Archive for the ‘glow plugs’ Category

Glow Plug Selection Guide

The folks at have taken the trouble to journalize a selection guide for the respective brands of popular glow plugs. I.e. McCoy, NovaRossi, Enya, OS. Engines, FOX. Different brands use slightly different naming convention, i.e. Rossi’s R2 plug – which the other’s don’t have. Hope this helps!

Glow Plug Specifications

A good guide for selecting the correct Glow Plug…

[bullet] This is a great selection guide for R/C Glow Plugs. Hopefully, it’ll help take the mystery out of the correct plug needed by your engines!

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General Glow Plug Information – Consolidated

By James McCarty, Brian Cooper, and Brian Gardner

OS Glow Plug Information

# 8 Hot Recommended for most current O.S. (and other) 2-stroke engines
Type F Mildly Hot Special long-reach plug recommended exclusively for O.S (and other) 4-stroke engines
Type RE Hot Special long-reach plug designed exclusively for O.S. Wankel rotary engine
A5 Cold Recommended for most current O.S. (and many other) 2-stroke engines particularly for 1/10th & 1/8th scale off-road car engines
A3 Hot Dependable O.S. quality makes A3 the most durable and longest-lasting glow plug available at an economical price
R5 Very Cold Recommended for high-nitro fuel and high r.p.m. engines, particularly 1/8th track racing car engines

ENYA Glow Plug Information

# 3 Hot All Enya engines such as TV & four cycle engines
# 4 Mildly hot All Enya engines, especially those used with 10%or greater nitromethane fuel
# 5 Medium All Enya engines, especially the .40CX, .45CX and high nitro methane fuel
# 6 Cold High compression engines and high niro methane fuel used in racing.

Fox Glow Plug Information

All 1. 5 Volt Plugs are Dry Cell or Ni-Cad All 2 Volt Plugs are Lead Acid Battery

Standard Short Hot 1.5 Volt, Standard Short Hot 2 Volt
Standard Long Hot 1.5 Volt, Standard Long Hot 2 Volt
Gold STD Long Plug Hot 1.5 Volt, RC Short Mildly Hot 2 Volt
Gold RC Long Hot 1.5 Volt, RC Long Mildly Hot 2 Volt
RC Short Mildly Hot 1.5 Volt
RC Long Mildly Hot 1.5 Volt
Miracle Plug Hot 1.5 Volt
Pro 8 Short Cold 1.5 Volt
Pro 8 Long Cold 1.5 Volt

McCoy Glow Plugs with OS Equivalent

MC-8 Medium Hot #8 (thanks for correction,
MC-9 Cold A5, R5 (thanks for correction,
MC-55 Medium Hot A3, #8
MC-59 Hot

STD ROSSI GLOW PLUGS BI-TURBO GLOW PLUGS (without idle bar) (conical w/o washer)

Rossi Glow Plugs (cold for pattern type work / high nitro fuels, hot for sport / low nitro flying)

R1 Extra hot 0.8 to 2cc RB4 Hot
R2 Hot from 2 to 3.5cc RB5 Medium
R3 Medium from 3.5 to 6cc RB6 Cold
R4 Cold from 6 to 10cc RB7 Extra cold
R5 X-cold for nitro fuel & R/C RB8 Super cold
R6 Cold nitro 10 to 13cc
R7 Cold for nitro 13 to 15cc
R8 Cold for nitro 15 to 30cc GLOW HEAD FOR R15
G1 Hot


G2 Medium (with idle bar)
G3 Cold nitro 15 to 30%
RC Hot for 2.5 to 6cc
G4 X-cold nitro 30 to 50%
RC Cold for 6 to 15cc
G5 Cold nitro 50% or more

Glow Plug Usage Tips

Your glow plug temperature range is too cold when:

  • The engine power is weak or has weakened from previous levels.
  • The engine slows down considerably or stops after removing the glow plug battery, despite correct adjustment of the needle valve. For example (Enya), if a # 4 plug gives you these problems in your engine, switch to a # 3 plug instead.

