Originally Posted by performula
What is the difference between F and C on the Nova turbo plugs?
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 dissipate heat better and faster 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.
On Another note: The Old OS standard plugs such as the Nº8, Nº5 have fewer threads than Nova based plugs, so they sit higher in the combustion chamber of a Nova based engine, and won't work addecuately, thus your problem.
AFM