ORIGINAL: submikester
The weight of the liquid makes no difference. It isn't the weight that does - it is its presence and the quantity.
What it's "dark matter" now?
Weight has everything to do with it as the fuel must be brought up through the tubing against gravity.
Overly long runs can be problematic for that very reason... and this is why we perform nose up/down tests too.
ORIGINAL: submikester
I've done my own testing to validate my own experiences too. Inverted OS 70 on a test stand - properly tuned with the engine at the centerline of the carb with the engine inverted. It idles well until the cows come home. If I place a block under the tank it starts to load up and via the pinch test at idle you can demonstrate a longer 'run up' indicating a richer fuel environment while with the tank lowered back to the proper level the engine behaves back to a proper 'needle' setting.
If offsetting the tank 1" higher or lower is making such a difference on your engine, you have other problems.
Look elsewhere.
If I were there I'd find and fix the problem for you.
ORIGINAL: submikester
Gravity does not care how much something weights - simply that it has mass is enough. A simple test of dropping a bowling ball and a baseball in a vacuum can demonstrate that. They will drop at the same speed - their actual mass has no bearing on the fact that they fall.
Which has NOTHING to do with what I said or this problem...
The liquid has mass and weight, the amount of both is negligible and does NOT affect the flow of fuel to the carb over a 1" or so displacement.
If it did our engines would cut out in flight every single time the plane goes nose up, due to the then MUCH larger offset between the tank and the carb.
ORIGINAL: submikester
Bottom line here is that we will have to agree to disagree. I don't see you're 'reason' and you don't see mine.
Disagree if want. If I had your engine in front of me, I could prove to you, that you are quite wrong. I'd find and fix the real problem for you and you would end up with a much better performing engine as it sounds like you have something amiss.
Inverting the engine offsets the fuel level a typical .5 to .75" no more and that simply has NO effect on the engine, it's idle or it's performance in any way what-so-ever.
Move the tank A LOT further and you start to see the effect of the weight of the fuel in the tubing, on the engine's performance... e.g. a nose up/down test, but even then, once tuned PROPERLY the effect is negligible.... though the displacement is well over 5+ inches or more....
A nose up ( veritical ) flight condition is also a "worst case", where the engine is also experiencing the greatest loads too.
All of my engines run just fine at idle nose up with that big offset to the fuel level. Don't yours?
I own well over four dozen different engines... I have a pretty good sampling to go by.
None of my O.S.'s react when inverted as you've indicated. They don't seem to care.
