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TELEDYNMCS(at)aol.com
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 Posted: Tue Sep 25, 2007 4:30 am Post subject: Jabiropa performance |
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In a message dated 9/25/2007 2:58:31 AM Eastern Daylight Time, europa-list(at)matronics.com writes:
| Quote: | Thank you for providing those much interesting numbers.
Very interesting data, indeed, and I'm sure many homebuilder will be
interested in how you achieved a successful engine installation.
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Hi Gilles,
You're quite welcome.
It's really no mystery as to how to arrive at a successful engine installation:
Pay attention to the folks who are successful and ignore the folks who aren't.
The real trick is being able to wade through those spreading minutia and get to those who are real achievers and who have had real success and mimic what they did. That can be a tough row to hoe, especially considering the millions of soap boxes out there, courtesy of the Internet.
Regards,
John Lawton
Whitwell, TN (TN89)
N245E - Flying
See what's new="_blank">Make AOL Your Homepage.
[quote][b]
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TELEDYNMCS(at)aol.com
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| Posted: Tue Sep 25, 2007 5:01 am Post subject: Jabiropa performance |
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In a message dated 9/25/2007 2:58:31 AM Eastern Daylight Time, europa-list(at)matronics.com writes:
| Quote: | thanks a lot for that. There are three or four Jabiropas here. One I
know of is very happy but the others less so. My main question is do you
have any baffles to force the cooling air throught the fins, or do you
rely on the pressure in the plenums? My friends are using deflectors
rather than baffles which I feel is a bit imprecise. I am more familiar
with the sort of baffles EZ guys use on Lyconental engines where careful
baffling works well.
The Jabiru agents here in UK do not seem to have much in the way of good
ideas. |
Hello Graham,
My 3300 is one of the newer ones with the larger head cooling fins, but just before they switched to hydraulic lifters.(S/N 33A756 or #756) The engine came with fiberglass ducts of unknown origin, IOW, not Jabiru factory ducts, that fit over the top of the cylinders. I'm pretty sure Andy had the same guy who made the cowls make the ducts, but I've not verified that to be fact. Two, round 4" aluminum intake rings are captured by the cowl (similar to a Lancair) and serve to direct air into the ducts. I used 3mm rubber sheet to make a transition from the ring to the duct. This rubber helps damp vibration between the cowl and the engine and allows the two to move independently of each other. The two 4" rings together give me 25 square inches of intake and that should be more than enough for adequate cooling and it is has shown to be adequate on all but the hottest days. I only really see one cylinder that gets a bit hot in climb above 95F ambient temperature and it's still 30F below redline. I do have internal baffling to direct air over the center cylinders, but it is very subtle, maybe 3 mm tall on the inside top of the duct, parallel to the cylinder. Small changes in the height of these baffles make huge differences in CHT's. The height of the baffle is determined by trial and error. I'd start at about 5-7mm and whittle it down from there until a balance is achieved. You could make an internal baffle with successive layers of duct tape to determine the height, then replace it with either flox or a flat fiberglass piece cut to the shape of the inside of the baffle, then flox that into place. Initially, I was told to start with 1 cm high baffles, but it only took one short flight to realize that was way too much for my installation.
I've been doing some manometer testing on the pressure differential between the inside of the cowl and the inside of the duct and it has left me thinking that my left duct just isn't the right shape. Using Jabiru's manometer testing method, my results have been completely contradictory to what Jabiru says it takes for adequate cooling. So, I'm testing a new left side Sonex styled sheet metal duct today. I'll let everybody know if it works. If it does work, I'm going to do some manometer testing on it and get some hard numbers to play with in terms of what it really takes to make the left side run cool. Film at 11:00PM......
Regards,
John Lawton
Whitwell, TN (TN89)
N245E - Flying
See what's new="_blank">Make AOL Your Homepage.
[quote][b]
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grahamsingleton(at)btinte
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| Posted: Tue Sep 25, 2007 8:40 am Post subject: Jabiropa performance |
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John
thanks again! btw, why not use an ASI connected wrong way round to
measure the pressure differential inside the cowl, easier and more
convenient than flying with water filled tubes in the cockpit?
There is a table somewhere of indicated airspeed versus delta P
regards
Graham
T
| Quote: |
I've been doing some manometer testing on the pressure differential
between the inside of the cowl and the inside of the duct and it has
left me thinking that my left duct just isn't the right shape. Using
Jabiru's manometer testing method, my results have been
completely contradictory to what Jabiru says it takes for adequate
cooling.
Regards,
John Lawton
Whitwell, TN (TN89)
N245E - Flying
|
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