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Old 04-25-2010, 06:05 PM   #1
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Default Tuning an engine question...

I have set my travel on my remote to 30% so I can focus on the low speed needle and the idle screw.

When I spool up the engine, it engages and speeds up smoothly. When I release the trigger and let it slow down by itself the engine doesn't slow down smoothly. About 70% of the time, it seems to hesitate making a

DiggaDiggaDiggaDigga sound

rather than the smooth

rrrrrrrrrrrrrrrrrrrrrrrrr sound

it made on acceleration. The smoke is much less noticeable now then when it was running richer, but it is still there especially when I initially punch the gas.

The Digga sound it makes is very similar to what happened on acceleration when it was running rich and the engine seemed to be overburdened with gas.

Now I am pretty sure the engine is still running rich, but I don't know how to tell for sure. Thoughts?

Thanks.
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Old 04-25-2010, 06:09 PM   #2
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I have set my travel on my remote to 30% so I can focus on the low speed needle and the idle screw.

When I spool up the engine, it engages and speeds up smoothly. When I release the trigger and let it slow down by itself the engine doesn't slow down smoothly. About 70% of the time, it seems to hesitate making a

DiggaDiggaDiggaDigga sound

rather than the smooth

rrrrrrrrrrrrrrrrrrrrrrrrr sound

it made on acceleration. The smoke is much less noticeable now then when it was running richer, but it is still there especially when I initially punch the gas.

The Digga sound it makes is very similar to what happened on acceleration when it was running rich and the engine seemed to be overburdened with gas.

Now I am pretty sure the engine is still running rich, but I don't know how to tell for sure. Thoughts?

Thanks.
a little more info please
motor type
how much fuel is ont he motor ..is it new used ?
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Old 04-25-2010, 06:13 PM   #3
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a little more info please
motor type
how much fuel is ont he motor ..is it new used ?
It is a new Jammin .21 JPX Engine, modded and broken in by Clockworks Racing. I have put about 8 tanks on it.
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Old 04-25-2010, 06:32 PM   #4
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If the engine is still at factory settings it is likely it is too rich with too much idle gap....This would cause it to to want to "run On" when you let off the trigger....I would suggest closing the idle gap and leaning the LSN slightly..... Now this is just a guess from reading what you posted, a lean motor makes a sound almost similar to what a rich motor with too much idle gap ill make when letting off the trigger....How the engine idles and takes off will tell you if its lean or rich...a lean engine will have a very fast almost runaway idle...a rich engine will want to stall out at idle and will sometimes flame out as you apply trigger.... Truly the best bet is to shoot a short video of the engine....do some starts and stops in front of the camera.... varying the amount of time between starting and stopping..... Then after the stop take the machine for about a 100 foot blast wide open, then blast back wide open and stop right in the front of the camera..Vary the time of idle from a instant stop and go, all the way to a 10 second stop and go...by watching this on video we all can help you dial it in...
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Old 04-25-2010, 06:50 PM   #5
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ok so its a picco base motor ..****disclaimer**** i have never ran a picco motor

that being said ..i wouldnt really be limiting your epa to dial in your bottom end ..just set you epa where it needs to be for the motor ..meaning set it to where the carb barrel only travels to the end of the opening and not past it ...
with the motor fully heated up to operating temp .....when you rip the motor up and down the street a few times ...let the motor sit at idle for about 10 seconds then give it the gas ...does it sit there and kinda bog down for a second billowing smoke? or does it immediately take of with awesome power and little smoke ? there is a fine line between good and not good ...if it is hesitating and bogging and billowing smoke ..it can be to rich ...if so lean the lsn 1 hour at a time and repeat until you have a decent puff of smoke and good rip from an idle ....if it just takes off like a batt out of hell with little smoke ...it could be too lean ...if so richen the lsn 1 hour at a time and repeat until it takes off decent with a good puff of smoke ...

all this being said you should really be tuning your hsn first then dialing in the lsn ...on the top end you just want good power and a steady stream of light smoke fromt he exhaust ......

the ding da ding da ding da ding sound you are hearing ? so this is at idle after reving up the motor ? if its like dingdingdingdingpingping ping ping ....at a high pitch this sounds like a lean lsn ...hard to say though without hearing it or being there ...

