Recently I had my turbo (Borg Warner/KKK) refurbished (core was replaced) on my 2003 (pre face lift) vRS.

 

When I re-fitted it I found that there was no boost at all, and after taking a look at VCDS logs I found negative deviation errors and a N75 duty cycle that was screaming "more boost please".

 

I found a way to adjust the actuator setting in situ, but I have to do it by feel. Several test runs and adjustments later I managed to get the duty cycle off its end stop but I just can't quite get it spot on.

 

On a previous run I ended up with it overboosting, and I've managed to dial it back a bit.. but the boost actual is either tracking under specified (low down in the revs) or running higher (higher up the revs)

 

How sensitive is the actuator adjustment? Are we talking fractions of a turn between good and bad?

 

I've attached a spreadsheet with a couple of runs (VCDS logs). Yellow highlighted sections are 100% throttle 3rd gear WOT.

2023-02-26 - overboost condition at the end of the last run

2023-03-15 - after adjustment still looks like it's running away (req: 2340 / actual >2500)

 

Thanks in advance,

Phil.

2023-03 N75 adjustment logs.xlsx

As long as you've dialled it back from overboost there's not much more you can do for now, a different core may well behave differently from the standard core since the impeller is different.

11 hours ago, sepulchrave said:

As long as you've dialled it back from overboost there's not much more you can do for now, a different core may well behave differently from the standard core since the impeller is different.

 

Thanks. Interestingly this isn't a hybrid or modified setup. The replacement core was because they had one in stock and it was quicker than repairing the old core (bearings on the way out). It did come with a new actuator installed.

2 hours ago, pyromorph said:

 

Thanks. Interestingly this isn't a hybrid or modified setup. The replacement core was because they had one in stock and it was quicker than repairing the old core (bearings on the way out). It did come with a new actuator installed.

 

Ok, but the new core came with new impeller and exducer so performance will not be the same as the OE core, the parts are simply not as well made.