[s-cars] By-pass valves

Thu Aug 12 17:42:00 PDT 2010

Bypass valve analysis from S4 group...

http://www.s4biturbo.com/art-dvtests.php

http://www.s4biturbo.com/art-dvtests2.php

Tony
96 S6 with 034 bypass valve.

-----Original Message-----
From: s-car-list-bounces at audifans.com
[mailto:s-car-list-bounces at audifans.com] On Behalf Of dgraber460 at aol.com
Sent: August 12, 2010 3:51 PM
To: captmagu at gmail.com
Cc: quattro at audifans.com; benswann at verizon.net; s-car-list at audifans.com
Subject: Re: [s-cars] By-pass valves

Oh Yeah, now I remember reading that on the stall door at the truck stop.

Dennis 
Denver

-----Original Message-----
From: Hap Maguire <captmagu at gmail.com>
To: DGraber460 at aol.com
Cc: qshipq at aol.com; djdawson2 at aol.com; benswann at verizon.net;
esanborn at gmail.com; quattro at audifans.com; s-car-list at audifans.com
Sent: Thu, Aug 12, 2010 10:23 am
Subject: Re: [s-cars] By-pass valves

Hey Dennis
I've seen Dave Jones test a bypass valve by sucking on it. He is called
Tufty 
or a very good reason.
Hap, wit dakine Tuftyism not from Evahboost, Maguire

n Aug 12, 2010, at 4:10 AM, DGraber460 at aol.com wrote:
> 
 Thanks Scott, Dave, et al;
 I understand the Bosch Audi OEM's operation pretty well as described by
Dave 
nd Scott.
 Having said that, my question was, and is, should the OEM plastic valves
open 
n the bench with vacuum applied to the small control port? The Forge
aluminum 
alve does, but neither of my OEM plastic units will, and I hear what seems
to 
e air bleeding by the diaphragm when vacuum is applied.
 They have never (at least in my ownership) been installed backwards, but 
ondering if they need to replaced and tossed, or if they are as normal for a

tock OEM. I'm guessing from this behavior that the diaphragm is ruptured and

hey are toast?
 TIA

 Dennis 
 Denver

 -----Original Message-----
 From: qshipq at aol.com
 To: djdawson2 at aol.com; benswann at verizon.net; esanborn at gmail.com; 
graber460 at aol.com
 Cc: s-car-list at audifans.com; quattro at audifans.com
 Sent: Thu, Aug 12, 2010 7:36 am
 Subject: Re: [s-cars] By-pass valves

 Agree, many are mixing bypass valve operation with blow off valve.  I have
not 
een any bypass valve that boost helps 'blow open' from below.  Most (all
audi 
pps) are oriented as DJD explains with the boost 90degrees to the diaphram.

he HKS sequensial bypass valve is oriented with the diaphram in line with
the 
oost pressure.  However, it's operation is spring adjusted and operates as a

tepped  'needle valve', so it's still the feed line on the device that
dictates 
alve opening and close.  

 A blow off valve oriented with the diaphram in line with boost pressure,
has 
o intake feed, it is an absolute boost pressure device that pops when the
boost 
n the intake manifold exceeds a set pressure.  

 Scott J

 -----Original Message-----
 From: djdawson2 at aol.com
 To: benswann at verizon.net; esanborn at gmail.com; dgraber460 at aol.com
 Cc: s-car-list at audifans.com; quattro at audifans.com
 Sent: Wed, Aug 11, 2010 11:20 pm
 Subject: Re: [s-cars] By-pass valves

 Mixing terms... and what you're saying isn't really accurate.

 The valve, is normally closed.  Apply a vacuum and it opens.  Apply boost
and 
t 

 remains closed.  The signal comes from the intake manifold.  The intake 
anifold 

 in a naturally aspirated engine is always in some state of vacuum.  This
means 
> 
 that if you are not making any boost, there will be a vacuum in the
intake... 

 inclining the BPV towards opening.

