ORIGINAL: FlatSpin
Thanks to everyone for your expert insight. I’m not trying to drain every last RPM out of this engine but it did strike me as odd that I got so much extra RPMs w/o the pressure line. I bet the LS is still a little off, so I will take the time to do more experimenting with the LS and HS settings this weekend. I'll even try a larger diameter fuel pressure line to see it that helps.
Dave
I did some needle tweaking today. With the APC 12x6, the engine maxed out at 10,100 RPMs but I finally got the engine to peak at 10,900 RPMs on the ground. The LS needle definitely interacts with the HS for rich/lean and max RPMs and 1/16” makes about a 500 RPM difference. At the peak needle settings, removing the muffler pressure line caused the engine to die. I flew it at these needle settings and got 13,850 RPMs unloaded in a dive. I left the LS needle alone and opened the HS for a 200 RPM decrease. The transition to WOT is solid and my idle is around 2100.
I now have 2/3 gallon thru this little beast which equates to about 5-5 ½ hrs of flight time and decided to see what the piston and crank pin looked like. There is just a light golden brown hue on the piston, near the exhaust port and the crank pin still looks brand new. The spark plug tip is a light tan. All OK so far! Now to mount this in my new Meridian and maybe get in a maiden flight it this weekend.
Dave