[Vwdiesel] Is it wierd oil pressure?

Libbybapa at wmconnect.com Libbybapa at wmconnect.com
Tue Apr 19 21:45:33 EDT 2005

Well, I'm back, kinda sorta.  We haven't moved yet, but both properties are 
under contract and it looks like things will go through.  My fingers are still 
crossed.  I have missed the group considerably, but did manage to get done 
all/most of what I needed to get done.
Perhaps some of you might remember a little while back, my concern regarding 
the oil pressure in my 1.6 TD vanagon.  Here's the refresher.  First off, the 
engine runs great.  A while back I installed an electric oil pressure gauge at 
the cylinder head port.  After working out ground path issues, the gauge 
seems to work fine.  It does, however, register oil pressure behavior that to me 
is disconcerting.  I also installed a mechanical boost gauge that gets it's 
signal from the line going from intake manifold to injection pump aneroid.  When 
coming off of idle oil pressure begins to increase according to rpm until 
boost pressure starts to increase.  While boost pressure increases oil pressure 
decreases until maximum boost is achieved.  At that point oil pressure increases 
according to rpm.  The correlation between boost and oil pressure becomes 
more obvious when cruising on the freeway.  While holding a steady foot on the 
pedal, boost will decrease (and oil pressure increase).  When hitting a hill and 
pressing more on the pedal, rpm and speed remain constant, boost increases 
and oil pressure decreases.  When coming off the hill the opposite occurs.  Same 
is true for acceleration, except rpm and speed increase.  
My big question:  
Is it normal with a TD for oil pressure to decrease while boost increases and 
vice versa?
If it is abnormal, what could possibly be the cause?  I recently swapped 
turbo's, to no avail.  I also ran it briefly, heaven forbid, without the air 
cleaner attached to the turbo inlet, in order to eliminate any possibility that it 
was caused by my "custom" air cleaner, again to no change.  I also set the 
plumbing back to stock and eliminated the intercooler, again no change.  I still 
need to run it with a mechanical oil pressure gauge attached, but have not 
done so while driving yet, as it is a LONG run for the tube in order to get the 
gauge where it is visible to the driver.  Before spending a whole lot more time 
I would love to hear from those with oil pressure gauges on turbo diesels 
whether or not that situation is normal.  Thanks in advance.

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