![]() |
Your Time?
Did you factor in your time driving at $100/hour?? ;)
|
Seems to me the following somehow need to be figured in:
Cruise ground speed- power setting, fuel/air mixture Some allowance for time saved (quality of companions...) Head/tail winds Weather limitations, diversions Type of fuel used (big advantage to mogas) Hanger/storage fees Fun factor- who really wants to drive anyway??? :D |
PRKAYE brings up an interesting point
How does the gph of a 118hp compare to a 160hp lycoming?
Now that is an interesting idea (especially since I am building a RV9-A with the Lycoming o235 L2C 118 hp engine with a Catto two bladed prop). Extrapolating Van's numbers for the 118 hp engine (and checking the Lycoming Engine Manual) we get an estimation that follows: Full power 173 mph 4.53 flight hrs 7.5 gal/hr (assuming 34 gal. usable..start/taxi/takeoff...) 75% power 166 mph 5.27 flight hrs 6.45 gal/hr 55% power 150 mph 6.90 flight hrs 4.92 gal/hr I drive from Ozark, MO to Wichita, KS often. 257 miles 4 hours 15 minutes and get barely over 20 mpg with my Jeep Grand Cherokee for a total fuel consumption of 12.85 gal at $2.89 per gal equals $37.14 Lets use full power RV9-A (using AeroPlanner.com) full power 229 sm 173 mph 1.32 flight hrs 11.9 gal used (2 gal. for start/taxi/takeoff/altitude @6000 ft.) 75% power 166 mph 1.38 flight hrs 10.9 gal used 55% power 150 mph 1.53 flight hrs 9.5 gal used Assuming 100LL is $4 per gal........ Full power would cost $47.60 :o 75% $43.60 :) 55% $38.00 :D The 0235 118 hp engine isn't looking so bad after all. Of course, only true flight will tell us how close the extrapolated numbers really come but it is an interesting exercise with fuel prices rising. I can't wait to get this bird in the air. Pat Garboden Ozark, MO RV9-A 942WG (reserved) 0235 L2C 118 hp RV9-A 942 PT (reserved) 0320 E2A 150 hp |
10 gph?
Quote:
While a smaller engine seems like it should burn less gas we repeatedly are reminded that the planes running the bigger engines powered back do as well or better. The injected 200hp RV's running LOP seem to use the least amount of fuel in any group when flying together. Just another opinion, but go with the biggest engine that can be used for your plane. I'd be prepared to spring for a coke if your not happy after a year or so. Regards, |
Funny you were running these numbers because I was doing the same over the weekend only I was comparing my O-290 powered RV-9 to Corey Bird's 240 knot Symmetry.
Lots of SWAGS were used but here is what I came up with. RV-9 w/ O-290-D2 75% power = 101.5 HP 7.1 GPH 175 MPH 24.6 GPM 200 mile trip = 1:10 minutes +/- 1:10 minutes * 7.1 GPH = 8.1 gallons * $4 = $32.46 Symmetry w/ IO-360 75% Power = 150 HP 12 GPH (I'm guessing here) 240 knots / 276 MPH 23 MPH 200 mile trip = 45 minutes +/- 45 minutes * 12 GPH = 8.7 gallons * $4 = 34.78 Quote:
|
mpg
I have an RV-9A and an O-320 fixed pitch prop rated at 160 hp. At 8000 feet and 75% I get 185 mph true and 21 mpg. At 55% I get 165 mph and 25 mpg. At 65 mph, my S-10 Blazer gets 21 mpg. At $3/gal, the car get 7 miles/$. At $4/gal, the airplane gets 5-6 miles/$. The 118hp at 75% is about the same as the 160hp at 55%.
Tom Green had a nice write-up in the recent RVAtor on the relative costs of bicycle, car, and RV. Tom used 175 mph and 22 mpg for the RV. Meals, motels, time on the road are all factors. Speeding tickets, insurance, hangar rent, etc. Of course, I spend about $2k a month to garage my car, but my wife and I stay free in the house. Regards, John. |
When the CFO isn't looking
Dayton, Ohio to Fond Du Lac, WI via Sterling Rock Falls and Rockford, Illinois ~483 statute miles, 45.7 gallons 100LL, ~2.5 hrs, $178.23 (@ $3.90/gal), O-360-A1A. Driving not an option.
Bob Axsom |
I've flown round trip from Minneapolis to Fort Myers FL about 5 times in my O360 FI, EI RV6A. It is 1214 n.m. straight line, or 1400 s.m., and I typically use 120 gallons round trip. That equates to 23.3 statute miles per gallon (at 185 statute miles per hour). We've driven the route also, and it is 1750 s.m., so comparing apples to apples the RV's mileage would be 29.
The mpg performance numbers for RVs probably varies more than any single other parameter, since the fuel flows vary so widely. For that reason alone, I am very glad I have FI and EI, both of which contribute appreciably. |
118 HP VS 160 HP
Consider this. Go ahead and put the 160 HP Lyc in and when prudent throttle back to a fuel burn of the 118 HP engine. I realize that would take a lot of self control, but when you really need the power for those high density altitude take-offs you would have it. When you really want to conserve just throttle back. Also, you would get to altitude a lot sooner where you could really save (assuming no winds).
Tom |
On average, flying distances are about 80% as far as driving distances. So an RV getting 22 MPG (180 mph burning 8 gph, rounding down) would be equivalent to a car getting 27.5 mpg.
The poster listed a 150 HP RV-9, which could burn mogas (I know, we had that discussion a couple days ago), so fuel per gallon need not cost more than gas for a car if he doesn't have to refuel at an airport. If you have to burn avgas, around here it is about 30% more than mogas, so that gives you effectively 19.5 mpg (27.5 x 0.7). RV is much faster & more fun, but you have to rent/borrow a car when you get there. Cars rarely get delayed for weather. RV's rarely get tied up in traffic. |
| All times are GMT -6. The time now is 09:03 AM. |