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In a message dated 10/11/2007 12:49:41 P.M. Eastern Daylight Time,
bbradburry@bellsouth.net writes:
Lynn, I don’t know what
we would do without you.
I have several
questions.
Where can I get a
good accumulator tank?
Circle track
racing catalogs, hot rod shops.
I was thinking of
making one out of a used fire extinguisher and was also looking at one
from Moroso that looks like a flat canteen. The one from Moroso has an
inlet on the bottom and one on the top side as well as one for the pop off of
the radiator cap. Due to space constraints, I will probably try and make
one. I need something about 3” diameter and maybe 12” or so long.
Will I need the inlet on the top
side?
I have no idea what the top one would be used for, maybe a pressure
gage?
If so, where does it
plumb to?
I suppose I will
still need an overflow tank from the pop off of the radiator
cap?
In racing it is required that a 32 Oz. catch tank be supplied to
accept that hose. Just to keep coolant off of the track. Being able to catch
that coolant, is of no value, as it will not return to the system until the
engine is close to cold. If a seal blows out and coolant uses up the remaining
volume of the make-up tank, it will then overboard into the catch tank, or, you
could route that hose up in front of the windscreen, and you will be the first
to know that you need to be on the ground looking at this coolant problem. In a
conventional system, no coolant can return to the system until the system drops
below ambient pressure. That will be when the engine is just about cold. With
the coolant slugged tight against the cap, coolant leaves as pressure builds
above the relief pressure. So it pees out coolant until top temperature is
reached.
So the coolant is at top temp, and at relief pressure, say 24
pounds. When you power back a bit, and the coolant temp drops, the coolant
shrinks, and the pressure drops. But nothing can get back into the system from
the make-up tank. So after a long climb you level off and cool things down a
bit, and now you have little or no pressure.
The air cushion in the Mazda system keeps pushing coolant back into
the system with temperature changes. The air cushion stays at the relief
pressure, or close to it, the whole time the engine runs. Every time the
system finds a little bubble of air it pops up into the make up tank, and is
replaced by coolant..
After talking
with Tracy yesterday, I tried to see if the engine
would stabilize temp somewhere below 230* at 2600 rpm. No joy! I
suspect that I will need to increase air flow to get this to happen. I
will try an leaf blower on the cowl today.
My pressure
stabilized at 22 lbs (cap in constant blow off relief) but the temp would not
hold. If I had this same condition with the system you described, what
would prevent the air from blowing off and then water from the
accumulator?
As the engine heats the coolant, it expands a bit. The pressure in
the air bottle goes up compressing the air.
Should the air reach the relief pressure, the cap will vent to the
cap value, 22 pounds. (now I remember why I have a Shrader valve in the bottle).
Once all of the air is removed from the coolant, it may not expand enough at 180
degrees, to generated the cap pressure, so I add air until the cap cycles. Then
start the engine. A few days after a race, and there is still pressure in the
system.
It seems to me that
no matter what system you have, the pressure has to stabilize below the
pressure rating of the radiator cap, else you will be losing first air, then
water????
The coolant won't expand very much from just heating it. If the
bottle volume is too large it won't even trip the cap. Some car systems now just
have a fill cap with no relief function at all just the air volume to compensate
for volume changes.
Bill
B
Lynn E.
Hanover
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