From O.S. Engines
Choosing the Right Glow Plug
Several factors influence the use of the correct
glow plug for your engine. Here are some guidelines:
Engine Type
Standard
engines
(engines with a 1-piece head) are most common.
Standard plugs are easily available, inexpensive,
and fit almost all standard engines. Standard plugs
are installed with a washer, which creates a
compression seal with the head.
Turbo.
Many new O.S. engines, which feature a special
2-piece turbo head. The biggest benefit of turbo
plugs is superior performance. Unlike standard
plugs, turbo plugs (identified by a “P” in the
description) feature a tapered “seat” that matches
perfectly with the head. That creates a superior
compression seal and with it, maximum efficiency and
power. Turbo plugs are the choice for racers, who
want, and need, top performance.
A word of
caution:
you should never install a turbo plug in a standard
engine or vice versa. Doing so risks doing serious
(and expensive) damage.
Displacement
Small displacement engines need a hotter plug than
larger displacement because larger engines have more
mass and retain heat better.
Nitro Content
Use of higher nitro fuels will require a colder plug
than lower nitro fuels.
Temperature
The hotter the day, the colder the plugs need to be.
Additional Things
to Know:
•
Hot plugs promote better idling and acceleration. If
your engine runs rough or accelerates sluggishly, a
hotter plug will help.
•
Cold plugs produce more power and may improve
performance if your engine runs hot. The downside is
rougher idling and more difficulty in tuning.
•
Fuel-air mix not only affects how your engine
performs; it can also have an impact on how long
your plug lasts. If you run rich, it means that
you’re using more fuel than necessary for top
performance. Modelers are often advised to run rich
during engine break-in, because it helps cool the
engine. However, running too rich can also cause an
engine to bog down or quit entirely. In addition, it
also means that the glow element is being exposed to
more contaminants than necessary, which shortens
plug life. Running lean means that you’re using less
fuel. “Leaning in” an engine has a positive effect
on performance. However, care is needed here,
because over-leaning an engine can harm it, by
raising operating temperatures, and burn up a plug
[Tech Editor’s
Note:
More than the plug might be lost, excessive leaning
can ruin an engine!] before it’s time. Do not over
lean!
Final Thoughts
Choosing the right glow plug not only improves
performance, but can also extend the life of your
engine and the glow plug itself. With the guidelines
above and the tips below, you’re well on your way to
achieving both.
• Buy quality plugs. You’re protecting your
investment.
•
Store plugs where it’s dry. Moisture can ruin them.
•
Use the right glow plug. Follow the guidelines
above.
•
Follow the proper break-in procedures.
•
Tune your engine carefully. Running too lean will
make your engine “blow” plugs more often. Proper
tuning helps extend plug life.
•
Never touch the filament of a glow plug. Doing so
can break the filament and ruin a plug.
•
Don’t over tighten your plug. Tighten it until it’s
just snug.
•
Be sure to shim your engine correctly. A plug that’s
too close to the piston can cause pre-detonation,
which will quickly damage a glow plug.
•
Use only a glow starter or 1.5V battery to heat your
plug. Otherwise, your plug may burn out ahead of
it’s time. Don’t be afraid to ask for help.
Experienced modelers have already “been there, done
that.” Their experience can save you time and money;
and most are glad to help.
•
Glow plugs get very hot, enough to glow the filament
red or white hot, and removing a glow plug while
power is applied can cause burning if appropriate
care is not taken. [Tech
Editor’s Note:
Removing the plug while it’s still being “heated”
strikes me as nearly impossible, since any
attachment to the plug, that would be doing the
heating, must be removed so that you can have access
to remove the plug. The only other way to heat the
plug is from the combustion in the engine, so if you
are handling the engine, it’s generally a good thing
to have stopped it running while you “fool” with
it.] Special caution must be taken while near fuel
sources.
•
Some connectors for glow plugs can short circuit and
damage batteries, or cause them to explode.
Batteries may get hot during the use of a glow plug.
This especially applies to homemade or nonstandard
connectors.
[Tech
Editor’s Note:
One source of material that can ruin glow plugs is
detritus left in the engine during/after
manufacture. Before you run any new engine, it’s a
good idea to flush, at least the combustion volume,
to eliminate as much “stuff” as you can. Flush it
with fuel or methyl alcohol, never water. The best
way to flush is to remove the head and the back
plate and flood the engine with the flushing fluid.
If you are uncomfortable removing the engine parts,
then take the glow plug out, move the piston down so
that the top of the piston is below the exhaust port
and run the flushing liquid down the plug hole and
out the exhaust. If you catch the flushing fluid on
a white paper towel, you should be able to see
anything that the flush eliminated.] Q
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