by Onex107 » Sat Apr 29, 2017 9:50 am
I've been running the #3 needle for the last 100 hours with good results. I did a lot of needle testing, even making four needles with varying dimensions. What I found is, there is a thickness of the taper, when it's located at the orifice opening, that gives you the best wot, and a different thickness that gives you the best idle. These two "sweet spots" have to be located within the travel of the slide. If they aren't, you have to make large mixture changes at idle to keep the engine running after landing. The #3 needle does this. I fly with the needle set 2 1/2 to 2 3/4 turns lean from "0", the beginning of the taper. Mark the bottom of the needle with a sharp file, the felt marker line is 1/2 turn wide. We're talking about 1/8 to /1/4 turn adjustments here. It's a 3/8 X 16 screw. One turn equals .060 movement. Remove any slop in the needle holder ball joint. Hold the needle while you tighten the locking screw. Accuracy counts. I make a slight mixture adjustment, about 1/4 inch, at takeoff to richen up a little to keep the temps in the green, and lean it back at cruise for economy. I make no mixture adjustment at idle, 1000 rpm, after landing and no seasonal adjustments. With the other two needles I had to do a run up before takeoff to guarantee max rpm and after landing move the mixture almost to cutoff to idle smooth. My experience may not be typical, but it couldn't be simpler.
OneX 107
N2107X