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12-10-2010, 03:40 PM
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Join Date: Dec 2006
Location: Arroyo Grande, CA
Posts: 938
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First, Rob, a correction. The fuel burn per hour goes up with the increased HP, but because the speed is going up also, you spend less time on the trip so that the fuel burn per distance only goes up with the square of the speed, not the cube.
I would also take exception with your characterizing the CS prop as having higher propulsive efficiency. They dont; they only allow you to turn up more rpm for higher static and climb power. In cruise a well designed FP will be more efficient.
Since Jim Smith put the wingtip extensions on his RV-6, he's seeing from 1.5%more speed at 7000' dalt to 4.9% more speed at 12,000' dalt. That's equivalent to a power increase of 4.4% (160 to 167) at 7000' to 15.4% (160 to 184.7) at 12,000'. Some don't like the looks of them, but they surely do make the plane takeoff faster, climb faster, cruise faster, and land slower. In cruise above 8000' dalt, the nose is much lower, giving a better view ahead. To me, that gives more benefits than more power!
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12-10-2010, 03:41 PM
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Join Date: Nov 2006
Location: Albuquerque
Posts: 297
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a lesser RV
OK I can't keep up with most of you guys it seems but........
My 150 HP, wood prop -9A is an absolutely delightful airplane!
If you got the $$$ (I don't  ) go for the big engine & CS prop.
But don't let your finances delay getting your RV in the air. These are great airplanes!
The money I didn't spend is going to buy alot of fuel (86 oct car gas BTW).
Dave
-9A flying
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12-10-2010, 03:50 PM
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Join Date: May 2005
Location: Tuttle, Oklahoma
Posts: 2,563
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Quote:
Originally Posted by Scherminator
My own personal decision trees have led me towards a fuel injected 180hp f/p (preferably with hollow crank for future upgrades path). Always subject to change of course.
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My personal decisions led me towards a fuel injected 185 hp f/p (with a hollow crank for future upgrades) that weighs only 8 lbs more than the IO-320 ( I know this because I weighed every component of my engine and compared it to the published weight information of the IO-320).
The performance of those 185 horses with only 8 lbs of additional weight is truly incredible. I wouldn't trade the extra 25 horses for anything. Especially when I am still cruising at 145-150 mph true airspeed while burning 6.5 to 7.0 gph at 65%. I can still push the airplane even faster if I want to at the expense of more fuel. It is there if I need it. I am also sure I will be able to get even better fuel economy the first time I am able to take a cross country trip that will allow me to climb high and lean out even more aggressively than I already am.
I have discovered that there is not a linear relationship between the weight of an engine and the amount of HP produced. I can have my HP and carry less weight too! For anyone interested in learning what I found out: Click Here!
I LOVE THIS ENGINE!
Live Long and Prosper!
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12-10-2010, 04:13 PM
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Join Date: Apr 2005
Location: KSLC
Posts: 4,021
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Quote:
Originally Posted by elippse
I would also take exception with your characterizing the CS prop as having higher propulsive efficiency. They dont; they only allow you to turn up more rpm for higher static and climb power. In cruise a well designed FP will be more efficient.
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A C/S also allows the pilot to pull back the RPM's in cruise flight, to lessen the noise. That's something I always do................and I wouldn't be too happy, without that capibility. The C/S is also excellent for braking ability, which opens up a lot more options coming downhill or in the pattern. Would "I" buy an RV6 without a C/S, or that extra 20 HP..................No!
L.Adamson --- RV6A 036/Hartzell CS
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12-10-2010, 05:06 PM
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Join Date: Aug 2007
Location: Wichita Falls, TX
Posts: 2,182
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The first RV I ever got to fly from the left seat was a 150hp carbureted O-320, fixed pitch wooden prop RV-6. Takeoff, climb, and cruise were fantastic compared to my Cherokee. It was great fun.
The second RV I ever got to fly from the left seat was a -7A with a hotrodded angle valve IO-360 and Hartzell blended airfoil constant speed prop. It was simply mindblowing in short takeoff roll, climb and cruise. A rocketship that hit 180kts in level cruise effortlessly with two aboard. Sucked down a fair amount of fuel pretty quickly too.
The third RV I got to fly as PIC and log a significant amount of time in was a 160hp carbureted, fixed pitch wood prop RV-4. Excellent performance, especially since this is the first RV I soloed. Distinctively stronger performer in takeoff and climb than the aforementioned 150hp RV-6. The extra 10hp, plus a little less weight made a difference.
