NefMoto

Hi

helping a friend out with his audi 8l a3 1.8t aum, we fixed the wastegate issue in the following thread (the previous owner/tuner manually adjusted the wastegate too stay closed)

http://nefariousmotorsports.com/forum/index.php?topic=1380.0title=

I am trying too understand why in the latest log we did last night, that at 100% throttle in 3rd gear 2000RPM wot the n75 duty cycle is sitting at 94% when actual boost isnt anywhere near requested (this is off the tune that was on his car already), the way I understand n75 duty cycle is that if actual is higher than requested then n75 duty cycle would be higher ie 94% but if actual boost isnt at requested n75 duty cycle would be 0 ie closed too allow boost too climb?

0 means N75 fully closed (boost pressure can open waste gate)

95 means N75 fully open (bleed boost pressure away from waste gate, so that it says closed)

All of this is moot, of course, at 2000rpm where boost hasn't had time to build.

At 0% dc, all the pressure goes through the n75 and to the wastegates forcing them open to limit boost. As dc goes up, the n75 is bleeding off the control pressure to keep the gates closed and make boost.

(https://lh3.googleusercontent.com/-qNoiIot3z9M/TxZrGVeD52I/AAAAAAAAAng/-MYTLyy0jNg/s507/n75.JPG)

then surely at WOT from 200RPM n75 duty cycle should be 0 instead of 94% like the log reflects so that actual can meet requested as soon as possible, the thing is my car is showing the same sort of thing not as high as 94% but its not 0%

No. 0% would cause the wastegate to open as soon as cracking pressure is met, and boost would not rise past cracking pressure.

nevermind I am just confusing myself, thanks guys  ;D