Your glow plug temperature range is too hot when:

  • The engine suffers from pre ignition and loss of power.
  • The overall engine running is rough
  • The glow plug filament is broken or collapses frequently.

These are several cures to these problems. We suggest using a fuel with less nitro methane content, using a larger size propeller or using a colder plug than the one currently in use. For example if an Enya # 3 plug gives you these problems in your engines, switch to a # 4 plug.

Model glow plug engines are extremely dependent upon the type and quality of the glow plug used. Enya glow plugs use a platinum alloy coil, which uses a thick diameter wire for long life. The thicker wire coil also eliminates the need for an “idle bar” as found on other brands of glow plugs; idle bars tend to reduce top speed slightly, to achieve a more stable idle speed. Enya’s glow plug design insures both good top end speed and stable idle speed.

Enya glow plugs also have a thicker battery contact at the tip of the plug for greater heat dissipation and better electrical contact. Altech Marketing presently stocks glow plug battery cords specifically for Enya glow plugs, which are standard equipment with Enya four-cycle engines. Other glow plug cords usable with Enya glow plugs are available from several other manufacturers.

HOT GLOW PLUGS (for low nitro and FAI fuels)

Enya: # 3
Fox: Miracle, Standard, and R/C Long (2V)
Fireball: Hot (1.2-3.0V), and S-20 R/C Long
Fire Power: F 6 (warm), and F 7 (hot)
K&B: 1 L
McCoy: MC 55 R/C Long, MC 59, and MC 14 (very hot)
O.S. Engines: # 0, # 1, # 5
Rossi: R 1 (extra hot), and R 2
Sonic Tronics: Glowdevil # 300
Thunderbolt: R/C Long

MEDIUM GLOW PLUGS (for 10%-15% nitro fuels)

Enya: # 4 (medium hot), and # 5 (medium cold)
Fireball: Standard (1.2-2.0V)
Fire Power: F 5 (medium), and F 6 (warm)
Fox: R/C Long (1.2-1.5V), and Gold
Hanger 9: Sport Long
McCoy: MC 50, and MC 8
O.S. Engines: # A 3, # 8, # 9, # 7 (with idle bar)
Rossi: Medium, and R-3
Sonic Tronics: Glowdevil Standard
Tower Hobbies: Tower Power Performance plug, and Reg. (w/bar)

COLD GLOW PLUGS (for high nitro; 25% +)

Enya: #6 (cold)
Fireball: Cool (1.2-1.5V)
Fire Power: F 2 (extra cold), F 3 (cold), and F 4 (cool)
Fox: R/C (1.2V), and # 8
K&B: Long & Short high performance nitro plug
O.S. Engines: R-5
Rossi: R 4 (cold), and R 5 (extra cold)


Fox: Miracle plug (often used in 2C’s W/low nitro)
McCoy: MC 14 (very hot, often used in inverted 4C’s)
O.S. Engines: Type F
Sonic Tronics: Glowdevil ST 301/302


Idle bar glow plugs came about because some engines were having trouble transitioning from idle to high speed. When the throttle was opened from idle, the incoming air and raw fuel would strike the glow plug’s heated coil, cooling it to the point where it would no longer support the combustion process, so the engine would die. To help prevent this, the idle bar was added to the glow plug to serve as a physical shield, helping to keep the coil from cooling off too quickly.

A glow plug with an idle bar will not increase peak RPM (it may even reduce it in some cases), but it may improve the idle with some engines, since it simply helps to keep the plug hot enough to light the fuel. If your having transition problems, you might want to try using a glow plug with an idle bar. Some modelers use idle bar plugs in the winter only, since the glow plug tends to loose heat faster in the colder environment.

Naturally, all of this assumes that you have the low speed mixture adjusted correctly to begin with.


So what is a ‘hot’ plug, and how does it differ from a ‘cold’ plug?

