X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 2 [X] Return-Path: Received: from m12.lax.untd.com ([64.136.30.75] verified) by logan.com (CommuniGate Pro SMTP 5.1.7) with SMTP id 1931720 for flyrotary@lancaironline.net; Tue, 20 Mar 2007 01:30:16 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.136.30.75; envelope-from=alwick@juno.com Received: from m12.lax.untd.com (localhost [127.0.0.1]) by m12.lax.untd.com with SMTP id AABC986KGADHZPX2 for (sender ); Mon, 19 Mar 2007 22:29:10 -0700 (PST) X-UNTD-OriginStamp: L941HVjjYzDhN3itp//mkN5kjSiIpB62hctXzN6buVhMSFMD9OX3tw== Received: (from alwick@juno.com) by m12.lax.untd.com (jqueuemail) id MG9K5VYP; Mon, 19 Mar 2007 21:28:22 PST To: flyrotary@lancaironline.net Date: Mon, 19 Mar 2007 22:12:48 -0700 Subject: Re: [FlyRotary] Re: water boiling point Message-ID: <20070319.222751.2592.13.alwick@juno.com> X-Mailer: Juno 5.0.49 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary=--__JNP_000_70db.76ef.5cbd X-Juno-Line-Breaks: 8-6,13-14,16-19,21,23-27,29-31,33-34,37-38,42-43,51-52,62-63,65-68,71-74,77,79,85-92,94,96-97,98-32767 From: al p wick X-ContentStamp: 30:15:913113087 X-MAIL-INFO:18d8d861dd9848f838c95961b559c14c1128ad5975395885dd75ad28751c75a9d18c9d7cd8bc615c61f5dd18c1b17118f898698cb935dc614d8cc1c5ac25ac4d6c756925fcf9ec09fc X-UNTD-Peer-Info: 127.0.0.1|localhost|m12.lax.untd.com|alwick@juno.com This message is in MIME format. Since your mail reader does not understand this format, some or all of this message may not be legible. ----__JNP_000_70db.76ef.5cbd Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Interesting points. If I added a 1/4 cup more coolant, then my pressure would peak at 12 psi instead of 7. I like your theory. I'll dial it in to higher psi on new engine. So you can adjust your normal peak pressure using that method. The important concept is to not allow the system to reach cap psi. This little change improves understanding and safety. Yet you want a high psi cap just in case something goes wrong. Safety margin. I know it sounds like trivial difference, but it isn't. I've seen results of cavitation. Not on water pump, but others. Pretty profound. -al wick Cozy IV powered by Turbo Subaru 3.0R with variable valve lift and cam timing. Artificial intelligence in cockpit, N9032U 240+ hours from Portland, Oregon Glass panel design, Subaru install, Prop construct, Risk assessment info: http://www.maddyhome.com/canardpages/pages/alwick/index.html On Mon, 19 Mar 2007 15:59:47 -0800 "Al Gietzen" writes: Al W; I don’t disagree with your concept, but I think there are other considerations. The air volume number of 2 cups only applies to your system. The 7 psig you mention implies that you only get a bit over ½ cup expansion of coolant. In my system I know I get at least 6 times that much. In addition to the boiling point protection, there is the consideration of pump cavitation. When I was designing my system, I recall some pretty awful photos (on the ACRE list) of what cavitation can do a pump impellor. Since we generally run at high rpm, it’s likely an issue. And “ideal” pressure depends on where you measure it, and where the cap pressure is. There is likely at least a few psi difference between the pump inlet and the outlet. If the 7 psig (gauge pressure) you mention is on the outlet side, then it may be close to 0 psig at the inlet, and considerably lower behind the vane in the pump. At 180F water flashes to steam bubbles at about -7 psig (8 psia), so there could be a have high probability of cavitation. And that’s at sea level. If the 7 psig is at the pump inlet, you’d be a bit better off. That’s why I designed my system to have a ‘cap pressure’ of 23 psig on the pump inlet side, why I have no air under that cap, and why I have a pressure cap on the expansion bottle; so even when the coolant temp is decreasing, and the cap pressure is 0 psig, there is still some positive pressure at the pump inlet. Of course designing for this consideration takes care of the boiling protection as well, and provides some margin for altitude, since we generally fly considerably above sea level. It has worked fine for me so far. Concerning masking a compression leak, I think whether the pressure is 7 or 27 it is negligible compared to combustion pressures. I don’t know that this is necessary, right, wrong, or ideal; but it made sense to me. Al G There's one coolant design that's substantially better than the others. I discovered it when doing severe ground testing...deliberately overheating my engine. Three basic requirements: 1) Place your radiator cap and reservoir above engine. The higher the better. This allows trapped air in system to rise out of the flow and stay there. 2) Put a 24 psi cap on the system. You can throw away your overflow stuff. Not needed. 3) Always keep around 2 cups of air under the cap. This is the key item. It brings a big safety advantage. It allows you to use coolant pressure to predict well in advance how good your system is doing. It minimizes pressure. Mine never exceeds 7 psi. But if something goes wrong, then my pressure rises and I gain boilover protection due to the increase in system pressure. -al wick Cozy IV -al wick Cozy IV powered by Turbo Subaru 3.0R with variable valve lift and cam timing. Artificial intelligence in cockpit, N9032U 240+ hours from Portland, Oregon Glass panel design, Subaru install, Prop construct, Risk assessment info: http://www.maddyhome.com/canardpages/pages/alwick/index.html ----__JNP_000_70db.76ef.5cbd Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Re: [FlyRotary] water boiling point
Interesting points. If I added a 1/4 cup more coolant, then my = pressure=20 would peak at 12 psi instead of 7. I like your theory. I'll dial it in to = higher=20 psi on new engine. So you can adjust your normal peak pressure using that=20 method. The important concept is to not allow the system to reach cap psi. = This=20 little change improves understanding and safety. Yet you want a high psi = cap=20 just in case something goes wrong. Safety margin. I know it sounds like = trivial=20 difference, but it isn't.
 
