Dhawk12
Veteran Member
I have a 2002 Golf ALH TDI with Manual trans (VNT-15 turbo) and I recently got VCDS. I was doing some logging to check the health of various components and noticed that there were some issues with actual vs requested boost. So I did a few power runs in third gear on flat from about 1800/1900 RPM to ~4000 RPM and below are my results:
I also have the log created by VCDS if that would be more helpful than the picture.
As you can see the boost spikes up to ~2500 mbar for a couple seconds and then drops below requested and doesn't really ever get back to requested during the power run. It is above the requested boost for 5.65 seconds before it drops below. It is not currently throwing any overboost codes (which is strange because in the logged data the actual boost was over 300 mbar over requested for 4.21 seconds), although it has done it once on this turbo set up (it used to regularly throw overboost codes on my previous turbo).
The duty cycle for the N75 is at ~80% at 4000 RPM.
Where should I start with resolving this? I am guessing I will need to verify the vacuum lines and actuator functionality but I will have to find a vacuum tester to do that. Could it also be the stop screw needs to be adjusted?
I also have the log created by VCDS if that would be more helpful than the picture.
As you can see the boost spikes up to ~2500 mbar for a couple seconds and then drops below requested and doesn't really ever get back to requested during the power run. It is above the requested boost for 5.65 seconds before it drops below. It is not currently throwing any overboost codes (which is strange because in the logged data the actual boost was over 300 mbar over requested for 4.21 seconds), although it has done it once on this turbo set up (it used to regularly throw overboost codes on my previous turbo).
The duty cycle for the N75 is at ~80% at 4000 RPM.
Where should I start with resolving this? I am guessing I will need to verify the vacuum lines and actuator functionality but I will have to find a vacuum tester to do that. Could it also be the stop screw needs to be adjusted?
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