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lors01(at)msn.com
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 Posted: Thu Jul 06, 2006 1:09 pm Post subject: RV-List:Fuel economy / was Fossil energy fuel..... |
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<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]-->
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RV planes aren't gas guzzlers! At 8000 ft on an economy cruise setting
you get over 24 mpg (assuming no head wind) I would say that's pretty
good. Fly at 10,000ft or 11,000ft and you get even better millage.
That's better than I get in my Ford Ranger. It's only about 6 mpg away
from what some call a high millage for cars. My 24 mpg figure was based
on the range listed on Van's website for an RV-7 at 55% power with the
160 hp engine.
do not archive.
Chris W
KE5GIX
Good data point, I hadn't read that on Van's site.
I typically fly higher than 8000 feet, and since I've always been an efficiency freak, my engine monitor has a readout directly in MPG (based on TAS and fuel flow). I spend a lot of time tweaking & tuning to eke out that last possible .1 mpg on those long cross countries. At 15,500 I can do a little better than 30 MPG at 175 mph TAS. Anyone else into fuel efficiency? I'd love to hear your numbers. I honestly don't know how the rotary engine compares to a Lyc when flown for max efficiency. But I suspect it isn't much different.
While I have always been into energy efficiency, I have grown weary of the painfully stupid mass media debate on the subject. Many of the same folks who demand better fuel economy standards are often the same ones to decry small cars as dangerous. Now I intend to use all the fuel I want while dreading the day someone decides that private aviation is too much of a security risk.
Tracy Crook (Wacko of many types)
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dan(at)rvproject.com
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ebundy(at)speedyquick.net
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| Posted: Thu Jul 06, 2006 2:27 pm Post subject: RV-List:Fuel economy / was Fossil energy fuel..... |
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I've always been an efficiency nut as well. I fly all cross countries at what I consider the "sweet spot" altitudes of 11,500/12,500'. At 8000' I get 183mphtas on 8.25gph or 22mpg. 11,500' gives 178tas on 7gph for 25+mpg, and 13,500' rewards me with 171tas on 6gph for 28.5mpg. Above 15000' the efficiency starts to drop off as my 160hp Lycoming can't keep the airplane "on the step" and the reduction in TAS is greater than the reduction in fuel burn.
Most people scoff at giving up 5mph, but saving 1.25gph has always been worth it to me, even back when 100LL was <$2 a gallon.
Ed Bundy
| Quote: | | Quote: | I typically fly higher than 8000 feet, and since I've always been an efficiency freak, my engine monitor has a readout directly in MPG (based on TAS and fuel flow). I spend a lot of time tweaking & tuning to eke out that last possible .1 mpg on those long cross countries. At 15,500 I can do a little better than 30 MPG at 175 mph TAS. Anyone else into fuel efficiency? I'd love to hear your numbers. I honestly don't know how the rotary engine compares to a Lyc when flown for max efficiency. But I suspect it isn't much different.
Tracy Crook (Wacko of many types)
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lors01(at)msn.com
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| Posted: Sat Jul 08, 2006 10:28 am Post subject: RV-List:Fuel economy / was Fossil energy fuel..... |
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<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]--> That was seriously Cool data Dan.
Thanks also to Ed Bundy who supplied his numbers. It is surprisingly hard to find RV drivers who keep track of this stuff (too busy having fun in these things which I also understand : )
From the data than Dan linked to I could tell he had a CS prop which can be a significant advantage. If you ever get the chance Dan, I'd like to see you do the same test but instead of dropping manifold pressure only, try dropping the prop rpm to get the same fuel flow numbers you used. This should reduce pumping losses and result in even better numbers. "Do not operate" zones on the prop rpm is the only possible problem I can think of. I don't have that problem with my fixed pitch wood prop but I have to put up with very high pumping losses, especially at low altitude (which is another reason I cruise high).
Bottom line is that based on this info, I don't see a nickel's worth of difference between the Lyc (when run LOP) and my Mazda rotary when it comes to fuel economy. Cleanliness of the airframe makes more difference than the engine. I always burn less fuel than the guys who run Lycs ROP.
The horror stories about the fuel consumption of the rotary are based on automotive experience. Ironically, the rotary is at it's worst in auto use. The lower the engine load, the worse the rotary is. Car's typically run at 10% or less power settings. At low power settings the flame goes out in the large quench areas of the rotary combustion chamber resulting in more unburned mixture. The higher the power load is, the longer the flame stays lit and more complete combustion results.
The crumby results on the rotary RV-8 comparisons they did at Van's home drome were the results of two factors.
1. The fixed prop RPM rule put the rotaries at a disadvantage. They should have allowed the pilots to set it at best economy for the two engine types (it is not the same).
2. The EFI controllers used with the Powersport engines do not allow the pilot to optimize the mixture. They were essentially running at full rich the whole time. The designers of it did not consider the users capable of deciding this and programmed what they thought was the safest mixture setting (rich).
Tracy Crook
[quote] ---
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rv8ch
Joined: 10 Jan 2006
Posts: 250
Location: Switzerland
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| Posted: Sat Jul 08, 2006 11:04 am Post subject: RV-List:Fuel economy / was Fossil energy fuel..... |
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| Quote: | 1. The fixed prop RPM rule put the rotaries at a disadvantage. They
should have allowed the pilots to set it at best economy for the two
engine types (it is not the same).
