[s-cars] DahlBack Racing BYpass Valve, why not two.

[QSHIPQ at aol.com]

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See numerous Blow Off Valve vs Bypass Valve posts in the archives.  The
bypass valve isn't found often on race cars, but the BOV on the Indy car is a
different animal.  The Blow Off Valve reaches a boost limit, then dumps all boost.
It's a WOT (on boost) device.  The Bypass Valve is a closed throttle (off
boost/vacuum) device.  Indy car drivers have a piece of hose that allows them to
hear impending doom.  If you ever watched an Indy car reach BOV boost, it's
like it stands still.  It takes seconds to recover.  Just like the enforcers
intended...

An Indy car Blow off valve opens with too much boost (it's an overboost
failsafe device, or a boost limiting device), an audi Bypass Valve closes on boost
(or is supposed to:), and is a closed throttle pressure wave limiting device.

Trevor, for 2 valves, use that purple big dog pre IC, then use the HKS
sequential near the T-body.  It's a pintle type with adjustable preload, which means
it's one of the faster ones you can get.

HTH

Scott J
In a message dated 9/24/2003 6:37:50 PM Central Daylight Time,
strangconst at rogers.com writes:

The Indy and F1 cars have it on the plenum so that it will blow off with too
much pressure.
These valves are inspected by the officials before and after the race AFAIK.
I asked a mechanic about it this year when I was in the paddock during the
Toronto Molson Indy.
Actually the had a bit of a write up on them on one of the sites around.

I don't really think they require a BYPASS valve for the reason of closed
throttle.
They don't slam the throttle shut to shift, they don't de clutch for that
matter either.
Ain't sequential air powered shifting wonderful :)

I have heard of a sequential box for the Audi, any BTDT or similar on it ?

Mark S