Mailing List flyrotary@lancaironline.net Message #36214
From: Russell Duffy <rusty@radrotary.com>
Subject: RE: [FlyRotary] Water Plumbing
Date: Wed, 14 Mar 2007 19:07:17 -0500
To: 'Rotary motors in aircraft' <flyrotary@lancaironline.net>
Message
Is it possible to plumb the system without a pressure tank? 
 
Hi Steve,
 
When you say pressure tank, I'm assuming you mean what Mazda called the AST or air separator tank.  This is a pressurized tank with a hose at the bottom, one in the middle, and a cap with overflow at the top. 
 
You certainly can run without it, and I believe the 1st and 2nd gen RX-7's did just that.  Mazda added it on the 3rd gen, and from what I understand, it's a good feature, because getting all the air out of the system is good for cooling.   
 
   I have an inline radiator cap with AN connectors on both ends and was wondering if I can just use that without the pressure tank. 
 
You could, but it won't be ideal. 
 
   Or can a pressure tank be located below the highest point? 
 
Yep, it sure can.  The only problem would be filling the system, so you'd need a higher point on the engine to do that.  
 
How about putting an AST as high as you can, then put your inline radiator cap in the high point of the system at the pump outlet.  That would make a dandy fill port.  The radiator cap on the AST would need to be lower pressure than the one on the fill port.  BTW, the above situation is exactly what the 3rd gen RX-7 has :-)
 
Cheers,
Rusty 
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