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pbaker4(at)windstream.net
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 Posted: Sun Jun 24, 2007 5:15 am Post subject: egt temp |
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I own a 601 hd with a 912usl. The egt runs in the mid
1500s at cruse.If you advance the throttle, the egt will
run mid 1400.I checked the settings on the bing carb.
the adjusting ring has 5 slots and the clip is in the next
to the bottom slot. I was told to move the clip down one
slot to increase the mixture. Do these temps seem to
high? The engine runs smoth and I don't want to mess
something up. The plugs are a light brown and show no
sign of being too hot
paul baker
zodiac 601 190total hrs 50 by me
[quote][b]
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Roger Lee
Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.
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| Posted: Sun Jun 24, 2007 6:34 am Post subject: Re: egt temp |
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Hi Paul,
Need to know a few things first. What altitude is your field and most of your cruising done at? What is your cruise engine RPM? Rotax 912's run hotter usually between 4400-4800 rpm and starts to cool down around 4800 and keeps cooling right on up to 5100-5200 rpm depending on the individual engine. 5000-5100 should see its coolest cruise. Rotax engines were set up to cruise between 4800-5200 rpm for several different reasons. It should start cooling down again once you go down to 4300 rpm and below.
What are your cyl. head temps running?
These temps do seem a little high. My temps at 4700 rpm can go up to 1450-1475 egt and will cool down to 1350-1375 egt at 5000 rpm.
People with enclosed engines under cowlings may see some higher temps verses people that have open air engines. My engine is enclosed under a cowling.
What is your WOT rpm? It should be 5500 rpm? If it is pitched too much you might want to consider taking out a small amount of pitch so the engine is not working so hard at your cruise rpm.
All these things can have an influence on your temps. These answers can help diagnose your problem. If you don't have the answers fly it once and write them down, then we can probably figure it out without guessing and doing things just to do something.
What type of coolant are you using? They make two different size of radiators, which do you have?
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_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056 |
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dave(at)dreamwings.co.za
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| Posted: Mon Jun 25, 2007 1:46 am Post subject: egt temp |
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Hi Paul
It also depends on the location of your EGT probes. The installation manual
specifies a normal temperature of 1470, max of 1560, and 1620 at max at
take-off power. This is with the EGT probes mounted 2.75" from the exhaust
flange.
Dave
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Float Flyr
Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland
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| Posted: Mon Jun 25, 2007 5:17 am Post subject: egt temp |
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Paul:
Unless your EGT gauge has been properly set up and calibrated, few homebuilt
aircraft are, it is not the most accurate method of reading EGT temps. The
important thing is they do tend to be pretty consistent unless you end up
changing locations of the thermocouples or something. They are more than
accurate enough to follow trends in temperature.
You say your plugs are the right colour. Then you are doing something
right. If the plugs start to look lighter then, and only then, drop the
clip a notch. The way to do this is to check your plugs on regular
intervals and if you notice any increase in egt, from where it usually is,
check your plugs at the next opportunity. 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. It is possible in cases of more extreme lean
operation that the EGT can actually peak and drop slightly.
You seem to have a pretty good idea of where your engine is operating
properly and your observations are being supported by your plug inspections.
If you were using a compensated, calibrated EGT gauge similar to the types
used on turbine engines then you may have something to worry about. In the
mean time feel confident that your readings are probably all in the gauge.
Noel
| Quote: | Time: 06:15:13 AM PST US
From: "paul baker" <pbaker4(at)windstream.net>
Subject: egt temp
I own a 601 hd with a 912usl. The egt runs in the mid
1500s at cruse.If you advance the throttle, the egt will
run mid 1400.I checked the settings on the bing carb.
the adjusting ring has 5 slots and the clip is in the next
to the bottom slot. I was told to move the clip down one
slot to increase the mixture. Do these temps seem to
high? The engine runs smoth and I don't want to mess
something up. The plugs are a light brown and show no
sign of being too hot
paul baker
zodiac 601 190total hrs 50 by me
|
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Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
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Thom Riddle
Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)
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| Posted: Tue Jun 26, 2007 2:49 am Post subject: egt temp |
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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
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Thom Riddle
Buffalo, NY (9G0)
Don't worry about old age... it doesn't last very long.
- Anonymous |
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Float Flyr
Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland
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| Posted: Wed Jun 27, 2007 6:20 am Post subject: egt temp |
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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
| Quote: | Time: 03:49:40 AM PST US
From: Thom Riddle <thomriddle(at)roadrunner.com>
Subject: Re: 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
|
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Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
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Thom Riddle
Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)
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| Posted: Thu Jun 28, 2007 2:55 am Post subject: egt temp |
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Noel,
When you used the term "backfire" I mistakingly thought you were
referring to the explosion in the exhaust system phenomenon, which is
what many (maybe most) people erroneously call "backfiring" when in
truth that is an "afterfire". Afterfiring being generally caused by
unburned fuel (from overly rich condition) in the exhaust system
hitting a hot spot and exploding. With your further explanation I now
know you were speaking of firing back through the intake system, which
indeed can be caused by lean condition among others. Thanks for the
clarification.
You are also correct when you state that when the fuel level in the
float bowl is low that would cause a lean condition, whether it is
caused by the fuel supply being exhausted or the float level is set too
low.
I'm well acquainted with the rich of peak and lean of peak situations
and in general, especially with engines that are not fuel injected or
in which instrumentation does not include EGT for every cylinder, your
recommendation to run a bit rich of peak EGT is a good one. However, in
a system with manual mixture control, as long as I'm running at normal
cruise power or less, I generally lean very slowly until the slightest
roughness begins to be noticed and then enrichen mixture until smooth
again. As long as the fuel is of the proper octane and everything else
is normal in the engine, this will yield best fuel economy without
risking the engine in any way. Unfortunately, we don't have a manual
mixture control on our 912UL.
Thom in Buffalo
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_________________
Thom Riddle
Buffalo, NY (9G0)
Don't worry about old age... it doesn't last very long.
- Anonymous |
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Float Flyr
Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland
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| Posted: Fri Jun 29, 2007 9:03 am Post subject: egt temp |
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100 % in agreement
Noel
| Quote: | Time: 03:55:22 AM PST US
From: Thom Riddle <thomriddle(at)roadrunner.com>
Subject: Re: egt temp
Noel,
When you used the term "backfire" I mistakingly thought you were
referring to the explosion in the exhaust system phenomenon, which is
what many (maybe most) people erroneously call "backfiring" when in
truth that is an "afterfire". Afterfiring being generally caused by
unburned fuel (from overly rich condition) in the exhaust system
hitting a hot spot and exploding. With your further explanation I now
know you were speaking of firing back through the intake
system, which
indeed can be caused by lean condition among others. Thanks for the
clarification.
You are also correct when you state that when the fuel level in the
float bowl is low that would cause a lean condition, whether it is
caused by the fuel supply being exhausted or the float level
is set too
low.
I'm well acquainted with the rich of peak and lean of peak situations
and in general, especially with engines that are not fuel injected or
in which instrumentation does not include EGT for every
cylinder, your
recommendation to run a bit rich of peak EGT is a good one.
However, in
a system with manual mixture control, as long as I'm running
at normal
cruise power or less, I generally lean very slowly until the
slightest
roughness begins to be noticed and then enrichen mixture until smooth
again. As long as the fuel is of the proper octane and
everything else
is normal in the engine, this will yield best fuel economy without
risking the engine in any way. Unfortunately, we don't have a manual
mixture control on our 912UL.
Thom in Buffalo
|
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_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
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