[BiturboS4] Abt chipped car down on expected performance

Edwards, Dave Dave_Edwards at iOra.com
Thu Aug 22 15:46:31 EDT 2002

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Admittedly it is louder for me as I have the APR bipipe (enlarged
recirculation ports) and Forge Valves (solid diaphragm), however I could
still just pick out the noise when my car was stock. There must be very
little background noise (so you mustn't be going too fast) to hear it
though. If you can't then don't worry. I can only just hear my turbos spool,
and that doesn't worry me (quite the opposite ;-)

The cause is a sudden pressure differential across the diverter valve,
caused by going from high boost, open throttle to closed throttle which
happens when you accelerate fairly hard and then change gear (assuming that
you lift off when you change gear like I do ;-). The valve opens and the
pressure behind the throttle is suddenly released to the turbo inlet pipe
(which is sucking). This causes a rapid airflow which can cause a 'whoosh'

-----Original Message-----
From: daniel chisholm [mailto:dbc112 at yahoo.com]
Sent: 22 August 2002 14:34
To: Edwards, Dave; biturbos4; 'David'
Subject: Re: [BiturboS4] Abt chipped car down on expected performance

I never hear a woosh... ???  What would be the primary cause

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