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Threadcharmer(at)cs.com
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 Posted: Tue Oct 23, 2007 10:48 am Post subject: Rotax 912ULS overheating issues |
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Is anyone else out there flying an Allegro 2000 with a 100 hp Rotax 912ULS? I'm interested in finding out about any overheating issues. I just completed my kit on amphibious Shark Floats after 18 months and can't get around the pattern more than twice before having to land with the temp creeping up close to 275F. I've added more intake area to the front of the cowling, including one set of openings that allows fresh air to flow directly over the cylinders. I've also added a 2" naca vent to the top of the cowling with a hose flowing directly to the radiator. In my last attempt, I removed the spinner (I was using a 10" UHS) and the temperature came down about 10 degrees.
Most of the Allegros I've heard of are using the 80hp Rotax, which in my opinion, can get away with the smaller radiator they left us space for. Any further thoughts on the subject?
Dale Hackworth
splashlanding(at)comcast.net
Allegro 2000
N306AD
Hobe Sound, FL [quote][b]
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hgmckay
Joined: 23 May 2006
Posts: 397
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| Posted: Wed Oct 24, 2007 5:50 pm Post subject: Rotax 912ULS overheating issues |
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Dale:
I do not fly an Allegro 2000 with a Rotax 912ULS, but I do fly an Allegro 2000 with a Rotax 912UL in North Carolina. I can tell you this from experience, you don’t want to keep an Allegro 2000 with a 912UL running long on the ground (especially on a hot day). If the plane is not flying and not getting the ram air (80 to 100 mph air) forced in through the engine compartment, the CHT will climb very quickly. Because the engine is fully coweled in the Allegro, and has very little frontal opening for air to pass over the engine (especially with a spinner and the large connection flange), and the fact that the radiator location is just opposite of where it should be (in my humble opinion), the engine can quickly overheat while on the ground. In the air flying, everything is fine on my plane. No problems.
<![if !supportEmptyParas]> <![endif]>
I can only imagine what you are dealing with having the same (small) radiator with a 912ULS, and floats on top of every thing else. I don’t believe Fantasy Air has given very much thought to this problem, and I don’t expect you will get much help from the US Distributor. My suggestion is don’t stay on the ground longer than necessary, leave the spinner off, get as much air as possible in, around the engine, and through the radiator, and if there is any way possible, put a larger radiator on the plane. Also, the fact that you are in a hot humid climate (Florida) doesn’t help things with this small radiator.
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Hugh McKay in North Carolina
Allegro 2000
Rotax 912UL
N661WW
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-----Original Message-----
From: owner-allegro-list-server(at)matronics.com [mailto:owner-allegro-list-server(at)matronics.com]On Behalf Of Threadcharmer(at)cs.com
Sent: Tuesday, October 23, 2007 2:48 PM
To: allegro-list(at)matronics.com
Subject: Rotax 912ULS overheating issues
<![if !supportEmptyParas]> <![endif]>
Is anyone else out there flying an Allegro 2000 with a 100 hp Rotax 912ULS? I'm interested in finding out about any overheating issues. I just completed my kit on amphibious Shark Floats after 18 months and can't get around the pattern more than twice before having to land with the temp creeping up close to 275F. I've added more intake area to the front of the cowling, including one set of openings that allows fresh air to flow directly over the cylinders. I've also added a 2" naca vent to the top of the cowling with a hose flowing directly to the radiator. In my last attempt, I removed the spinner (I was using a 10" UHS) and the temperature came down about 10 degrees.
Most of the Allegros I've heard of are using the 80hp Rotax, which in my opinion, can get away with the smaller radiator they left us space for. Any further thoughts on the subject?
Dale Hackworth
splashlanding(at)comcast.net
Allegro 2000
N306AD
Hobe Sound, FL [quote]<![if !supportEmptyParas]> <![endif]><![if !supportEmptyParas]> <![endif]> - The Allegro-List Email Forum - --> http://www.matronics.com/Navigator?Allegro-List - NEW MATRONICS WEB FORUMS - --> http://forums.matronics.com<![if !supportEmptyParas]> <![endif]>[b]
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aerosiam
Joined: 26 May 2008
Posts: 59
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| Posted: Mon May 26, 2008 10:29 am Post subject: Re: Rotax 912ULS overheating issues |
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We fly an Allegro 2000 100hp in Thailand with temperatures around 28 to 35 degrees (82 to 96F). It would overheat within 10 mins of startup at 2200 rpm and needed very gentle climbouts.
We fitted EvansCool and opened a circular hole in the lower cowling and enlarged the oil cooler opening about 3 times. (See picture)
The oil runs too cool now and once a day we have to get the oil temperature over 100C (250F) - Rotax say this must be done to avoid condensation problems in the oil system.
The additional oil cooling and reduction in cyl head temp with the extra airflow is now acceptable and it never goes over 130C. (Max 150C) We checked the senders in boiling water - they were underreading on the guage by about 10F.
The best solution is probably to fit the Rotax cooling baffle. I have a friend with an 80hp who has it fitted and the opening is only about 1.5 in diameter but it never overheats. The problem is that the baffle is very expensive.
Regards
Paul
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