Blow off valve vs. By-pass valve (semantics aside)

[JShadzi at aol.com]

    I have been running an Audi/Porche/Bosch watchamacallit valve on my 80qt 
now for a few months.  I have had it configured in blow-off mode where I am 
feeding boost to the bottom of the diaphram, and also feeding boost via a 
vacuum line to the vacuum nipple and restricting vacuum via a one way valve 
so it will not open during idle.    Overall, it has run well like this, 
making a sexy hiss between shifts (a nice touch if you are in a little stop 
light race, as you are rapidly passing someone you can give them a little 
hiss between shifts to really let them know they are being beat).  Of course, 
the downside to this configuration is a very rich condition for about a 
second, when throttle is lifted rapidly, and the mixture goes mostly fuel 
because most of the air has been force out to atmoshpere. It causes the car 
to hesitate and jerk, also wrecking havoc on your cat. converter (although 
great for night driving, I could often see the flames behind me at night-also 
a great touch when racing , icing on the cake along with the hiss =)
    So the other day I configured the valve in by-pass mode.  Now boost is 
being fed to the top of the diaphram, and is rerouted back into the intake 
right before the turbo inlet hose in a metal-T.  I definitely recommend that 
metered air stay that way, the car drives as it was intended, smooth and fast 
with no rich-jerking anymore, but no more hisses or fireballs either.  Man, 
growing up is hard to do  =)
Javad Shadzi
80qt (now smoking other stop light dragsters quietly and maturely)