Question for you turbo...

james accordino ssgacc at
Thu Aug 24 17:40:48 EDT 2000

--- Jorgen_Karlsson <jurg at> wrote:

> It is really pressure difference between the upper
> and lower side of the
> diagraphm that opens the valve. If you have 10psi in
> the intake and 20psi
> before the throttle body the vavle will open.

Certainly no turbo expert, but I thought that you are
describing  a pop-off or blow-off valve.  High boost
pressure opens it, pressure escapes and equalizes, and
the spring slams it shut.  Under the impression this
is usually used as a means to limit boost to a certain
level.  I thought a bypass valve was controlled. 
Usually high vacuum, like when shifting.  Throttle
slams shut, manifold vac goes sky high, and airflow in
the "pipeline" upstream of the throttle body "stops". 
The valve passes some air back farther in the pipeline
to keep airflow up and turbo spinning.  Yes, NO,
partial credit?

Jim Accordino

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