S3 - Only full boost after vacuum

[The Stig]

Hi all,

I am still having boost problems, 0.8 bar as max boost.
Last i noticed when i accelerate hard and suddenly release the trottle by 4k rpm (a vacuum is created) and continu accelerate hard i can get 1,2bar of boost.

Second issue, when doing a pressure test my oli filler cap is big pressure.

So i was thinking maybe some check valve (one way valve) is broken. So i replaced:
- PVC valve
- Pressure regulator valve
- Diverter Valve

No luck

I hope you all have some new ideas!


S3 8L 2000 APY
Also replaced N75, N249 Bypass, No fault codes

 

[Westy]

When you did your pressure test what pressure could the system hold? Have you checked hoses for any splits?

 

[The Stig]

It could hold 1,5bar presurre, but only for 10sec. Then the pressure was dropping because air was leaving trough the oil filler cap.

Also sealed the inlet tip, then started the engine. after a few secs it cuts out and all the pipes hold the vacuum..

 

[The Stig]

anyone more ideas?

 

[<tuffty/>]

Is your car mapped? 0.8bar sounds about right for a std S3, remapping takes it too between 1 and 1.2 bar depending and K04 will peak up to 1.5bar then drop down and hold.

<tuffty/>

 

[The Stig]

mmm you suspect the map? The car was remapped by digi-tec, or with digi-tec software, german stuff...

The car used to peak at 1.3 and hold a good boost. Today when i hit the paddle it tops at 0.8. But as i told when i suddenly release the trottle around 4000rmp and the continue accelerate it can get to 1.2 bar.

Because i know it can hit 1,2 bar i suspect it is some hardware....
And pressure leaving the oil filler cap either istn't right, i thought it might be related.