Zu langsamer Ladedruckaufbau? | Posts 64+

@DocSnydor:

Thank you for your comparison data. It seems familiar somehow. There's a very slow build-up of boost pressure until approximately 2500 1/min, and then a rapidly decreasing mass airflow signal above 3000 1/min. However, it seems that this problem is even more pronounced in your case than in mine (or your mass airflow sensor is in worse condition).

Hopefully, one of us will soon find the cause and, most importantly, the solution to the problem!

Regards,
Alex.

My mass airflow sensor (MAF) isn't the newest. I also noticed that the 'turbo boost' was much more noticeable than with the diode. After the test drive, the MAF was replaced with the diode again, and a significantly better throttle response was felt...

Okay, let's go back to the theory: If the diode tricks the control unit into thinking that the maximum airflow is being achieved, the fuel injection amount will also increase accordingly. Now, if the engine isn't getting enough air (decreasing values at higher RPMs), but the fuel injection amount (thanks to the diode) is still at its maximum, why doesn't the car stall?

DocSnydor wrote:

But let's go back to the theory: If the diode, acting as a replacement for the mass airflow sensor (MAF), tricks the control unit into thinking there's a maximum amount of air, then the fuel injection amount is also increased accordingly. If the engine isn't getting enough air now (decreasing values at higher RPMs), but the fuel injection amount (thanks to the diode) is still at its maximum, why doesn't the car stall???

Hi Doc.

probably because there is still enough excess air (although not the normally high amount) in the cylinders .

Without increasing the turbocharger's boost pressure, it would likely start producing black smoke earlier than usual.

Hello everyone!

After a long break (due to a lack of time for car projects), there's finally some new news to report.
Last week, I milled a camshaft timing tool from 10mm thick flat steel. Yes, you read that right, not a setting gauge, but a custom-made tool. With this, I can check the valve timing without having to remove the valve cover.
My inspection revealed that the valve timing is correct or only slightly off (estimated at 1-2° kW). Therefore, my power loss and the slow build-up of boost pressure are likely not caused by this.
It's a shame, it would have been too easy.
But at least now I have a lesson that I can use the next time I change tires.

Well, not many possibilities remain: either the intake channels are clogged, or the turbocharger is faulty.

I'm really starting to wonder if I should remove and verschandeln the intake manifold this Saturday, because I'm leaving for vacation on Monday, and the car needs to perform at its full potential on the highway!
Here are some questions that came to mind, which I would like to ask everyone who has already done this activity:

What torque should be used when tightening the intake manifold mounting bolts?

Can the old screws be reused?

3. Does the flange gasket need to be replaced? If so, will any gasket residue remain on the cylinder head or the intake manifold? Are there any other things to consider regarding the gasket or the sealing area?

"Will gasoline or brake cleaner be sufficient to remove the deposits?"

Thank you for your suggestions.

Regards,
Alex.

Hi Alex,

Have fun, if you decide to go through with it.
First, think about your hands! I did everything with my bare fingers, and I also cleaned the intake channels in the head as much as possible. After 2 weeks, my hands were verschandeln again...
Okay, so, to answer your questions:

1. Unfortunately, I can't tell you, I acted on the principle of 'what goes up must come down,' and with my 1Z, there were so many screws on the exhaust manifold that I don't think it's that important.

2. yes (see 1.)

3. It is recommended to replace the gasket (mine wasn't fully intact; a piece was stuck to the exhaust manifold, and another piece to the engine block).

4. What worked for me was gasoline and fire (this stuff is like rubber), and I didn't even bother trying anything else.

Best regards.
David.

Hello everyone,

Preparing for a vacation always takes more time than you think. Therefore, I didn't have enough time to verschandeln my intake manifold and runners before the trip.

I'm hoping that it will still be able to handle the Kassel hills well, and that I won't starve due to a lack of power or torque.

But as the saying goes, "procrastination is the thief of time." The right flange gasket is already ready. I just need a mostly free weekend in September, and then I can get started.

See you in two weeks.

Regards,
Alex.

Hello fellow DIY enthusiasts,

I'm back from vacation and already conducted some measurements today.
Apparently, the approximately 1400 km of highway driving during the vacation trip had no effect on the engine's performance, as the maximum boost pressure is still reached too late (around 2600 rpm).
However, the Ulf's DZR test actually shows that my engine produces slightly more than the rated power of 66 kW (approximately 4-5% more power). This may seem contradictory at first, but it could be because the engine was already running very well from the factory, without any modifications.

Here are some figures regarding the vacation trip:
vmax = 200 km/h (according to the speedometer)
Highway intersection with very high traffic volume, approximately 130 km/h.
Average fuel consumption: 5.6 liters per 100 kilometers (with a brisk, anticipatory driving style).

