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Dreaming of what engine for my RV9A

georgedouglas

Active Member
I am dreaming about what engine would be good for my new to me RV9A flying aircraft that presently has a 0-320 B1A engine installed. I plan to remove this engine and either rebuild it myself or may be upgrade to a higher HP engine instead. For you RV 9 folks what would be your dream engine over the 0-320?
george
 
I am running stock O-320D2G. When it was new and I was based at sea level it was plenty. Now I moved to a higher elevation (6561?) and would love to have a 360. :)
 
I was leaning towards a Thunderbolt IO-320 when I get to that stage, but I know guys who have IO-360's in RV-9's
 
I?m pretty sure my next engine will be a Titan O-340. Would go fuel I injected but I?m already plumbed for the carb and I have had no issues with it.

Chris
 
Definitely talk to the guys who have put 360s in theirs. Every one I talked to during my search said they absolutely LOVE their plane with the 360. I'm hoping I have the same feeling when mine is flying.
 
Io360

For me the cost of a 360 or 320 were about the same. I went with the 320 because there have been reports that the RV9 could exceed Vne in level flight with the 360. To me this is dangerous. To those who have tons of time and are really good pilots, they can handle it. But I don't think all those who will fly my plane will be that experienced. But that is just me. Everyone makes there own choices. I chose the injected to get the most out of LOP operation; although others have reported good LOP operation with the carb and a little carb neat. YMMV.
 
The Titan IO-340 is the perfect engine for my 9. Weighs as little as a 320 but can put out 180hp. I have 400+ hours on mine so far and love it.
 
I was all set for a 360 since I lived at 8500', but an O-320 D2A appeared for a price I couldnt refuse. I am just getting ready to fly and Im ok with the 320, but would go with 360 if I were to do it again.

Reasons:

Pros - my kids live in the Rock Mountain area. We travel there quite often so the added hp would be nice.

Cons - none I could think of. Maybe a bit more weight in the nose but that can be worked with pretty easy. Some say it can overspeed in level flight. A 9 with a 290 in it can overspeed at a slight dive. Dont do that with either engine and problem solved.

Unless you can get a screaming deal on a 320 like I did, go for the hp.
 
Stop dreaming and put in an IO-360, fixed pitch Sensenich 72 x 85. It wil cruise at 155 kts, 8.5gal/hr at 10.5 alt. LOP at same altitude 7.2 at 143 kts and no wind, Mr. Dynon will says 27.2 kts/gal. Less than 10 kts of wind, that's how I lean, 27 kts/gal plus or minus. Dan from Reno
 
We're 13yrs in, and I will be looking for more horsepower for the -9 when the time comes to do something with the engine. Mostly for the anemic nature of the 320 at 14-16k' where the wing is very happy.
 
IO360 in mine since the beginning. My fuel burn is the same or perhaps a bit less (believe it or not) than similar RVs with 320s. Possibly because of the injection vs. carb plus I lean aggressively. Flying (near gross) in the mid-teens at ~165-170 mph, I burn around 7-7.2 gph. Catto 3-blade prop, pitched for cruise. Easy to throttle back if necessary (at lower altitude). Weight penalty for going 360 vs 320 was about a dozen pounds. Only reason to go with a 320 would be a really (!) good deal on an engine, in my opinion.
 
.... our RV9a flies great behind a O320 D1A with dual emag ignitions, needs 28L /h. 160 hp are plenty ... but I would love to fly a smooth balanced engine, I guess a IO320 would be nice ...
 
Bingo. IO-360 and WW200RV prop makes the airplane come alive.

I would agree with Finley Atherton and Greg Niehues above ?IO-360 and a Whirlwind WW200RV?. Take off like you are leaving an aircraft carrier and smooth to cruse.

BUT never forget, as someone has stated, you can overspeed at level flight. I am what I consider a low time pilot, but I know the limits of the RV-9 and I have a serious respect for those. I limit my speed to 160 MPH indicated at 8500? that is about 180 MPH true. Which put my fuel burn at under 7 GPH. I love the combination.
 
My -9 started life with an O-290d2 of 140 hp for takeoff and 135 hp continuous.

That is the perfect engine for the -9. Plenty of power and very light. After a prop strike, I replaced it wittan O-360 and a two bladed Catto cruise prop.

I think the only way you could exceed Vne in level flight is if you were flying at 5 feet MSL. AT 8,000' DA it will cruise right at 175 knots TAS, five less than Vne. When you point the nose down, you do have to throttle back. I never fly it that fast as that 360 gets really thirsty at 75% power. My typical cruise is 155 to 160 knots at around 7.2 GPH.

