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Old 08-30-2017, 08:14 AM
  #407  
Kelly W
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Join Date: Jan 2002
Location: Delta, BC, CANADA
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Originally Posted by turnnburn
You seem to be suggesting that by running the engine at lower RPM the fuel consumption will go UP ? This is simply not true. If that was true the engine would burn the most fuel at idle and the least at full throttle. The specific fuel consumption for the power produced is probably less efficient and goes down but not the actual fuel consumption for a given period of time.

I have a Jet Tech kevlar tank in my Hotspot. 105 ounces made specifically for the Hot Spot $ 145.00. I know its enough capacity for a reasonable flight time, and would be even with a RXI 180, especially since you are going to turn the thrust down to that of a 140 or 120 or 100 .

Google search Jet Tech Fuel Tanks.
I was talking about 'thrust specific fuel consumption' That's what the GTBA used to rate efficiency in turbines back in the home built days. I think the units of measurement were [(oz / min) / unit of force generated]. You'll find the curve is largely parabolic, meaning the engine is most efficient at or very near full throttle. Fuel efficiency is largely a function of the engine's pressure ratio, and the pressure ratio is highest at full power. It also means the thrust specific fuel efficiency drops off quickly if you're not at full throttle. This is the biggest downside of getting a huge turbine, and detaining it for a smaller jet, in addition to possibly more residual thrust. Running a P180 at 30 lb will probably force you to land sooner than a P120 at 30lb and the same fuel capacity.

I know about the jet tech. I have a few of them in other jets, good quality products... I was looking to see what configurations of tanks might have been tried, and what max fuel capacity might have been achieved. I might do the jet tech (3.1L), but I'd like to get 3.5L or better total.
Thx,
Kelly