I have the Great Plains 2180 with a Prince P tip prop (52x48) and it burns 4.0 US gallons per hour. So Larry’s calculation is correct. My header tank holds 10 US gallons so I usually flight plan for 2 hours with 30 minute reserve . Chris Gardiner CGkRZ KR2S
Sent from my iPhone > On Jan 14, 2024, at 15:32, Larry Flesner via KRnet <krnet@list.krnet.org> > wrote: > > >> On 1/14/2024 1:56 PM, Adam Deem via KRnet wrote: >> I don't know about a fuel flow chart, but the math to calculate it is pretty >> simple. The 2180 is 75 hp takeoff power at 3600RPM. 2180cc=.077cu ft. >> 3600RPM=1800 intakes/min for 138.6 cu ft/min or 8316 cu ft/hr. 8316x.08 >> lbs/cu ft air=665.28 lbs air/hr. Correction for normally aspirated >> volumetric efficiency 665.28x.95=632 lb/hr. 632lbs air+60 lbs gasoline/hr = >> 100% power at 10.5:1 F/A ratio. 60lbs/6 lbs/gal = 10.0gph. Best power ratio >> would be 12:1. You want your fuel system to deliver enough fuel in any >> scenario on takeoff (SL@10.5:1 standard day) with 150% safety margin to >> avoid starving the engine under worst case scenario (winter day with very >> low DA) >> >> For that motor you'd want to run a fuel flow system test and verify it can >> deliver at least 15gph. For comparison, my electric pump fed system (Facet >> 3psi cube pumps) delivers a verified 19gph through the system. I hope this >> is helpful. >> >> Adam Deem > > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > A bit less cumbersome math / rule of thumb that is quite accurate for the > type of engines we use is 1/2 pound of fuel per horsepower per hour. The > 0-200 at 100 hp / 2 = 50 pounds of fuel / 6 ppg = 8.33 gph at full throttle > at takeoff if its actually producing 100 hp. A VW producing 75 hp on takeoff > would be 75/2=37.5 / 6ppg = 6.25 gph. Multiply that number by 1.5 for > minimum acceptable fuel flow. This holds true for any % of power hp fuel > flow. > > The 0-200 for example at 65% power at cruise is 65hp / 2 =32.5 pounds of fuel > / 6 =5.42 gph at an acceptable fuel / air mixture (moderate lean mixture of > 14:1) > > A 75 hp VW at 65% power cruise = 48.75 hp / 2 = 24.37 pounds of fuel / 6 = 4 > gph fuel burn. I've never flown a VW engine but I'm guessing that is pretty > close. > > Larry Flesner > > -- > KRnet mailing list > KRnet@list.krnet.org > https://list.krnet.org/mailman/listinfo/krnet -- KRnet mailing list KRnet@list.krnet.org https://list.krnet.org/mailman/listinfo/krnet
