andy86na

My Feedback: (3)

I have several engines with this issue. Basically, if I tune them to peak rpm on the ground (and then richen just a hair) they start bogging down in a knife edge flight. Not a roll but a flight that lasts 3 seconds or more. It's not erratic running or anything. Just slow smooth rpm loss. Really sounds like they are slowly leaning out.

If I richen the high needle bogging down slowly disappears. It sounds a bit richer in straight (and upside down) flight but in knife edge the engine smoothes out. Nearly the same effect on both left and right sides. The usual mod of running a tube from carb plate into the fuse to equalize the pressue has been done on all engines. One engine has side carb (Brillelli 46), the other one rear carb (ZDZ 210)

If I just do rolls the effect does not have a chance to manifest. It's more annoying than anything.

What could be causing this?

ahicks

My Feedback: (2)

My bet would be a change in the load placed on the engine, with the plane moving from flying on it's wing (pretty efficient), to pretty much flying on the prop (big time drag)? Will it do the same thing in an extended vertical run?

pe reivers

lack of constant reference pressure on the carb regulating membrane.
Use all the available solutions. If none work as they should, try a static port or static tube as last resort ^)

ahicks

My Feedback: (2)

>>

I think he's tried the static port?

pe reivers

Running a tube into the fuse is not at all like a static port.
See here for the total story:
http://www.prme.nl/forum/viewtopic.php?t=205