5ktq and Boost isn't everything..turbo, cam, flywheel, 034efi..but still needs help.

[Bernard Littau]

[snip]
> Now the disappointment has been that the engine no longer develops the
> expected boost.  I played with the schrap.knob and even  resorted to
> disconnecting any wastegate control whatsoever and the most I
> have observed
> is 1.7 bar(~11 PSI) and that is when going full bore over 5k reaching
> speeds that ask to get thrown in jail fast.
>
> Prior to the work, I could easily dial in over 2 bar of boost and had set
> to around 15-18 PSI, and reached the set boost around 4k RPM.  A leaking
> exhaust manifold(small cracks) and gasket prompted me, or should I say,
> gave me the excuse to perform this major undertaking.
>
[snip]

Hi Ben,

I'm coming in late on this, and have seen that I overlap much with other's
comments.  However, you need to make sure the ECU is not a factor.  This is
best done by disconnecting the lower waste gate hose.  I assume by your
comment on removing waste gate control you mean the WGFV hoses.  Did you
disconnect the lower waste gate hose from the waste gate, and plug it?

If the lower waste gate hose is not connected, there should be no opening of
the waste gate, and the turbo should make boost like crazy.  With the lower
waste gate hose off, ECU control and WGFV are not a factor. If it does not
boost right up to 2.2 bar, then here are some possibilities:

1) Your measurement device is incorrect.  If you are using the ECU
transducer, hook up a real pressure gauge to one of the manifold lines and
check that it too reads 1.7 bar.

2) Your waste gate is not shutting completely.  Try pulling a vacuum on the
upper chamber of the WG, and release it suddenly.  It should make a clunk as
it closes.  See: http://www.sjmautotechnik.com/10vwaste.html under LEAK TEST
THE WASTE GATE DIAPHRAGM.
Your diaphragm should not be an issue, as when it goes, you get lots of
boost.  Clunk the WG a few times to make sure it is closed, and try the
boost test again keeping the lower Waste Gate hose off.

3) Your bypass valve is leaking.  Somewhere I have a picture of my bypass
valve test fittings :-)  I took a 1" dowel and cut two pieces off.  Use the
two pieces to plug the hoses after you have removed the bypass valve.  Run
the Boost Test again with the lower Waste Gate hose off.

4) Your plumbing between the turbo exit and the intake manifold is leaking.
This is usually accompanied by some rich running.  Hard to tell normal rich
from way rich at high boost :-)  What kind of Intercooler are you running?

5) Your turbo is leaking/broken.

2 & 3 are your most likely cases.  1 & 5 are reaching.  4 is a
possibility -- I initially had my hoses, from turbo to IM, with the hose
clamps as tight as I usually make them for the cooling system.  Below 1.5
bar, this was an adequate tightness.  When I raised the boost, I kept
blowing hoses until I made the clamps way way tight.  Sometimes the hoses
blew off completely, sometimes they just vented under higher boost.

Good luck,

Bernard Littau
Woodinville, WA
'88 5ktq