Hi Whee,
Here is another ''real world'' results for your consideration.
But before, Let me describe my set-up:
O-540 carb engine, with mechanical fuel pump + Facet back-up pump
Gascolator , Flowscan Transducer.
Newton fuel Selector (OFF/Both/Left/Right)
Fuel line: standard routing, with NO up- slope from the tank (all downhill)
One of my Test Run (during the first 25 hrs) was to run one tank dry. I did that test while circling over my local airfield. The test was conducted Feb.10-2019
I initially took off with about 20 gal in each tank, with the selector on both. I went away and did some other tests and came back over the airfield. At that point, I had about 8 Gal remaining in each tank.
I then select the Left tank, and start circling around, at 75% power, with the Facet pump ON.
I kept an eye on the Fuel Pressure all the time. After what seem way too much time, the FP start varying quite a bit between 6 psi to 0, and then went down to 0 psi for about 5 seconds...at that point the engine start backfiring. I switch the tank to BOTH, and it took 4 seconds to restore normal power. After that, I switch the tank to RIGHT and proceed for landing.
After landing, I filled the LEFT tank. It took 93.5L (24.7 Gal US) to fill....So my Un-usable fuel is negligible.
Mike
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