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Old 09-02-2010, 01:18 PM   #1
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Default Give me a lesson on Glow Plugs if you would please

Getting back into R/C and a few friends as well. The thing that blows my mind is how to decide what glow plugs to use. For example...I run a Novarossi C6G based on suggestions from some people. I understand this is a medium plug. When do you use a cold plug or a hot plug? Does it depend on nitro %, engine size, weather, a combination?

Thanks for schooling an idiot
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Old 09-02-2010, 01:39 PM   #2
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Ir depends on everything. What are you running? TC or 1/8th or buggy based GT? What nitro, how big a track, etc.?

Generally, .12's like a bit hotter plug. 5's for really short tracks and/or really cold weather, 6's for most all around average conditions, 7's for really long tracks and/or high nitro.

.21's like a bit colder plug. Add one to the above and you're good to go (6,7 or 8).
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Old 09-02-2010, 06:11 PM   #3
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you want a lesson here it is...
A glow plug’s temperature range is critical to proper performance. Small-block engines generally use warm to hot glow plugs, while big-block engines use plugs in the colder range. If you choose a plug in the wrong temperature range, you could be chasing the tune of your engine till the sun goes down. Changes of the relative temperature of the glow plug can be beneficial, however.

A combination of compression, heat and a catalytic reaction between the platinum in the glow-plug coil and the methanol in the fuel creates combustion in a nitro engine. Altering the heat range of your glow plug can alter the timing of the combustion process. Nitro engines don’t have an ignition system that can be used to advance or retard combustion timing, but a hotter plug that causes ignition a little earlier in the combustion process can have the same effect. “Advancing” the ignition timing can increase overall power output, especially at higher rpm. There are limits, however, and installing too hot a plug causes pre-ignition (detonation) and risks damaging your engine.

It’s a challenge to figure out a glow plug’s temperature range. Manufacturers don’t use a consistent and universal standard to rate the temperature ranges of their glow plugs. You will probably know the temperature of a plug relative to others within a given product line, but currently, no rating system allows comparisons among manufacturers. Here again, plain old experience with a variety of glow plugs will help you to know which are best for the effect you want.

“Reading” the glow plug is a tuning technique advanced by Ron Paris. It suggests that looking at the glow plug tells you something about how your engine is running. The element in a glow plug will turn gray in an engine that is close to the optimum fuel mixture. This method requires a new glow plug, as the element will eventually turn gray regardless of the needle settings; the length of time it takes to turn gray is the issue. Plugs that turn gray in just a tank or two of fuel (running at race pace, not diddling around) indicate a fuel mixture close to ideal—but also close to trouble. If the plug stays wet and shiny for a few tanks of fuel, you’re in the safe zone; a little rich but safe. When the plug wire gets distorted or broken, however, you’re in real trouble. It’s a sure sign that the mixture is way too lean, or that there is too much compression and the engine is detonating.

hope this helps
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Old 09-03-2010, 03:13 PM   #4
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Originally Posted by Dredd View Post
Getting back into R/C and a few friends as well. The thing that blows my mind is how to decide what glow plugs to use. For example...I run a Novarossi C6G based on suggestions from some people. I understand this is a medium plug. When do you use a cold plug or a hot plug? Does it depend on nitro %, engine size, weather, a combination?

Thanks for schooling an idiot
Turbo Glow Plugs where designed to give more performance to an engine, for the following reasons:

1.- It forms an uninterrupted combustion chamber.
2.- The advantage of better heat transfer or heat dissipation, and a leak proof seal, generated by the conical seat of the plug.
3.- Greater choice of thermal ranges, that allow for a more precise tuning according to variations in weather conditions (temperature, humidity, altitude, barometric pressure, etc.).

The numbers and characters on the plugs, are the product number, wire thickness, and thermal range of the plug’s body. Example: The Novarossi C6TG (F) or (C)
Product: C (Conical)
Wire Thickness: 7
Plug Type: T (Turbo)
Plated: G (Gold)
Thermal Range: F (Fredda = Cold) C (Calda = Hot)

The plugs with cold thermal range F (Fredda), have a body with thinner walls and shorter body, so they dissipate heat better and faster to the engine head. The plugs with hot thermal range C (Calda), have a body with thicker walls and longer body, so they retain heat and dissipate heat slower to the engine head. The number of threads is the same on both types of plugs.

How to select the proper plug:

1.-When the ambient temperature is high, we have to use a plug with thicker wire.
2.-With higher compression, we have to use a plug with thicker wire.
3.-Humidity determines if we use a Cold (F) thermal range, or Hot (C) thermal range.
4.-With high humidity percentage we should use a Hot (C) thermal range plug.
5.-If we have high temperature and high humidity, we should use a plug with thick wire and a Hot(C) thermal range.

The best instrument to determine which Turbo Plug to use, is those table digital weather stations, that have Temperature, Humidity, and some also Barometric Pressure on them. That is the key to success or failure tuning engines with Turbo Glow Plugs, because they are so sensitive to weather variations that it is unbelievable.

Following is a selection chart for Novarossi Turbo Glow Plugs

Type Therm Range Nitro% Air C° Air Fº Humidity%
C5TGC Hot/hot 10-20 0-10 32-50 70-100
C6TGC Hot/medium 10-20 10-16 50-61 70-100
C7TGC Hot/cold 20-30 16-25 61-77 70-100
C8TGC Hot/ultra cold 30-up 25-up 77-up 70-100
C5TGF Cold/hot 10-20 0-10 32-50 40-70
C6TGF Cold/medium 10-20 10-15 50-61 40-70
C7TGF Cold/cold 20-30 16-25 61-77 40-70
C8TGF Cold/ultra cold 30-up 25-up 77-up 40-70

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