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Old 04-03-2007, 09:14 PM   #1
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Default Engine tuning question - sputters at high RPM but plenty of smoke

Hi, I picked up a used 8ight for my first nitro car and I'm learning the tricks of tuning the engine. I'm getting some of them down - I know how to at least tune the low and idle enough to get it started and keep it running.

When I punch the throttle it'll fly on an open parking lot for 1-3 seconds but then it sputters and seems to idle despite my trigger being all the way down. Then it will come back to life for another second or two. 1 out of 4 times it'll stall out completely.

I was told that the stuttering is a symptom of being too lean and that I need to make the high needle richer. But I don't understand why I'd be seeing plenty of smoke if it's rich.
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Old 04-03-2007, 09:29 PM   #2
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That sounds like a major lean bog to me. Back out the high needle a full turn and re-tune. DONT touch the mid range if it has one. What engine r u running?
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Old 04-03-2007, 09:40 PM   #3
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The engine is the 427 that comes with the RTR 8ight. You're advice is the same as what I've heard elsewhere as well. The only thing I'm confused about is that there's plenty of smoke - more smoke already than my brother's HPI Lightning RTR. You still think it's a lean bog?
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Old 04-04-2007, 06:59 AM   #4
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The base settings for the 427 engine are:

High-Speed Needle- 2.5 turns out from bottom
Low-Speed Needle- 2.5 turns out from bottom

Reset the needles to this and see if your problem goes away. The high speed needle on this motor is touchy. It will go from too rich to too lean in a half a turn so make small adjustments.
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Old 04-04-2007, 07:06 AM   #5
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Quote:
Originally Posted by sport10
The base settings for the 427 engine are:

High-Speed Needle- 2.5 turns out from bottom
Low-Speed Needle- 2.5 turns out from bottom

Reset the needles to this and see if your problem goes away. The high speed needle on this motor is touchy. It will go from too rich to too lean in a half a turn so make small adjustments.


Mhhh had same problem with my last STS .21 Team Engine ... and the problem was that i was using a too cold plug, try to go to a hotter one and retune the engine ... at least that resolved the problem for me ...

cya,
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Old 04-04-2007, 09:59 PM   #6
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I returned my settings to factory and then got it all worked out. I'm almost fully tuned at this point. Thanks for the input.
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Old 04-04-2007, 11:03 PM   #7
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It kind of seemed like you might have leaned the high end needle until you got good throttle response. Rule #1 is engine tuning is always tune the high end first. It controls the total flow of fuel to the engine and is the only needle affecting the mixture at more than 1/2 throttle. When you can open it up and get a nice crisp sing from the engine accompanied by a smoke trail then you can go ahead and tune the low end for throttle response.
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Old 04-18-2007, 09:49 AM   #8
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Quote:
Originally Posted by Arboleda
Hi, I picked up a used 8ight for my first nitro car and I'm learning the tricks of tuning the engine. I'm getting some of them down - I know how to at least tune the low and idle enough to get it started and keep it running.

When I punch the throttle it'll fly on an open parking lot for 1-3 seconds but then it sputters and seems to idle despite my trigger being all the way down. Then it will come back to life for another second or two. 1 out of 4 times it'll stall out completely.

I was told that the stuttering is a symptom of being too lean and that I need to make the high needle richer. But I don't understand why I'd be seeing plenty of smoke if it's rich.
Richen the high end needle 1/2 - 1 turn. If it still does it, then start to lean it back out. You can still see exhaust fume from the pipe because it has some fuel to burn in the chamber, just not enough. My Dad found this out the hard way with his t-maxx and burned it up.
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