[whmc]

The 10,000 dollar question I,m sure has been asked! First 180hp, 200hp? Kit engine, certified engine, find a used one to rebuild etc. What do you experts recommend as the best combo for a -8. I,m a tall, 250 lb. newbee pre-planning a -8 and would appreciate any input. Thanks Wayne

 

[Andy_RR]

IO-375

Next question?

 

[Ironflight]

I'll get back to you, as soon as I answer my current puzzler "What is the nature of Truth?"

Fact is, there is no single answer, and it all depends on your circumstances, what you want the airplane to do, and what you mean by "best". If we can't even get folks to agree on the definition of "performance", it's pretty hard to pick a power plant to maximize it....

Paul

 

[whmc]

IO 375 ? Paul yes your are right with what you say, however comments are good and educational just as long as the receiver uses the comments to make his/her decision. You like the 180 in yours? Wayne

 

[N208ET]

whatever makes you happy

I will say that if you have a good engine mechanic that you could help rebuild a engine I would do it that way, or go to one of those experimental build schools. Knowing what exactly goes into the engine will pay dividends later on in the ownership of the plane. Knowledge is power.

Randy 8A Flying
0-360
sensenich FP
Bendix Mags
Basic 6 Pack
Dirt Simple

 

[Ron Lee]

No smaller than O-360. Constant speed prop highly desirable to most pilots.

 

[Crossbow]

The 10,000 dollar question I,m sure has been asked! First 180hp, 200hp? Kit engine, certified engine, find a used one to rebuild etc. What do you experts recommend as the best combo for a -8. I,m a tall, 250 lb. newbee pre-planning a -8 and would appreciate any input. Thanks Wayne

I asked Van that same question at Oshkosh a few years ago, and while he did not give a specific reccomendation, he did explain that the RV-8 was designed for an O-360 at 180 HP.

So, after talking to him and several other people about this same issue, what I plan to use is an:

IO-360 at 180 HP,
fixed pitch, 3-blade, Catto prop (but with a plugged, hollow crank just in case I decide to later upgrade to constant speed),
most likely a certified Lycoming.

However, you will have to make your own call on this issue.

 

[Doug Lewis]

Will it make a difference if the question is biggest bang for the buck? I've been considering the same question. Though I'd love to have a new Thunderbolt, I doubt it's in my future. Suggestions for reliable "good" performance for the best price? It seems when people ask if this used engine is a good deal, there are many replies that by the time it's rebuilt they're up to near the same price as new 180hp.

 

[mikegraycmg]

Fly

I thought I wanted an IO390 for the RV8 I'm building. Then, I flew in an RV4 with an O320 rated at 150 HP, and I realized that I didn't need all of the HP a 390 brings. The airframe performs amazingly well with moderate power, and you may find, no matter what you put in it, that it has more capacity than you do. I bought a mid-time O360A1G6D that I am overhauling, and have replaced the 8.5-1 pistons with 8.9-1 pistons. I'll have less than $15,000 in the engine when it's complete, about half the cost of a new O390.

The short answer is to try to fly in several aircraft and observe the performance. Then, get what you want and can afford.

 

[Black8]

I put an O-320 D2J (160hp) in mine(first time runout and the price was right $0). But before putting it in though I put in 9:1 pistons and a different crank and used a C/S prop. Painted it weighed 1044#. I weighed 235# at the time and it will out run a "V"tail Bonanza!!! It's a Van's plane, no matter what you put in it's gonna go like stink and will be the best plane you've ever flown!!! Can you tell I'm a "Van Fan"!!! Have fun with your 8. Oh, and BTW I talked to Van himself about my choice of engine and he said that the 160hp O-320 with a C/S prop was the best choice for W&B, performance , and fuel burn...about 6.5 GPH!! and with 42 gals -man you better have a relief tube!!!

 

[flyeyes]

I asked Van that same question at Oshkosh a few years ago, and while he did not give a specific reccomendation, he did explain that the RV-8 was designed for an O-360 at 180 HP.

I recognize this, but note that nearly every airplane with a significant production run was designed around a smaller, lighter engine and wound up with more weight and power.

Off the top of my head:

Bonannzas/Navions/T=34 originally had either a continental E=185 or 205, later models had IO-520s or bigger with 285+ HP. In fact pretty much every single or twin Beech ever built.

