Lynn, My
system does not have an accumulator in it presently.
My system is just like the older
cars. The radiator cap on the radiator has an overflow tube that allows
burped coolant to go into the bottom of a catch can. When the pressure
lowers the coolant can be sucked back into the radiator through the cap.
The catch can is not pressurized. This is like both my cars.
Yesterday, I visited the local Mazda
dealership and had a mechanic show me the system on the RX8. That system
has a hose that comes from the inlet of the water pump and goes into a
pressurized plastic container. This container has a pressure cap on top
that can burp water out into a hose that appears to go on to the ground. (I didn’t
see a catch can?)
I will try and rig up an accumulator as
you describe.
Why do you pressurize the system before
you start the engine? Seems that after start, the pressure would build
higher, causing it to burp out. Are you trying to cause a minimum constant
22 lbs by pre-pressuring?
Bill B
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Lehanover@aol.com
Sent: Wednesday, October 03, 2007
10:28 AM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Coolant
Water Pressure
In a message dated 10/3/2007 9:08:53 A.M.
Eastern Daylight Time, bbradburry@bellsouth.net writes:
I think that I would see air under the radiator cap if I had a
compression gas leak? I never see any air.
To check a piston engine for head gasket leaks, you would put the
cylinder at TDC and pressurize the cylinder to about 150 lbs with compressed
air and check the radiator for air bubbles…How do you check a rotary?
I will check the pressure sender against a mechanical gage.
There is obviously a heating problem, but I think the pressure is
higher than it should be until just ready to boil. I shut the engine off
at 210*, and at 22+ lbs, the boiling point should be well above 250*??
Thanks for the suggestions of where to look, guys…
Bill B
It is extremely difficult to remove all
of the air from a rotary engines cooling system. It is also extremely
important. If air is under the pressure cap in a static situation, it will
remix with other coolant when the engine is at speed. The coolant moves very
quickly through the system. The coolant volume appears to increase slightly
because much of the air is reintroduced into the water. This coolant then
becomes a poor conductor of heat. You need the anti foaming agent in
Antifreeze. Just a bit, perhaps 10%. The system with the relief cap right on
the radiator or filler point, starts to offload coolant as soon as the engine
is started. It is in hydraulic lock, and has a small volume. The actual boiling
point calculated for this coolant makes no difference at all. The cap opens a
bit when the trip pressure is attained, the pressure drops to 22 PSI or
whatever for your cap, and a bit more heating trips the cap again. It is
exactly the same as most cars.
So, at first in each heat cycle, there
may be no correlation between coolant temperature, and the actual amount of
coolant dumped by the cap. This is only true closer to a constant operating
temperature. And then pressure may be alarmingly unstable with power changes.
The accumulator system makes pressure rock solid.
Make the pressure cap into a filler cap,
sealing only the top lip of the radiator or filling port. Connect only a
bleed hose and run it to the bottom of a recovery bottle, and put the
pressure relief cap on that bottle. Keep the bottle about 1/3 full. Note after
several heat cycles, the amount of water you need to add to keep that bottle
1/3 full is reduced each time. Once all of the air is out of the cooling
system, no more coolant need be added to the bottle.
Heating and cooling of the system, makes
sweeping changes in coolant volume. The air cushion in the bottle acts as an
accumulator (used in thousands of aircraft) to maintain a constant pressure and
coolant supply.
Race cars use a Rolairtrol or spin bottle
in the hose from the top of the engine to the radiator. Water enters the bottle
at about half height on a tangent and adds a spinning motion. Water leaves
through a center hole at the bottom.
Trapped air pops to the top of the bottle
and that is plumbed to the bottom of the accumulator as above.
You used to get the plans for this thing
when you buy a Cosworth race engine. Does Cosworth know something you
don't?
Anyway, after about three heat cycles
(operating temperature and back to room temperature) the coolant system will be
solid coolant with all of the air removed. It will not be hydraulically locked
against the cap.
It will have the relief cap pressure, and
will hold that for as long as the engine is hot.
I have a Shrader valve installed in my
accumulator tank, and before I start the engine I charge that bottle with
compressed air until the cap relieves at 22 PSI. Now I know it has pressure,
and I know it has 22 PSI.
This was the stock system on all Mazda
cars in the 70s. I didn't invent it.
It is unlikely that you have leaking
compression seals, unless there is coolant blowing out of your makeup tank, or
coolant is running out of your exhaust system after shutdown.
My recovery bottle is mounted where the
passenger foot well would have been. Even with the bottom of the engine. So
long as the hose ID is less than 1/4" and the hose enters the bottle on
the bottom of the coolant supply, it matters not at all where that bottle is
located. There is a money back guarantee with this system.