The 320 is an engine for a four place Cessna 172. It is plenty of power for a -9.

I went with the O-360 because at the time there was only $500 difference in price between it and an O-320. I also ordered tappered cylinders, lightweight starter, and dual P-mags. With a Catto prop I'm lighter than an O-320 with a fixed pitched metal prop.

I took a close look at the 340 but decided I would rather have a "common" engine as I was worried about future parts availability.
 
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My Bad

I apologize, Bill you are correct. The published Vne for the RV-9 is more like 207 MPH. However, my personal Vne is 180 MPH TAS, and here is why.

If you look at the V-N diagram for the RV-9 the ?envelope? get kind of thin above 180 MPH (the RV-9 is not aerobatic). So, in my humble opinion, unless you can guarantee my smooth air, I draw the line, for me, at 180 MPH.

Bill, I also realize you know all this, but all RV-9 pilots that fly with a 180HP or greater engine or are considering flying with 180HP plus, need to carefully consider this.

There is an article that does a much better job than I can do of describing this. Google ?Flying High and Fast by Ken Krueger?

Also, I would not recommend having this conversation with Mr. VanGrunsven.
 
Also, I would not recommend having this conversation with Mr. VanGrunsven.

Heh heh.... funny you should say that - I had that exact specific conversation with him at the beer social in Oshkosh this past summer. He just asked if I watched it on descent, to which I replied "Of course, as any pilot should", and he nodded his head and said "OK!"

opD.jpg
 
Heh heh.... funny you should say that - I had that exact specific conversation with him at the beer social in Oshkosh this past summer. He just asked if I watched it on descent, to which I replied "Of course, as any pilot should", and he nodded his head and said "OK!"

...

I had a similar conversation with him. Great guy, he is.

Personal limitations are just that, personal. An O-320 powered -9, with some simple aerodynamic cleanup could probably run circles around an 360 powered -9.

If someone is worried about turbulence, they should probably slow to Va or below. The -9 has proven itself to be an amazingly strong aircraft.
 
Love my IO360 with a catto 3 blade. I usually run LOP at or above 8500 and use 7.5ish at 155 knots. Only need to really watch Vne on descent.
 
RV9a-IO360

I have been flying a 9a equipped with a 360 since 2006. Started out with an 0360/180 with a Catto 3 blade and over the years have converted to an AFP FI system and a WW 200RV composite CS propeller. It is a really sweet combination and works well out of my 5200 ft elevation base airport.

My typical cruise is 2350 to 2400 rpm, WOT, and LOP at 7.8 to 8.0 gph which gives me 63 to 65% power. The cruise speed is impressive as are the take offs with that incredible 9 wing.

Keep a 9 clean, light, and pay close attention to perfect rigging and either the 180 or 160 hp engines will leave you with a big smile--and go high--that wing absolutely loves 12 to 15k ft.

Cheers,

db
 
Only need to really watch Vne on descent.

It is these type of comments that make those that know, take pause.

Vne has little to do with the reason that a 160 HP engine is the largest recommended for an RV-9.

It is Vno (otherwise known as the top of the green arc on the ASI).

Any flight above that indicated speed is risking exceeding the max gust loading that the wing can endure. The higher you are above that speed.... the higher the risk.
AN RV-9(A) with more than 160 HP can easily exceed Vno in level flight at lower altitudes. Even more so in a decent, even at higher altitudes.
 
The question for Van's is, are there any structural design reasons for not recommending engines over 160 HP? Because the RV-9s have the same Vno and Vne as the RV-6s, and Van's recommends up to and including 180 HP for the RV-6s.

Yes, same speeds but the RV-9 is designed for utility category limit loads and the rest are designed for aerobatic limit loads.
 
But that really doesn't matter if Vno and Vne are obeyed. So I take it that as long as Vno and Vne are obeyed, there are no structural design reasons that preclude the RV-9s from handling the 180 HP engines.

Correct

Regardless of engine power, the pilot must ensure that he/she does not exceed the design speeds at all altitudes.

I agree and I don't think anyone would dispute that. The problem is that there is often a misunderstanding of what design speeds should be obeyed, and how they impact they way the airplane is operated.

It only takes a little time reading through past forum threads to see this.

But I understand Van's concerns that with the higher power, it is easier for a pilot to inadvertently exceed those airspeed limits, with possibly bad outcomes.

