Boost Overboost G4 ALH: How High?

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Bertil wrote:

While the engine is idling, disconnect the vacuum line from the sensor located under the car. With a mechanically fully functional VTG system, the sensor should immediately return to its starting position (minimum boost pressure). However, if the sensor is stuck, it will remain in the maximum boost pressure position for some time. The error can only be reproduced under vacuum conditions! . . .The lid didn't get stuck, it was glued. Flushing it with alcohol solved the problem. A lot of black/brown sludge came out. Since I unfortunately don't have a schematic diagram of this device, I can't form a picture of what happened.

*dusting*

Hi Bertil,

I may have a similar case with an ALH G4 engine, with approximately 200,000 kilometers on it.
The logs show pressure overshoots of up to ~0.4 bar during the transition to full load, which persist for a short time. Then, the pressure drops to approximately 0.7 bar (apparently because the EDC was over-regulated), and then rises again to the target value, which is now being achieved and maintained quite accurately.

Question: For approximately how long did your VTG (Variable Transmission Gear) need to be at its maximum setting for the adhesive effect to occur? Is the 10-second duration from the basic setting of the MWB 11 sufficient to trigger the adhesion?
Assuming I should use the ~4 seconds for the adhesive setting time, as mentioned in your initial post, is that correct?

How did you spray-clean the can?
Left it installed and sprayed the substance upwards through the hose connection?
Or expanded?
Did you also flood the (external pressure) rod side of the can?

Hi Ulf,

Sorry for the late reply, I just got back from the Netherlands.

ulf wrote:

.... Hi Bertil, I may have a similar case with an ALH G4 engine, with approximately 200,000 kilometers on it. The logs show pressure overshoots of up to ~0.4 bar during the transition to full load, which persist for a short time. Then, the pressure drops to approximately 0.7 bar (apparently because the EDC was over-regulated), and then rises again to the target value, which is now being reached and maintained quite accurately.

... But then, without any error messages!
It sounds exactly like what happened to me back then.

Quote:

Question: For approximately how long did your VTG (Variable Transmission Gear) need to be at its maximum setting for the adhesive effect to occur? Is the 10-second duration from the basic setting of the MWB 11 sufficient to trigger the adhesion?

That should be enough.
Unfortunately, but probably not always.

Quote:

Assuming I should use the ~4 seconds for the adhesive setting time, as mentioned in your initial post, is that correct?

Yes.
Somewhere in my previous posts, I shared a test setup. You just need to disconnect the VTG pressure hose while the engine is idling and observe the movement of the VTG.

Quote:

How did you spray-clean the can? Left it installed and sprayed the substance upwards through the hose connection? Or expanded? Did you also flood the (external pressure) rod side of the can?

Simply "flood" the container from the bottom while it's still in its original packaging. Then, let the container sit and evaporate for some time. The WL (likely referring to a specific substance) will evaporate on its own.
I haven't touched the outside. However, it could also be a source of error.

Bertil wrote:

.... But then without any error entries! It sounds exactly like what happened to me back then.

Hi Bertil,

First of all, thank you for your tips.

The ALH error memory was (rather surprisingly) also clear.

In addition, the engine also produces black smoke when starting, even with just a little gas (I'm not sure if it happens every time or just sometimes), as if a large 10c tuning chip were installed, but there's nothing like that installed.
Furthermore, the results aren't particularly exciting. However, the LMM values are still so high that the turbidity (even with the LD set correctly) is only 1-2 mg below the rotation speed, which is "still somewhat acceptable."
My initial suspicion was a stuck-open EGR valve, but the valve moves freely during the pressure test, and the basic settings in the diagnostic data also appear to be correct.
I believe that the presence of a large amount of soot should not necessarily cause excessive soot buildup, but rather, in the absence of sufficient air (despite a full load), it should activate the turbidity limit.

It seems there's still an issue with the late-closing injection system, which I'll need to check out soon.
While the nozzles are still the original ones, at least the Long-Term Reliability (LLR) is still within the acceptable range.

As I said, the error memory is clear... I'm curious to see what the cause of the soot turns out to be.

ulf wrote:

. . . I'm curious to see what turns out to be the cause of the soot.

Mein Tip .... Nozzles.
However, this does not explain the behavior of the boost pressure control.
Keep us updated.

Bertil wrote:

Mein Tip .... Nozzles.

Yep, I've already suggested that to the owner. He's willing to take a look at it initially...

Quote:

That doesn't explain the boost pressure control behavior. Keep us updated

.
Sure. But it might take some time, because we don't have time to work on someone's car every day - probably about once a week, and not for too long .

Okay, today the LD solenoid valve was replaced as a precautionary measure.
The parts reseller gave him an AGR valve after an endless search through documents using the VIN and other information , even though he had written down the VAG part number of the original part.

Well, the behavior of the lambda control system didn't change or improve significantly with the EGR valve.
The log of the speed control system appears normal across the entire load and speed range, which indicates that the pump and its settings seem to be working correctly.

In the initial setup of the MWB 11, the load cell (LD) and motor noise immediately respond to the ON-OFF-ON transitions, which means that a stuck load cell is initially unlikely.
However, the LD difference is in the range of 70-80 mbar (instead of 100-200), even though I kept the engine running at approximately 1300-1400 rpm using gas.
This could indicate either a VTG adjustment range that is too small (leading to soot buildup), or excessive play between the VTG shaft and the vanes.

Next up, sometime soon, we'll head to the quarry to inspect the loader... to be continued.

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marzocchi wrote:

@ Ulf, my ALH engine would always spike to 1.5 bar when I suddenly applied full throttle, then drop to 0.8 bar, and then to 0.95 bar. The turbocharger lasted for tens of thousands of kilometers until I removed it. I've observed this multiple times with ALH engines. There's not even an error entry. It seems to ignore "overshoots."

Hi,

Our ALH Ibiza consistently stays within the generally accepted limit of 0.2 bar (maximum) during LD overshoot, and afterwards doesn't drop significantly below the target pressure.
Currently, it has just under 60,000 kilometers on the odometer.

Okay, here's the result of today's loader inspection at ALH-G4:

The VTG (vertical travel gauge) operates smoothly during the injection test, moving fully from stop to stop.

The vacuum pressure at the VTG sensor in the default setting of the MWB11 fluctuates between approximately 100 mbar and atmospheric pressure, which is perfectly normal.
The LD solenoid valve is new, as mentioned above (although it's intended for the EGR system, it functions the same as the old one).

The manual rotation and edge-checking test of the loader shoe indicates "all OK" (nothing is rubbing).

Here's the translation:

"Consider this as an explanation for the pronounced overbites and underbites."

a) That the G4-ALH software is written so poorly -> then everyone using a G4 would have to deal with it, regardless of whether it's old or new.

b) that the V-groove guide (VTG) is loose between the rails and the guide vanes -> in that case, the problem should worsen with increasing mileage.

I'm leaning towards option b) and the recommendation to replace the charger soon, before its impeller is damaged by over-speeding and causes problems with the motor... What do you think about that?
"Or are all G4-ALH models behaving this way from the moment they are new?"

Hello Ulf,

My G4 ALH, manufactured in 2001 and with 123,000 km on the odometer, also exhibits overboost up to 1.5 bar.
These were present both before and after the tuning.
There are many ALH drivers in this forum who report similar issues with low fuel consumption.
The VTG (variable torque generator) switches smoothly during the initial setup, and there have never been any error messages.

Regards,

Borys.