[200q20v] RE: [s-cars] blowoff valve questions

Adam Dieckerhoff fourquattros at hotmail.com
Mon Jun 18 10:40:20 EDT 2001

>Has anybody tried setting the valve up as a blow off valve by not 
>the IM line and setting the adjustment to equal the desired maximum boost ?
>The valve would still be plumbed to return the blow-off air back into the
>system in the same manner as when it is configured as a bypass valve, but
>would be actuated by excessive boost pressure in the intake tract instead 
>vacuum in the IM.

Keep in mind a bypass valve and a blowoff valve serve completely different 
functions.  They are not interchangable.  A bypass valve prevents the turbo 
from stalling during shifts.  A blowoff vlave is a method of controlling 
maximum boost.  Its a supplement to, or possibly a replacement for the 
wastegate.  If you were to reroute the air exiting the blowoff valve back 
into the intake tract while under boost, not only are you defeating the 
purpose of the blowoff valve, but you're exacerbating the problem.  Also, 
the blowoff valve tends to be a last ditch, all or nothing effort at 
controlling boost.  When it goes off, you loose ALL boost.  I think Scott J. 
hit the nail on the head in one of his prior posts on the subject when he 
said if you need a blowoff valve, your wastegate is too small.


Adam Dieckerhoff
'93 S4 (black/ecru)
'00 TT quattro (silver/gray)
'00 A6 2.7t (black/melange)
'86 5kcstq (gone, but not forgotten)
fourquattros at hotmail.com
Bellevue, WA

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