Cessna 120/140/150/152 started with C-85 continental, last production airplanes with O-235 @ 115hp. same for the bigger Cessnas

All the pipers from the cub through the PA-28, Comanches, and even the Malibu went through successively larger motors.

I'm having a harder time remembering any airplane that had more than a few years of production that didn't get more horsepower in later models. I can't think of any except relatively limited airplanes like the beech skipper or Piper tomahawk. Am I missing any good examples?

 

[Toobuilder]

...What do you experts recommend as the best combo for a -8...

That's a little like asking "how high is up?"

"Best" depends on your mission. The -8 I fly has an angle valve 205 HP and a Hartzel BA prop. It goes like a bat out of ****, but is heavy in pitch with all that hardware hanging off the firewall. But for me, its "mission" is (west coast) cross country in a straight line as fast as possible. Heavy in pitch is fine, but I still find the airplane too slow.

On the other hand, if you are looking for local "fun" flying, then a smaller engine and fixed pitch prop would result in a much better "flying" airplane, but at the expense of some climb performance.

Define your mission, then pick the equipment to match.

 

[N941WR]

Can a non -8 builder / flier comment?

First, the 180 HP Lycoming seems to be the default engine for the -7 and -8?s. Think about what the smaller engine will do for resale value.

With that in mind, let me tell you a short story.

When I built my -9, I installed an O-290-D2 of 135 HP (140 for takeoff) and was very happy with it. Even when the 160 HP RV?s left me behind, it wasn?t by very much. The reason for the 290 was that I was able to buy one with 0 SMHO for $3500. It turned out to be a great engine, right up until I hit that blasted trailer.

When it came time to select a replacement, I found the cost difference between an O-320 and O-360 was only $500. $500 bucks for 20 extra HP sure sounded like a great deal. Then I looked into the engine weights, the 290 came in at 264 lbs, 277 for the O-320, and 284 pounds for the 360 (200 HP IO-360?s jump to 320 pounds.)

So for $500 bucks I gain 20 hp and seven pounds over the 160 hp O-320. (45 hp and 20 pounds over the O-290.)

Options include putting on dual P-mags (saving 3 pounds over standard mags.), Sky-Tec flyweight starter, ECi tapered cylinder barrels (saving six more pounds), and a composite Catto prop (saving around 30 pounds over a FP metal prop.)

In the end, I will gain a lot of HP for little weight gain over a standard O-320 installation. If you want a CS prop, put a Whirlwind 200RV composite prop on it and you are still lighter than an O-320 w/ a metal FP prop.

 

[Rick6a]

Just how skilled are you?

......best combo for a -8. I,m a......newbee pre-planning.......a -8 and would appreciate any input.....

Lot's of responses to your query Wayne, yet no one has addressed what may be an important, even game changing factor that you should consider. According to your post, you are a self-described "newbee." Newbee can mean many things. You really should ask yourself what you bring to the table by way of skill set. Seeing an RV project through to completion is challenging enough without reinventing the wheel. Obvious in the responses to your query so far is you can opt for this engine/prop combo or that. No surprise there and predictably as responses have shown, opinions can be all over the map. There is, however, another dimension in all this. My advice is to seriously consider purchasing a Van's OEM engine/prop combo and firewall forward package. Whichever engine you choose, doing so gets you 99% of what you need to finish all things FWF and doing so without having to re-engineer things to fit. It is convenient and a huge time saver to have premade hoses, critical accessories and accurate firewall penetrations called out and correct accessories provided to you in the FWF kit. The FWF drawings are fairly complete, easy to understand and if reasonably followed, many technical hurdles you might otherwise face are completely eliminated. Little things included in the drawings, like a simple call-out of a part number for a required fluid fitting not only eliminates frustration, guesswork and additional (time consuming) research, but can save you a significant amount of build time at increased efficiency in the bargain.

Alternatively, if you buy an engine from some other supplier you will likely find some things will have to be changed or modified and simply making necessary alterations can easily cause your build time to balloon and sometimes quite dramatically. If you are sufficiently skilled in turning a wrench and the ways of FWF magic, that may not be much of a problem. But if you are not particularly gifted in such matters, an OEM package makes perfect sense. It is a form of insurance that increases the odds you too will finish your dream project and ultimately enjoy the RV experience from the pride, perspective and command of the pilot's front seat.

