Quick update on the radiator hose experiment. I got it trimmed and installed,
and it looked like a perfectly smooth 90 degree bend. Ran it on the ground, everything
was great, so a re-cowled it and test flew it.
I was quite surprised. There's a lot going on during takeoff, with vibration from
the engine as well as the rolling tires, so it was only after I was airborne
that I realized the engine was vibrating pretty hard.
I throttled back slowly, and after pulling the throttle back about 1/2 inch the
vibration ceased and the RPMs increaed!
I left it there during climbout, and after reaching a safe altitude I firewalled
it again. Immediate vibration, and drop in EGT on cylinders 2,4,6. In fact,
I was getting higher RPMs with lower fuel flow when it wasn't firewalled.
So, I don't know what to conclude exactly. Throttled back 1/2-3/4" the engine
runs smooth as silk now that I've balanced the prop. The EGTs all line up within
about 30 degrees of each other. But the closer to firewalled it gets the
worse it runs.
At this point, I can conclude that the full throttle problem is not related to
the swirl from the SCAT tubing. That's not to say it isn't related to the 90
degree bend that close to the carburetor, but it seems unlikely. The problem
is actually worse now, since the engine didn't run this rough with the SCAT tubing.
Not sure what to try next, but I'll make a posting if I have a breakthrough.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=272988#272988
