Today's Message Index:
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1. 09:25 AM - Re: RotaxEngines-List Digest: 3 Msgs - 01/04/11 (Stan Tew)
2. 08:12 PM - Re: drop of rpm on take off (moosepileit)
Message 1
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| Subject: | Re: RotaxEngines-List Digest: 3 Msgs - 01/04/11 |
Georg,
Warm air is rich air, cold air is lean air. At -15 C, which very few of us
experience, you could very well be getting an extremely lean mixture. This can
cause a variety of problems including but not limited to detonation and
preignition.
My suggestion would be to lower the clip/raise the needle 1 notch to richen the
mixture.
STAN 2
N29TD
________________________________
From: RotaxEngines-List Digest Server <rotaxengines-list@matronics.com>
Sent: Wed, January 5, 2011 1:58:49 AM
Subject: RotaxEngines-List Digest: 3 Msgs - 01/04/11
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Total Messages Posted Tue 01/04/11: 3
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Today's Message Index:
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1. 02:34 PM - drop of rpm on take off (georg.stiller@arcor.de)
2. 03:55 PM - Re: drop of rpm on take off (Simon Lancashire)
3. 06:33 PM - Re: drop of rpm on take off (ruruny@aol.com)
________________________________ Message 1
_____________________________________
Time: 02:34:11 PM PST US
From: georg.stiller@arcor.de
Subject: RotaxEngines-List: drop of rpm on take off
Hi all,
I just subscribed to the list. What a great forum!
I have trouble with my 80 hp 912. Maybe someone has a good idea and can give me
some help.
Background:
912 with 150 hrs. in a Kitfox, no troubles so far, 98 octane auto fuel, alcohol
test negative, aircraft parked in heated hangar, properly drained and engine
run up, fuel always filtrated, filter visually clean, carbs freshly
pneumatically
balanced, mag drop ca. 200/300 rpm (has recently deteriorated).
What happened:
Very cold outside temperature, about -15 centigrade. Max. ground rpm ca. 5000
rpm
(should be 5100, has deteriorated somewhat - under cold conditions?),
acceleration
and take off normal, a couple of seconds after take off sudden drop of
rpm to ca. 4500-4600 rpm. After another couple of seconds and the engine catches
up and returns to 5000 rpm. At least, so far it always did. No problems in
cruise with 4300 rpm.
I usually take off and cruise also under these cold conditions without carb
heat.
I tried a take off with carb heat and a couple of seconds after take off: rpm
drop as obove!
All this happened four or five times.
Next I plan to change the spark plugs, although they still look good and the
manual
says change after 200 hrs.
Any help would be highly appreciated!
Thanks, Georg
Kitfox, 912 80 hp
Germany
________________________________ Message 2
_____________________________________
Time: 03:55:41 PM PST US
From: "Simon Lancashire" <simon@design24.org.uk>
Subject: RE: RotaxEngines-List: drop of rpm on take off
Georg,
I am new to this forum and have a Pulsar with an early 912. My aircraft is
low wing and has a boost pump as the fuel tanks are below the engine. Is it
possible that your problem may be due to low fuel pressure due to the angle
of incidence at the point of takeoff in the kitfox? (very nose high) The
standard Rotax pump can only suck so hard and may be o0n the limit without
help. Fuel boost pumps are inexpensive and easy to fit and i use mine always
for take-off, landing and fuel tank switching.
Good luck!
Simon, UK Pulsar XP G-BUZB
-----Original Message-----
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of
georg.stiller@arcor.de
Sent: 04 January 2011 22:30
Subject: RotaxEngines-List: drop of rpm on take off
Hi all,
I just subscribed to the list. What a great forum!
I have trouble with my 80 hp 912. Maybe someone has a good idea and can give
me some help.
Background:
912 with 150 hrs. in a Kitfox, no troubles so far, 98 octane auto fuel,
alcohol test negative, aircraft parked in heated hangar, properly drained
and engine run up, fuel always filtrated, filter visually clean, carbs
freshly pneumatically balanced, mag drop ca. 200/300 rpm (has recently
deteriorated).
What happened:
Very cold outside temperature, about -15 centigrade. Max. ground rpm ca.
5000 rpm (should be 5100, has deteriorated somewhat - under cold
conditions?), acceleration and take off normal, a couple of seconds after
take off sudden drop of rpm to ca. 4500-4600 rpm. After another couple of
seconds and the engine catches up and returns to 5000 rpm. At least, so far
it always did. No problems in cruise with 4300 rpm.
I usually take off and cruise also under these cold conditions without carb
heat. I tried a take off with carb heat and a couple of seconds after take
off: rpm drop as obove!
All this happened four or five times.
Next I plan to change the spark plugs, although they still look good and the
manual says change after 200 hrs.
Any help would be highly appreciated!
Thanks, Georg
Kitfox, 912 80 hp
Germany
________________________________ Message 3
_____________________________________
Time: 06:33:50 PM PST US
Subject: RotaxEngines-List: RE: drop of rpm on take off
From: ruruny@aol.com
Carb float bowl vents run to bottom of firewall?
Message 2
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| Subject: | Re: drop of rpm on take off |
I think the air may be too cold for your carb needle setting. 30 degrees C below
standard needs about as much extra fuel as when I moved my plane from 5000'
MSL to sea level.
My issues were LESS severe than yours. Setting the carb needle clips down from
#2 to #3 position (3 is normal) fixed the issue nicely.
Hopefully someone like Roger Lee can help you out.
I had sync'd my carbs just before finally isolating my issue, after moving the
clips the carbs needed only slight rebalance, then it was smiles all around.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=325755#325755
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