few notes just wanted to add.
as far as engine operating temperature, do not forget, the chassis is also acting as a heat sink, so make sure the chassis is also saturated with heat before really starting to lean it out. 230-270F is the operating temperature range of nitro engines. there are other factors to be mindful of like gearing, if geared to tall the engine has to work too hard and will run hotter, and air leaks.
just to kind of clear up, pinging is pre-detonation of the fuel and air mixture, the mixture lighting itself before its actually supposed to in the combustion zone.
this can happen for a few reasons:
-too lean of a mixture being unstable enough to ignite earlier than it is supposed to
-the combustion chamber is too hot so its detonating off heat alone vs, the glow plug igniting the mixture, these are not diesel engines, they do not ignite off compression, but the reaction to the *methanol and the platinum in the glow plug filament*
-not enough space in the burn room for the glow plug and nitro-methane content used
the video during warm up at approximately the 26 minute mark is running incorrect in a different way,
trailing idle if it drops down to regular idle after a few seconds is caused by "a lean condition", though yes it is lean, but not necessarily the needle(s) being "lean" per se.
there are two scenarios that can cause this, the most common I've seen is:
Idle Gap too wide and LSN too rich, the transition from wide open throttle burns the fuel off, and any residual fuel left over is mixing with the too far open idle gap causing too much oxygen to get into the mixture revving it up until the LSN can compensate adding more fuel richening the condition dropping the idle, which it is doing so in excess to even out the situation. that is why it is such an erratic firing engine.
causing what you think is a faux good idle, but is really a loading up LSN.
once tuned correctly, the LSN should take over instantly after coming off the throttle from a wide open pass dropping the immediately.
typically see this when leaning out from factory or known rich settings as both needles are starting rich and wide idle gap, and most start with tuning the HSN as called for in most manuals.
Correct Idle Gap, with the LSN is too lean, you should typically have around a 0.7mm+/- idle gap, depending on the engine.
typically break in settings are very rich, thus why it is recommended to start with a 1mm or larger idle gap, because the LSN is rich and will need more air to be introduced to the engine to fire properly and continually without flooding out.
in the case of the video by the same guy at 26 minute(ish) the HSN was also pretty rich on the top end, you can hear it slightly stumbling, raspy, and gurgle sounding, and never got to its full RPM range, not "screaming" if you will. again the video was before it was warmed up, so at that exact time would not be a good time to be leaning it out.
i really really recommend checking out the following:
JQracing tuning video
(kind of a shorter version without as much explanation:
)
the Ron Paris Tuning Bible.
https://www.rcuniverse.com/forum/rc...-paris-guru-nitro-engine-tuning-pdf-file.html
agreed, never tune by temperature, always tune by smoke, sound, and performance, it is better to be on the slightly rich side then lean, run as rich as you can while having good performance and sound.
EDIT** realized i left a sentence unfinished above.
