1.8t Bam low boost

[AceD909]

Hello guys,

I can't resolve my low boost issue on my 1.8T BAM. Boost is peaking at 1.0-1.3 bar and then drops to 0.4-0.5 bar, holding steady there. It may even drop to 0.3 bar or lower at high RPM.

Sometimes the boost spikes to 1.5-1.7 bar at peak and then surges, fluctuating between 1.5 and 0.5 bar, but this happens very rarely.

The turbo has been rebuilt with a new wastegate and a new hot side, using a Melett core.

Here is the VCDS log with 3rd and 4th gear WOT.

 

[mty12345]

Looking at the logs the boost (actual) is following the boost (requested) pretty closely. Intake air temps look good. Have you checked all the connections to the N75 valve for leaks? Also check the electrical connections to it. Item 7

 

[AceD909]

I did smoke test on cold engine there was no leak. How to test for the electrical connection what should the reading on multimeter be?
I will try in couple of hours to do another leak test i will use soapy water and fill the hoses with air pressure and will come back with the results

 

[mty12345]

I did smoke test on cold engine there was no leak. How to test for the electrical connection what should the reading on multimeter be?
I will try in couple of hours to do another leak test i will use soapy water and fill the hoses with air pressure and will come back with the results

Sorry, I meant just take the connector off, check for corrosion inside or any loose wires. I think the valve itself is working ok as your boost pressure follows the requested, but if it's only an intermittant problem then could be related to vibration or heat etc. Is the car on a standard map or remapped?

 

[AceD909]

The car is with standard map and has the following mods
N249 removed
70mm downpipe
Cold air intake


Also the n75 connector is good.
When i did smoke test my turbo inlet pipe was smoking a little so i unplugged my maf sensor and my boost holds steady 0.7bar.

 

[mty12345]

It's a difficult one mate. Was the turbo rebullt to standard BAM (K04) specs or is it modified? If it's modified then that coupled with the downpipe it may need remapping.

 

[AceD909]

It was rebuilt with k04 specs.
I just noticed it started to surge the boost all the time but even the surge is smooth.
It is not overboosting cause it goes to max 1.2bar and drops to 0.5 and then build the boost back to 1.2.
I don't even know what to check anymore