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Old 07-05-2005, 02:12 AM   #1
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Default Tuning Problem - High End

Hi All,

It's been a steep learning curve going from electric to nitro, I am almost there but haven't quite been able to tune the engine, GS15R, to my liking.

I seem to have got the idle fuel mixture sorted out by playing with the low speed needle, also the idle speed is sorted.

However I am having issues in the top end. For instance if I slowly bring the car to max throttle and leave it there for a couple of seconds, it will hit a dead spot where it will either a) stop revving and cruise (as if it hits a flat spot) or b) if the throttle is left on at this point, the engine shuts off.

Now I've tried leaning and richening the mixture at this point but it didn't make much difference. Anyone have any ideas?

Thanks!
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Old 07-05-2005, 05:10 AM   #2
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Also- should the idle be tuned rich enough so that the exhuast emits smoke? I have a theory that my idle is too lean, so when I get into the high rpms it gets hit with too much fuel? Can anyone verify that theory?
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Old 07-05-2005, 05:43 AM   #3
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Do it the other way around. Set your high speed first, then your low end. Make sure you have a good plug and richen everything up, or better yet, start with factory settings. Then start leaning out the top till you get the nice top end that you're looking for. THEN set your bottom.

i've noticed somethign similar with my Mega ZX12. Once it gets to operating temp, if it's too lean, the engine will seem to level out and not accellerate just for a second in the middle towards the end. Almost hitting a flat spot like you said. When i richen it a little it opens up. If it's too rich, well then it just sounds like it's 4 stroking. I haven't had it to the point where it shuts off at full throttle. Good luck.
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Old 07-05-2005, 05:55 AM   #4
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Thanks for the info Gonzo, I'll try tuning it based on the high speed needle.

Can you confirm wether the exhuast should be emitting smoke at idle? If it isn't, is the idle too lean?
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Old 07-05-2005, 07:52 AM   #5
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Like Gonzo said; tune the main first!
The visibillity of smoke depends on too many variables, ie; humidity, fuel type, etc.
AFTER the main is set, richen the low speed until it loads up badly at idle. Clear it out by making high speed pass. Then lean the low-end a little & re-test. continue untill you get it to load-up only a little bit after a 20 - 30 sec. idle. You also have to look at the transition from low to high when advancing the throttle gradually. Try to make it seamless.. that is, no sudden richening or leaning when it transitions from low to high. Re-adjust idle speed after all mixtures are set properly.
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Old 07-05-2005, 10:04 AM   #6
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Quote:
Originally Posted by linds
Thanks for the info Gonzo, I'll try tuning it based on the high speed needle.

Can you confirm wether the exhuast should be emitting smoke at idle? If it isn't, is the idle too lean?
Yeah smoke at idle isn't a big deal. You'd like to see smoke when you punch out of corners, but sometimes it won't be as noticable depending on what fuel you're using. Duneland's advice is pretty good. One more thing to look for is that after a good hard run, the car should come in with a low idle. It's shouldn't sit high before dropping.
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Old 07-06-2005, 03:49 AM   #7
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Thanks for the info guys, much appreciated. I'll take these tips onboard at the next tuning session
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Old 07-06-2005, 04:51 PM   #8
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Theres some good tuning info on here-
www.cefx.net
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Old 07-06-2005, 06:43 PM   #9
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Default Factory setting for GS15R

The manual says to set the main needle to 2 turns out and the low end so that the head of the screw sits about .5 of a mm out. The idle adjust should be set so that when the drum is closed the hole left is 1 mm wide at its biggest point. Note: this is the break in settings.

I have this engine in my V-one-S and after break in the needle settings for me where about:

Main 1 turn to 1 1/4 turns out depending on the day and weather etc;

Low end still about .5 mm out maybe slightly leaner (be carefull with this it only takes a small turn to make a huge difference, you should only try to nudge the screw about 1/16 of a turn or less.

Idle Once again closed the idle a little but not much definatly did not need to close the gap to less the 05 of a mm.

Hope this makes sense and helps.

Dishy
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Old 07-10-2005, 06:20 AM   #10
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[QUOTE=HELLION]I don't know who started this tuning thing by adjusting the low end first!!! The fact is that the low speed is feeded from the high speed. I set the high speed first but make sure your engine is at running temp. before you adjust it. That said I know alot of guys that do the low end first. so It's debatable
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Old 07-10-2005, 05:26 PM   #11
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I am far from an expert on tunning an engine. Just let me repeat that FAR FROM AN EXPERT. But I think it doesn't matter high or low speed first or second, just make sure you only change one at a time. As Hellion said lots of people do the high and first others do the low end first just don't do both at once. Just for the record I usually do the high end first.
But I do strongly agree that you must have the engine at running temp before making any changes.

Dishy
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Old 07-11-2005, 10:27 AM   #12
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Dishy,
It makes a big difference! The high-end (main) adjusts for the entire range! Any adjustment you make to the high-end affects the low-end, but not the other way around. Any adjustments made to the low speed needle assembly, have no effect on the high speed.
You can make adjustments to the low-end before finishing-up with the main, but you must be aware that your final adjustments to the low-end must be made after your final adjustments to the main (high-speed).
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Old 07-12-2005, 02:19 AM   #13
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Default Feeded?

[QUOTE=HELLION]
Quote:
Originally Posted by HELLION
I don't know who started this tuning thing by adjusting the low end first!!! The fact is that the low speed is feeded from the high speed. I set the high speed first but make sure your engine is at running temp. before you adjust it. That said I know alot of guys that do the low end first. so It's debatable
Is that a word???
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