Adjusting Boost

[Michael McBroom]

DemonTSi at aol.com wrote:
> 
> In a message dated 97-08-09 04:53:34 EDT, you write:
> 
> << > Would an electronic pressure bleed-off system (I'm thinking specifically
>  > of the Saab APC) aid in preventing the spring from partially opening
>  > throughout the boost range?
> 
>         Hmm, good question....anyone else care to answer? I'm not sure. >>
> 
> The Saab system basically just bled off excess boost through a pop off
> valve...if I remember correctly. So it had nothing to do with the exhaust
> wastegate at all.

Not true.  The line which would normally run directly from the
compressor outlet to the waste gate actuator instead is routed through a
solenoid, which bleeds off pressure to the air intake side upstream of
the turbo.  The APC ECU both controls the amount of air that is bled off
by the solenoid and monitors the resulting charge pressure via a
pressure transducer.

-- 
Best,

Michael McBroom

'87 745T 123k w/APC                 Visit the Volvo Performance Site:
'88 765T 156k                           http://mcbrooms.com/volvo
_________________________________________________________________________

Graduate Student, Linguistics                         Author of 
Research Interest: Biological Origins       =McBroom's Camera Bluebook=
of Language                                     http://mcbrooms.com
California State University, Fullerton			
_________________________________________________________________________