Tuning Question for you

[emu67]

I've noticed this in my engines. I tune the engines til they are running good. I noticed that I have to increase the idle on the engine to keep it running for 2 to 5 minutes til it builds up heat. Then I can reduce the idle back to normal and it idles just fine. Anyway, when I go in to refuel, I notice that the engine wants to die at the idle setting and so I need to increase the idle again for 2 minutes or so before I can return the idle back to normal.

Any of you guys see this happen? Also, how do I prevent this because when I start racing I don't want a flame out when I refuel.

 

[gdc02]

I think it's set to rich at the low speed needle setting
then the engine will slowly die out at idle
if it's to lean , it will increase idle rev slowly

you can check this out by warming up the engine at temperature
letting it idle for 12sec
pinch then the fuel line just in front of carburator inlet
when idle is dying immediatly without increasing idle the setting is to lean
same way , if idle increases dramaticly and then dies, it set to rich

ideal idle should increase slightly some 200 rounds p/m before dying
if the engine won't start easily or not at all (new engine), it usualy is set to lean at LSN also

could be the tank also, like a Swift has troubles reaching the end of the fuel take

 

[niggle]

Anyway, when I go in to refuel, I notice that the engine wants to die at the idle setting and so I need to increase the idle again for 2 minutes or so before I can return the idle back to normal.

Any of you guys see this happen? Also, how do I prevent this because when I start racing I don't want a flame out when I refuel.

Almost every nitro powered RC car suffers from this to some degree.

Basically, there is more fuel pressure at the carb on a full tank than when the tank is almost empty, due to the "head" or weight of the fuel sitting above the pick up point in the bottom of the tank. As the tank empties the head reduces and so does the fuel pressure seen by the carb.

The best that you can do is optimize your carb settings for a half-full tank. It will be slightly too rich when the tank is full and slightly too lean when the tank is almost empty. Just make sure that you don't run too hot when the tank is nearly empty.

 

[mikeburgin]

EMU how low are you setting your idle, theres no prise for how low you can get your idle set, i tend to set mine just before the clutch engages, and i set my clutch to engage quite late, reason for the higher idle is basicaly to ensure on a roll over that the engine dosnt die, may well be caused by idle set to low and slightly to rich in the bottom end, remeber that ajusting your idle screw in your car also effects your low end mix.