5ktq and Boost loss (after MC rebuild/upgrade & T3/K26 turbo) - it was bypass valve!

[Ben Swann]

Allright!  Ken wins the lucky cigar!  It was the bypass valve.

I overlooked this completely before since it is/was brand-new.  I thought
it would at least get me through testing things out.  It seems to pass gas
at around 1.5 bar which is why I was not obtaining more than that without
really pushing it.

It blew out the cork when I hit the 1.8 bar cutout and shifted.  Now it
acts more like a blowoff valve, since with the cork out you can hear it
start hissing when 1.6 bar is reached.  Ok, I put the cork back infor now
until I get a proper one.

Thanks all who took a stab at this.  Definately helped expedite finding the
problem.

So what are the recommendations on bypass valves?  Who has the good price
on them?

Ben
Hoping to post a writeup on my website in the near future for details.

'87 5000 tqa - Engine rebuilt incl. following -
T03/K26 hybrid turbo.
Elgin 270i260e cam removed and swapped the stock cam back for
 troubleshooting - I will likely regrind to a slightly tamer 260/254.
adjustable cam sprocket -  currently set for 3 deg retard
new valve seals, lifters & techtonics springs
new piston rings, connecting rod and main bearings,
all new seals.
2-Piece Exhaust manifold, highflow cat and 2.5" Stebro exhaust.
All visible casting flash removed from components.
Mild port and polish to head and manifolds with ports matched.
Bypass valve located in intercooler where untapped hole was with bypass
flow directed toward turbo - The Bosch unit failed me.
Supplimentary fuel injector installed in intercooler (but not connected to
fuel or 034EFI yet)
 			- injector is inline just prior to throttle body hose.
200 Flywheel, Clutch and Pressure plate, slave cyl.
QLCC chip & Schrapnel Knob and 2 bar SJM spring for control.

[On Thursday, June 13, 2002 2:17 PM, Ben Swann
[SMTP:bswann at worldnet.att.net] wrote:
> On Thursday, June 13, 2002 11:34 AM, Ken [SMTP:auditude at get.net] wrote:
>
> [Ben, it really seems like you may have the boost(meant bypass) valve
hooked up
> incorrectly.  I would perhaps take it completely out of the equation,
> plugging the holes, and see what kind of boost you build then.]
>
> Ok I will try that, especially since I have tried most everything else.
<snip>
> [It's probably not leaking to the outside, it's just letting your turbo
> potentially overspin, since the air is is circulating around and around
> itself.]
>
> Ok, that is what I thought,  and just wanted to hear it from someone
else.
>
> > Let's assume the bypass might be leaking (internally) -
> > why/how would that effect the observed boost pressure?
>
> Because the turbo is spinning around and around, but the boost isn't
> "building" because it's not filling cylinders with a fixed volume.  It
just
> circulates, even with the throttle open (if it's hooked up wrong or
> incompletely)
>
OK - that is a good description of what was happening.

> [If it's a stock valve, it could be that the diaphragm is ruptured.]
>
> Yes it is a stock bypass valve.
>
> I'll replace it with a "cork" inline and see what happens.  I hope I
don't
> blow anything..else.
> ]