It doesn't work that way. Your operating atmospheric pressure, humidity and temperature factor into the equation, as does the prop size and the heat range of the glow plug that you are using. Even your high speed needle setting can make a big difference. But, the only way to learn and keep it in your noggin' is to do it.

Engines that are over compressed for the amount of nitromethane or prop load being used, not to mention a too hot glow plug, will tempt you to tune the high speed needle very rich. This does retard the timing and it helps the engine tolerate the conditions that are existing, however, it will leave you with a very rich midrange mixture, which can lead to dead sticking and raggy acceleration from idle to full throttle. What to do?

Drop the prop size if you don't have any way to reduce the nitro or the compression. Or, change to a colder glow plug than you are presently using.


Ed Cregger


Oh, one more thing. There is no such term as predetonation. pre-ignition and detonation are two completely different terms, which mean two completely different things.