Burning out a Magneto Drop

Obviously not someone who is familiar with GAMI Injectors or the
Advanced Pilot Seminar where they have data to say opposite!

Contrary to what the self proclaimed gear head states here, your
engine should always be leaned when on the ground to avoid the fouling
that gives you the roughness when one mag is switched off during
runup.

On Sat, 28 Feb 2004 10:37:00 -0500, " jls"
wrote:

When you lean your engine and rev it up on the ground you are super-heating
the heads, the sparkplugs, the pistons, the valves, seats, and guides ---
just to clean a fouled plug or two by burning the lead or carbon fouling off
the electrode. It's best to clean the fouled plug. Of course, the problem
is NOT with the mag.

My instructor (who was not at all a gearhead) once did that burn-it-off
thing in a 152's O-235 Lycoming, and it wasn't long before that engine was
in the shop for new cylinders. I remember well the heat. We could feel
it and smell it coming through the firewall, and being a gearhead I knew
that THAT was not good for that engine. Besides, an aircraft revved up on
the ground can hardly cool itself, irrespective of the fact you have leaned
the **** out of it.

I haven't seen it but have heard of burning holes in pistons by overleaning.

By the mag drop you already know which set of plugs, upper or lower, and
then all you have to do is find the misfiring cold cylinder. That's easy
enough and what if the problem is a sparkplug wire or injector? You've just
managed to fry your cylinders in the hopes of getting one out of four or six
to fire.

Leaning an engine takes a little finesse. It shouldn't be done on the
ground unless you're in Denver or on a high-altitude ramp. A small fraction
of that fuel charge is cooling your heads as it evaporates and flows through
the combustion chamber and out the exhaust port. Ideally it is rich enough
to give you a perfect stoichiometric charge plus just a little for cooling.
If you burn it all by leaning you have lost your mixture's ability to
dissipate heat. In addition, some of a lean charge is burning as it
departs the combustion chamber because a lean mixture burns more slowly than
a rich one. Damned if I want my exhaust valve to glow just to clean a
sparkplug.

It's best to clean the fouled plug. Of course, the problem
is NOT with the mag.



Does that mean that you would shut your airplane down in the run up
area, get out, open the cowling (top and bottom), get out your tool box,
pull the spark plug and clean it on the spot right there? That might
look a little odd, especially at a busy airport. Perhaps I am not
understanding you correctly.

-Sami

"O. Sami Saydjari" wrote in message
...
It's best to clean the fouled plug. Of course, the problem
is NOT with the mag.



Does that mean that you would shut your airplane down in the run up
area, get out, open the cowling (top and bottom), get out your tool box,
pull the spark plug and clean it on the spot right there? That might
look a little odd, especially at a busy airport. Perhaps I am not
understanding you correctly.

-Sami

Obviously you don't work on your own airplane. Fry it if you like, and in
spite of warnings from TCM.

The previous poster talked about an additive. If you've read all that has
been said (other than some jabbering) and the two Sacramento Sky Ranch
links, you probably have a few ideas about prevention, including the legal
additive, Alcor TCP. It is an old formula quite successfully used in auto
gasoline way back when to prevent lead fouling of sparkplugs.

jls wrote:
"O. Sami Saydjari" wrote in message
...

It's best to clean the fouled plug. Of course, the problem
is NOT with the mag.



Does that mean that you would shut your airplane down in the run up
area, get out, open the cowling (top and bottom), get out your tool box,
pull the spark plug and clean it on the spot right there? That might
look a little odd, especially at a busy airport. Perhaps I am not
understanding you correctly.

-Sami


Obviously you don't work on your own airplane. Fry it if you like, and in
spite of warnings from TCM.

Well, I was not trying to be sarcastic, I was just asking a stratight
question about what exactly you were suggesting one do if one is running
up his plane and encountered this situation. I honestly could not tell
from your post, what alternative you were suggesting.

Other than prevention, I have not yet heard a good alternative on the
thread yet. Perhaps I am being dense.


