Leaning Procedure for a Carbureted 182

Hi Thomas;

Well I didn't think it was too low a power setting. What do you prefer to
use?

As for Deakin's articles, I've not read them, thanks for the tip on that!
But which one should I start on?

Thanks again for the input!
Jeffrey

"Thomas Borchert" wrote in message
...
Jeffrey,

Typical cruise power setting is 20"
manifold pressure 2300 RPM.

Wow! Why so low?


Can someone please give me the proper leaning procedure for both cruise
flight and ground operations (taxing)?


For taxi: lean right after start-up and stabilized RPM very aggresively
until a slight rise in RPM occurs. If you lean any further, the engine
should quit. The RPM rise should be around 25 RPM. If it is higher, have
your idle mixture adjusted. If you advance the throttle for the mag check,
the engine will stumble because it is so lean. That's GOOD because it
reminds you to enrichen again for take-off power. You cannot hurt the
engine by leaning at taxi power.

For flight: Lean whenever the power is below 75 percent. Lean until the
first cylinder peaks (that's not identical with the cylinder having the
highest EGT, it is the first cylinder whose EGT goes down again during
leaning). Then leave the mixture there if the engine runs smoothly or
enrichen until abojut 100 F rich of peak.

Have you read John Deakin's columns on engine management at www.avweb.com?

--
Thomas Borchert (EDDH)

Jeffrey,

Well I didn't think it was too low a power setting. What do you prefer to
use?

75 percent as long as it's available, all that's there when not. And yes, it
could be too low a power setting influencing the scavenging process through
lower temps and pressures. But the main culprit is likely not enough leaning
on the ground.

As for Deakin's articles, I've not read them, thanks for the tip on that!
But which one should I start on?


There's a trio in succesion dealing with Mixture, Prop and Manifold
Pressure, IIRC. The latter is easy to recognize by its title, which is
"Manifold Pressure Sucks" (get it? - if not, you will after reading).
There's a general one dealing with engine management older than those. These
are the foundation. But basically, you'll be ok if you read all of them in
chronological order. It's a lot to read, but well worth it.

--
Thomas Borchert (EDDH)

TBO Advisor recommends the peak EGT method of leaning for the O-470 series
(except O-470-U), but it also warns that "In some engines, such as the
O-470-R, it may not be possible to operate smoothly at peak EGT (when EGT is
measured from a single probe that averages one bank of cylinders), since
mixture maldistribution can cause lean misfire to appear in the leanest
cylinders before peak EGT for the engine-as-a-whole has been reached." It
also says that running at peak EGT also means that detonation protection is
at its lowest.

What does your POH say? Continental does not recommend leaning to peak EGT
at settings above 65% power for normally-aspirated engines.

"Jeffrey" wrote in message
. com...
Greeting to all;



I own a 1964 Cessna 182 with a Continental O-470-R25 engine. This is
equipped with an E.I. 6 pt EGT gauge. Typical cruise power setting is 20"
manifold pressure 2300 RPM. I seem to have a plug fouling issue.



Can someone please give me the proper leaning procedure for both cruise
flight and ground operations (taxing)?



I'd really appreciate some experienced input. Thanks in advance!

Jeffrey

Juan,

It
also says that running at peak EGT also means that detonation protection is
at its lowest.


Which is probably not so.

Some people have had good results with a little addition of carb heat to even
out the mixture distribution across cylinders, it seems.

--
Thomas Borchert (EDDH)

At power settings above 65% you need to be concerned about running too
lean, thus too hot. With monitoring all 6 cylinders it should be
possible to run 50 to 100 rich of peak at these high power settings.
You will have to lean until you hit peak, then richen. Use this EGT as
a guide. I would use 100 degrees rich of peak on power settings above
75%. This is on your hottest cylinder.

At power settings below 65%, you do not need to worry about running too
lean, so just lean until it runs rough and richen slightly. Note the
EGT on the hottest cylinder and use this EGT all the time.

Most of us pilots lean to a specific EGT. I use 1350, but I only have
one probe on one cylinder. The exact temperature varies with probe
installation. On my carb Lycoming 360, 1350 is all the way lean at 50%
power and maybe 100 degrees rich of peak at 75% power and 50 degrees
rich at 65% power. I have an engine that is well over TBO and still
going strong using this technique. One thing you can do is lean all the
way to roughness while at full throttle at 10,000' then richen till
smooth. Note the EGT and use this as a target setting at all power
settings. This will give you rich of peak at higher power settings and
all the way lean at 50% power.

You will read articles about running lean of peak, but most of this
only applies to engines with fuel injection and GAMI injectors. They
run these engines lean of peak at high power settings to help cooling
and fuel economy. It usually wont work with carbureted engines as you
will have uneven air and fuel distribution.

Lean on the ground for taxi as much as possible. Lean for takeoff at
airports above 3000'. Don't go full rich on landing unless landing at
airports below 3000'. Leaning for takeoff involves doing a runup and
leaning until you get an rpm drop, then richen 3 half turns on the
mixture knob. This works well. For landing, just lean to the takeoff
setting judging on how far out the mixture knob was set on takeoff.
This is all for airports above 3000'.

Hope that helps.

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.

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.

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.

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'.

Density altutide, not actual altitude, I'd like to add. VERY important!

--
Thomas Borchert (EDDH)

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.

"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.

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.

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)