Tuning Puzzler
 

Okay guys, got a tuning issue for which I can not find an answer. I have a Losi 8ight 2.0 rtr with 350 nitro engine. Ran everything stock with 20% for about one gallon. Ran perfect. Tuned perfect. Decided to upgrade to turbo head conversion and go to 30% nitro. Tune is way out of wack now. Car cranks only if warm. It idles very high. Haven't touched idle screw. Idle screw is set at about the width of a dime. Since idle was high, I set lsn about a quarter turn richer. Idle came down. I can pull throttle a couple of times no problem. Then about the third time of pulling throttle it bogs down a little and then when I let of the throttle it idles high again. Leaning lsn only increase idle speed. Did a pinch test on the fuel line. When I restricted the fuel line about an inch from the carb, the engine raced out of control. Conflicting information, idle suggests go richer, restricing fuel line says go leaner. Any suggestions?:confused:

You idle gap is way to big. You should only be around .5 to 1mm gap. If your pinch test the engine idles up a lot your rich on the lsn. I would set my idle gap and start over with your hsn and lsn settings.

It's hard to help from a keyboard, but, I'm guessing your idle gap is way to big. Pull you air filter off and set your idle gap to .5 to .7mm. That's about half the thickness of a credit card. Set your needles to factory or flush( not sure what kind of engine you have). Once that idle gap is set, adjust your idle with the low speed needle adjustment ONLY! That will get you in the ballpark with your lsn. Adjust your hsn as needed. If you start with flush or factory settings, You'll have to lean it to find your sweet tune....Hope this helps...:tire::tire::tire:

......
 

Once you get your idle set ,and back to factory settings remeber to set your hsn before you ever touch the lsn.

Shimming ;)

Yep, that's probably a lot of it. I'm not familiar with engines that are shimmed for anything but 30%. I don't wanna step on toes but was my advice good? I can take it if I'm wrong cause if I am, I'll keep my mouth shut, or my keyboard. I don't wanna give bad advice. I know what works for me.

Thanks for all the feedback. The engine is a Losi 350. Still not ready to upgrade to new motor so just trying some mods to use will I continue to learn and train. Pulled engine and did a leak check. Has some leakage around carb. Have it sealed now. I will try again tomorrow. I will follow advice and set everything back to factory stock and try from there with idle set at about .5mm. As far as shims go, the turbo conversion came with three shims. Two that are .2mm and one that is .1mm. Instructions said to use both the .2's (which I did) and only add the .1 if I live in a high humidity area, which I don't. I'm going to leave shims as set and try again tomorrow with smaller idle gap. Still not sure why idle setting was fine before and now isn't. Does going from 20% to 30% make that much difference? When changing to 30% what carb adjustments usually have to be made?

well
 

If it worked great before why not just go back to what worked. If it aint broke, don't fix it.

Are you really asking this?:weird:

The guy is looking for performance!

Obviously

Turbo
 

I have a 350 and the turbo head will for sure wake it up alot.I think your problems are first the idle gap and second is that when you went from 20% to 30 % you need to richen it quit a bit. If you use the same shimms that were on the standard head it will be fine. Hope this helps.

Sounds like you may have the shimming correct but should triple check just to be certain

Problem Solved
 

First of all, thanks for the feedback everyone. It is forums like this that help all of us learn. I had an air leak at the carb and back plate. Sealed both. Also backed off the idle. Engine idles great now. I will have to do some fine tuning when weather warms up, but what a difference the turbo conversion makes on this Losi 350. Going to make this 8ight 2.0 a great car to continue to learn on before I make the big investment into a better engine.:nod:

Good deal Drew

The odd thing is you must have had this issue before right?