Boost problems (?)

Hello.

I have a Skoda Octavia mk1 2003 with an ALH engine.
Yesterday I used Torque (ELM327) to watch the turbo boost pressure. Torque was set to calculate boost using MAP.
At peak it showed around 21-22 psi.
Here's a screenshot of the Torque logging of boost. It was 3 pulling in 3rd gear from 2000 to ~4000RPM. (after the middle one was just a turn in 2nd gear)


Today I set it to calculate it via MAF and it showed 56 psi at peak. ��
But MAP still showed around 21-22 psi.

I didn't have boost 2 times, the turbo became silent at any RPM and the performance went down. I guess it went to limp mode. (after restart it worked again.)

Is it bad? At the end of July we are going on an 1800 km trip with my family.
Is Torque shows stupid things? It shows no error codes.

PS.: Everything is stock in the car. My turbo always sound a bit loud, compared to my friends modified car with open exhaust.
Next week I am getting cruise control installed, and we will take a look at it with VCDS/VAG-COM.

Thanks,
Erik

The MAP pressure calculates the atmospheric AND the boost above it. You are seeing 22 PSI including the 14.7PSI of atmosphere. You have 7.3 PSI of actual boost if I am reading your post correctly. The stock boost @WOT is well over 7.3 and the ECU should pull the power after 3 seconds of "invalid" boost.

I see. What can cause the problem? Where to start?

Edit: I did some pulls again, and the car went into limp mode after a 5 or more seconds WOT. After that, in limp mode Torque showed a maximum of 5 psi MAP pressure. Isn't that a bit low?

There's a log again:


The first one is a short WOT, after that, its a 3rd gear pull from 1500 to 4000 RPM, maximum MAP pressure is about 22 psi, then after that the third and fourth small "spikes" are 3rd gear pulls from 1500 to 3000 RPM, with a maximum MAP pressure of like 5psi? How is that possible? The car become very slow.

I am not much good at reading non VCDS graphs, but if I were you I would check the vacuum lines from the pump to the anti-shudder valve. Your not getting the "normal" amount of boost has to start somewhere; the trick is to figure out where and why.

I got the fact from a friend that Torque shows only the boost pressure, this means i am having an overboost, 22 psi instead of 14.7 psi. Maybe sticky vanes?

gebhaard said:

Is Torque shows stupid things? It shows no error codes.

PS.: Everything is stock in the car. My turbo always sound a bit loud, compared to my friends modified car with open exhaust.
Next week I am getting cruise control installed, and we will take a look at it with VCDS/VAG-COM.

Click to expand...

When you loose power (limp mode) you have to scan for the codes before you shut the car off.
Shutting the car off clears the code so you get power back.

It could be over or under boost.

Is the turbo loud as in whining, roaring, or ??

wonneber said:

When you loose power (limp mode) you have to scan for the codes before you shut the car off.

Click to expand...

I tried that but didnt show any faults, will try later.*

It could be over or under boost.

Click to expand...

I am sure for now that it overboosts.

Is the turbo loud as in whining, roaring, or ??

Click to expand...

Typical, healthy turbo sound, like straight piped TDIs, but I have stock exhaust. Nice turbo whistle when accelerating, and owl-like blowoff sound when clutching/stepping off the gas. (maybe an exhaust leak?)

*: Meanwhile I got a suggestion that maybe the N75 valve is bad. I bought a new one, replaced it. Now the car doesnt go into limp mode, but it still overboosts. (1.5 bar instead of stock 0.9 bar) In my free time I will take a look at the vanes and clean them. I also have taken a look at the vacuum line that goes from the N75 to the actuator, it seems okay, it holds vacuum and when I made vacuum with a syringe, the engine tone became a bit deeper, but the turbo didn't make any sound. ( I have read somewhere that it should make a sound at idle when I do this )
What can cause the problem? Any suggestion? I hope the vane cleaning solves it.
Also I forgot to mention that the car has 195k miles on it.

Thanks!

You can take the actuator off the turbo, it's 2 nuts, the vacuum hose, and an e-clip.
There's a VW bulletin about it rusting internally and sticking.
Shake it, you may hear the rust in it.

While it's off you can move the arm going into the turbo to see if it moves full range freely.