 Positive manifold pressure will NOT  "assist to force or blow the valve
open 

 when vacuum is applied to the control port" because those 2 things can't
ever 

 happen at the same time.  If there is pressure in the intake, there is 
ressure 

 forcing the BPV to remain closed.  When there is vacuum in the intake,
there 
s 

 vacuum at the BPV opening it up.  Furthermore, boost hits the *side* of the

 piston (Forge) or diaphragm (Bosch)... never able to assist in opening the 

 valve, unless you have it improperly installed.

 If as stock BPV is installed backwards, you will blow the diaphragm in
short 

 order... it's just rubber, and it won't last long fighting 20+ psi.

 The BPV's purpose is to alleviate pressure stall in the intake plumbing
(and 

 therefore the turbo) when the throttle closes.

 Anyway....

 -----Original Message-----

 From: Ben Swann <benswann at verizon.net>

 To: esanborn at gmail.com; dgraber460 at aol.com

 Cc: 'Quattro List' <quattro at audifans.com>; s-car-list at audifans.com

 Sent: Wed, Aug 11, 2010 6:51 pm

 Subject: Re: [s-cars] By-pass valves

 No, just the opposite.  The Bypass valve is normally closed.  The control
port 
> 

 is vacuum

 actuated and tends to open the valve.  Positive manifold pressure will
assist 
o 

 force

 or blow the valve open when vacuum is applied to the control port.  This 
appens 

 only

 when the throttle valve snaps shut while engine is under positive pressure
- 

 like

 between shifts.

 So the mityvac test is not necessarily going to tell you if the valve is 
pening

 properly and some valves have beefier springs for higher boost pressure.

 Also, if the valve is installed backwards then it may not open or flutter
when 
> 

 opening,

 or open when it should not open.  Funny thing is the way most valve are 

 oriented, the

 correct way does not look correct.  You  might want to verify that the 
irection 

 of the

 valve is correct.

 See: http://www.gtquattro.com/Bypass-Valve.html that has a picture of how
the 

 valve is

 connected/oriented.

 Ben

 [Date: Wed, 11 Aug 2010 17:56:43 -0400

 From: Eric Sanborn <esanborn at gmail.com>

 Subject: Re: By-pass valves

 To: dgraber460 at aol.com

 Cc: s-car-list at audifans.com, quattro at audifans.com

 Message-ID:

    <AANLkTin-vkgjJaotOtbbX3ToE1Ab-yLvLzkJ2293n-xq at mail.gmail.com>

 Content-Type: text/plain; charset=ISO-8859-1

 I might be misunderstanding what you were testing, but they should only
open

 during boost.

 On Aug 11, 2010 5:12 PM, <dgraber460 at aol.com> wrote:

 List-et-al;

 I have been chasing a full throttle issue on my 3B'd URQ for a few months

 now. The symptoms have been a flattening and lack of power under full

 throttle. My boost gauge has always shown full boost at 19-20, and it
throws

 no codes. I started to notice the moaning (not whooshing) noise when off

 throttle, which I had heard before and found to be an aluminum bypass valve

 that needed cleaning.

 Since it had been running an OEM Bosch plastic valve, I pulled the Forge

 valve off the S-Car and cleaned it up and installed it. On the drive this
AM

 it seems to have cured the issue. Time will tell if total cure.

 The question I have is that I tried to test all 3 valves that I have while

 messing around last night. I have 2 plastic, and 1 Forge valve. I hooked up

 a vacuum pump that pulls 14 lb hg to each valve individually and _none_ of

 them would pull open. Then I used my little Mighty Vac hand pump and the

 Forge valve would pull open and stay. Neither plastic OEM valve would open

 with either test. Does this indicate both OEMs are toast?

 I assume the vacuum pump did not have a check valve and therefore could not

 "build" vacuum as the Mighty Vac did, thus letting the valves flutter but

 not pull open. Sound reasoning?

 Also - is there a recommended lubricant that keeps the aluminum valves

 happy, and functional, or should they remain dry?

 Dennis

 Denver

 ]

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