-------------- Original message from Lehanover@aol.com: --------------

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 3â€? diameter and maybe 12â€? 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

 

---

See what's new at AOL.com and Make AOL Your Homepage.