Back to the technical details. I have slightly visualized the measurements I took and created three diagrams based on them.
The diagrams show the boost pressure behavior with active boost pressure control, with boost pressure control deactivated (the connector at the N75 solenoid valve is disconnected), and a comparison of the actual pressure curves over engine speed with and without boost pressure control. Please note: This is a wastegate turbocharger that is operated with overpressure. By disconnecting the connector at the N75, the valve bypasses the boost pressure directly to the turbocharger's pressure sensor, resulting in no pressure modulation and therefore no active control!
According to the repair manual, at 3000 RPM and full load, a pressure of 1550...1750 mbar should be achieved. The actual pressure is approximately 1580 mbar, which is actually within the acceptable range.
According to the repair manual, the target values with active control are also reached at 3000 rpm. However, in my opinion, the boost pressure build-up at low engine speeds is still inadequate.
This test, therefore, doesn't really provide any meaningful information.
What I find remarkable is the direct comparison of the boost pressure curves as a function of engine speed. The measurement conditions were ideally identical: a straight, level stretch of road where both measurements were performed (only in opposite directions). In each case, a full-throttle acceleration was performed in 3rd gear from a slightly elevated idle speed.
The regulated curve deviates upwards from the unregulated curve starting at approximately 1350 mbar, as the N75 valve reduces the control pressure to the membrane dosage system in this region.
According to Ulf's article, the membrane should not deflect until approximately 1600 mbar (if I remember correctly). Therefore, I would have expected the two curves to be identical up to around 1600 mbar.
Perhaps my nib has become lodged in the ink cartridge or has become loose. Has anyone else experienced this issue before?
Or could this indicate a leaky wastegate (slightly open in idle), because the unregulated maximum boost pressure of almost 1600 mbar should actually be reached at around 2000 RPM?
I also find it strange that the two curves are shifted parallel to each other in the lower RPM range, because there shouldn't be any difference there, right?
"Does anyone have any advice? How would you interpret these curves?"

Thank you in advance.

Regards,
Alex.

Hello everyone!

Just a small additional note regarding my ongoing topic (problem).
Yesterday, with the vehicle raised, I operated the wastegate valve from a slightly lower angle using a long screwdriver. I was unable to detect any play or stiffness.
When releasing it, you could also hear a metallic "click," as if the valve was closing properly. Of course, the problem could also be in the pressure sensor, causing the wastegate to remain open. This difference cannot be detected using this method.
However, I actually don't believe anymore that the wastegate is stuck open or not closing completely.

I'm really running out of ideas. Are there any other solutions you can suggest?

Okay, just a small thing. The values for the idle speed control have changed in the meantime. Previously, they were around +/- 0.4 at most.
Currently, cylinder 1 is deviating by up to .0. I also think I can hear a distinct knocking sound from one of the cylinders when the engine is idling.

Regards,
Alex.

Hi Holgi,

In the worst-case scenario, yes, but let's not jump to conclusions right away. It might also be enough to reactivate the VTG (Variable Turbine Geometry) by moving it (see the Zlfs frequency generator or Bilnker method), or, as Ulf suggested, simply install the large pressure vessel. He has provided information on where to obtain them in another post, and that is SIGNIFICANTLY cheaper than a new charger.

Best regards,

Jan
Hey everyone, although this thread is quite old... BUT: In my case, it was the mass airflow sensor! Now, my engine, with 262,000 km on it, is running like it was brand new again!!

Holgi.

@Holgi:

I think I need to clarify a few things here that I already mentioned quite a while ago:

1. It is a wastegate turbocharger (not a variable geometry turbocharger).
2. The wastegate valve can be moved with a screwdriver and appears to be functioning freely. It also seems to close (mechanically) when released.
3. The mass airflow sensor (MAF) can be ruled out as the cause, as a new one has already been installed (unnecessarily), and the diode test did not reveal any differences.
4. Kat is also fine.

Okay, now you can continue guessing to your heart's content.

Regards,
Alex.

Hi,
After everything you've already tried, there aren't many options left to consider.
Perhaps the wastegate is opening too easily because, for example, the spring in the pressure sensor has become weakened.
You could test this by disconnecting the hose from the LDR (Lambda Dynamic Reservoir). However, be careful during test drives because the boost pressure and turbocharger speed will then only be limited by the emergency mode.
However, if the result still looks like the diagram with the control system active, even up to 2000 RPM (or whatever the maximum achievable speed is), then the only likely solution is to remove the turbocharger, test the wastegate valve on a workbench, and, if not already done during the cleaning of the intake manifold, check the turbocharger for axial play and ease of rotation.

'Are you saying that valves and hydraulic lifters can really be completely ruled out?'
Could the boost pressure be escaping through a valve that isn't closing properly?