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Old 01-25-2014, 12:34 AM
ScottSchmidt's Avatar
ScottSchmidt ScottSchmidt is offline
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Join Date: Dec 2005
Location: Salt Lake City, Utah
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Default RV-12 RPM, Speed and Efficiency

Today I did some flying and wanted to see how the -12 was in efficiency at different power settings. I need to try this again at a higher altitude where I would typically cruise. I know this is not perfect data and there are more accurate ways of accomplishing this.

I was flying at 5200 ft with an OAT of 32F, only one person and 6 gallons of fuel.

Prop pitch setting would change these numbers between -12's. I would be interested in seeing what others are seeing.
I only measured TAS from the Dynon. WOT (wide open throttle) had a max RPM of 5770.

I will try lower RPM settings to see how efficient the -12 can be.

Scott Schmidt
Salt Lake City, UT

RV-10 N104XP (1280 Hours)
RV-12 N321UT (Sold)

Last edited by ScottSchmidt : 01-25-2014 at 12:38 AM.
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Old 01-25-2014, 08:25 AM
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DonFromTX DonFromTX is offline
Join Date: Oct 2010
Location: La Feria Texas
Posts: 3,785

Thanks for sharing that, very interesting and I too wish others would do the same.
A&P, PP-SEL, Pathological Flier, EAA Technical Counselor
EAA Chapter 595 President,
Retired US Army Officer
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Old 01-25-2014, 08:44 AM
AZLeeJay AZLeeJay is offline
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Location: Phoenix
Posts: 111

Nice, thanks for the data points.
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Old 01-25-2014, 09:42 AM
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N941WR N941WR is offline
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Location: SC
Posts: 12,123
Default Playing with numbers

Let's say you were going to take a 200 nautical mile trip. The time difference between running at 4800 vs 5770 RPM is 25 minutes ( 1.9 vs. 1.5 hours) and the fuel burn difference is .4 gallons (8.7 vs. 10.3 gallons).

Interestingly, if I take that same 200 nautical mile trip in my -9, it will take me 1.3 hours at 150 KTS and only 9.5 gallons burning 7.1 GPH, slightly better than the -12 running full out.
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
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Old 01-25-2014, 10:45 AM
RFSchaller RFSchaller is offline
Join Date: Oct 2010
Location: Phoenix, AZ
Posts: 2,441

The fuel burn seems high. Have you checked your K-factor?
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Old 01-25-2014, 11:41 AM
rvbuilder2002 rvbuilder2002 is offline
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 8,145

For the altitude Scott was flying at, if you run the engine at right near the max continuous of 5500 RPM, they will typically burn just shy of 6 GPH, so his chart looks pretty close.
Any opinions expressed in this message are my own and not necessarily those of my employer.

Scott McDaniels
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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Old 01-25-2014, 11:45 AM
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az_gila az_gila is offline
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Location: 57AZ - NW Tucson area
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Thumbs up

Pretty amazing.

To put it in automotive terms, even at the worse point on your chart you are getting 22 mpg at 150 mph...
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
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Old 01-25-2014, 11:59 AM
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gblwy gblwy is offline
Join Date: Jun 2007
Location: Perth, Scotland
Posts: 494
Thumbs up A couple more points

As it happens, I noted a couple of parameters last week. Slightly lower temperature, one-up, but with full fuel, at 4000 feet, with spats. I've had to translate into your funny fuel units ;-)

rpm fuel speed
4700 4.2 100kt 115mph
5000 4.8 109kt 125mph
5500 5.6 120kt 138mph


Last edited by gblwy : 01-25-2014 at 12:01 PM.
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Old 01-25-2014, 12:03 PM
NASA515 NASA515 is offline
Join Date: Nov 2011
Location: Hansville, Washington
Posts: 536

Keith, what's 5000 rpm in metric???

Bob Bogash
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Old 01-25-2014, 12:08 PM
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gblwy gblwy is offline
Join Date: Jun 2007
Location: Perth, Scotland
Posts: 494

Well, for an ex-Lycoming driver it's much too fast in any currency ;-)

Having said that I wouldn't swap my engine - starts in a heartbeat, sounds fine in the cockpit, and people on the ground have commented how quiet the plane is in the air.

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