Naturally, a hot plug will heat up faster and stay hotter, but that’s not the whole story. When discussing this aspect of glow plugs, another very important aspect must be considered, the amount methanol in the fuel. The more methanol we’re using (i.e., less oil and less nitro), the hotter the plug we should use. Conversely, the more nitro and/or oil we use, the less methanol we’re using, so we use a cool(er) plug. An extreme example would be when using a very high nitro content fuel in a very high RPM engine (a typical ducted fan engine, for example). Here we’d use a very cold plug. For most sport pilots using fuel with just 5-15% nitro, however, a hotter plug would probably do well.

Probably? Yes, trial and error is often the best (and sometimes ‘only’) way to determine the right glow plug for your application. Most 4C engines need either high nitro or hot plugs to run at their best, since they have combustion strokes only half as often as 2C engines.


  • Use a hot plug with low nitro (less than 24%), and a cold plug with high nitro (more than 25%).
  • If you remove the glow starter from you idling engine, and notice an immediate drop in RPM, you may need a hotter plug or more nitro.
  • If your engine has a tendency to backfire a lot, you may be using a glow plug that’s too hot, or you may need fuel with less nitro.
  • Most hot plugs can take up to 2.0 volts starting power without burning up, while most cold plugs prefer 1.2 to 1.5 volts starting power.

via O.S. Glow Plugs:

If you are using O.S. Engines, or perhaps these are the only glow plugs available at your local hobby shop, here’s a selection guide that you should look at. Don’t simply buy the LC3 plugs for your .21 engine like they tell you so. An LC4 plug is good for overall response and rev band for offroad bashing. But if you plan to race… use a No. 8 or R5 for cooler temps and higher revving band.

Tough Enough to Take the Heat.

Getting the best engine performance means choosing the right glow plug, which depends on a number of different factors – the engine type, air–fuel mix, nitro percentage, and even air temperature.

What’s more, the right glow plug will change as conditions change. Keeping a range of glow plugs on hand will help you fine–tune glow heat and enjoy maximum performance under all conditions.

Generally, hot plugs provide better idle and acceleration than cold plugs. Cold plugs will produce more power but may idle more roughly and be harder to tune.

How to Choose the Right Glow Plug

A long-lasting plug for most .10-.60 2-strokes
Ultra Hot
For 21VZ-B V-Spec and most .18-.28 off-road racing Turbo head engines
Super Hot
For 21VZ-B V-Spec and most .18-.28 off-road racing Turbo head engines
Very Hot
For 21VZ-B V-Spec and most .18-.28 off-road racing Turbo head engines, especially when the temperature is high or for leaner needle settings and high-nitro/high-rpm running
Long reach, for 1/10 scale off-road engines such as O.S. 21TMs and Traxxas® peak needle settings and punchy throttle response
Medium Hot
For 2-stroke airplane, helicopter and car (except Turbo head) engines. Offers stable idling, broad peak needle settings and punchy throttle response
For most .12-.21 on-road racing Turbo head engines
Long reach, for 1/10 scale off-road engines such as O.S. 21TMs and the Traxxas TRX2.5 & 3.3™ engines
A favorite for most 2-stroke engines
For most .12-.21 on-road racing Turbo head engines
Outlast the hottest heats with Turbo head engines
Ideal for aircraft engines .60-size and up
For leaner needle settings and high-nitro/high-rpm scale racing
Long reach and long life for 4-stroke engines

How to Read your Rc Glow Plug. Do you have your Nitro Engine Tuned Correctly?.

This is one of the best glow plug articles I’ve found online. Hope it serves you well!

How to Read your Rc Glow Plug.

Do you have your Nitro Engine Tuned Correctly?

What exactly is our glow plug telling us.

So you are wondering if you have rc nitro engine tuned correctly.

You check your temperature on a regular basis, but you are still not sure.

You can examine your glow plug to get a very good idea. Examining the glow plug is a peek inside the combustion chamber.

But let’s get the big picture and take the head button off, while leaving the glow plug installed in the head.

What we are going to see by looking at the head button and the glow plug is the entire combustion process.

This is going to show use just what is left after the burn process.

By looking at the entire combustion chamber we can analyze what was happening during the burn.

