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Re: Pop-off valves in STX?

To: Jake Hodges <jake@codeworm.com>
Subject: Re: Pop-off valves in STX?
From: "John J. Stimson-III" <john@harlie.idsfa.net>
Date: Wed, 28 May 2003 09:33:24 -0700
On Wed, May 28, 2003 at 09:08:07AM -0700, Jake Hodges wrote:
> I'm asking for a friend..  I don't actually know what a pop-off valve is, 
> but apparently it's desirable in some way.
> 
> 1. Is it legal in STX?
> 
> 2. For my own information, what does it REALLY do?  I've heard some "fast 
> and furious" explanations, if you know what I mean, but I'd like someone 
> with some understanding of the English language to show off how much they 
> know on the subject to help my friend make an informed decision.

2. As I understand it, a blow off valve or pop off valve is a valve in
   the pressurized segment of the intake manifold which opens to vent
   some air when the pressure reaches a certain level.  They can be
   used for either safety (to make sure that the engine never gets too
   much boost) or for tuning (to choose the desired boost at a given
   operating point).  It's the thing that makes the Psssh! noises when
   you're playing Gran Turismo :-) The car probably already has a BOV,
   but it probably opens at some wimpy pressure like +6psi and doesn't
   make a sufficiently intimidating whoosh noise.

1. No, I don't think that they are legal for STX, since STX's engine
   prep rules are generally as or more restrictive than SP and SP
   doesn't allow them.  BOVs are a direct way of controlling your
   boost, and you're not allowed to mess with the boost anywhere other
   than Mod, and *possibly* Prepared.

"NO BOOST FOR YOU!"
             -The Boost Nazi
-- 

john@idsfa.net                                              John Stimson
http://www.idsfa.net/~john/                              HMC Physics '94

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