Air Shrouded Injectors (and low boost)

[Nate Stuart]

> > The rushing air noise I can hear is exactly the same and seems to be co=
ming
> > from the same place (though quieter) as when I suddenly release the
> > accelerator and there is a rush of air from the wastegate.
>
> I don't know why you'd hear a rush of air from the wastegate when you let=
 up on the gas.  Bypass valve maybe, but not wastegate.  I could be wrong o=
n this tho'.  I just don't think the wastegate makes all that much noise, a=
ltho' I've heard others here refer to wastegate noise, so I guess it does m=
ake some.
>
> I just tried to think it through (it's early), and I don't see why the wa=
stegate would do anything related to the throttle closing.  It runs off of =
intake manifold pressure, which means it only opens when there is pressure =
in the intake.  So, if you close the throttle, the wastegate remains closed=
.  However on the other "outside" of the throttle, boost is being "stacked =
up" with nowhere to go.

If I remember correctly. the wastegate actually gets it's pressure
reference before the throttle body, on the same line as the idle
stabilizer.So when you drop the throttle shut the WG sees a surge in
pressure and opens up. Though if the line was plugged as he mentioned
before this is all a moot point.

> I just think you are leaking boost somewhere between your turbo and your =
throttle body.

I agree, there has to be a leak somewhere if your WG is constantly shut
(via the plugged line) and you are still not attaining proper boost
levels.

> > I have checked
> > the "michelin man" hose and it is fine. I have also checked the hose fr=
om
> > the turbo to the intercooler, though not the intercooler itself. I am
> > fairly sure that the rushing air is from the wastegate or somewhere clo=
se
> > to the wastegate due to the noise that I can hear. I don't have an anal=
og

When you say you checked the michelin man hose, how did you check it?
You really need to take it off completely and twist it and contourt it
into all sorts of shapes before you can confirm that there is no hidden
crack there, BTDT with a hose I _thought_ was good.

Have you double checked all the hoses and connections at the back of the
IM, like the idle stabilizer hoses, and ensured that the seal for the
fitting that the ISV nipple is on on the back of the IM is making a good
tight seal? These are the only things I can think of in that region that
would allow enough air under boost to escape.

Take care,
-Nate
'89 90tq
www.newtsplace.com/90tq