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Tracy,
What is the fixed prop RPM rule? I don't recall reading anything
about this in the article. Apologies if it was there and I missed it.
Thanks,
Mickey
--
Mickey Coggins
http://www.rv8.ch/
#82007 finishing
do not archive
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_________________
Mickey Coggins
http://www.rv8.ch/ |
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dan.beadle(at)inclinesoft
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| Posted: Sat Jul 08, 2006 2:55 pm Post subject: RV-List:Fuel economy / was Fossil energy fuel..... |
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From: Dan Beadle
Sent: Saturday, July 08, 2006 3:49 PM
To: 'rv-list(at)matronics.com'
Subject: RE: RV-List:Fuel economy / was Fossil energy fuel.....
And, airplane mileage is often 10-25% less, improving real economy to right up there with a micro car.
From: owner-rv-list-server(at)matronics.com [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of Tracy Crook
Sent: Thursday, July 06, 2006 2:05 PM
To: rv-list(at)matronics.com
Subject: Re: RV-List:Fuel economy / was Fossil energy fuel.....
| Quote: |
RV planes aren't gas guzzlers! At 8000 ft on an economy cruise setting
you get over 24 mpg (assuming no head wind) I would say that's pretty
good. Fly at 10,000ft or 11,000ft and you get even better millage.
That's better than I get in my Ford Ranger. It's only about 6 mpg away
from what some call a high millage for cars. My 24 mpg figure was based
on the range listed on Van's website for an RV-7 at 55% power with the
160 hp engine.
do not archive.
Chris W
KE5GIX
Good data point, I hadn't read that on Van's site.
I typically fly higher than 8000 feet, and since I've always been an efficiency freak, my engine monitor has a readout directly in MPG (based on TAS and fuel flow). I spend a lot of time tweaking & tuning to eke out that last possible .1 mpg on those long cross countries. At 15,500 I can do a little better than 30 MPG at 175 mph TAS. Anyone else into fuel efficiency? I'd love to hear your numbers. I honestly don't know how the rotary engine compares to a Lyc when flown for max efficiency. But I suspect it isn't much different.
While I have always been into energy efficiency, I have grown weary of the painfully stupid mass media debate on the subject. Many of the same folks who demand better fuel economy standards are often the same ones to decry small cars as dangerous. Now I intend to use all the fuel I want while dreading the day someone decides that private aviation is too much of a security risk.
Tracy Crook (Wacko of many types)
|
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
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klwerner(at)comcast.net
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| Posted: Sun Jul 09, 2006 8:27 am Post subject: RV-List:Fuel economy / was Fossil energy fuel..... |
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But with a SIGNIFICANT SPEED DIFFERENCE over said micro car . . . . . .
do not archive
| Quote: |
From: Dan Beadle
Sent: Saturday, July 08, 2006 3:49 PM
To: 'rv-list(at)matronics.com' ([email]\'rv-list(at)matronics.com\'[/email])
Subject: RE: RV-List:Fuel economy / was Fossil energy fuel.....
And, airplane mileage is often 10-25% less, improving real economy to right up there with a micro car.
From: owner-rv-list-server(at)matronics.com (owner-rv-list-server(at)matronics.com) [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of Tracy Crook
Sent: Thursday, July 06, 2006 2:05 PM
To: rv-list(at)matronics.com
Subject: Re: RV-List:Fuel economy / was Fossil energy fuel.....
| Quote: |
RV planes aren't gas guzzlers! At 8000 ft on an economy cruise setting
you get over 24 mpg (assuming no head wind) I would say that's pretty
good. Fly at 10,000ft or 11,000ft and you get even better millage.
That's better than I get in my Ford Ranger. It's only about 6 mpg away
from what some call a high millage for cars. My 24 mpg figure was based
on the range listed on Van's website for an RV-7 at 55% power with the
160 hp engine.
do not archive.
Chris W
KE5GIX
Good data point, I hadn't read that on Van's site.
I typically fly higher than 8000 feet, and since I've always been an efficiency freak, my engine monitor has a readout directly in MPG (based on TAS and fuel flow). I spend a lot of time tweaking & tuning to eke out that last possible .1 mpg on those long cross countries. At 15,500 I can do a little better than 30 MPG at 175 mph TAS. Anyone else into fuel efficiency? I'd love to hear your numbers. I honestly don't know how the rotary engine compares to a Lyc when flown for max efficiency. But I suspect it isn't much different.
While I have always been into energy efficiency, I have grown weary of the painfully stupid mass media debate on the subject. Many of the same folks who demand better fuel economy standards are often the same ones to decry small cars as dangerous. Now I intend to use all the fuel I want while dreading the day someone decides that private aviation is too much of a security risk.
Tracy Crook (Wacko of many types)
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No virus found in this incoming message.
Checked by AVG Free Date: 7/7/2006
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| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
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lors01(at)msn.com
Guest
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| Posted: Sun Jul 09, 2006 2:33 pm Post subject: RV-List:Fuel economy / was Fossil energy fuel..... |
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<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]--> The fuel economy test was based on a side by side cross country trip where the prop rpm was to be held at a certain rpm (2500 as I recall) and the speed held at various airspeeds by throttle position. This test was reported in two places, the RVator and in Sport Aviation (or was it Kitplanes, memory slipping) and I can't remember which one reported the specifics of the test conditions.
I'll see if I can dig up the article in my stacks of stuff for attribution.
Tracy Crook
[quote] ---
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
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