When 'calling' for higher boost (over 10 psi) with the right foot, the boost swings (no spikes) between 10-15 psi during mid range RPM (around 3k).

I have not observed this behavior on my other (identical setup) two AEB cars.

This one has:
K04
AFPR
FMIC
NGK copper 1 colder (BKE7E or so), new. Gapped to 0.028
DV APR R1, relocated
3" downpipe
Stock cat back


History:

Car was overboosting (25 psi) during part throttle. Found out that the previous owner had installed the N75 reversed (long leg going to wastegate actuator, short into turbo inlet tube). After fixing that, boost is normal (16 psi in current cold weather), but I notice the 'boost swing', see video (sorry for the bad quality).

At that time, I also installed phenolic spacer, cleaned throttle body, new valve cover gasket.

I played with the fuel pressure (43.5 psi - 3.0 bar, 40 psi - 2.8 bar, 37 psi = 2.6 bar) since some users say the PC16 runs better on 2.7-2.8 bar (one of my other PC16 runs 3 bar fixed FPR, the other AFPR with 2.8 bar). No change.

a) I don't have any fast data logging software aside from VAGcom (on my 2.7T I can log with ECUx, etc). Is there something faster for the AEB?
The more parameters/blocks, the slower. Which parameters/blocks should I log to shed some light on what is going on here?

b) On the hardware side, what might be causing the 'boost swing'? How to check?

c) When N75 fail, do they just 'go out' or are they 'fading', getting lazy?

d) Does the DV have anything to do with it? Could if have been damaged (during the time boost went to 25 psi with reversed N75)?

e) Once out of the 3k RPM range, everything seems normal

f) Does the TB need a 'reset' (VAGcom) after it was disconnected from the car?

Any suggestions?


http://s853.beta.photobucket.com/use...51-16.mp4.html

 

It sounds like your n75 valve is failing. not holding boost. overboosting are some signs too look for. my car did this same thing but i went with a new n75 valve from ecstuning and fixed the problem

 

Warming this up again, since I now have 3 cars that show this behavior:

1) AEB, Giac PC16, larger than K04 turbo, FSI coils, BKR7E plugs, OEM N75 (original), high flow log exhaust manifold

2) AEB, Giac PC16, RS4 type turbo (smaller than 1.), FSI coils, BKRE7E, brand new OEM N75 06F906283F, high flow log exhaust manifold

3) Allroad 2.7T, custom JFonz stage 2, pre cat gutted, main cat delete, rest stock

All 3 cars exhibit a boost swing (0.5 to 1 Hz or so) of 4 psi (or so) when 'calling' for boost over 10 psi (example: swings between 15-18 psi).

What can be done to get the N75/boost control out of this 'resonance' situation? Note: on AEB, the tune (Giac, chipped) cannot easily be changed, so mostly looking for any hardware 'tweaks'.

 

So the issue is that the boost is bouncing? Any chance this could be gas related seeing that the problem started on 1 car and is now doing it on all 3 of your cars?


As for one of your questions in the main post, yes a Throttle Adapt needs to be done every time you unplug the battery.