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-   -   can a to rich high speed needle (https://www.rctech.net/forum/nitro-off-road/381750-can-rich-high-speed-needle.html)

dreaux 03-20-2010 06:41 PM

can a to rich high speed needle
 
load up the case on the bottom end?

Just curious. If this happens then you theoretically could have a to lean lsn to compensate for a too rich high end and loading up the case making you assume the lsn is too rich?


I know it usually goes the other way, but wanted to know if this was possible as well.

Quad Racer 34 03-20-2010 06:48 PM

thats weird u asked that because this exact thing was happening to me today. i reset the needles to factory settings and going to retune it on another nice and warm day.

absolutemayhem 03-20-2010 06:52 PM

im my experience, yes it can...just tune your top end first,dont even touch the bottom end. so do high speed passes till you feel its at race tune...then work on your bottom end so it idles good and the responsivness if right, still doing high speed passes to clear out the motor.:tire:

dreaux 03-20-2010 07:37 PM

thank you. I thought so. No one really talks about this. It seems like a major pitfall.

But then again, a too lean low end is better then a too lean top end.

chris c 03-20-2010 08:37 PM

what you need to remember is that the high speed needle has control over all the fuel that goes into the motor....Think of it as a water valve the more open more water etc...

dreaux 03-20-2010 09:00 PM


Originally Posted by chris c (Post 7163317)
what you need to remember is that the high speed needle has control over all the fuel that goes into the motor....Think of it as a water valve the more open more water etc...

it has the most control over the medium to high speeds. But if it is to rich on the high end, some will remain that won't get burned off and load the case.
thinking you have a rich low end. So you lean the low end until the low end is running off the residual fuel left over and if it sits long enough it will lean bog at take off. So i guess technically it is never really lean, just a really bad tune. And i guess if your low end

mudslinger 03-20-2010 09:02 PM

Absolutely it can happen. I think it's one of the more common tuning problems people run into. The water hose analogy is a pretty good one too. I use that one all the time.

dreaux 03-20-2010 09:02 PM

are you also saying the hsn gives the lsn the fuel it needs to work with?

so a lean hsn automatically makes a lean lsn??? a rich hsn gives the lsn more fuel to work with?

dreaux 03-20-2010 09:14 PM


Originally Posted by mudslinger (Post 7163389)
Absolutely it can happen. I think it's one of the more common tuning problems people run into. The water hose analogy is a pretty good one too. I use that one all the time.

to bad it's not in the "tuning bible".

This has been my tuning pitfall. I rarely if ever tune a lean high end and a too rich low end.

because i set my idle screw. I never tune my idle to the fuel mixture on my lsn.

But, if your hsn is to rich you can set your idle gap pretty small and lean the crap out your lsn and get a false idle.

This is what happens to me. Not the other way around.

Now I finally understand just about all the dynamics of tuning. I can be absolutley aware of the carburator balance.

the trick it seems is to tune the hsn first but you would have to do high speed passes and keeping your lsn out of the equasion and to get a acurate read on your hsn by not letting the case load at all.

smokinu 03-20-2010 09:18 PM


Originally Posted by dreaux (Post 7163392)
are you also saying the hsn gives the lsn the fuel it needs to work with?

so a lean hsn automatically makes a lean lsn??? a rich hsn gives the lsn more fuel to work with?

the LSN and HSN are ALWAYS talking to each other and you need to tune them together... just one at a time.

dreaux 03-20-2010 09:25 PM


Originally Posted by smokinu (Post 7163436)
the LSN and HSN are ALWAYS talking to each other and you need to tune them together... just one at a time.

i hear you. That is what i try to do and usually end up with a bad tune on top or bottom. I am not that good yet.

I did however whip my motor into a really good tune by going high to low. The only thing is, my high is to rich and my low is to lean. I can tell because if i blip it several times and it idles long enough it will race to a high idle.

mudslinger 03-20-2010 09:44 PM

I like to richen them way up until both needles are just pig rich. Then start from there. Lean the hsn until you get good smoke trails, and good top end performance. Then lean the lsn 1/16th at a time. It won't take much at all on the lsn. On the lsn you can use the pinch test to get it in the ball bark, then do a punch test to dial it in. Of course you have to start off with the idle gap set properly or as stated earlier the lsn will have to be off to compensate.

dreaux 03-20-2010 10:00 PM

yeah, but to even get started you have to have the lsn in the ballpark. Maybe outfield but still in the park somewhere.

absolutemayhem 03-20-2010 10:36 PM

also set your idle gap....witch i belive is .5mm and LEAVE IT THERE....i your car wont idle check your lsn, it may be to rich .

merdith6 03-21-2010 02:30 AM

What I see most...
 
At the track is others making the high speed needle too lean then making the bottom too fat. This causes way too many issues. I always fatten the top then lean the bottom then check to see if the idle drops after being warmed up and sitting at idle. If it drops then lean it more on the bottom. when it gets steady then adjust the idle a bit, only a bit. Then go drive it on the track and if it's slow then lean the top in small steps until it hauls butt. If you go past that then you will shorten the life of the engine.... Finally recheck the bottom end to make sure it has enough fuel at idle after driving it at race speed. If it idles fast it may need more fuel on the bottom. If it races then drops then your idle is off and you need to lower idle and lean the bottom to get it steady....The top is usually fine....Maybe a little lean but this is only one hour adjustment at this time. Hope this helps.


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