Good luck whatever you decide and welcome aboard.

 

[jthocker]

Lot's of responses to your query Wayne, yet no one has addressed what may be an important, even game changing factor that you should consider. According to your post, you are a self-described "newbee." Newbee can mean many things. You really should ask yourself what you bring to the table by way of skill set. Seeing an RV project through to completion is challenging enough without reinventing the wheel. Obvious in the responses to your query so far is you can opt for this engine/prop combo or that. No surprise there and predictably as responses have shown, opinions can be all over the map. There is, however, another dimension in all this. My advice is to seriously consider purchasing a Van's OEM engine/prop combo and firewall forward package. Whichever engine you choose, doing so gets you 99% of what you need to finish all things FWF and doing so without having to re-engineer things to fit. It is convenient and a huge time saver to have premade hoses, critical accessories and accurate firewall penetrations called out and correct accessories provided to you in the FWF kit. The FWF drawings are fairly complete, easy to understand and if reasonably followed, many technical hurdles you might otherwise face are completely eliminated. Little things included in the drawings, like a simple call-out of a part number for a required fluid fitting not only eliminates frustration, guesswork and additional (time consuming) research, but can save you a significant amount of build time at increased efficiency in the bargain.

Alternatively, if you buy an engine from some other supplier you will likely find some things will have to be changed or modified and simply making necessary alterations can easily cause your build time to balloon and sometimes quite dramatically. If you are sufficiently skilled in turning a wrench and the ways of FWF magic, that may not be much of a problem. But if you are not particularly gifted in such matters, an OEM package makes perfect sense. It is a form of insurance that increases the odds you too will finish your dream project and ultimately enjoy the RV experience from the pride, perspective and command of the pilot's front seat.

Good luck whatever you decide and welcome aboard.

Absolutely the best advice you're going to get!

 

[whmc]

SOLD Will go the Vans route. Thanks guys

 

[Andy_RR]

SOLD Will go the Vans route. Thanks guys

You don't need to be in a huge hurry to make such a decision (aside from the budgetary aspects), especially if, as it seems to me, you're still ordering or yet to order your empennage kit. You will learn a lot along the way before you get to placing an order for finishing kit and engine/prop.

Who knows what will come along in the mean time.

 

[lucky]

You don't need to be in a huge hurry to make such a decision (aside from the budgetary aspects), especially if, as it seems to me, you're still ordering or yet to order your empennage kit. You will learn a lot along the way before you get to placing an order for finishing kit and engine/prop.

Who knows what will come along in the mean time.

yeah, really, there's no rush. It's good to ask but don't get your brain brainwashed right now into any suggestion as 'best'. Until you you get to the point where you are going to plan for your battery and ELT location and then order your engine mount, cowl & the FWF kit it's a who cares question.

I have a the 'heavy' 200hp angle valve io-360-A1B6 engine with a hartzell CS prop. When solo, cg is at the forward range. When I take my teenage son camping with equipment, i can load the **** out of it and never get too tail heavy and still get there really fast and climb very safely out of anywhere. But acro is decidedly not as enjoyable as with a lighter engine and I don't like adding dead weight to the aft cargo just for acro to get lighter stick forces. So I don't consider my RV a great acro setup but barely acceptable. If you want great acro, go partners on a Pitts or 1D while keeping the RV for CC.

If I had to do it all over again, I'd probably go for a lighter engine but would have to first fly a 320 vs a 360 and see for myself - not take anyones word over the internet as this is a real feel decision, keep it fuel injected, and if the lighter CS props were finally what I would consider mature and with a decent TBO, with no restrictions about flying through rain or RPMs in cruise, with no more histories of leading edge pieces flying off in flight, etc, I'd go for one of those too if I could save half the weight of a hartzell...

