The pop quiz on nitro engine regarding the high-end only

[newnitro2020]

Disclaimer! I'm not saying or claiming to be an expert I want to see if I'm right about the things that I've been studying about within the last 2 months. The video I am representing is showing guesses of what I believe to be true in terms of shooting the high-speed exclusively for performance. Thank you for reading.

This is part 2 of the topic I had on the end of last month. I did this in a form of a video and so I like to show that video. I went ahead and was curious about the high-speed thing because I was very surprised at some things I didn't know and in this video I'll be discussing and reminiscing basically.

 

[monstertruckier15]

You're too lean on the high needle setting. Open 1/4 turn Know you factory settings and know how far you can turn them in. Stay away from the maximum lean setting and you will be fine. You should also open the low 1/8 turn to richen engine.

The % of Oil lube will change you tuning window.

 

[newnitro2020]

You're too lean on the high needle setting. Open 1/4 turn Know you factory settings and know how far you can turn them in. Stay away from the maximum lean setting and you will be fine. You should also open the low 1/8 turn to richen engine.

The % of Oil lube will change you tuning window.

Have you seen the whole video?

 

[cbaker65]

The engine should idle down shortly & smoothly with little or no chatter at all ,in those vids ,it is possible
that their Lsn need to be richened up just a tad ,it appears that the engine is running lean on the off throttle ,
hence the high idling!
The engine should settle down instantly after you let off the throttle!

 

[monstertruckier15]

You can tune all you want but I can tell you will never be happy. Everyday it will be different. You want to protect your engine from pining and have good acceleration. Running rich is the best option. Know where your factory start settings are and know how far you maximum lean setting is on high and stay away from it. The low is simple it usually is where factory setting is and no more than 1/4 turn open. Running wide open like that isn't the best for a nitro engine. It still sounded to lean on the high. If you want motor speed then you have to change the clutch bell. 2 teeth up for on road driving. Then it will change the load on the engine and sound better.

 

[alfredwong2003]

I will have to disagree that the engine actually ping, what I think is the clutch hitting the clutch bell. The so call pinging is heard usually when breaking. When the idle is too high, you can easily get into that. When the engine is still revving when break is applied, you are basically choking the engine. The conclusion is still the same, lower the HSN. If you have tighter clutch sprigs, it will help.

 

[alfredwong2003]

Also what Joel Johnson video about tuning the engine with the LSN first and make sure the engine can run for 15-20 seconds before it is loaded and quit is not a bad idea, it will then allow you to lean the engine and eventually, it will not load up anymore. I think that is the idea. A tuned engine should allow you to run a full tank at idle speed.

 

[D3MON]

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.