stumped! help me understand

[Nitroaddict]

okay - went bashing last night and here is the problem:

FIRST - engine would accelerate fine, but would stall if I full throttled it, and then let off. No gurgles, it would just stop running. would idle all day, but seemed to flame out, under heavy power.

SECOND - after tuning the settings back to factory specs, now it doesn't stall, but has no low end power, takes off real slow, doesn't idle well, and will die if it idles for more than about 3-5 seconds. grrr - driving me crazy.

BTW - the engine is a rossi .12 pixie, and the car is an NTC3

I am thinking that the LSN is too lean, but when I richen it or lean it, it gets worse. that makes me even more confused.

Same with the HSN - running a little lean right now - but when I richen it up, it starts to really bog down. grrrrr - I'm so confused.

If an engine sputters, and feels sluggish at idle, doesn't that mean its too rich? HELP!!!!

 

[NCNitro]

Originally posted by nitronewbie
okay - went bashing last night and here is the problem:

FIRST - engine would accelerate fine, but would stall if I full throttled it, and then let off. No gurgles, it would just stop running. would idle all day, but seemed to flame out, under heavy power.

It sounds to me like the HSN was the problem, if it accelerated fine from a stop and took off good until it got to mid range, then died, imo the LSN seems to be fine.

The HSN can be a little tricky since both a lean and rich condition will have similar symptoms. Is it bogging (too much fuel), or is it starving for fuel when you get on it? Does it have a nice stream of smoke from the exhaust? Is it spitting raw fuel out the pipe?

Start from break in settings and lean it in tiny increments, no more than 1/16th of an inch at a time, run it a little see how it acts. if it runs worse go the other way in 1/16 increments. Temperature, and humidity will also play a big part in tuning.

Only adjust one needle at a time, this way you will know exactly which adjustment you made bad or good, that way if it was bad you can turn it back easily.

SECOND - after tuning the settings back to factory specs, now it doesn't stall, but has no low end power, takes off real slow, doesn't idle well, and will die if it idles for more than about 3-5 seconds. grrr - driving me crazy.

Now it sounds as if the LSN is too rich, which would account for the sluggish takeoff and it not wanting to idle, sounds like it's loading up with fuel and stalling.

 

[Nitroaddict]

yeah - i think the fact that i was adjusting the LSN and HSN at the same time could have been the problem. As i said before - the top end on it is now okay, but the low end is the problem. I am going to run it after work today, so i was trying to get some solutions before hand. is it possible that the LSN is set WAY too rich? as i have tried adjusting it both ways as much as a 1/4 turn with no avail. factory BREAK IN settings state the LSN should be 7 1/2 turns out. It is currently set at 7 1/4 out. Also - is it true that if u lean the LSN, it will cause the HSN to richen? and vice verse?

 

[FastEddy]

Have you replaced your plug lately?
A weak plug will cause all sorts of tuning issues some of them much like the ones listed above.

Its worth a try.

All needle adjustments should be made independent of each other. Run the car 1-2 minutes between each adjustment. Don't over due it. On the High performance mills especially the small ones, the sweet spot may lay somewhere in-between a 1/16th of a turn.

Get a new plug and take your time.

 

[mjime714]

Here is what I would do:

-From the stock settings. start to lean out the LSN. Do the pinch test to make sure you are around the correct settings. Pinch the fuel line to the engine. The RPMs should rise and then the engine cuts out in about 3-5 seconds. If the engiine cuts out faster, its too lean. If it takes longer than 5 seconds, its too rich.

-Once the LSN is tuned, start to lean out the HSN by 1/8th of a turn at a time. blip the car around and see how it performs and check temps.

-The more you lean out the HSN, you may notice that you are loosing low end power. If this happens, you need to start to RICHEN the LSN by 1/12th turn. Like the hands of a clock.

Try this, and I hope it helped! :thumbsup: Good luck!

 

[NCNitro]

Thats what it sounds like to me, see if it is spitting raw fuel out the pipe. Also if you have to keep clearing it out just to get it to idle would be another indication it is too rich. Dont limit yourself to factory settings as a tuning guide, but merely a starting point. I have never seen two engines have the same settings. Turn it in (lean) in 1/16 increments, look for any performance gains or losses then adjust it accordingly, you may have to go a full turn or more. Just keep an eye on the temps. Do you have a temp gun?

Great point Eddy, any time I have a tuning issue I always start with a fresh plug.

 

[Nitroaddict]

yes - i have a digital temp gun. leaning out the HSN will cause me to have richen the LSN or lean both? yes - i have to keep "clearing it out at idle" i am assuming that this means it is too rich. Eddy - yes - i tried to simple things first, and replaced the plug. it was not an issue. i know the pinch test - but what are other RUNNING CONDITIONS that would indicate a lean/rich setting on the LSN?

 

[mjime714]

When you lean out the HSN, it also slightly further leans out the LSN. You need to compensate for that by richening up the LSN ever so slightly.

I retune my car everytime I go out. It helps me to figure out the engine and at the same time, you make sure you are running at its full potential no matter what the environment is like.

 

[Nitroaddict]

thanks for that clarification, mjime - luckily though, i dont have to worry too much about climate, as it is usually the same temp and humidity about 10 months a year here in Florida. Does the reverse happen too, when i lean out the LSN (which is what i am supposed to do to correct my problem, right?) will i need to lean out the HSN too?

 

[mjime714]

When you lean out the LSN, it mostly effect the low end only, but the HSN effects a broader range. That is why you could have a single needle carb that only has an HSN.

All you got to remember is if you lean out the HSN, you cause the low end to lean out slightly also. So compensate if it causes problems on you low end by RICHENING the LSN.

 

[Çh®i§tiªñ]

The HSN will more accommodate your higher RPM's while the LSN will accommodate your idle and launch. If your high end is good but you stall at idle after 3 seconds, then I would lean the LSN as well. From stock, go about 1/16th in, run it for a couple minutes, see how you like it. Only go in 1/16th increments. I have 2 mills where the LSN is turned in about 1/4 from stock and the HSN are the only ones I turn now. Very rarely will I touch the low once I find its sweet spot.

Changing gearing can also cause you to richen or lean your LSN.

When you lean the LSN you sometimes have to riched the idle (just a hair)

Like Eddy said, 16th of a turn and run a couple minutes to let the settings take.

Good Luck!

 

[Nitroaddict]

Thanks for all the help - It was the LSN being too rich that was causing the sluggishness. And by the time I got it lean enough, the HSN was too lean and needed to be richened up a bit. All is good not though - runs like a top. Got a new body for it too, painted white, with neon green/yellow fades, and all of the parts between colors i left clear! looks really clean - and man what downforce that stratus body has! I'll post some pics. I have a race Thursaday night, and then all weekend, so wish me luck!

 

[mjime714]

can't wait for the pics. Lets see that monster