 

[Trapper]

Engine choice

I?m a ?newbee? too but I've got Aerosport Power building an experimental ECI IO-375 for me as we speak. It's a "stroked" IO-360 (different crank) that gives it greater displacement and a resultant power increase. I wanted more power while avoiding the angled-valve architecture of the 200HP IO-360 and the extra nose-end weight of the IO-390. The IO-375 is a good solution for a higher power, parallel-valve engine with the exact size and weight of a stock 180HP PV IO-360. With 9.6:1 pistons, it'll generate 205HP in the same package/weight as a stock IO-360 with about the same burn. I'm going with 8.5:1 which will give me ~200HP but allow me to burn 91 U/L if 100LL goes away (according to Bart and Sue at Aerosport). And unlike the stock, no frills engines available from Van's, Aerosport will port/flow each cylinder and balance the engine. Cosmetically, I got to choose a color (other than Lycoming gray) and went with polished rod tubes and chrome valve covers. Here's their link:

http://www.aerosportpower.com/default.htm

Another good shop is Barrett Precision Engines in Tulsa, OK but they don't build the IO-375 and no longer do Lyc kits. Talking to Rhonda at their shop, there are apparent corrosion issues with Lyc's new roller cam technology. BPE tore down one of these engines after only 150hrs and the cam was trashed to the point that it was not restorable. If you don't fly your airplane very often, corrosion supposedly can build up on the cam lobes and the roller tappets just roll over the corrosion, allowing it to build. Standard flat tappets supposedly prevent this from happening by "scrubbing" the lobes during normal operation. All this plus the fact that ECI offers nickel carbide cylinders (vs. steel) swung my vote over to ECI.

Recognize that this is all just my two cents and the result of my personal due diligence in selecting an engine.

Hope this helps,

Trapper
RV-8 flyer wannabe

 

[Andy_RR]

I admire your choice Trapper!

Like you, I reckon the IO-375 is a great compromise between weight, cost and fuel consumption.

From my calculations, unlike road vehicles, a larger engine is actually more fuel efficient than a smaller one for aircraft fitted with a CSU. It's all about gaining the as much TAS advantage of higher altitudes as you can while still being able to run lower engine speeds at the same time.

To me an IO-360-A1 series makes little sense.

 

[David-aviator]

I'll get back to you, as soon as I answer my current puzzler "What is the nature of Truth?"

Fact is, there is no single answer, and it all depends on your circumstances, what you want the airplane to do, and what you mean by "best". If we can't even get folks to agree on the definition of "performance", it's pretty hard to pick a power plant to maximize it....

Paul

Might that be like "Fact" vrs "Theory"? It seems fact is too narrow and subject to review, whereas well thought out theory lends itself to more satisfactory results, or something like that.

I'd go with a theory, that being less weight is better in an airplane than more weight. Seems to me the Wright Brothers were quite focused on that theory and finally got off the ground.

Go Barrett light weight IO360 (187 HP with balancing and flow porting) and a 16 pound Catto. It will leave at least 75 pounds at the gate.

 

[trackdom]

Personnaly I 'll use a o-320 to keep light and nimble

 

[DanH]

Did a dawn patrol this AM.....glorious! The best engine is any which (1) runs good and (2) is hauling your butt into the sunrise.

 

[William Slaughter]

Go Barrett light weight IO360 (187 HP with balancing and flow porting) and a 16 pound Catto. It will leave at least 75 pounds at the gate.

I went with a similar program - Aerosport Power modified parallel valve motor and a Whirlwind 200RV composite prop. Considerably less weight and within spitting distance of the horsepower of a stock IO-360 angle valve motor.

 

[Joe Parish]

Lot's of responses to your query Wayne, yet no one has addressed what may be an important, even game changing factor that you should consider. According to your post, you are a self-described "newbee." Newbee can mean many things. You really should ask yourself what you bring to the table by way of skill set. Seeing an RV project through to completion is challenging enough without reinventing the wheel. Obvious in the responses to your query so far is you can opt for this engine/prop combo or that. No surprise there and predictably as responses have shown, opinions can be all over the map. There is, however, another dimension in all this. My advice is to seriously consider purchasing a Van's OEM engine/prop combo and firewall forward package. Whichever engine you choose, doing so gets you 99% of what you need to finish all things FWF and doing so without having to re-engineer things to fit. It is convenient and a huge time saver to have premade hoses, critical accessories and accurate firewall penetrations called out and correct accessories provided to you in the FWF kit. The FWF drawings are fairly complete, easy to understand and if reasonably followed, many technical hurdles you might otherwise face are completely eliminated. Little things included in the drawings, like a simple call-out of a part number for a required fluid fitting not only eliminates frustration, guesswork and additional (time consuming) research, but can save you a significant amount of build time at increased efficiency in the bargain.

