larry(at)macsmachine.com
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 Posted: Mon Jun 27, 2011 5:44 pm Post subject: [Probable Spam] Zenair601HDS Stratus/Ram cooling problem |
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HI Ron,
The cooling issue is very common, but coolant temps should never see more than 200 on a hot day in a perpetual climb. My cowl opening just ahead of the oil pan for some reason cools better in a climb than going fast flat and level. As you’ve done the jetting, you might consider the propeller pitch. My Warp Drive 70-inch 3 blade set for 17-1/2 degrees per their instrument does a much better job of cooling flat out at or near
120 mph. The pitch allows lower rpms, better speed. I trim nose down carefully to get best speed by setting rpms to 4300 for best fuel burn until the rate of climb gage indicates level flight. You feel the center of lift move slightly back on the wing and get optimum cooling this way too. Odd, I flew for a year or more before realizing that trimming in the last bit of down elevator at a cruise rpm would increase performance and cooling so much. Used to also worry that the nose was always slightly up before discovering this.
I seldom fly flat out as there’s no way to justify the fuel burn and engine wear at 5000 rpm.
Note the links show the hole in front of the oil pan and heat from the exhaust pipes is fed cool air either side of the cowl looking straight in
at aluminum sleeve clearance aluminum. They made a significant difference.
http://www.macsmachine.com/images/completion/full/601ezclosefrtrt.gif
http://www.macsmachine.com/images/cowling/full/cowelfrtlower.gif
Hope this helps,
Fly safe
Larry McFarland 601HDS at www.macsmachine.com
From: owner-stratus-list-server(at)matronics.com [mailto:owner-stratus-list-server(at)matronics.com] On Behalf Of ron hansen
Sent: Monday, June 27, 2011 5:53 PM
To: stratus-list(at)matronics.com
Subject: [Probable Spam] Zenair601HDS Stratus/Ram cooling problem
Hi listers,
I've been quiet a long time due to life interfering with my plans, but I need some help. I had about 60 hours on my 601HDS with a Stratus on it. I was fighting temp. issues from the start, adjusting the carb jets and such. I had Ram modify the heads before it flew. Anyway, I never went past the Stratus 230 deg. "water temp" redline, but often approached it. Taxiing in after 60 flight hours I broke a valve seat and later learned broke a piston. I have not been pleased with Stratus support for years so I had Ram Performance rebuild the engine. He also made some other changes and it now runs stronger and cooler, but still not cool enough. I moved the "water temp" probe from the Stratus setup in the cylinder head dry-hole to actual water as it comes out of the engine. Ram says water temp redline should be 220 deg. and the engine should run at the thermostat setting of 190 deg. Research I've done would indicate the same for long engine life.
Anyway, I still get water temp climbing to 220 a few minutes after takeoff on a warm day and I suspect it would go higher. My radiator is the stock Zenair radiator installed per plans. Gaps are sealed. Coolant is 50/50 per instructions. I'm beginning to think the Zenith setup is not suitable for a 100HP engine that is water cooled. The Rotax they designed it for only uses water to cool the heads.
I don't want to ruin my new Ram-rebuilt engine. It is running really well: stronger, cooler, lower fuel burn......but it's not running at the temps it should do to a weak cooling system. If anyone has data or ideas that would help I would appreciate hearing from you. I recall all sorts of discussion from years past (this plane took me many years to build from plans), but I can't remember where all those ideas ended up. I know some were abandoned, but others probably solved some or all of the problem. I've gone through the archives, but you never know if you're missing something important that came later.
Thanks,
Ron Hansen
Los Angeles
601HDS, Ram-Rebuilt (formerly Stratus) Subaru EA81 | Quote: | | http://www.matronics.com/Navigator?Stratus-List |
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