Date: Tue, 26 Nov 2002 22:24:35 -0600
Reply-To: Stan Wilder <wilden1@JUNO.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Stan Wilder <wilden1@JUNO.COM>
Subject: Ten Bar oil pressure .......... you gotta be kidding. Long
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Several weeks ago I secured a Ten Bar oil pressure Gage and sender from a
944 Porsche.
Lets see; ten bar thats about 147 psi gauge.
Out of boredom I decided to install the gage on my 83 Air Cooled
Westfalia.
The sender appears to be the same as what I've been using on the Audi
gauges I've been running and selling for a couple of years and easily
installed on my T fitting.
After installing the gage I cranked the engine (40 degrees + or - 5
degrees) with 15/50 Mobil 1 oil.
Surprisingly the gage dial jumped up to 8 bar immediately.
I decided to make a 40+ mile trip that I was sure would bring my engine
to full operating temperatures of 210 + or - ten degrees.
Within a few minutes the gage was indicating approximately 5 bar and that
is about what I would be reading with the Audi 6 bar gage at 70 mph that
I've been using.
Since the trip involved no time at idle I was interested to see if the
idle pressure would settle down at the 22-27 psi that I normally have at
900/1000 rpms on a warm engine and Yoh! There it was as I waited at a
stoplight. Convincing me that I was getting true readings from the gauge
setup.
On my return trip I ran the Westy up to about 75 mph and held it there
for a full ten minutes (no wind, no hills). Even calculating for
Speedometer error I was running a full hard 4000 rpms. The Ten Bar gauge
registered 7 bar with the oil temp gauge hovering at 100 Celsius and not
moving. The CHT showed 350 and just hung there without fluctuation.
Once again entering normal traffic flow the gauge responded accordingly
showing 3.5 bar at 2400 rpms.
My oil pressure sender is mounted at the stock location on top of the
main oil gallery.
After arriving home I let the Westy sit for an hour and pulled the oil
pressure relief valve out of the port and found it to be free moving both
with and without the spring installed. The plunger dropped out easily
with just gravity and returned to the upmost position with almost no
force from my #2 pencil I was using to exercise the plunger.
It seems a mystery to me that this spring is supposed to relieve pressure
and go to bypass at approximately 47 psi (I've never seen this
specification in print).
I built this as a stock engine and the only non stock modifications was
the installation of Porsche oil pump gear set in the VW housing and an
external oil cooler sandwich plate that required blocking the stock
bypass check ball in the oil filter mounting pedestal.
Since I've driven this engine in almost every type of hill, cross wind,
head wind situation for the last 18 months and I've never seen any drop
from the original oil pressures that I saw in the first 1000 miles I'm
assuming that the bearings aren't washed out and the pressure hasn't hurt
anything internally. I haven't had case leaks or oil consumption or loss
of any memorable amount.
I'm accustomed to seeing 5.5 to 6 bar at normal highway speeds of 70/75
mph at full operating temperatures I often questioned the gauge but
accepted the stability of the needle as proof if proper function.
I'm very tempted to go out tomorrow and buy a good quality Stewart Warner
150 psi mechanical oil pressure gauge and install it since I've already
got a 1/8" steel line installed for a mechanical gage.
I've never seen these types of pressures on a type 4 engine in the seven
or eight engines that I've installed gauges on.
Another thing that strikes me as purely strange is that the little
Splittie I've got with the modified engine will gin out 60+ psi at 70 mph
and full temperatures.
I've seen a lot of acceptable ranges quoted on oil pressures but very
little on the actual pressures that engines routinely run at.
I decided to get this into the archives since so very little is ever
posted that relates to experiments with oil pumps and various operating
temperatures.
Stan Wilder
83 Air Cooled Westfalia
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