Does anyone have some insight as to what the root cause of these symptoms might be....? (I'll do my best to describe without going on infinitum...)
It all starts with trying to get to lean of peak.
At cruise power the mixture can be leaned back to about 7.1 - 7.2 GPH.
As it is leaned further, a periodic vibration runs through the airframe... can fell it particularly in my feet. The period is approx 2-3 sec.
The more lean, the more severe the vibrations.
Typically one would lean until the engine runs rough, then add a bit of mix to yield a LOP condition... but this engine seems to start running rough on the rich side of the max EGT.
I have captured EGT for each cylinder and the fuel flow as shown in the attached plot (manually captured on video then entered into Excel) which shows a 175°F difference between cylinders 1/2 and 3/4... not sure this is significant but the peaks and shape of curves are.
The vibrations start when leaning back to 7 GPH and worsens thereafter.
My thoughts are; one (or more) cylinders are running leaner than the others (intake leak(s), and or propeller balance are the contributors to this issue.
Thoughts?
It all starts with trying to get to lean of peak.
At cruise power the mixture can be leaned back to about 7.1 - 7.2 GPH.
As it is leaned further, a periodic vibration runs through the airframe... can fell it particularly in my feet. The period is approx 2-3 sec.
The more lean, the more severe the vibrations.
Typically one would lean until the engine runs rough, then add a bit of mix to yield a LOP condition... but this engine seems to start running rough on the rich side of the max EGT.
I have captured EGT for each cylinder and the fuel flow as shown in the attached plot (manually captured on video then entered into Excel) which shows a 175°F difference between cylinders 1/2 and 3/4... not sure this is significant but the peaks and shape of curves are.
The vibrations start when leaning back to 7 GPH and worsens thereafter.
My thoughts are; one (or more) cylinders are running leaner than the others (intake leak(s), and or propeller balance are the contributors to this issue.
Thoughts?