throttle before or after turbo

[John Dammeyer]

Hi,

I should be so lucky and you are tempting fate.  Actually the 900 series
Turbo (1986) didn't have water cooling on the Turbo Bearing so a quick
non-idle shutdown tended to carbonize the oil creating those nasty
granules that are extremely abrasive.   What did in our Turbine was the
PCV valve and a turbine that was already noisy.  It failed open during
mountain passage.  High levels of boost caused positive pressure on the
crankcase forcing oil out the filler cap and assorted other seals.
Normally the PCV valve prevents this by allowing low manifold pressure
to suck out the blowby and other crankcase vapours but the valve,  is
supposed to close when there is boost.

There wasn't a turbine bearing left after that.  Lots of blue smoke,
limping home the rest of the 250Km.  New turbine and head gasket.  Runs
like a top but now we do make sure we idle down too.  And,  the PCV
valve ($45Cdn) is new and will be replaced in 100,000Km (that's the
325,000Km mark.).

That's my SAAB story.  (Slow And Always Broken.)


John

-----Original Message-----
From: xwiredtva at msn.com <xwiredtva at email.msn.com>
To: diy_efi at efi332.eng.ohio-state.edu
<diy_efi at efi332.eng.ohio-state.edu>
Date: Monday, March 08, 1999 6:19 PM
Subject: Re: throttle before or after turbo


>  My question is aside from the oil
>>being sucked out thru the oil seals, are there any other problems ?
>
>Run an oil cooler before the oil inlet into the turbo. This will cool
the
>oil down and help it from being sucked through the seals or blown
through
>the exhaust side (cooler oil is thicker). Also makes the turbo run
cooler
>and last longer. See Saab's 4cyl turbo setup on how to make a good
turbo
>setup. 240,000 miles on a hard beaten 9000 and no turbo failure to
date,
>never ideled after running either.
>
>
>
>