Absolutely right Rocky, though the issue of the sun heat is not
eliminated. If the accusump was full and the valve was closed when the oil
was cool, the pressure would rise from the sun's heat. But the only way it
would be likely to blow the sump would be when the bladder has failed and
the system is completely full of oil.
For that matter, my accusump has a relief valve on it. I thought they were
standard. It's never lifted, but I always thought it would sure be messy
if it did. I think it's on the air side though.
I've never been completely sure how much oil to put in my car with an
accusump installed. In theory you could run the sump quite a bit lower
since the accusump will deal with any loss of pressure due to the pump
inlet getting uncovered. In practice I like the idea of having plenty of
oil, so I rev the engine to fill the accusump with about 80 pounds of
accumulator pressure, close the valve and let the oil get to about 180
(the water temp usually reaches 210 about the same time), shut the engine
down and let it drain to the oil pan and then set the level at the bottom
mark of the dispstick. I figure that's pretty conservative. If you run the
engine at about 2K revs and get the oil pressure to about 30-40 pounds,
let it heat up, close the valve, shut off the engine and measure the oil
level it will be right about the high mark or even a bit above.
When I'm racing I don't spend any time at that low an RPM (2K), so I
suspect the oil pan level is down around the bottom mark, but I don't ever
see oil pressure higher than what I can get with cool oil and a bit of
revs, so I'm reasonably sure I'm keeping everything where it should be.
The valve on an accusump should be open for as long as the engine is
running (unless you're trapping the volume to pre-oil), otherwise it's not
doing you any good. I hate it when I forget to turn off the valve and I
don't have pressure to pre-oil the engine. Not only am I dredging the
crank through oil, but it feels bad to crank over unlubed bearings, once
you have the option.
-----Original Message-----
From: Rocky Entriken [mailto:rocky@tri.net]
Sent: Tuesday, October 01, 2002 1:27 PM
To: VANDECARR@aol.com; fot@autox.team.net
Subject: Re: Accusump
Not true.
For example, my Spitfire race car engine. 4-quart sump, 3-quart Accusump.
If the Accusump is empty because the valve is open, I now have seven
quarts of oil in a system designed for four (WAY high on the dipstick,
maybe the crank is splashing in it, and foamy oil does not lubricate
well). All you'd be "draining from the engine" at start is what is not
supposed to be there in the first place. And the extra oil is performing
no useful function, it is just over-filling the sump.
OTOH, when you have it charged, at start first you open the valve, then
hit the key, You have indeed just increased your oil volume in the engine
from 4 to 7, but the new oil is up in the galleys, in the bearings, etc.,
not down in the sump. It is performing its intended function of oiling the
engine BEFORE you start it. I have 30-40 pounds of oil pressure before I
start. This helps engine life. And as soon as you hit the key and build
engine oil pressure, it goes back into the Accusump. So yes, you do leave
the valve open. That's how it is supposed to work.
You do not close the valve until just before you shut off the engine. You
do that precisely so you can have pressure in the Accusump for the next
start.
Otherwise, why have an Accusump? And why would it even need a valve?
And again -- my Accusump gauge goes to 150 pounds. I typically run about
80 in the engine. That's what's in the Accusump when the valve is closed.
Sun heat is NOT going to raise that pressure significantly that it will go
beyond design limitations. Won't even come close. Hell, when the engine is
running, that oil is twice as hot as sun heat would make it on a warm day.
That was 180-degree or hotter oil you put IN that Accusump when you shut
the car off. It's cooled considerably to less than half that when you turn
it on again. Trust me, the Accusump should then be able to handle it
sun-heating up to even 120 or so.
--Rocky Entriken
----- Original Message -----
From: <VANDECARR@aol.com>
To: <fot@autox.team.net>
Sent: Tuesday, October 01, 2002 6:42 AM
Subject: Re: Accusump
> You don't want to leave the valve open on the accusump. As start you
drain 3 quarts from the engine when you need it most. If you don't want
to leave it charged in the sun you can drain it but be sure to close the
valve before startup and then crack it open slightly until it's charged.
>
> Dean VanDeCarr
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