Alternatively, if you buy an engine from some other supplier you will likely find some things will have to be changed or modified and simply making necessary alterations can easily cause your build time to balloon and sometimes quite dramatically. If you are sufficiently skilled in turning a wrench and the ways of FWF magic, that may not be much of a problem. But if you are not particularly gifted in such matters, an OEM package makes perfect sense. It is a form of insurance that increases the odds you too will finish your dream project and ultimately enjoy the RV experience from the pride, perspective and command of the pilot's front seat.

Good luck whatever you decide and welcome aboard.

Great advice! I am a newbee soon to be ordering an emph. I was thinking right along those lines to increase my odds of tackling a project of this size. Thanks

 

[Rob Erdos]

Parameters for Engine Selection

Guys,

I've been following this thread with interest, and I can't resist offering my 2 cents.

I'm building an RV-6, and the selection of an engine has become an interesting challenge for me precisely because there seems to be a complete absence of rational criteria for decision-making. People often say things like, "yur gonna put a 360 in it, right?" The question is spoken with the implication that I would be deficient in testosterone if I didn't put the largest permissible engine in my RV.

I offer these thoughts for the purpose of inviting argument, so here goes...

Imagine that I build two otherwise identical RV-6's. One has an O-320 (160 HP). The other has an O-360 (180 HP). Same prop. Same carb. Same toys. Let's imagine that they're both operating at gross weight. Which one is "best"? Well, the relative performance numbers are right there on the Van's website.

The 360-powered RV-6 would have 20 additional HP, and would have modest but measurably improved climb performance (290 ft/min). The additional power would get me to cruising altitude faster, but would only normally be of significant value during aerobatics or when flying from very short strips. Take-off distance would be reduced by 60 ft.

On the other side of the coin, let's consider cruise. Van's lists the 160 HP O-320 powered RV-6 as 8 mph shower both at top speed and at 75% power, 8000 ft. Sure, because 75% of 160HP is less power than 75% of 180 HP. That proves that if you want to go fast you need to maximize horsepower. However, if one were to select an equal power setting (i.e. same horsepower) then the O-320-powered RV-6 would have a slight advantage since it's carrying around about 25 lb less engine. This would equate to either a slightly greater payload or a very slightly increased cruising speed (1-2 mph) owing to reduced operating weight.

Airplanes are expensive, and I want to maximize my bang-for-buck ratio. RV's are efficient transportation by virtue of clean aerodynamic design, but even Van can't escape the diminishing returns caused by drag rise. Power Required increases with the cube of airspeed. Fuel flow and fuel cost are directly proportional to engine horsepower. Ergo, fuel cost increases with the cube of airspeed. Further ergo, slow down. Even a lowly O-320 will push an RV-6 well up the front side of the power curve.

How does that bear upon engine selection? Well, it requires a clear statement of mission to optimize the engine for its intended usage. It's a personal decision, but to my mind airplanes spend most of their time in cruising flight with the throttle set at a particular value, and that value is increasingly determined by the amount of fuel we can afford to burn per hour. Time spent climbing or the reduction of take-off distance margins are rarely a crucial consideration, especially for the RV's, since their performance is already spectacular. It's a personal decision, but for me fuel burn, and the associated costs, are the more critical factor.

I spent a fun-filled day today looking over the Lycoming Type Certificate Data Sheets for the O-320 and O-360 engines. I was curious whether there were any difference in the efficiency of the two engines that would assist in selection. I discovered that the BSFC of each engine was related to the compression ratio. The 7:1 engines have a slightly higher (worse) BSFC than the 8.5:1 and higher engines, which in retrospect is no surprise since BSFC is probably a function of volumetric efficiency. I also noted that the higher compression engines require higher octane fuel for anti-detonation protection. Hmm, this would factor in the bang-for-buck equation, since we are all concerned about the cost and availability of avgas. This leads me to another factor in engine selection: trading efficiency versus fuel flexibility. The lower compression (and typically lower power) engine variants are more accommodating of mogas, premium mogas, etc.

Concluding, I think that the RV-6 performance is sufficient in take-off and climb, and I will probably opt to take a small benefit where it spends most of its time, in cruise. That speaks for an O-320 engine. Among the numerous O-320 variants, I will need to do some serious crystal ball gazing to anticipate which engine will burn the fuels that will exist in the future, with the understanding that lower compression means greater flexibility.

