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  #31  
Old 01-06-2019, 11:35 PM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 8,147
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Quote:
Originally Posted by NinerBikes View Post
Assuming summer time heat, and flying at 7500 to 9500 ft, 110kt TAS, with the prop set for cruise not climbing performance, what type of GPH do you see, real world, in your plane.


I understand the relative density of air is less at elevation and in summer heat... Assume 50F air temps at 9500 feet.

And next question is GPH in the new 912 iS FI motor without the Bing Carbs.
There are numerous variables from one flight to another but on average Van's prototype/demonstrator RV-12 will true out at about 120 Kts at about 5.2 GPH at altitudes above 10K
The RV-12 and RV-12iS has been flown to OSH and back together. Flying the same flight profiles and speeds, the is airplane burned about 30% less fuel on any given leg.

Quote:
Originally Posted by Harvey rv12 View Post
Hello Scott;
Did you record your static runup RPM at full throttle?, or rpm achieved during climb out?.
I'm always interested in other folks numbers. I am trying to satisfy the Rotax service letter SL-912-016R1 (no less than 5200rpm at 29.1" hg MAP), while also allowing max rpm in level flight of no more than 5800rpm.
I am getting a static full throttle runup of about 4920rpm, DA -1386', 43 deg f, 29.9" MAP

Thanks
Maximum continous RPM for the 912ULS is 5500, not 5800. 5800 is the limit for take-off, and I think is restricted for 5 minutes.

Your static RPM sounds a bit low. It should be in the neighborhood of 5000

Because of the min:max speed ration of the RV-12, you will not be able to achieve meeting the 5200 RPM in climb and get the cruise speeds that most people do.
Climb RPM is typically in the 5100-5125 range with the the prop pitch that most RV-12 owners are using.
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Scott McDaniels
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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  #32  
Old 01-07-2019, 09:55 AM
NinerBikes NinerBikes is offline
 
Join Date: Dec 2018
Location: Granada Hills
Posts: 133
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Quote:
Originally Posted by rvbuilder2002 View Post
There are numerous variables from one flight to another but on average Van's prototype/demonstrator RV-12 will true out at about 120 Kts at about 5.2 GPH at altitudes above 10K
The RV-12 and RV-12iS has been flown to OSH and back together. Flying the same flight profiles and speeds, the is airplane burned about 30% less fuel on any given leg.


About 3.64 gallons per hour? Anyone done the break even point analysis on the iS vs the ULS in fuel expenses at $4.00 a gallon? About 800 hours on the motor?
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  #33  
Old 01-07-2019, 10:37 AM
DaleB's Avatar
DaleB DaleB is offline
 
Join Date: Sep 2012
Location: Omaha, NE (KMLE)
Posts: 2,025
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Our RV-12 was always slower and burned a lot more fuel than others typically reported. I could get 120 K true out of it, but at the cost of burning 6.5 GPH or more. Climb was a little anemic for an RV-12, too. The original builder had it way over-pitched, maybe trying to squeeze out a little more speed. I got the pitch close to recommended settings, which helped, but we were still burning too much gas and my friend's 12 would easily walk away from me.

I tried getting it closer when we did the prop hub inspection last summer. We're slightly over-pitched still; static RPM is just a little below 5000. We're around 4980, if I remember right. During the carb teardown process we found a bad choke cable on the left side that was probably not allowing the left side starting carb to completely close off, which would probably explain our previous high fuel consumption. The damage was not visible until the cable was pulled out of the sheath -- there was a broken strand wrapped around the cable, up inside the sheath. Getting the carbs balanced was a WHOLE LOT faster and easier once that was fixed! We're still getting the K-factor zeroed in, which is more of a challenge when you're filling the plane from 5 gallon cans and not a pump.

We are seeing 120 knots at around 4500 MSL, 25" MAP, between 5300 and 5400 RPM, burning around 5.5 GPH. Numbers are sketchy at this point, since so much has changed. Flying 110 or even 115 kt TAS saves a lot of fuel, though. I think during the upcoming CI we'll de-pitch the prop just a little bit to get the static RPM up to 5000 and see how much good that does. We've also got some areodynamic cleanup to do with the gear leg intersection fairings and such. It's an ongoing project.

Oh, and we've pretty much never paid $4/gal for fuel. We burn ethanol free premium MOGAS at under $3/gal.
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Omaha, NE
RV-12 # 222 N980KM "Screamin' Canary" (bought flying)
Fisher Celebrity (under construction)
Previous RV-7 project (sold)
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  #34  
Old 01-07-2019, 11:16 AM
Piper J3's Avatar
Piper J3 Piper J3 is offline
 
Join Date: Nov 2014
Location: Hinckley, Ohio
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Here are a few data points…

Shoot for 5100/5200 RPM in initial climb. My field elevation is 800MSL.

One person w/ half fuel = 1100+ FPM initial climb.

Prop pitched per above should yield 110 knots at 3000 MSL and 5500 RPM.

Cruise flight at 5500RPM should have throttle positioned about 1” pulled out from full throttle.

My fuel burn per above is right around 6 GPH, which pretty much agrees with published Rotax specs.

No fun having an airplane if your not going to go fast…

Another data point... E9310 at Costco is $2.12/Gal today.

https://www.rotaxservice.com/wp-cont...5/912Sperf.pdf

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Jim Stricker
Hinckley, Ohio (1OA2)
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
RV-12 E-LSA #120058 AWC July 2012 N633CM
RV-12 Bought Flying Oct 2015 with 48TT - Hobbs now 429

LSRM-A Certificate 2016
Special Thanks... EJ Trucks - Crew Chief A-4 Skyhawk
and MJ Stricker (Flight Instructor) - 1st Lt./Captain B-17H

Last edited by Piper J3 : 01-07-2019 at 11:33 AM. Reason: added Costco fuel price...
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  #35  
Old 01-07-2019, 01:03 PM
NinerBikes NinerBikes is offline
 
Join Date: Dec 2018
Location: Granada Hills
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Owner of said RV-12 I fly with is old school... Runs 100LL... no interest in Mogas. Those Bing Carb floats turning to sinkers has him concerned.

Add in living in California, with road taxes through the roof on Mogas... and fuel is expensive, about $3.55 to 3.75 for 91 premium, with ethanol. Ethanol definitely cuts into MPG in our cars.

Finding ethanol free Mogas in Commiefornia, is impossible, I don't even think it still exists.. we only get corn gas E-10.
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