Especially if they have a lack of understanding of what all of the limits are or what they mean.
 
I didn?t mean to cause a stink on the forum by introducing science/safety into the discussion. However, I wanted anyone who is considering a 360 with 180HP in their RV-9 to fully understand what they are doing. I am assuming all of us that are flying a 180HP RV-9 have been through this thought process and already know all this.

If you are still a little murky on the subject, please search ?Flying High and Fast by Ken Kruger? and spend as much time as is necessary to fully understand where the concerns of 180HP in an RV-9 exist. If you don?t fully understand find a friend to help you.

And?thanks for the great discussion.

It?s a jungle out there, let?s be safe.
 
Interesting

Stop dreaming and put in an IO-360, fixed pitch Sensenich 72 x 85. It wil cruise at 155 kts, 8.5gal/hr at 10.5 alt. LOP at same altitude 7.2 at 143 kts and no wind, Mr. Dynon will says 27.2 kts/gal. Less than 10 kts of wind, that's how I lean, 27 kts/gal plus or minus. Dan from Reno

These are interesting numbers.
I would have thought you'd see much more speed.
It'd be great to get everyone's numbers for comparison.
I have an O-320.
I see (and plan) 152kts, WOT, 8GPH, ROP at 8000.
CHT does seem to run a bit hot though...
 
One thing that I really like about modern EFIS's (EFII?) is that they calculate Vne in TAS while you are flying and let you know as you approach it. As for the Vno, I will have to see if it moves the next time I fly, I really don't recall if it changes but I kind of doubt it will.

Scott is correct in that a 180 hp -9 can run in the yellow without pausing. However, as you climb, it becomes more and more difficult to do so, as pointed out.

If you elect to go with a 360, just watch your speeds.
If you elect to go with a 320, you will still have a great aircraft that runs at the same speeds most of us with 360 run and because in the end, we are more impressed with low fuel burns than high cruse speeds and high fuel burns.

I second the comment about the -9's wing, it is just amazing! (Someday, I would like to hear why that airfoil wasn't used again.)

Back when I had my O-290d2 in my -9, I would fly whit the gang that eventually became Team RV and later Team Aerodynamics. A bunch of us took a 160 NM trip from Charlotte, NC to 12VA (middle Virginia). I took off first and by the time I entered the pattern, the last of the "fast" planes were just touching down. You really have to take a LONG trip for a few extra knots to make much of any difference and even with that little engine, I could easily climb at well over 1400 FPM, if I needed to.
 
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I think you meant "Vne" instead of "Vno".

The pic in Post #29 illustrates that feature (for RV-8s and -7s).

No, the SkyView calculates the Vne based on altitude and temperature. I think the Vno stays the same, but need to verify it. I'll change my post.

Thanks for point that out.
 
I started this thread and was wondering the pros and cons of increasing the compression in my 160 HP 0-320 while I am rebuilding the engine. It most likely is 8.5 compression presently.
george
 
I started this thread and was wondering the pros and cons of increasing the compression in my 160 HP 0-320 while I am rebuilding the engine. It most likely is 8.5 compression presently.
george

You can burn lower grade fuels with that compression if that's an attraction for you.
 
You can burn lower grade fuels with that compression if that's an attraction for you.

Curious as to if the old 7.0 : 1 compression ratio on the 150HP 0-320 could run on regular 87 octane unleaded pump gas or Mogas. Did it originally run on 80 octane Leaded fuel? The lower compression would seem to be a much lower stressed engine, on all components.
 
Curious as to if the old 7.0 : 1 compression ratio on the 150HP 0-320 could run on regular 87 octane unleaded pump gas or Mogas. Did it originally run on 80 octane Leaded fuel? The lower compression would seem to be a much lower stressed engine, on all components.



We have a 1969 C-172 with the O-320 E2D. It's STC'd to run 87 mogas.
 
O-320 E2D Mogas concerns

My 9a has the O-320 E2D rated 80/87 Mogas. The engine runs great on the Mogas until it doesn't. The issue seems to be the vapor pressure of the Mogas and temperatures in the engine compartment. Make special considerations for your fuel system especially at the carb. The crossover design of the exhaust saturates the carb with heat creating good conditions for boiling fuel in the carb bowl especially in the winter when the Mogas is formulated with a higher vapor pressure (lower boiling point). Once boiling, the float goes to the bottom and flooding of the engine occurs. This happened again to me on a warm winter day ealier this winter. The engine quit me at 11,500 msl when I ran the Mogas. The Avgas was turned back on and all was well again. We unloaded the Mogas and put it in my friends Super Cub that has the same engine but different cowl set up. The engine ran fine throughout takeoff, cruise, and landing in the Super Cub.