Does that clarify anything? Arguments and opinions most welcome.

Rob Erdos

 

[Rob Erdos]

Oh, And Furthermore...

[Does this stuff ever become obsessive to you, or is it just me? ]

It occurs to me that maybe our dialogue is too slanted toward how much horsepower is "enough" horsepower. The more fundamental trade-off is between horsepower and payload, since the design gross weight is fixed. Bigger engines cost more in terms of weight (oh, and dollars).

Again, in the context of my notional RV-6's, let's look at the trade-offs and see how they effect engine selection. (I appreciate that this thread was about an RV-8. I don't mean to hijack it, since it's safe to presume that the same considerations will apply.)

Most -6's come out of the shop weighing around 1050 lb. plus or minus a bunch. Van's design maximum gross weight is 1600 lb. Of course, some people fly them heavier - in part because they shoehorn so much horsepower into them - but that was the gross weight designed into the structure. Consequently, the payload breaks down roughly as follows:

Empty: 1050 lb
Me and wife: 300 lb
Full fuel (38 gal): 250 lb
Baggage: 0 lb
Take-Off Wt: 1600 lb

It seems that we have a classic design for a light airplane; a design that allows a functional trade-off between range and payload. In relation to engine selection, and in light of the loading scenario above, would you trade payload for increased performance by installing a bigger engine? The weight difference between an O-320 and O-360 is on the order of 20 lb, and that's 20 lb that you can't carry in the cabin. I don't presume to have an answer, because it's a question of your intended mission. If I let testosterone speak, I'd opt for horsepower any day. The extreme example of that logic, in an RV-sized package, is the Extra 300. Incredible performance, but you can't carry anything.

Another way of looking at it: For roughly the same weight (dollars aside) I could have either an O-360 with a fixed-pitch prop or an O-320 with a constant speed prop. My bet is that the propulsive efficiency of the constant speed would more than make up for the lower horsepower.

Just thinkin' aloud. Opinions most welcome.

Rob Erdos

 

[terrye]

CS efficiency

Van's instruction manual (RV-9A) says, in the section about propellers, that a constant speed prop at cruising speed will have about a 1 gph advantage over a fixed pitch. That's about $4.00/hr advantage. This and the better climb performance (for mountainous terrain) made me decide on a CS prop. So I think you're right, an O-320 with a CS prop is probably a better choice than an O-320 or O-360 with a fixed pitch.

 

[L.Adamson]

How does that bear upon engine selection? Well, it requires a clear statement of mission to optimize the engine for its intended usage. It's a personal decision, but to my mind airplanes spend most of their time in cruising flight with the throttle set at a particular value, and that value is increasingly determined by the amount of fuel we can afford to burn per hour. Time spent climbing or the reduction of take-off distance margins are rarely a crucial consideration, especially for the RV's, since their performance is already spectacular. It's a personal decision, but for me fuel burn, and the associated costs, are the more critical factor.

Take this for what it's worth. If my "heavy RV6A" is powered back just like a lighter 9A with a 0320 (both have C/S props)............I can match the fuel efficiency. On the other hand, I can climb faster & top speed is faster. That 20 additional horsepower is something I much prefer. And knowing what I know after 16 years of this, I don't have to stick with 1600 lbs gross weight either. I do fly out of a 4600' msl airport to start with.

L.Adamson --- RV6A

 

[Rick6a]

My Engine is Bigger than Your Engine

......It occurs to me that maybe our dialogue is too slanted toward how much horsepower is "enough" horsepower. The more fundamental trade-off is between horsepower and payload, since the design gross weight is fixed. Bigger engines cost more in terms of weight (oh, and dollars).....Rob Erdos

Rob,

You are NOT alone in that sage observation. We can read all the "huff and puff" we want and rightly conclude that opinions can and will be all over the map. Fact is, despite evidence to the contrary some people will continue to cling to the curious notion that more horsepower is always better. But is it ....really?

When I built the -6A, I too compared Van's published performance stats before making an engine selection. In the end, I concluded that an 0-320 gave me more bang for the buck. It was obvious to me that considering the price and performance difference between that engine and an 0-360, I did not see a commensurate difference in efficiency and performance. Fact is, I am extremely pleased with my O-320. Compared to the IO-360 fitted to my -8, that O-320 is more economical to operate. Comparing fuel burns, the IO-360 is significantly more thirsty and in the end cruise and top speed differences are entirely consistent with what Van's own in-house testing, data and long experience tell us.

