Originally Posted by THE DOCTOR
Do you always run the same plug all summer long or do you change for differant types of tracks or track conditions? What plug temp do you usually use?
It depends on weather conditions, asuming same Nitro %.
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: 6
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:
• When the ambient temperature is high, we have to use a plug with thicker wire.
• With higher compression, we have to use a plug with thicker wire.
• Humidity determines if we use a Cold (F) thermal range, or Hot (C) thermal range.
• With high humidity percentage we should use a Hot (C) thermal range plug.
• 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 and Humidity measurements on them.
Following is a selection chart for Novarossi Turbo Glow Plugs
Type Range Nitro% Air Temp.C° Humidity%
C5TGC Hot/hot wire 10-20 0-10 70-100
C6TGC Hot/average wire 10-20 10-16 70-100
C7TGC Hot/cold wire 20-30 16-25 70-100
C8TGC Hot/ultra cold wire 30-up 25-up 70-100
C5TGF Cold/hot wire 10-20 0-10 40-70
C6TGF Cold/average wire 10-20 10-15 40-70
C7TGF Cold/cold wire 20-30 16-25 40-70
C8TGF Cold/ultra cold wire30-up 25-up 40-70
Now if you want to use the plug as a timing tool, advance or retard ignition, you can, depending on particular track layouts.
Experience dictates that just by lowering the head (more compression) you gain more power especially in lower rpm range, idle quality can suffer, but the engine also runs cooler . Also, that a higher head (less compression) will increase top rpm speed on bigger tracks.
A decrease in head shims (an increase in compression ratio) will increase torque because as the compression ratio goes higher, the actual ignition timing occurs sooner. However there is a point of diminishing returns where detonation occurs or engine temps can soar, and if this happens a colder plug can help.
A colder plug will also increase torque, except in the instance of a colder plug the ignition is slowed until a greater point of compression build occurs.
When you increase head shims (a decrease in compression), top end is enhanced as the ignition timing is retarded and occurs later. Generally a hotter plug is needed to advance the ignition cycle so that timing does not occur to late in the cycle, but at this point you end up over leaning the engine to get it to rev properly and the engine life will suffer dramatically.