[BiturboS4] s4 engine noise

[Robin Gibson]

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Hi

I run a 1999 S4 manual with ABT chip (310bhp) which was fitted 2 years ago.=
  Over the last 6 months I have noticed more induction-type noise from the =
turbos; rather than the usual crisp high pitched whistle from 1500rpm, it s=
ounds like a muted moaning sound between 1500-2000rpm, almost like one of t=
he turbos is slow to speed up and slow down.  It is most noticeable on ligh=
t throttle or when decelerating.  No noises or problems when driven hard.  =
Feels like some loss of response below 3000rpm, but difficult to tell if mu=
ch loss at higher revs.  Sound familiar to anyone?

Robin

e-mail: robingibson at cowanlinn.co.uk

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