I've seen results of cavitation. Not on water pump, but others. Pretty= =20 profound.
 

-al wick
Cozy IV powered by Turbo Subaru 3.0R with variable = valve=20 lift and cam timing.
Artificial intelligence in cockpit, N9032U 240+ = hours=20 from Portland, Oregon
Glass panel design, Subaru install, Prop construct= ,=20 Risk assessment info:
http:= //www.maddyhome.com/canardpages/pages/alwick/index.html
 
On Mon, 19 Mar 2007 15:59:47 -0800 "Al Gietzen" <ALVentures@cox.net> writes:

Al=20 W;

 

I don=92t = disagree=20 with your concept, but I think there are other=20 considerations.

 

The air = volume=20 number of 2 cups only applies to your system.  The 7 psig you = mention=20 implies that you only get a bit over =BD cup expansion of coolant.  = In my=20 system I know I get at least 6 times that much.

 

In addition = to the=20 boiling point protection, there is the consideration of pump cavitation.= =20  When I was designing my system, I recall some pretty awful photos (= on=20 the ACRE<= /FONT> list) of = what=20 cavitation can do a pump impellor.  Since we generally run at high = rpm,=20 it=92s likely an issue.  

 

And =93ideal= =94=20 pressure depends on where you measure it, and where the cap pressure is.&= nbsp;=20 There is likely at least a few psi difference between the pump inlet and = the=20 outlet.  If the 7 psig (gauge pressure) you mention is on the outlet= =20 side, then it may be close to 0 psig at the inlet, and considerably lower= =20 behind the vane in the pump. At 180F water flashes to steam bubbles at = about=20 -7 psig (8 psia), so there could be a have high probability of=20 cavitation.  And that=92s at sea level. If the 7 psig is at the pump= inlet,=20 you=92d be a bit better off.

 

That=92s why= I=20 designed my system to have a =91cap pressure=92 of 23 psig on the pump = inlet side,=20 why I have no air under that cap, and why I have a pressure cap on the=20 expansion bottle; so even when the coolant temp is decreasing, and the = cap=20 pressure is 0 psig, there is still some positive pressure at the pump = inlet.=20  Of course designing for this consideration takes care of the = boiling=20 protection as well, and provides some margin for altitude, since we = generally=20 fly considerably above sea level. It has worked fine for me so far.=20  Concerning masking a compression leak, I think whether the pressure= is 7=20 or 27 it is negligible compared to combustion pressures.=20  

 

I don=92t = know that=20 this is necessary, right, wrong, or ideal; but it made sense to=20 me.

 

Al=20 G

 

There's one= =20 coolant design that's substantially better than the others. I discovered = it=20 when doing severe ground testing...deliberately overheating my engine.=20

 

Three=20 basic requirements:

 

1)=20 Place your radiator cap and reservoir above engine. The higher the better= .=20 This allows trapped air in system to rise out of the flow and stay there.= =20

2)=20 Put a 24 psi cap on the system. You can throw away your overflow stuff. = Not=20 needed.

3)=20 Always keep around 2 cups of air under the cap. This is the key item. It= =20 brings a big safety advantage. It allows you to use coolant pressure to=20 predict well in advance how good your system is doing. It minimizes = pressure.=20 Mine never exceeds 7 psi. But if something goes wrong, then my pressure = rises=20 and I gain boilover protection due to the increase in system=20 pressure.

 -al=20 wick
Cozy IV

 

 

 

-al wick
Cozy IV powered by Turbo = Subaru=20 3.0R with variable valve lift and cam timing.
Artificial intelligence = in=20 cockpit, N9032U 240+ hours from Portland, Oregon
Glass panel design, = Subaru=20 install, Prop construct, Risk assessment=20 info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html
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