dump valve RE: Max Boost/HP? 87 5kcstq

["Avi Meron" <avi@cosmoslink.net>]

You are correct, it is the pressure spike (while slamming the throttle
shut), that causes the massive rise in boost not the throttle boost, a dump
valve assist substantially in alleviating the problem. That is also the
reason that almost every newer car (turbo) has a dump valve built in.
Avi

-----Original Message-----
From:	owner-quattro@coimbra.ans.net [mailto:owner-quattro@coimbra.ans.net]
On Behalf Of Robert Houk - WorkGroup Server Firmware
Sent:	Friday, March 26, 1999 7:04 AM
To:	quattro@coimbra.ans.net
Subject:	Re: Max Boost/HP? 87 5kcstq

   > 	You are Correct about the IC.  14psi will not only blow it apart
   > in time but it is not efficient enough to do 14psi and keep intake
charge

	   I don't believe that it is the 14psi boost that blows apart the IC.
   I've found that
	   when the hose or IC blows it is not under max boost, but just after
   the throttle
	   released after full boost.  At this point the pressure in the IC
   goes way up.  Well
	   beyond the 14psi, because the turbo is still generating max boost
   and you have just

Actually, now that you mention it . . . I do recall reading [somewhere]
that 50PSI spikes are easily realized when slamming the throttle shut on
full boost!

	   closed off the airway by closing the TB.  I've also destroyed an ISV
   from this.
	   Once the TB is closed, the ISV is the only open airway.  I believe
   it is the ISV that
	   makes the whistling sound after throttle release.

	   After blowing up the IC in my 87 5K, I bought a hot water heater
   blow off valve from the hardware
	   store.  It opens at 30psi.  I drilled a hole in the plastic tank of
   the IC and mounted it.
	   Since the plastic tank had already been removed for me, it was
   simple.
	   I never had any problems afterward.

The only potential problem I see from this is the transient fuel en-
richement issues (you're pulling air through the metering system -- on
some cars [mine] at least the airflow is measured prior to the
turbo/intercooler/blowoff-valve) then dumping it, while still flowing
sufficient fuel for all the air you've dumped. Whether that is
significant or not, I dunno.

					-RDH