Set up to test fuel flow rates with Aux Boost Pump, including determining Unusable Fuel in tank, and to flush fuel tank, pump, and fuel lines. Disconnected fuel line from Fuel Servo ("throttle body"), connected to test equipment borrowed from Bill Lane, local RV-7 owner. Bill's recommendation was to measure fuel in grams, not volume for best accuracy. So I set up small digital scale (seems accurate, but capable up to 30 lbs or 13,607.7 grams...so I can measure a 5 gal fuel container if needed. Confirmed plane was level from side to side, and in normal attitude on main gear. Started w/ RH Tank (dry), weighing fuel added to nearest gram. Added 2391 grams fuel (or 0.88 gallons). Then, with G3X on w/ engine instruments page shown, started Boost Pump. Collected output in 1 gallon container ( Bill had equipped with copper grounding wire for safety).
Test Run 1: 2,391g added, 2282g collected. Unusable fuel left in tank = 248g = 11.6 fluid oz.
Flow was 36.1 gph at 0.3psi (valve at exit left wide open for max flow)
Notes: very small amount redish fluid (preservative) in lines and Boost Pump cleared in 1-2 seconds. Bubbles at first, but cleared away within few seconds ( test equip has clear line prior to ball valve to check for bubbles, which would indicate air is being sucked in somewhere). Found NO LEAKS at Wing Tank or fittings, at Wing Root fuel lines, at Valve, Filter, and Fuel Pump in center tunnel, nor at Firewall inside or outside. No leaks at Mech Pump on engine or Red Cube flow meter.
Very satisfied with 1st results. Next tests add restriction to mimic real performance.
Test Run 2: 2, 142 g fuel added, 2150 g fuel collected. Unusable = 240 g = 11.2 fluid oz
Flow stabilized at 24.4 gph at 16.3 psi
Test Run 3: 2,150 g added, 2,126 g collected. Unusable = 264g = 12.4 fluid oz*
Flow stabilized at 16.8 gph, 25 psi
Notes: * slightly higher Unusable in 3rd run is likely due to shutting off Boost Pump prior to last dribbles being pushed through - to minimize pump running in "dry" mode. Both Run 2 and Run 3 also had no bubbles in fuel flow, and no leaks found anywhere. I simply poured collected fuel from prior test back into RH Tank, using a fine paper filter to insure no gunk or debris was transferred back. Found nothing in filters ( in-line fuel filter should be stopping 1st)
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| approx 1 gallon collected. Note gnd wires. Weighed all fuel to nearest gram for accuracy |
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| poorly focused pic shows Run 1 with sensors showing 36.1 gph and 0.3 psi (no extra restriction) |