Today's Message Index:
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1. 05:43 AM - engine shudder (Darryl Braun)
2. 07:33 AM - Re: engine shudder (Richard Holder)
3. 09:14 PM - Re: engine shudder (Darryl Braun)
Message 1
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--> RotaxEngines-List message posted by: "Darryl Braun" <dvbraun@telus.net>
I have a situation I hope someone can shed some light on. I'm running a
912 with a 3 blade Warp Drive prop on a 94 Ultravia Pelican PL. If I pitch
the prop for climb and throttle back at altitude I'll get an occasional
engine shudder. It actually feels more like someone hit the engine mount
with a hammer or something, just a quick thump. The engine never misses a
beat. I've tried 2 and 3 blade wood props and finally the Warp Drive to no
avail. I've found that keeping a course pitch on the prop kills the proplem
completely during cruise, but I'd like to be able to pitch for climb on hot
days. When set to a course pitch I can still get the shudder if I decend
too fast with out throttling back. So basically if the engine isn't working
very hard it tends to have this problem. If I keep it working hard... no
problem. I've synced the carbs at every oil change and had the PSRU
inspected and nothing changed. I've talked to my mechanic and even to Rotax
and they don't know what the deal is. Anyone out there know what's going
on?
Darryl Braun
Ultravia Pelican PL
C-GGVS
Cold Lake
Message 2
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| Subject: | Re: engine shudder |
--> RotaxEngines-List message posted by: Richard Holder <rholder@avnet.co.uk>
Darryl Braun wrote:
> I have a situation I hope someone can shed some light
> on. I'm running a 912 with a 3 blade Warp Drive prop
> on a 94 Ultravia Pelican PL. If I pitch the prop for
> climb and throttle back at altitude I'll get an
> occasional engine shudder. It actually feels more like
> someone hit the engine mount with a hammer or
> something, just a quick thump. The engine never misses
> a beat. I've tried 2 and 3 blade wood props and
> finally the Warp Drive to no avail. I've found that
> keeping a course pitch on the prop kills the proplem
> completely during cruise, but I'd like to be able to
> pitch for climb on hot days. When set to a course
> pitch I can still get the shudder if I decend too fast
> with out throttling back. So basically if the engine
> isn't working very hard it tends to have this problem.
> If I keep it working hard... no problem. I've synced
> the carbs at every oil change and had the PSRU
> inspected and nothing changed. I've talked to my
> mechanic and even to Rotax and they don't know what the
> deal is. Anyone out there know what's going on?
I would bet that the engine DOES miss a beat, one or two !
if it happens at the top of the climb when you reduce
power for the cruise then it could well be fuel
vaporization. How close to the exhaust does your fuel pipe
to each carb go ? In the climb there is enough fuel
flowing to avoid the problem. then Immediately after
reducing power everything is "climb-hot" and and the fuel
is flowing slowly -> gets hot -> vaporises -> misfire !
Which stops after 30 seconds or so.
I had this and it took me 6 months to find it ! I run my
fuel pipes to the carb _over_ the carb now, rather than
underneath/ You need a made up union as the banjo won't
move to allow an upwards pipe. Even pointing the banjos
rearward - away from the exhaust - might help !
A hiccup in the cruise after many minutes is most likely
to be carb ice.
I assume it is not a continuous problem so it won't be
anything to do with the prop ! (Famous last words - sorry !)
Richard
G-OWWW Europa 912S Airmaster
Message 3
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--> RotaxEngines-List message posted by: "Darryl Braun" <dvbraun@telus.net>
Thanks Richard
Unfortunately it's not carb ice or vapor lock. It will happen from -20 to
+30 and my fuel lines are all on top of the engine. It's something related
to how hard the engine works. If the engine is turning the prop then it's
smooth as silk... if the prop is turning the engine (or the engine is just
not working hard) I get a little kick in the pants every few minutes, and it
is continuous. I'll keep looking into it and try to record some more data
on when it happens. It seems like a harmonic vibration between the engine
and the prop, but after 3 different props I know that's not it. I'm
wondering if it's ignition. The engine doesn't want to loaf but works well
under load. My truck was doing almost the same thing and it turned out to
be bad plug wires.
If you can think of anything else or hear of anything, please let me know.
Thanks again.
Darryl Braun
Ultravia Pelican PL
C-GGVS
Cold Lake
-----Original Message-----
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com]On Behalf Of
Richard Holder
Sent: Tuesday, May 09, 2006 7:31 AM
Subject: Re: RotaxEngines-List: engine shudder
--> RotaxEngines-List message posted by: Richard Holder
<rholder@avnet.co.uk>
I would bet that the engine DOES miss a beat, one or two !
if it happens at the top of the climb when you reduce
power for the cruise then it could well be fuel
vaporization. How close to the exhaust does your fuel pipe
to each carb go ? In the climb there is enough fuel
flowing to avoid the problem. then Immediately after
reducing power everything is "climb-hot" and and the fuel
is flowing slowly -> gets hot -> vaporises -> misfire !
Which stops after 30 seconds or so.
I had this and it took me 6 months to find it ! I run my
fuel pipes to the carb _over_ the carb now, rather than
underneath/ You need a made up union as the banjo won't
move to allow an upwards pipe. Even pointing the banjos
rearward - away from the exhaust - might help !
A hiccup in the cruise after many minutes is most likely
to be carb ice.
I assume it is not a continuous problem so it won't be
anything to do with the prop ! (Famous last words - sorry !)
Richard
G-OWWW Europa 912S Airmaster
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