by jjbardell » Mon Mar 21, 2016 10:23 am
I am also struggling with CHT temps. I have talked to Kerry and just sent a follow-up. To recap my issues:
Mine were running 420-450 with RPMs of 2,600 at 31"MAP. Speeds of 110mph. I couldn't climb past 300ft/min. I tried the tuning per the directions several times. So, we tried a different approach. Yes I am aware I am open to ridicule from everyone (so please keep the negative comments out...It's experimental and I am experimenting). The directions just were not working. I set the mixture rich on the ground (just to the point of black smokey exhaust), then leaned it to eliminate most of smokiness, but not all. I performed a run-up and readjusted my idle speed (as I would expect, the idle dropped down to 600...so I tuned it back to 800). I have to lean the mixture control to keep the engine alive on the ground. It runs rough on the ground and I have to keep the RPMs up (1100+). I can climb at 700+ft min.
But, when I took off, the temps dropped from 415 to 355-365. My RPMs jumped from 2600 to 3000 and speeds went from 110 to 135-140.
I thought that was my solution. Landed and observed slightly higher idle RPMs. I figured this was the warm oil and lower oil pressure making the engine spin easier. This was Saturday.
Sunday I went flying again. Changed nothing on the plane. Idle speed was still slightly higher. I went for a 3 hour flight. First half the temps were slightly warmer (380s) but everything else was great. I stopped for lunch and flew home after. Idle speed was higher yet (back to 1100) and temps jumped right after takeoff. Mixture was full rich but it clearly felt lean again. Temps were 400-410 for the short flight home with 31" map at 2600rpm. Same issue as before.
It seems as though the mixture is leaning out as I fly. I confirmed the set screw was tight against the needle. I am at a loss. I can richen it back up and then go fly and all is good. I am on the 2.5 needle and contemplating the 3.0 needle. I don't have the cross bar (tri-gear) but am also considering going from 50sq in to 60 sq in on the exit.
Let me know if you find the magic solution.
Josh