could it be centrifugal forse , transfers on the inside compared to the out side of circle

What engine doesn't like to run upside-down?  As far as I know, any engine will run just fine upside down.

Well, most car engines suffer oiling systems problems when you run them upside down, and the carburetted ones get kind of cranky about the fuel running out the bowls.

 

normally they run better mounted inverted than side winder mounted, The fuse is stiffer in that direction on most planes

Randy

I would not make it this stupid-looking without a good reason:)
L

Like a mole in cheek. Tribute to Lemmy?

Andrew,

A seemingly simple thing like this has quite a complex explanation.
I don't know much about diesels but reasons between glow and diesel are partly differend. A glow is more sensitive for stability of combustion process because the explosion has to start from one point, glow plug. Diesel instead explodes more spontaniously everywhere in the combustion chamber.
As I see it, due to 4-2-4 -shift (or in general a more rich average run than peak power), the engine is more often out of its comfort zone. And when engine is running rich, you have lots of unburned fuel bouncing about in the cylinder that either burns or doesn't burn, depending on load and temperature situation. I don't think that engine oriention has any important role in how the scavenging works.
But with engine orientation you can affect to what happens in bottom end, there are several places in carter where fuel can get trapped and then get loose when G direction changes. I have found that these things may happen only in outside/inside intersection but not just during static + or - G. It is a quite clear indication of fuel accumulation somewhere.
Also, the gyroscopic precession of engine and prop works the other way too; engine load is differend in inside and outside turn. Maybe it's a very small difference, I don't know. How could it be measured? Or calculated?
But to the original question, cylinder up is maybe the most difficult for starting. L

Does this mean that on a Yatsenko or other side-mount on a big full fuselage that they run better than on a profile?

If you could make a fuselage that was equally rigid in all directions (some stove pipe, maybe), do you think the motor would run equally well in any mounting angle?

Just curious -- I'm not going to run out and change any designs.

Normally they run better upright or inverted because of the stiffness, A molded full fuse that is stiff should run similar in any direction, less the effect of that particular motor that may have internal dynamics that make it run better at a certain angle, Centrifugal force and other factor will cause some anomalies in certain engines. Example Al Rabe's  Mustunt with Fox 35 is a profile with an upright Fox 35, it runs much better than the same plane mounted sidewinder. other engines may or mau not run as well, Frank Williams flew a profile Bearcat with a ST 60 for power, but it was mounted sideways and inboard. according to him it ran much better this way, and stayed cleaner in maneuvers.

Randy

I would think the polar moment of inertia of the airplane would enter into how the engine performs, if the fuselage is equally stiff in all directions.

I suspect going back to the original question that the engine's seller maybe didn't have the engine/ tank setup right, had a bad experience and so thinks the engine has issues which it may not really have.  It would be interesting to know what engine you are looking at.

Dave

That's my take on it too...because the only issues (once you get the setup dialed in) I've had with inverted engines is it takes more care in priming so you don't flood it for starting. Accessibility is the other issue for me but that's not an engine  running deal.