The 3rd RV I get to fly is the -8 in my avatar. It's got a 192hp ECI Titan IO-360 and Hartzell blended airfoil CS prop. It too is mindblowingly fast and climbs like a rocketship. It's not quite as powerful as that -7A that I got to fly a couple years ago, but that one probably had north of 200hp onboard.
On the way to Oshkosh, JetJ01 in his RV-4 (with carbureted O-360 and the same Hartzell blended airfoil prop as we've got on the -8) was flying right next to me (solo in the -8), with a pax in his back seat (who took the photo in my avatar), and I pretty much maxxed everything out on the -8 and JJ stayed right up alongside me, then he waved bye-bye and they simply walked off and left me behind. So if you really want to go fast, there's just no substitute for extra cubic inches.
__________________
Neal Howard
Airplaneless once again...
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12-10-2010, 07:27 PM
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Join Date: May 2007
Location: salem Oregon
Posts: 1,023
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Consider this. Both are 160hp engines. io-320 and io-360L2A. I maybe off 25rpms but on the 160hp on the io320 @2675rpms and 160HP on the io360 2400rpms. This version IO360 provides more HP at a lower RPM so its quiter than the IO320. The engine works less and maybe longer wear on the IO 360. If you live at a higher altitude you might consider IO360. Now Iam building a 9A and considered the IO 360 until I went hunting for a used 360. When they wanted $2K less (on a IO360L2A & 800hr engine) than a brand new IO320 from Vans it was a no brainer. So heres where I learned about the IO360 L2A. Cessna I believe 1996 came out with the IO360 but this version was the IO360 derated to 160hp with limiter plate on fuel/air mixture. So when the SP Skyhawk came out the limiter plate was removed and now you have 180HP. This way cessna's assembly line didn't need different engines for different HPs. I really loved the rented 160 HP Hawk flying around the Florida keys and west of Key West it was so quite. I try to treat myself to flying when Iam on vacation that I had to use a jet to get there. I rent a Hawk and a Instructor and tell the instructor I can fly the plane but you tell me where I can fly or not and have him work the com radio. This way I get the thrill of flying and support aviation and or instructor community. Enjoy,
Ron in Oregon
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12-10-2010, 07:55 PM
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Join Date: Oct 2008
Location: Schaumburg, IL
Posts: 2,053
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Here's my opinion - If economy and economics is the main consideration then go with the 320 (I did). If speed is the main consideration go with the 360 (or better yet, IO-390).
Everyone talks about going fast, but.....what's the hurry?
__________________
Tony Phillips
N524AP, RV 9 (tail wheel)
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12-10-2010, 07:59 PM
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Join Date: Dec 2009
Location: Lockhart, TX
Posts: 206
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I've been asking myself the same question. Twenty horsepower isn't all that much and I'm thinking that with some mods the less expensive 320 should be able to run close to a 360 and still weigh less. That's what I'm thinking at this point anyhow.
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12-10-2010, 08:06 PM
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Join Date: Jan 2005
Location: Round Rock, TX
Posts: 3,778
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An O-320... with a little work will keep up with the best of the O-360 RV's out there. I know because I have one. My flying Bud has a IO-360 200 HP in his RV7, we're neck and neck.
More important to this equation is a straight, true and clean airframe... AKA John Huft's RV8
__________________
Reiley
Retired N622DR - Serial #V7A1467
VAF# 671
Repeat Offender / Race 007
Friend of the RV-1
Last edited by LifeofReiley : 12-10-2010 at 08:15 PM.
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12-10-2010, 08:52 PM
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VAF Moderator / Line Boy
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Join Date: Jan 2005
Location: Dayton, NV
Posts: 12,256
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Climb, Baby ... Climb!
Quote:
Originally Posted by apkp777
Here's my opinion - If economy and economics is the main consideration then go with the 320 (I did). If speed is the main consideration go with the 360 (or better yet, IO-390).
Everyone talks about going fast, but.....what's the hurry?
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Why do people always associate more HP with speed alone? With an efficiently-powered airplane, getting more speed with a little extra horsepower is almost always pretty hard to do - you're already on the steep part of the drag curve.
For me, HP is about climb - and you can get a lot for a little! Additional climb rate goes a long way toward making an airplane that is truly fun and free in three dimensions. If, of course, that is important to you....
__________________
Paul F. Dye
Editor at Large - KITPLANES Magazine
RV-8 - N188PD - "Valkyrie"
RV-6 (By Marriage) - N164MS - "Mikey"
RV-3B - N13PL - "Tsamsiyu"
A&P, EAA Tech Counselor/Flight Advisor
Dayton Valley Airpark (A34)
http://Ironflight.com
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