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

Brett Dikeman brett at brettd.dsl.speakeasy.net
Tue Jun 19 15:58:14 EDT 2001

On Mon, 18 Jun 2001, Robert Pastore wrote:

> Has anybody tried setting the valve up as a blow off valve by not connecting
> 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 of
> vacuum in the IM.

...and this would be worse than stock.

Two reasons...#1, your valve would not prevent a spike(it would be closed
and only open once the pressure spike hit the throttle, and worked its way
back to the turbo, whereas the stock valve opens as soon as there's enough
vacuum in
the IM, which is before the throttle has completely closed, thus almost
entirely preventing a pressure spike) and #2, your valve would
immediately shut after the spike, whereas the stock valve stays open as
long as there's sufficient vacuum in the IM(read: quite a long time.)
So, your valve setup would not help keep the turbo spooled at all...it
would just prevent damage.  Set a little higher, this is in fact what
some blowoff valves are for(someone mentioned this somewhere in this mess
of a thread


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