When you put it back on tie a piece of thread or dental floss to the e-clip so it's easier to find if it pops off and flies when you try to put it back on.
I lost a few clips when I replaced the actuator.

Last, using a vacuum pump directly on the actuator the arm should start moving at about 3 inches vacuum and full travel at about 20 inches.
That's the starting point.

I had to lengthen mine a few times to stop the over boost.

We took a look under the hood.
The actuator rod was sticking a bit, but after some manual movement, it was moving freely. When the engine was running, we were watching the rod and it was moving properly. At idle it jumped to the full travel position, and as I revved up the engine it was moving back. Vacuum line from N75 to turbo is okay. Vacuum line and check valve from N75 is okay.
I took a ride on the highway afterwards, but it still overboosts.
Especially in 3rd gear at 3000 RPM WOT. In 4th and 5th gear it still overboosts, but not as much.

I am starting to run out of ideas (and money ?) whats the next step?
Thanks

I have the same movement on mine.

Did you check that the actuator rod starts to move at 3 inches vacuum and is full at 20 inches or so?

I had to lengthen my actuator after replacing it and check the start & full range.
I was getting to much pressure.

Don't remember exactly but it might have been 3 or to turns a bit at a time to get it very close to OK

wonneber said:

Did you check that the actuator rod starts to move at 3 inches vacuum and is full at 20 inches or so?

I had to lengthen my actuator after replacing it and check the start & full range.

Click to expand...

I didn't replace it, its still the stock one. (I guess, I don't know if the previous owner ever replaced it, but I doubt.)
How can I measure vacuum? I don't have a vacuum pump, only a 50 ml syringe or my mouth
My TDI-guru said that it could be sticky vanes.

You realy need the vacuum pump to test if the actuator is basically set and working corectly.
Maybe you can borrow one?

Could be sticky vanes.
I would take the actuator off to check it as mentioned above.

wonneber said:

You realy need the vacuum pump to test if the actuator is basically set and working corectly.
Maybe you can borrow one?

Could be sticky vanes.
I would take the actuator off to check it as mentioned above.

Click to expand...

I will try borrow one and test it. I have a 150km trip this weekend, mostly on county roads, will try to use it in the higher RPM range, maybe it helps cleaning out the vanes a bit.

I was reading on the forum in the last days and when using the car I noticed that (as you can see on the graphs) it doesnt really sustain 20-22psi of boost, it only spikes. It sustains about 14-15 psi, sometimes 16-17, is that really high? I know it is a bit high but I dont think that its really much. What can cause these spikes?

gebhaard said:

I will try borrow one and test it. I have a 150km trip this weekend, mostly on county roads, will try to use it in the higher RPM range, maybe it helps cleaning out the vanes a bit.

I was reading on the forum in the last days and when using the car I noticed that (as you can see on the graphs) it doesnt really sustain 20-22psi of boost, it only spikes. It sustains about 14-15 psi, sometimes 16-17, is that really high? I know it is a bit high but I dont think that its really much. What can cause these spikes?

Click to expand...

I ran down the road in 4th at 3000 RPM for several miles. Maybe 10 or so round trip.
I read the temperatures may help clean the carbon out.
Maybe it was me but I thought the car was more responsive after that.

14-15 LB sounds correct.
The spikes are from the turbo spooling up to 15+ then a delay for the N75 and turbo to respond to lowering boost.
Or such.

I still have the problem, I did the 1800 km trip with a detached vac line from N75 to the turbo, so it didnt overboost.
Tried flooring it on every bigger hill, to have a high exhaust temperature and burn out excess **** out of the turbo, but didn't work, it still overboosts.
Tonight I tried unplugging the MAF sensor, to see how much it boosts without it. It was around 1-1.1 bar (14.5-16 psi). Can it be that my MAF sensor is wrong? I will try out another one soon, but can it cause overboost?

You can get boost spikes if you have a vacuum leak or low vacuum pressure, so the wastegate actuator moves too slowly. I had this problem for years until I found a small crack on the underside of the brake booster line. It was small enough that the brakes still felt normal.

I was mistaken, it doesnt do spikes, it sustains overboost. Could MAF cause this?

The turbo is now cleaned. As we took off the exhaust pipe with the cat, we noticed that there isnt really a cat, it was empty.
Can it cause overboost?