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Leaning Procedure for a Carbureted 182



 
 
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  #21  
Old June 28th 05, 09:32 PM
john smith
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Thomas Borchert wrote:
Doug,


At power settings above 65% you need to be concerned about running too
lean, thus too hot.


Uhm, no, not at all. He'd have to be concerned to run not lean enough,
actually, since the temps decrease again when running leaner and leaner.
The point is: You have to worry to run at the right point in relation to
peak.


I don't fully agree with that. The O-470 is normally aspirated rather
than injected; without a tuned intake, the mixture arriving at each
cylinder is going to be more varied; it is likely that you may have one
or two cylinders lean, one or two cylinders rich and two cylinders in
the worst part of the pressure curve.

With monitoring all 6 cylinders it should be
possible to run 50 to 100 rich of peak at these high power settings.


50 rich is about the worst point to run at.


Yep, should be 100-150 rich.

Most of us pilots lean to a specific EGT.


Well, I sure don't. I don't know ANY other pilot (apart from you) who
does. Those numbers are completely irrelevant. The relation to peak is
key.


The 182R I fly only has the single probe CHT that Cessna installed; lean
it until it is rough, then enrichen it a couple of twists.

I have an engine that is well over TBO and still
going strong using this technique.


I can't see any curvature of the earth from the ground, so it must be
flat. Or, in other words: What proof do you have of a correlation?


Lean on the ground for taxi as much as possible. Lean for takeoff at
airports above 3000'.


I lean to peak RPM with idle initially full rich at 900 RPM.
  #22  
Old June 29th 05, 01:08 AM
Juan Jimenez
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"Thomas Borchert" wrote in message
...
Doug,

At power settings above 65% you need to be concerned about running too
lean, thus too hot.


Uhm, no, not at all. He'd have to be concerned to run not lean enough,
actually, since the temps decrease again when running leaner and leaner.
The point is: You have to worry to run at the right point in relation to
peak.


That's not what Continental says about their engine, and not what TBO
Advisor recommends.

Juan


  #23  
Old June 29th 05, 02:25 AM
Matt Barrow
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"john smith" wrote in message
.. .
Thomas Borchert wrote:
Doug,


At power settings above 65% you need to be concerned about running too
lean, thus too hot.


Uhm, no, not at all. He'd have to be concerned to run not lean enough,
actually, since the temps decrease again when running leaner and leaner.
The point is: You have to worry to run at the right point in relation to
peak.


I don't fully agree with that. The O-470 is normally aspirated rather
than injected;


Umm...it's normally aspirated vs turbocharged; it's carbureted vs injected.




  #24  
Old June 29th 05, 02:49 AM
Doug
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Yes, it is a carbureted engine. Leaning to peak at 50% power and then
using that temperature to lean to at higher power settings works. It
gives about 50 degrees rich at 65% power and 100 degrees rich at 75%
power and 150 degrees rich at 85% power etc. All without having to
actually lean to peak at these high power settings, which even one
time, can overheat and do damage.

All this talk about running lean of peak usually doesn't work with
carbureted engines because of uneven airflow. Running rich of peak
aviods the peak settings that can overheat things and do damage. It is
false economy to try and run lean AT HIGH POWER SETTINGS and possibly
damage your engine. Below 65% or so, you can usually lean all you want
and you will be fine. My method allows some "cushion" using the 50%
setting for lean as possible instead of 65%. I would not want to
advocate something that could cause damage, so I stayed conservative.
If you want to experiment around, you are free to do so. Just look in
your POH and see what 50%, 65% and 75% power settings are and jot those
down so you have a reference when you start experimenting. And don't
run things too hot. Heat weakens metal. That is what you want to avoid,
even if it means burning a little more fuel.

  #25  
Old June 29th 05, 03:17 AM
john smith
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Doug,
Do you run high RPM/low MP or high MP/low RPM power settings at cruise?
  #26  
Old June 29th 05, 04:24 AM
Doug
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I run my rpm at 2450, mainly because that is where it runs the
smoothest. Most of my local flights are at 20". I fly at 6500' MSL
locally (my airport is at 5300'). Cross country, I tend to run harder
going into the wind and throttle back a bit if I have a tailwind. But
if you want to save fuel, running at low rpm's and high manifold will
get you the most power with the least fuel and save wear on the engine
(fewer total revolutions). I've never heard an argument for different
leaning procedures with high rpm/low mp vs high mp/low rpm though.