The previous poster talked about an additive. If you've read all that has
been said (other than some jabbering) and the two Sacramento Sky Ranch
links, you probably have a few ideas about prevention, including the legal
additive, Alcor TCP. It is an old formula quite successfully used in auto
gasoline way back when to prevent lead fouling of sparkplugs.

For a fouled plug, running up and leaning is an old as old as aviation,
and very proven, method of clearing the plug I have been doing it for a
half century, works for me...
If it doesn't clear, then you taxi back in and have it serviced...
As far as all the dire warnings from the manufacturers, if you followed
their SB's to the letter, you literally would not be able to fly... Those
SB's are often cya position papers crafted by their legal department, not
engineer recommendations...

cheers ... denny

"O. Sami Saydjari"

Hey, don't worry about it. We get anal retentive engineer types in here from
time to time.

They either suck back in to the wisdom we've collected over the past few years
or have eventually disappeared back into their own wrong groups.

Welcome, if you choose to stay as a member of this group...


" jls"
shared these priceless pearls of wisdom:

-
-When you lean your engine and rev it up on the ground you are super-heating
-the heads, the sparkplugs, the pistons, the valves, seats, and guides ---
-just to clean a fouled plug or two by burning the lead or carbon fouling off
-the electrode. It's best to clean the fouled plug. Of course, the problem
-is NOT with the mag.

Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

Leaning an engine takes a little finesse. It shouldn't be done on the
ground unless you're in Denver or on a high-altitude ramp.

Woah! Don't spread this idea around! No amount of leaning can hurt your
engine at the low power that is usable on the ground. Most engines we fly
were designed for a different fuel and will foul if not leaned on the
ground. It isn't just the sparkplugs. The lead is building up on the valve
guides making them stick and putting strain on the valve train.

You want to lean on the ground so the engine will die if you try to run at
RPM above 1300 - 1500. That way you can't takeoff in a leaned condition
where you could hurt the engine at full power.

Leaning aggressively on the ground will minimize the plug fouling that
requires clearing mags.

--
Roger Long

"Roger Long" om wrote in
message news
Leaning an engine takes a little finesse. It shouldn't be done on the
ground unless you're in Denver or on a high-altitude ramp.

Woah! Don't spread this idea around! No amount of leaning can hurt your
engine at the low power that is usable on the ground. Most engines we fly
were designed for a different fuel and will foul if not leaned on the
ground. It isn't just the sparkplugs. The lead is building up on the
valve
guides making them stick and putting strain on the valve train.

You want to lean on the ground so the engine will die if you try to run at
RPM above 1300 - 1500. That way you can't takeoff in a leaned condition
where you could hurt the engine at full power.

Leaning aggressively on the ground will minimize the plug fouling that
requires clearing mags.

--
Roger Long

You are correct and if you had read along further in the thread's early
messages you would see that I clarified this statement, which was related to
clearing an engine by revving it up and leaning by pulling the mixture
control on the ground.

I have no problem burning off a fouled plug, just like last night. Left,
lower plug, seems to be a problem. Another pilot says it is a problem
that shows up just after re-fueling and you prime before a re-start.

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O. Sami Saydjari wrote:
I just received a booklet from TCM called "Tips on Engine Care" (a very
good book...available from TCM's website...http://www.tcmlink.com/). On
page 12 it says "Never but never attempt to "burn out" a magneto drop
with ground run-up. This 'time-honored' procedure succeeds only at the
expense of the engine's mechanical health."

Well, I was taught this time-honored way. What the book does not say is
what you are supposed to do when you get roughness in one magento. Ideas?

-Sami
N2057M, Piper Turbo Arrow III

Sounds to me like they are trying to err on the side of caution.

John Deakin's series of articles are a worthwhile read; the first is he
http://www.avweb.com/news/columns/182179-1.html

Of course, you have to have an injected and instrumented (EGT and CHT) engine
to use his advice.

--
Jim Pennino

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