I ran an accusump in my Midget, now in the hands of Ron Watson. Your
impression of how an accusump is constructed is essentially correct. I'l
put in ansswers to your questions below...
At 12:25 AM 5/11/99 -0400, you wrote:
>Hello list,
>
>I'm sure this thread/question has come up in the past, but somehow I'm sure I
>missed it.
>
>I'm building a new 5 main full race motor for my '64 MGB and I'm wondering if
>I should install an Accusump. I know that it is suspost to provide oil
>pressure for start up and when the oil pump pick-up is uncovered during hard
>cornering or braking. I've read that the chamber is a smooth cylinder on the
>inside and that there is a piston that seals the cylinder and provides the
>pressure. But:
>
>1. How does it work?
the accusump holds a quart or two of oil. There is a valve - manual or
electric - on the output of the accusump. When the valve is closed, the oil
pressure is retained in the accusump, when it's open the a/s can supply oil
to the engine whenever the engines oil pressure is lower than the pressure
in the a/s.
>2. Is the engine supplying engine oil pressure in the cylinder when it is
>running for future start ups?
Whenever the engine is running and the valve is open, the pressure in the
a/s and engine tend to equalize. So when you shut off the engine, you shut
the valve first, retaining the running pressure in the engine (I used to use
a manual shut off valve, and close it during the cool-cown lap, after
running up to a fairly high rpm to get the max pressure that the engine had
at that temp).
>3. What size accusump do I need. I will be running an 8 quart pan on my
>1800cc 5 main "B".
The big one (three quart??) is the only one that has the piston (to my
fairly uncertain knowledge) and you really want the piston to keep the oil
separate from the air that provides the pressure. On the other hand,
accusumps are designed really for engines that are using stock sumps, and
you may not need an accusump for *running* at all, only to help at startup.
You could get some of those trick quick disconnects and keep it on the
booster battery kart, or some such and only connect it at cold starts, which
is really the only time that the startup function is critical.
>4. Should I buy a manual and mount it in the passenger side floor?/or buy the
>electric model and mount it in the engine bay, perhaps where the heater was
>on the firewall.
I didn't trust the electric valve (no reason, just prejudice) so I went with
the manual valve (I actually have the electric valve in my junk drawer). If
you put it in the passenger bay, just tie it down well, and use braided line
for the connection. I put the oil directly into the pressure feed using a
"t" fitting at the input to the engine from the remote filter. That way the
a/s sees only filtered oil.
I put a tire air valve in both the air pressure side and the oil pressure
side ofor the thing. When I first installed it, I closed the oil output
valve and pressurized the oil side with air, while bleeding air out of the
air side. that forced the internal piston back, allowing me to pre-fill the
oil side with two quarts or so of fresh oil. Then I connected it all up the
the engine and pressurized the air side with 80 LBs of air. When I first
cracked the valve, the a/s then force-bled all of the air out of the oil
lines, filled the oil filter, oil cooler, etc, and put 50 lbs of oil
pressure in the brand new engine. I then closed the valve, started the
engine and was away to the races. What you need to watch out for is leaving
the oil valve open when the engine isn't running, the oil in the a/s will
fill the sump, possible overfilling it. On cold starts, I just crack the
valve, see 40 - 50 lbs of pressure in the non-running engine, close the
valve, then start the engine. After the engine is running, I open the
valve, re-pressurize the a/s, and close the valve again. When I go out onto
the track, I open the valve while leaving pit lane, and close while on the
cool-down lap.
one of the great claims on the a/s system is that you can run an
under-filled sump, so that oil is kept off the crank, reducing rotating
friction and oil airation. I used a stock sump, filled to normal levels,
and had no problems, so I pretty much recommend the system. I never
bothered to bleed out the oil in the a/s when changin oil, I just left it in
there, the thinking is that the oil in the a/s doesn't actually circulate,
and it's filtered oil anyway. The really neat thing is that my a/s would
hold 80 lbs of oil pressure all winter (6 months or more), so that when I
dropped the rebuilt engine in in the spring, all I had to do was crack the
valve and start the engine - no fuss, no muss!
cheers, Brian
>
>I hope some of you can help me out with these questions.
>
>Many thanks in advance,
>
>Rod Schweiger
>"64 MGB Sebring Replica
>
Brian Evans
Director, Global Sales
UUNET, An MCI WorldCom Company
|