So, as many others have pointed out, make great consideration of how you will keep the fuel system and carb cool if you are going to use Mogas with this engine.
 
I didn?t mean to cause a stink on the forum by introducing science/safety into the discussion. However, I wanted anyone who is considering a 360 with 180HP in their RV-9 to fully understand what they are doing. I am assuming all of us that are flying a 180HP RV-9 have been through this thought process and already know all this.

If you are still a little murky on the subject, please search ?Flying High and Fast by Ken Kruger? and spend as much time as is necessary to fully understand where the concerns of 180HP in an RV-9 exist. If you don?t fully understand find a friend to help you.

And?thanks for the great discussion.

It?s a jungle out there, let?s be safe.

Here...... https://vansaircraft.com/wp-content/uploads/2019/01/hp_limts.pdf
 
@pilotjohns I have an O-360, 180 hp, in my RV-9A with a Cato 3 blade fixed pitch prop. Mine gives a WOT TAS in level flight of about 185 mph. That?s way below Vne. Whatever the risk of an O-360 might be, exceeding Vne in level flight isn?t it.
At higher altitudes, available power drops so much that TAS is still limited.

There are some considerable advantages of a 360, such as better rate of climb, shorter takeoff roll, cruise at lower % rated power, etc. I?ve never observed any downside to an O-360 in my RV-9A nor have heard of any from others with an O-360. Of course any plane can exceed Vne- - just push the stick forward.
 
At a TAS of 185 at WOT, my IAS is well below Vno, which is 180 = the end of the green arc on my ASI. This is at around 8000?. At that speed and altitude, I?m indicating in the 160s (mph). Vno is an indicated airspeed. So I there is no problem with Vno either, at least not with my plane. Perhaps a constant speed prop makes a difference. Or my engine is underperforming. Maybe at higher altitudes it works out differently, but so far I haven?t seen it. It should be pretty simple: don?t exceed Vno in anything but calm air and don?t exceed Vne anytime. Whatever the risks of a 360, if any, the advantages are considerable: better short field performance, higher rate of climb, cruise at lower % rated power (less stress on engine), higher ceiling.
 
At a TAS of 185 at WOT, my IAS is well below Vno, which is 180 = the end of the green arc on my ASI. This is at around 8000?. At that speed and altitude, I?m indicating in the 160s (mph). Vno is an indicated airspeed. So I there is no problem with Vno either, at least not with my plane. Perhaps a constant speed prop makes a difference. Or my engine is underperforming. Maybe at higher altitudes it works out differently, but so far I haven?t seen it. It should be pretty simple: don?t exceed Vno in anything but calm air and don?t exceed Vne anytime. Whatever the risks of a 360, if any, the advantages are considerable: better short field performance, higher rate of climb, cruise at lower % rated power (less stress on engine), higher ceiling.

John,
This post is not made with the intent to pick at you personally, just to reemphasize the reason that the RV-9 has a maximum recommended engine HP of 160, and hopefully get more people like you to gain a proper understanding.

By your own admission, you were unaware that the engineering decision to limit HP to 160 was made primarily based on the Vno, limitation. That is not unusual. There are numerous long term RV-9 owners here in the forums that still mention only Vne when the max HP conversation gets revived.

Point being, that until this point, it sounds like you assumed you were fine as long as you are below Vne. That is not necessarily the case.

You mentioned that as long as you are below Vne, you are always below Vno IAS. This will probably be the case at higher altitudes like the 8000 ft example you gave, but a lot of the time not the case at lower altitudes. Down low, the actual IAS and TAS values start to converge and it is very possible to be operating in straight and level cruise within the yellow arc range (above Vno).

Your point about not operating above Vno in anything but smooth air is a good one, but in reality it is not realistic. Turbulance is not like speed bumps on a road. You can't see it ahead of time. It only takes one single acceleration event to overload the airplane.

The worst turbulence bump I have ever experience in 27 years of flying RV's was when my wife and I were over central TX headed west in our RV-6A, back towards PHX from S&F many years ago.
We had been in glassy smooth air for at least an hour. With zero warning we hit a bump that caused a major positive and then negative high G load event that put both out heads on the canopy (yes our belts were tight... no, the airplane didn't have 5th point crotch straps), and caused momentary loss of control. It immediately went back to glassy smooth for another hour. This whole event was over in less than 5 seconds.

