Re: By pass valve on an 88 5kcstq

["Dave Aukerman" <mhauk@ccsdana.net>]

Try taking the spring out of the BPV and stretching it.  If it helps then
you need a stiffer spring.  BTDT on my brothers car.  The spring in the
standard TAP valve is not strong enough for a car with an IA 2.0bar box and
spring.  Symtoms: very low idle and stalling on decel and at idle, along
with a hiss at idle.  After talking with Ivor(?) they sent out a different
valve, blue in color and containing a much stronger spring.  Problem
solved.  This may not be the case with yours but. . . .

Dave

----------
> From: Lewis, Gary M <Gary.Lewis@West.Boeing.com>
> To: 'Quattro List' <quattro@coimbra.ans.net>
> Subject: By pass valve on an 88 5kcstq
> Date: Monday, February 15, 1999 2:15 PM
> 
> Hi Folks,
> I installed a Samco sport TB hose and the generic Bosch 944 bypass valve
> (BPV) this weekend.  And I'm having troubles.
> 
> The Samco sport hose has a fitting for the BPV.  I had a fitting welded
into
> the metal turbo intake pipe.  I installed the BPV into the sport hose,
> connected the other end to the welded fitting, and ran the vacuum hose to
> the back of the mainfold, T-connecting to the second of the fittings at
the
> rear of the mainfold.  I made sure that the BPV was orientated per Scott
> Mo.'s direction.  
> 
> Here is the problem:
> 
> I have a K24 turbo on the car, and it spools to 1.8 bar  at around 2,600
rpm
> BEFORE the addition of the BPV.  After installing the BPV, the thing
spools
> to 1.8 bar at approx. 3,500.  Worse than the K26.  And I can hear a
whoosh,
> as if the BPV is opening under boost, causing the turbo to work extra
hard
> to make 1.8 bar.  Also, after boost returning to idle, the idle drops to
400
> rpm, then creeps back to 850 rpm.
> 
> This morning, I removed the vacuum line to the BPV to isolate it.  Now
the
> car won't make 1.4 bar.  But the off boost idle drop is gone.
> 
> I am going to remove tha valve and plug the sport hose and metal turbo
> intake pipe, to see if I have a leak elsewhere, like the Samco hose.
> 
> Here is what I think;
> 
> 1. I have a bad BPV, or the generic doesn't work with the 5kcstq.
> 2. I have a vacuum leak under boost other than the BPV, like TB hose, IC,
> etc.  (I checked at idle; no leaks).  
> 3. I plugged the vacuum line into the wrong place or there is a vacuum
leak
> at the rear intake manifold vacuum line.  However, if the valve had no
> vacuum, theoretically it shouldn't open, right?
> 4.  Some bonehead solution I've overlooked or forgot about.
> 
> TIA,
> 
> Gary Lewis 
> 88 5kcstq 1.8 bar 110km Pearl w/Fuchs, K24 turbo, 2-piece EM
> 86 5kcstqw Sapphire and Platinum, stock 
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