it seems like on all my motors i can tell which way to go on the lsn by listening to the motor idle up when it comes in after some passes back and fourth ..when it comes in and you listen to it ...i am trying to get my idle to drop within about 5 seconds of coming in to an idle ...it will drop off from a high idle to normal idle .im doing this by leaning or richening the lsn leaning the lsn will make the idle stay higher for longer richening it will cause it to come down quicker ..im hoping this makes some sense ..alot of the way i tune is by sound ...so its kinda hard since i cant hear you engine
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Old 04-25-2010, 06:52 PM   #6
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If the engine is still at factory settings it is likely it is too rich with too much idle gap....This would cause it to to want to "run On" when you let off the trigger....I would suggest closing the idle gap and leaning the LSN slightly..... Now this is just a guess from reading what you posted, a lean motor makes a sound almost similar to what a rich motor with too much idle gap ill make when letting off the trigger....How the engine idles and takes off will tell you if its lean or rich...a lean engine will have a very fast almost runaway idle...a rich engine will want to stall out at idle and will sometimes flame out as you apply trigger.... Truly the best bet is to shoot a short video of the engine....do some starts and stops in front of the camera.... varying the amount of time between starting and stopping..... Then after the stop take the machine for about a 100 foot blast wide open, then blast back wide open and stop right in the front of the camera..Vary the time of idle from a instant stop and go, all the way to a 10 second stop and go...by watching this on video we all can help you dial it in...
haha you beat me to it good info here also you would do good to read montys engine tuning bible ...that is how i learned to tune motors ...i would bet idle gap to high , lsn too rich , hsn too lean
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Old 04-25-2010, 07:24 PM   #7
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ok so its a picco base motor ..****disclaimer**** i have never ran a picco motor

that being said ..i wouldnt really be limiting your epa to dial in your bottom end ..just set you epa where it needs to be for the motor ..meaning set it to where the carb barrel only travels to the end of the opening and not past it ...
with the motor fully heated up to operating temp .....when you rip the motor up and down the street a few times ...let the motor sit at idle for about 10 seconds then give it the gas ...does it sit there and kinda bog down for a second billowing smoke? or does it immediately take of with awesome power and little smoke ? there is a fine line between good and not good ...if it is hesitating and bogging and billowing smoke ..it can be to rich ...if so lean the lsn 1 hour at a time and repeat until you have a decent puff of smoke and good rip from an idle ....if it just takes off like a batt out of hell with little smoke ...it could be too lean ...if so richen the lsn 1 hour at a time and repeat until it takes off decent with a good puff of smoke ...

all this being said you should really be tuning your hsn first then dialing in the lsn ...on the top end you just want good power and a steady stream of light smoke fromt he exhaust ......

the ding da ding da ding da ding sound you are hearing ? so this is at idle after reving up the motor ? if its like dingdingdingdingpingping ping ping ....at a high pitch this sounds like a lean lsn ...hard to say though without hearing it or being there ...

it seems like on all my motors i can tell which way to go on the lsn by listening to the motor idle up when it comes in after some passes back and fourth ..when it comes in and you listen to it ...i am trying to get my idle to drop within about 5 seconds of coming in to an idle ...it will drop off from a high idle to normal idle .im doing this by leaning or richening the lsn leaning the lsn will make the idle stay higher for longer richening it will cause it to come down quicker ..im hoping this makes some sense ..alot of the way i tune is by sound ...so its kinda hard since i cant hear you engine
what do you do when it drops a second time? a three stage idle so to speak. I have a jx and like you i listen after high speed passes. this is good to get a read on your hsn and lsn. Well i get it tunned the best i can and it comes in, idles high for about 5 seconds then normal for about 5 seconds then a low rich bog that will die if i don't pull the trigger. I have tried everything, lean the low, rich the high, richen the low, lean the high. Idle gap in, out and everything in between. I had some sucess tunning the mid range a little and had some success, but if i get it to idle like it supposed to it is too lean.

Anybody else have this problem?
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Old 04-25-2010, 10:06 PM   #8
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Your HSN is too lean and LSN is too rich. Your engine's behavior right after you let off the throttle is a good indication of what's happening with the HSN. If it holds a high idle for a short period of time, that means that, while it was running on the HSN, it wasn't getting enough fuel. Only when the engine is allowed to run for a few seconds on the LSN, will you know how well it's set. If the idle continues to drop until it stalls, it indicates that the LSN is too rich.
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Old 04-26-2010, 06:30 AM   #9
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Steve is right on the hanging idle. I like to have my lsn to where after about 15 seconds at idle it will be slightly rich.If you have a high idle right after a full throttle run you are using up all the fuel at high speed and the next thing that burns is aluminum!
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Old 04-26-2010, 06:59 AM   #10
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It sounds like your lost on your tune bud...... Im not a pro tuner, so I would go back to factory settings and work with the HS first........... IMO you should not set your epa lower for this. Set it how it would be set for racing.
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Old 04-26-2010, 08:15 AM   #11
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having the total throttle travel limited to 30% can also cause some weird running characteristics too.... as it will not fully open the fuel passage so the engine will want to run lean..
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Old 04-26-2010, 08:24 AM   #12
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having the total throttle travel limited to 30% can also cause some weird running characteristics too.... as it will not fully open the fuel passage so the engine will want to run lean..
Yes, the engine cant go through its full rev cycle.... and I think it will load up with fuel and not give you an accurate tune.... but again Im no pro at this
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