My Husky's Lycoming carbureted 0-360A1P has 2200 tach time on it. No
oil burn, good compressions, no metal in the filter. I use Aeroshell
15-50 and change it every 50 hours (along with the filter). I have put
all but the first 250 hours on this since new engine. As I stated, I
lean to 1350 degrees EGT on my one probe. Been all over North America
in my bird. (Just got back from Quebec). Based in Colorado.

I think the main thing is to lean enough to get proper burn, but don't
lean so much as to burn things up. I have some friends with probes on
all cylinders and carbureted engines who have tried to run lean of peak
and they have mostly given up. Just doesn't work on carbureted engines.
It doesn't on mine. Most of Deacons stuff is applicable to fuel
injected, and ususually turbo charged engines being run at HIGH power
settings (like 80% power). It is a technique that uses a lean mixture
to keep things cool. Only works if you have fuel injection, gamis
probes on all cylinders and a fuel flow meter. I don't run that type of
equipment, so I can't really comment on it, though from what I hear, it
does work, if done properly. The guy that asked the question has
normally aspirated, carbureted engine.

  #27  
Old June 29th 05, 05:45 AM
Frank Stutzman
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Doug wrote:

I think the main thing is to lean enough to get proper burn, but don't
lean so much as to burn things up. I have some friends with probes on
all cylinders and carbureted engines who have tried to run lean of peak
and they have mostly given up. Just doesn't work on carbureted engines.


If you said "most" carbed engines, I probably wouldn't quibble. However,
it does work on some. It certainly works on my Continental E-225 with a
Bendix PS-5C carb. Its harder to do, but can be done and does work. Here
is what I had to do:

1) overhauled my carb and had it flow tested to make sure its doing its
job.
2) Pull off the throttle back a bit less than one inch. This put the carb
out of the enrichment mode that it is with full throttle. I think it may
also put a bit of turbulence into the airflow that helps the fuel
vaporization.
3) If I can't get smooth LOP operations with the above, I'll play a bit
with carb heat (which is actually alternate air on my plane). Causing the
induction air to be a few degrees warmer will often help get the
vaporization (and hence good distribution) needed.

I believe I've heard the GAMI folks say that getting good distribution is
easiest on the large Continentals. Something to do with the way
the stock induction is done.

--
Frank Stutzman
Bonanza N494B "Hula Girl"
Hood River, OR

  #28  
Old June 29th 05, 07:17 AM
Howard Nelson
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I fly a C182P with O470S. Recently read the engine management and leaning
articles on AVWEB prior to a long (1200NM) cross country. I have a 6
cylinder analyzer with CHT and EGT for each cylinder. Cruising at 7500ft I
would lean to about 75-100 ROP on the first cylinder to peak. I would have a
large descrepancy between EGT temps between the cylinders due to uneven
distribution of fuel air mixture in the O470S. I then tried a trick
mentioned in those articles. I would back off the throttle until MP just
noticably fell (about 1/4 inch MP). After a couple of minutes the EGT's were
all within 25 degrees of each other. The idea put forward in the article was
that by partially closing the throttle the turbulence created resulted in
more even distribution of fuel. Don't know if there is any rational basis of
this but seemed to work in my plane.

Howard


  #29  
Old June 29th 05, 08:30 AM
Thomas Borchert
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John,

Uhm, no, not at all. He'd have to be concerned to run not lean enough,
actually, since the temps decrease again when running leaner and leaner.
The point is: You have to worry to run at the right point in relation to
peak.


I don't fully agree with that. The O-470 is normally aspirated rather
than injected; without a tuned intake, the mixture arriving at each
cylinder is going to be more varied; it is likely that you may have one
or two cylinders lean, one or two cylinders rich and two cylinders in
the worst part of the pressure curve.


Not sure at what point we disagree.

--
Thomas Borchert (EDDH)

  #30  
Old June 29th 05, 08:30 AM
Thomas Borchert
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Doug,

Running rich of peak
aviods the peak settings that can overheat things and do damage.


Not at all true. In fact, completely false. Sorry.

It is
false economy to try and run lean AT HIGH POWER SETTINGS and possibly
damage your engine.


lean? How lean? This statement is not true.


--
Thomas Borchert (EDDH)

 




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