Today's Message Index:
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1. 04:51 AM - Re: 912 starting problems (ElleryWeld@aol.com)
2. 07:20 AM - Re: egt temp (Noel Loveys)
3. 07:27 AM - Re: 912 starting problems (Roger Lee)
Message 1
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| Subject: | Re: 912 starting problems |
I have been adding a Primer pump to help get the 912's started faster with
success
Ellery in Maine
do not archive
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Message 2
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Thom:
Experience has shown me that as an engine is leaned the EGT will peak. That
peak is well above the recommended operating EGT. What is not commonly
known is that if the engine is leaned beyond the peak the EGT can actually
decrease at the probe while increasing at the crown of the piston.
Basically there is an intensely hot short flash at the piston, caused by
enough air to make the exhaust cooler at the EGT probe. Air craft with
mixture controls should be leaned to the peak then enrichened an amount to
keep the EGT below peak on the rich side of the peak.
If you continue to lean the engine past that peak point, the next thing you
will notice is some detonation or backfiring, rough running and finally the
engine will stop. Depending on how long the engine is running in that
condition will decide how much if any damage is done to the engine.
The point I was getting at being past time to refuel is that as the last of
the gas is being used from the fuel bowl in the carb the mixture will become
leaner and leaner due to lack of fuel causing the roughness and possible
backfiring just before the engine quits. Of course we all keep a minimum of
30 min (VFR) fuel in reserve so none of us should ever see that roughness
occur.
Noel
> Time: 03:49:40 AM PST US
> From: Thom Riddle <thomriddle@roadrunner.com>
> Subject: Re: RotaxEngines-List: egt temp
>
>
> Noel,
>
> .....When the engine is running lean you will notice more than an
> increase in EGT reading. You can get a drop in
> power and sometimes even a bit of back firing. This will also
> happen when it's past time to refuel.,,,,
>
> Can you elaborate on these statements? I don't understand how running
> lean can cause backfiring or what it has to do with being "past time
> to refuel".
>
> Not being argumentative, just trying to understand what you mean and
> how this happens. Perhaps you should begin with your definition of
> backfiring and quantify "past time to refuel".
>
> Thom in Buffalo
Message 3
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| Subject: | Re: 912 starting problems |
Hi Mark,
There are a few things here.
One Thom has touched on. The carbs being rebuilt, but I see you have addressed
this even though it was a while ago. How many hours do you have on the rebuilt
carbs? Having not synced the carbs could add to your troubles.
If your engine is that old does it have the newer high torque, high speed starter?
They come with that starter as of a couple of years ago. My Kolb had an older
starter and it was hard to start. The engine has to turn at least 220 rpm
(90rpm prop) to start. If it doesn't reach these values then you don't have the
spark/energy to start. I switched to the new starter and my battery was marginal
in amps so it put a better battery in and it started right away, no hesitation.
It was like a different engine. The battery is supposed to be an 18 amp.
I know they will start on a smaller battery, but it doesn't really have any
reserve power and it's not what Rotax recommends.
Technically, if you have the choke lever engaged, Rotax says it's better to not
add any throttle. I have found that when I use the choke and just barely crack
the throttle then both of my 912's have started better. I'm sure each engine
is different. During the summer I only use about 1/2 choke for my first start
of the day.
Just try a few different ways, but check the starter and battery issue, too.
--------
Roger Lee
Tucson, Az.
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http://forums.matronics.com/viewtopic.php?p=120870#120870
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