Let us explore a few different tuning examples below.
Rc glow plug picture

Pictured above is an example of a Rich Setting.

This is what your glow plug and head would look like after break-in.

The head and glow plug will be very wet with oil. Every thing still looks new.

No discoloring of the head, plug body or plug coil. If this is the look just after break-in that is great.

But, if this is post break-in then you are going to need to start leaning the engine out, to reach correct combustion.

If you run in a too rich state for a long period of time, oil will build up in the crank case and cause the front bearing seal to leak.

Rc glow plug picture

The previous example is of a Too Lean or Detonation Condition.

Upon examining your head and glow plug you find or feel little or no oil residue.

The glow plug body is blued. The coil wire has broken away from the plug body.

You see that the combustion chamber is silver to slightly tan. Plus the head and glow plug are extremely pitted.

Your nitro engine is running too lean.

The pitting is caused by detonation.

Detonation is when the fuel air mixture pre-ignites in many different areas of the combustion chamber at one time.

The top of the piston will show the same kind of damage. If you see this kind damage you need to richen up your engine.

You may need to also shim your head. Increasing your head clearance will lower compression and lessen the possibility of detonation.

Rc glow plug picture

In the above example you can see why it is important to look at the head and glow plug together.

This example shows a Borderline Lean with a Good Glow Plug.

By just looking at the glow plug you would think that your nitro engine tuning was correct.

But, looking at the head you see that there is some pitting occurring.

With seeing this damage you know that your rc nitro engine is tuned too lean and you need richen your carberator setting some.

Rc glow plug picture

If you are a serious racer, this is how your glow plug and head should look.

Above is an example of a Perfectly Tuned Race Engine.

As you can see on this head and glow plug there is an even coloring across the combustion chamber and glow plug.

If you do a lot of racing this is the coloring you are looking for, that light brown to deep golden color.

This shows you that you are getting the most out of your engine. Your nitro engine tuning is producing maximum power and you have the perfect tune on your engine.

The only thing that you will need to do is keep your eye on is atmospheric conditions, temperature and humidity.

As these conditions change, so is the tune on your engine. So, always be aware of the weather conditions to help with your nitro engine tuning.

Rc glow plug picture

The previous example is of a nitro engine that has a Safe Every Day Tune.

If your head and glow plug look likes this example and you are a novice racer or a basher, this is great.

You have done a great job of tuning your nitro engine.

The combustion chamber shows a little color, gold to tan.

Plus, the chamber and plug are still quite wet with oil residue.

The glow plug also shows some color on the body of the plug, grey to tan.

The coil wire will be shiny, silver and still have a new look to it.

The only place the coil wire should show some color is where it contacts the outer body of the plug.

At this point the coil wire should be slightly black.

This head and glow plug show an engine that is running great, a little on the rich side.

This type of tune on your nitro engine is very good to get the maximium life out of your engine.

Plus, this tune would be great for bashing and even for most of us weekend racers.

Taking the Mystery out of the Glow Plug

Rc glow plug picture

In this example we see a glow plug that has been run at a Lean Setting and has got very Hot.

On inspection we see that the outer body has turned black.

The coil wire has a white dusty appearance.

Plus, the coil wire has small breaks in the electrode wire.

All of this is due to the very extreme heat of running lean.

This glow plug is near failure, the coil wire is close to breaking free of the body.

If the tip of the coil wire was to break off it could travel down into the engine causing severe damage to piston, bearings and head button.

But, most times when the coil wire does break off it will just go out an exhaust port causing no damage.

This will not always happen, if the coils wire stays inside the engine it will destory many internal components.


I hope this has given you a little insight about nitro engine tuning. The glow plug what makes our nitro engines run.

Besides just looking at our glow plugs, it is important to remove the head button and look inside our engines on a regular basis.

Doing so is going to give us the whole picture of what is going on, not just a little peek the glow plug gives.

Yes, checking our glow plugs often is very important and gives a good look at what is going on inside our engines.

But, just remember that this is not the big picture.

Take a few minutes to clean your engine thoroughly, remove the head button and take a close look at what is going on inside.