I usually give the throttle a few blips to get the pressure up to 70-80
and fill the accusump before I close the valve. That way I can pre-oil the
bearing for at least 30 seconds when I'm starting (which I think is one of
the great reasons to have one of these things). But I see 70 pounds of
pressure at the end of the straight when my engine is at the redline (or a
ways past it). I just don't look at the gauges that often when I'm trying
to decide when to brake.
I'm not surprised to hear that it was a failed bladder that caused the
problem. It's a standard problem in piping and tank systems, whether it's
cars or nuke plants. Fill a tank completely full and close all the valves
and you're in for big problems if the tank gets hotter. An expanding
incompressible fluid, no where to go. Bang. Colder is not usually a
problem.
-----Original Message-----
From: Henry Frye [mailto:thefryes@iconn.net]
Sent: Tuesday, October 01, 2002 5:54 AM
To: fot@autox.team.net
Subject: Accusump pressure
This recent thread about Bob Kramer's Accusump letting loose got me
thinking about the pressures the thing actually sees.
My Accusump (3 quart) is plumbed directly into the oil gallery on my TR4.
I
run AN12 size hose back to the Accusump, which is mounted on the
passenger
side floor. I have a manual ball valve, not the electric solenoid that
Accusump sells. I pre-charged the air side of the bladder with whatever
the
instructions said, something like 8 or 12 PSI. I have the one-way valve on
the engine's external oil lines to prevent the Accusump from throwing it's
load out a bad oil cooler or the like. The Accusump gets very hot after a
session indicating it is doing it's job..
With the engine running, my Accusump gauge reads about 5 PSI less than the
oil pressure I have at that moment. I thought that was about right, taking
into account the big bore oil lines I use, gauge inaccuracies, etc. I
never
gave it much thought until I was at Watkins Glen and some guy comes up to
me and asks me what I know about Accusumps. His was not getting hot when
on
track. I looked at his car, and the gauge on his Accusump read about 80. I
wandered about the paddock and looked at a few others, and saw several
gauges that read about the same.
So how are all these cars I looked at capturing 80 PSI in their Accusumps?
It would seem to me they must closing the valve when the engine is
creating
80+PSI of oil pressure.
I never want to see that much oil pressure, even a the end of the longest
straight.
What I do is reach down and close the valve as I am entering pit lane. At
this point the engine is only turning about 3-4K RPM's, and I always seem
to capture only 45 to 50 PSI in the Accusump.
This sounded right to me, never gave it a second thought. Then I see
several people are capturing in the ballpark of 80 PSI in their Accusumps.
So, whaddahya'll think?
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