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bicyclop(at)pacbell.net
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 Posted: Thu Sep 21, 2006 3:04 pm Post subject: EGT Span |
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Steve,
Carbureted Lycomings have lousy fuel/air distribution and the EGTs are
gonna be all over the place. I've found that pulling off about a tenth
of an inch of manifold pressure helps even out the fuel distribution and
brings the EGTs closer together on our O-320. The slightly deflected
throttle causes turbulence and better mixing. You can experiment with a
touch of carb heat too which has a similar effect. If you use carb heat,
you may need to re-lean a little to account for the extra richness.
All that said, the EGT spread doesn't mean too much. Absolute EGT values
aren't very important and could be off because of probe errors anyway.
What you really want to watch for is changes in temperatures from the
normal way it runs that might tell you something has happened. A rise in
EGT in one cylinder might mean a fouled plug or a bad valve. A rise in
all of them could be a bad mag. If your 170 degree spread is normal for
your engine, you could always set the alarm for 180 and quit worrying or
just keep punching the acknowledge button when the alarm goes off.
Pax,
Ed Holyoke
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kbob(at)cox.net
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| Posted: Fri Sep 22, 2006 4:45 pm Post subject: EGT Span |
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My only experience with this issue was the result of carb ice. I was
cruising at 17K, WOT and checking on my engine EGT's. The carb O-320 is not
making much HP at this elevation, and DA of approx. 19-20K. The EGT's began
to spread and this really puzzled me. Messing with the mixture did nothing.
Remembering something I read on this list got me to pull the carb heat and
see what happens. After a few seconds the EGT's were even again and I
removed the carb heat. Didn't happen again, so I chocked it up to
experience.
Kelly Patterson
RV-6A N716K Chandler, AZ
O-320 carb 9.2:1 CR & Emag
108 hrs of good times
Time: 04:04:46 PM PST US
From: "Ed Holyoke" <bicyclop(at)pacbell.net>
Subject: RE: EGT Span
Steve,
Carbureted Lycomings have lousy fuel/air distribution and the EGTs are gonna
be all over the place. I've found that pulling off about a tenth of an inch
of manifold pressure helps even out the fuel distribution and brings the
EGTs closer together on our O-320. The slightly deflected throttle causes
turbulence and better mixing. You can experiment with a touch of carb heat
too which has a similar effect. If you use carb heat, you may need to
re-lean a little to account for the extra richness.
All that said, the EGT spread doesn't mean too much. Absolute EGT values
aren't very important and could be off because of probe errors anyway. What
you really want to watch for is changes in temperatures from the normal way
it runs that might tell you something has happened. A rise in EGT in one
cylinder might mean a fouled plug or a bad valve. A rise in all of them
could be a bad mag. If your 170 degree spread is normal for your engine, you
could always set the alarm for 180 and quit worrying or just keep punching
the acknowledge button when the alarm goes off.
Pax,
Ed Holyoke
--
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http://www.matronics.com/Navigator?RV-List |
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