Speaking of what Van's has to say on the matter, presented here are their observations as published in the RV-6A builders manual:

 

[Daver]

4600'??

I do fly out of a 4600' msl airport to start with.

What a piker LA

I fly out of 1N1 - 6550'. Sometimes the DA is 8000' or more.

No problem with my 150 HP, wood cruise prop RV9A.

Heck, I even flew to Angel Fire (8400') & back. Did just fine.

I suppose if I had $6 - $8K lying around for a CS prop, I could trim my time to altitude by 3 or 4 minutes but I'd rather buy fuel.

Arn't these wonderful airplanes?

Dave
-9A flying

 

[L.Adamson]

You are NOT alone in that sage observation. We can read all the "huff and puff" we want and rightly conclude that opinions can and will be all over the map. Fact is, despite evidence to the contrary some people will continue to cling to the curious notion that more horsepower is always better. But is it ....really?

Some pilots are "happy" with Cessna 150/152s...

Yes, to a point, bigger is better. I discovered that back in the Piper Warrior versus Archer days. I've flown RV's with 150 hp, 160, & 180. And I still would prefer the performance of an F-16!

L.Adamson --- RV6A

 

[Ron Lee]

I do fly out of a 4600' msl airport to start with.

What a piker LA

I fly out of 1N1 - 6550'. Sometimes the DA is 8000' or more.

I fly out of 00V at 6874 feet MSL (soon to be KFLY) so I hereby remove the piker moniker from L. Adamson and thrust it onto Daver. Runway density altitude in the summer reaches 10,000'.

Of course it is a matter of time until someone from Leadville passes the piker moniker/baton onto me.

There is no doubt that RVs perform well with any of the Van's recommended engines. Rob seems to feel that fuel flow is the best criteria. That is fine but my understanding is that similar aircraft...one with an O-320 and one with an O-360, will burn about the same fuel when run side by side (same speed).

So why give up the extra horsepower of an O-360? You would be hardpressed to find anyone at my airport who would recommend an O-320. One guy put a 150 HP O-320 in his 8A. He later rebuilt it to get more horsepower. Then he put a CS prop on it. I never did fly with him but assume that he was slower than most people here.

Nothing against guys with smaller engines, but I always tell people building to put no less than an O-360 in their 6/7/8. I recommend against buying any 6/7/8 with less than an O-360.

Perhaps my recommendations are flawed but they are what they are. Or maybe it is something in the water.

 

[gasman]

Van's instruction manual (RV-9A) says, in the section about propellers, that a constant speed prop at cruising speed will have about a 1 gph advantage over a fixed pitch. That's about $4.00/hr advantage. This and the better climb performance (for mountainous terrain) made me decide on a CS prop. So I think you're right, an O-320 with a CS prop is probably a better choice than an O-320 or O-360 with a fixed pitch.

Break even time would be about 1750 hours providing that you did no maintenance on that C/S prop.

 

[Daver]

piker baton

I hereby accept the piker baton from Ron (until the Leadville guy shows up)

Its really about budget I guess - some have it; some don't. I'm in the "don't" category but at least my plane flies.

Remind me NEVER to challenge LA to a climb performance contest....

Dave

 

[pierre smith]

While I was discussing LOP operation....

...a poster mentioned that he didn't build a fast airplane to go slow

Good point, neither did I...I just wanted the most bang for the buck, so, yes, horsepower rules. You can always throttle back or run LOP...you can never add more power than what's there.

Best,

 

[Daver]

fast vs slow

I'm confused about pilots who love to fly, but love to fly fast.

A guy flying along at 100 kts gets twice the flying time as a guy going 200 kts.

Unless, of course, you're really trying to get somewhere.

I suspect few of us are really needing to get somewhere but rather are just flying for the enjoyment.

My -9A will do 150 kts or, just as happily, 100 kts and at a few thousand feet above the ground, I can't tell the difference unless I look at the ASI (or GPS).

Someone once said "there's more to life than increasing its speed..."

So you guys in a big hurry with your hair on fire, go ahead and pass me.

I'm enjoying the ride!

