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Re: bypass valve presure openings

Brendan Rudack wrote:

> If you eliminate the wastegate and dump boost "overboard"(in essence,
> reducing any resistance acting on the compressor), wouldn't the turbo
> overspeed and puke its guts???  Just a thought...  WRT to the atmosphere
> dump-valve, they can make an oily mess as well as cooking 02 sensor/cats.

First of all, my apologies for sending the empty message.  I just hate
it when I hit "Send" when I'm reaching for "Get New Mail!"

In that case where the dump valve is replacing the wastegate, it will
open when the boost hits the preset limit and vent the excess manifold
pressure to the atmosphere.  Once the manifold pressure has fallen, the
dump valve will close.

It acts just like the wastegate, but instead of keeping the turbo from
_making_ boost by diverting the exhaust gases around the turbo it allows
the turbo to make the boost, and simply wastes out what it doesn't want
the engine to use.

The use of a dump valve over a wastegate does have the advantage that
there is no wastegate crack to be concerned about and the turbo will
spool up faster.

I'm sure Scott J. or Scott M. might be able to expound on this further;
this is what I understand from my reading and experience.



Gary G. Erickson         Secretary -- NW Quattro Club
 503-702-5789           mailto:erickson@teleport.com