andynfultz(at)bellsouth.n
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 Posted: Wed Jun 22, 2011 5:37 am Post subject: Another STRATUS/Soob EA-81 Cooling? |
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This is certainly a question I should have asked from the beginning and didn't. What size is your radiator? I see a couple of you are using the VW Rabbit radiator. Lowell yours looks similar to the one I'm using. Mine is 26.5 wide and 5 tall. The fin area is 23"x5" giving me a total of 115 square inches of surface area.
Per several suggestions, I have changed out the coolant to an 80/20 ratio and added "water wetter" as well. Due to weather I haven't flown this combination yuet to see what difference this makes.
Thanks guys for all the help. Gonna go double check my guages in a few minutes.
Andy
From: Fox5flyer <fox5flyer(at)idealwifi.net>
To: kitfox-list(at)matronics.com
Sent: Wed, June 22, 2011 5:49:15 AM
Subject: Re: STRATUS/Soob EA-81 Cooling?
--> Kitfox-List message posted by: "Fox5flyer" <fox5flyer(at)idealwifi.net (fox5flyer(at)idealwifi.net)>
Agree with Lowell completely. Good advice. I used the same ratio for my scoop/fairing and it has worked fine for my purposes. Another thing, if I can add to Lowell's post, ensure that no air (zero) can escape around the radiator. What I mean is that if you enclose it (best, IMO), do not leave any gaps anywhere for air to bypass it, because that is exactly what the air will do. It is like water and will take the easiest path. It is extremely important to have high pressure at the inlet and low pressure at the outlet, otherwise the air will just bypass the whole thing and very little cooling will result. The best way to achieve this is a simple "lip" on the outlet side which will create a suction. This combined with the high pressure in front will drag lots of air through the rad. Better yet is to make that lip controllable.
I'm attaching some photos to illustrate what I'm talking about.
Good luck,
Deke
S5/Soob
[quote="lcfitt(at)sbcglobal.net"]Andy,
First my disclaimer - I know nothing specifically about the Subaru installation - but I would like to offer some ideas from other applications. I have helped build two airplanes and am in my second Kitfox IV build. I understand that the later model Kitfoxes with internal radiators have suffered at times from inadequate cooling. I am currently helping with a Series V with a 7 FWF set-up. It has an internal radiator and I have been told that the reason for the larger - by at least a factor of 2 - radiator was to help with cooling, as with earlier models that was an issue. As I looked over the installation, it became pretty obvious that the cowl inlet area providing cooling air to the radiator is considerable larger than the outlet area. Switch to the Lancair IV I helped with. Given that it is an air cooled engine, and arguably quite different, what follows might not totally apply, but when builders of this airplane found cooling problems, the solution was!
to decrease - yes decrease - the inlet area. This provided a lower pressure within the cowl and more smooth, slower flowing air over the fins which picked up more heat.
With the 7 FWF on the V build, the total outlet area under the cowl is about 110 in. Sq. The inlet to the radiator is a NACA duct that expands to the area of the radiator which is about 103 in. sq. Add to that 15 and 17 in. sq. for the oil cooler and the openings on each side of the spinner and the inlet area to the entire cowl is 135 in. sq. The general rule of thumb for air cooled is a 1.5 to 1 ratio outlet to inlet. The Kitfox has it not quite exactly reversed. I think what is happening in the Kitfox is the inadequate outlet is simply acting like a dam and the cooling air is simply bypassing the cowl openings seeing essentially a partially blocked hole. The Speedster radiator shroud I had on my first Model IV had the inlet to outlet ratio pretty much like what the Lancair folks found to work best.
All this is opinion, but it may give some suggestions on where to look regarding possible solutions.
Lowell
From: fox5flyer (fox5flyer(at)idealwifi.net (fox5flyer(at)idealwifi.net))
Sent: Tuesday, June 21, 2011 5:16 AM
To: Kitfox List (kitfox-list(at)matronics.com (kitfox-list(at)matronics.com))
Subject: Re: STRATUS/Soob EA-81 Cooling?
Hi, Andy. Obviously, unless you use a thermostat, the engine temps are directly affected by outside ambient temps. Higher oat means higher engine temps. With mine, at about 70 oat, I warm up to 150f for takeoff and generally by 2k agl engine temps increase to about 195 where they stay when I level off for cruise. I have my radiator enclosed with adjustable rear cowl flap so that I have some control over engine temps. On hot days I keep an eye on the climb temps as they can creep up to 215 or even higher. When that happens I just level off for a little while, then climb some more. I rarely get more than 4k agl anyway, so it isn't a problem here in Michigan. The temps you indicate do not seem extremely high to me. Adding throttle increases power and power produces heat so it's normal for the temps to rise somewhat. Of course, no two experimental aircraft setups are the same so, if it is a big concern, you might take a look at yours to see what you can!
do to scavenge more heat out of the cowling/radiator.
Deke
S5/NSI Subaru/CAP
470TT
--------
Deke Morisse
Kitfox S5 TD
NSI/CAP
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=343739#343739
Attachments:
http://forums.matronics.com//files/scoopdoor1_738.jpg
http://forums.matronics.com//files/scoop_finished6_104.jpg
http://forums.matronics.com//files/scoop_front1_303.jpg====
[quote][b]
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