Dave

 

[Marnee']

Positives of the angle valve engine with counterweighted crank:
1. Smoother operation
2. Better cooling
3. No rpm limitations
4. More fuel efficient

I have 655 hrs on my IO-360-A1B6. Highest cyclinder temp I have ever seen is ~350F.

Negatives are the cost.....but that is highly compensated for over the life of the engine with lower fuel burn.

I have a Harzell constant speed and with the battery in the back, balance is not an issue. The airplane still flies slow, lands slow but goes fast and can maintain more power at high altitude.

 

[Thug]

engine

I am putting a new tbolt IO390 in my RV8. should hve no problem with performance.

 

[Mel]

Great Post, Dave.

I'm confused about pilots who love to fly, but love to fly fast.
A guy flying along at 100 kts gets twice the flying time as a guy going 200 kts.
I suspect few of us are really needing to get somewhere but rather are just flying for the enjoyment.
Someone once said "there's more to life than increasing its speed..."
So you guys in a big hurry with your hair on fire, go ahead and pass me.
I'm enjoying the ride!
Dave

Sometimes I just shake my head. Same thing with an auto-pilot. I had an A/P in my -6 for about 4 years. Turned it on once a year to see if it still worked. Finally took it out. I like to fly!

 

[David-aviator]

....... I like to fly!

So do I.

But I've found, being 4 years older than you, that using the red bottle on a cross country is more and more necessary rather than making a potty stop.

That is some trick without an auto pilot.

 

[Doug Lewis]

I'm confused about pilots who love to fly, but love to fly fast.

A guy flying along at 100 kts gets twice the flying time as a guy going 200 kts.

Unless, of course, you're really trying to get somewhere.

I suspect few of us are really needing to get somewhere but rather are just flying for the enjoyment.

My -9A will do 150 kts or, just as happily, 100 kts and at a few thousand feet above the ground, I can't tell the difference unless I look at the ASI (or GPS).

Someone once said "there's more to life than increasing its speed..."

So you guys in a big hurry with your hair on fire, go ahead and pass me.

I'm enjoying the ride!

Dave

So if you REALLY liked flying the smart ride would be a powered parachute or balloon.

I don't have enough time in RV's to give hands on experience but if you look at the numbers between a crotch rocket and a motor scooter the 1/4 mile differences can be measured in a few seconds. It might take only a few minutes (or less) longer to get to work, or the store on the scooter and think of the money you'll save on gas, not to mention the thousands you'll save on the initial purchase. Once you're at cruising speed the sensation is pretty similar but it's unlikely that people on the faster bikes are less biking enthusiasts than people on mopeds. For some feeling that extra 20+ ponies when the brakes are released and knowing it's there when you want them is part of the fun of flying.

It would be interesting to see actual sold resale figures comparing 320 to 360 in identical planes.

 

[Ron Lee]

I don't recall ever throttling back to 100 knots on a cross-country to get more flight time.

I will throttle back if I am loitering around the airport waiting for sunset or for paint to dry, but not cross-country.

 

[pierre smith]

In a 50 knot tailwind...

...I'll throttle back....a little

Best,

 

[humptybump]

Cost is a factor

I've been asking myself this question for a while now. I knew a thread had to exist!

I'm looking at 150 HP with a fixed wood or composite propeller. my thinking is that 89 mogas is common where I am because all the fisherman need it. Plus "simpler is better" for my type of flying. when I look at my buddies, they flight plan their Pipers and Cesnas at 9 gph and 120 kts. I'm having to throttle back or wait for their sorry @$$ at our destination.. Even my typical X-country is only 400-450 nm and that is only 3 hours. I didn't find enough benefit for more cost to get more horsepower to get a little more speed.

It's part of what makes the RVs so great. "Build for your mission"!


My mission just happens to be satisfied by 150 HP.

 

[mikeg]

IO390 fun

IO390 is the way to go
power when you want it, throttle back when you want to save gas like a O-320
200 hours on mine now and with two people on a hot summer day and still climb at 2500 ft/min, cruze at 200 knots IAS if you want to burn gas or idle at 7.5 gph and still cruise 140k

fun

 

[n5lp]

...cruze at 200 knots IAS ...

Wow, that is some IO-390 that causes the airplane to "cruise" at an indicated 230 MPH! What is your secret?