How was it measured (using VAGCOM / a cheap or branded LDA sensor), absolute or relative pressure?

I can't say for sure, because I'm already not giving it full throttle (Jan doesn't want to push the turbocharger too hard ).

I installed the original ECU (Engine Control Unit) without any modifications.

The LD (likely referring to a sensor reading) was measured using VAG-Com and also with an analog LD display; I don't recall the brand of the display offhand. However, both values were the same (as far as one could tell).

cksIT wrote:

I installed the original ECU without any modifications.

Okay, so the software can be considered safe (assuming you've recently acquired the MSG).

Quote:

The LD was measured using VAG-Com and also with an analog LD display; I don't remember the brand offhand. However, both values (as far as one could see) were the same.

"Gleich" can actually not be: VAGCOM provides approximately 1000 mbar more than an LDA due to the absolute pressure reading.
"I'm sorry, but in cases that are as puzzling as this, it's important to address or rule out all possible sources of misunderstanding."

Could there possibly be a pump with a larger displacement cylinder involved?

"Jupp" is the component that was installed from the beginning.

Subject: LD values: I have already subtracted the approximately 1000 mbar. After that, they were quite similar (deviations < 0.05 bar).


The rest of the car is currently original, except for a faulty EGR valve and the injectors.

cksIT wrote:

yes, "jupp" is the component that was installed from the beginning. Bitte gib mir den deutschen Text, den du übersetzt haben möchtest. The rest of the car is currently original, except for a faulty EGR valve and the injectors. Then yesterday I reinstalled the vnt15. However, even after disconnecting the vacuum hose, the LD (likely referring to "Ladedruck" - boost pressure) still goes above >1 bar.

Please create a MWB 8 + 11 log with the VTG hose disconnected, using full throttle in 3rd gear (or higher), from approximately 1300 rpm until the lambda value becomes too high, and indicate which turbocharger is currently being used.

Normally, a noticeable amount of lag only occurs at around 3000 rpm. Below that speed, there is almost no lag because the engine operates in an overly rich mixture due to insufficient air mass, and therefore cannot provide sufficient turbocharger boost (especially not with a fully open variable geometry turbine).

Depending on the specific error code related to the laser diode and the software configuration, some measurement systems may even enter a failsafe mode as a precaution, suspecting a defect in the laser diode sensor.

Okay, here are the measurement results. I'm not really sure how to interpret them in relation to the problem, but maybe one of you can make sense of it.

"The VNT 15 was used (it's a pain to have to rebuild the turbo every time...)"

cksIT wrote:

okay, here's the measurement data.

Hmm, it doesn't really seem unusual to me, but my previous experience with an AFN without vacuum advance only goes up to 4000 rpm.

Okay, the fact that the target pressure is almost reached without any vacuum might seem surprising, but the large nozzles could also contribute to this.

I'm gradually running out of explanations and ideas for your problem .

especially me... I haven't had any ideas for a long time.

How about the pressure vessel? Is it tightened with some pressure (i.e., pre-tensioned)? If so, that might be the problem... You could slide all the pressure vessels into place and tighten them without any pressure.

The lid should screw on tightly without excessive force. That's okay like that.

mullemaus wrote:

The lid should be able to be screwed on tightly without excessive force. That's okay like that.

... but if the retaining screws are loose, the VTG rod should push the can approximately 1-2 mm away from the mounting plate, so that the VTG is pressed against the open stop with a small amount of force when the can is fixed.

This is just for additional information .

Quote:

All the cans could be moved without pressure to their designated positions and then secured with screws.

If that statement is literally true, then all the VTGs (Variable Turbine Geometry) would be incorrectly adjusted, pointing towards too high of a load: which is exactly your problem... almost unbelievable - unless all the turbochargers are coming from a "specialist" source with pre-existing issues.

Quote:

Quote: All the cans could be moved without pressure to their place and then screwed in . If that is literally true, then all VTGs would be incorrectly adjusted, and in the direction of too high LD: which is exactly your problem... almost unbelievable - unless all chargers come pre-modified from a "specialist source."

That's likely what the too-short VTG rod was that I suspected.

Okay, please provide the German text you would like me to translate into English. I will only provide the translation.