I have always felt that it was probably caused by wake turbulence from a large aircraft that had crossed our path during climb from Dallas/ Fort Worth.

So to come full circle on the discussion.....
The largest recommended engine for the RV-9 was chosen because it is a high performance airplane (though many don't think of it that way since it is more at the bottom of the performance line up in RV models), and if higher HP is used, the typical pilot will probably at times be operating within a regime that is causing a reduction in safety ( this is in large part because a lot of pilots have experience in airplanes that would not come anywhere close to cruising in the yellow range regardless of what altitude they were flying).

In a nut shell.... Yes, if pilots properly control the speed (to do that they need to actually know what the limitations are) of their RV-9, then it doesn't really matter what engine is in it.
The scary thing though, (and these repeated discussions in the forums show it time and again) is that the majority of people (even those that have been flying big engine RV-9's for years and exclaiming things like "it hasn't fallen out of the sky yet"), don't have a full understanding of what the actual design limitations are.

If anything good could come out of these higher HP discussions, it would be that more people get educated on what the limiting factors are that people need to keep in mind, and possibly work to spread the word to others that don't know. Especially when they hear someone telling others that "as long as they keep it under Vne, they will be fine".
 
I tend to get into the weeds in technical discussions. You motivated me to read the Kruger article again.
Let me discuss it as I understand the article.

Here’s what appears on page 1 of the article “Flying High and Fast”.

“No, the real problem is not mechanical. The real danger is exceeding the Never Exceed Speed, noted as Vne.” So far, no mention of Vno, but will come back to that.

Yes, at extreme altitudes TAS will become very high with sufficiently high IAS. The example he gave was with a turbonormalized engine, which is very unlike what we are discussing. A normally aspirated engine dramatically loses power with altitude. Because of this, my 360 does not exceed Vne, or even come close, in level flight at any altitude that I have flown. In any case, my EFIS computes and displays TAS. So IMO, exceeding Vne is not in the cards, (except in a dive.)
Now, maybe my engine underperforms (carbureted, fixed pitch prop) and others can go faster. But my own experience doesn’t support the possibility of exceeding Vne in level flight.

About Vno. That is the upper limit of the green arc (or the lower limit of the yellow arc). It’s generally understood to mean only go above that limit when in smooth air. Is that a guarantee of no high loads from unexpected gusts like what you described ? No. Flying in the yellow arc is a matter of judgement and the assumption of risk. However that limit was defined for the RV-9 Just like it was for any other standard category plane. (I have experienced sudden gusts like you described, so caution is advisable). There is no reason to regard that limit as defined differently from other aircraft. For the RV-9 its 180 mph IAS. One should give due caution to that limit as one would with any other plane.

I suspect this hp limit on RV-9s was motivated by Vans fearing that RV pilots would think RV-6 and 7 performance was to be expected or considered safe in the RV-9. No, that wouldn’t be a good idea. It is not stressed for acrobatics, and has lower load limits.
 
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What engine?

I purchased a used O-320 engine with no logs. Completely torn apart, checked out and rebuilt, about $12g?s total. Added dual PMags and Catto 3 blade prop. This plane jumps off the ground at my (sea level) altitude. I flew in the Repucci aircraft back when it had the O-290 - also VERY impressive performance. I am, like a few others? in that I want flying to be fun. The RV-9 can hit Vne really quickly by just pointing the nose down so engine size is really not a factor unless flying from higher elevations. I usually cruise at around 125 - 130 MPH, sipping gas. Bottom line, the choice is your, get what YOU want.
 
I tend to get into the weeds in technical discussions. You motivated me to read the Kruger article again.
Let me discuss it as I understand the article.

Here’s what appears on page 1 of the article “Flying High and Fast”.

“No, the real problem is not mechanical. The real danger is exceeding the Never Exceed Speed, noted as Vne.” So far, no mention of Vno, but will come back to that.

Yes, at extreme altitudes TAS will become very high with sufficiently high IAS. The example he gave was with a turbonormalized engine, which is very unlike what we are discussing. A normally aspirated engine dramatically loses power with altitude. Because of this, my 360 does not exceed Vne, or even come close, in level flight at any altitude that I have flown. In any case, my EFIS computes and displays TAS. So IMO, exceeding Vne is not in the cards, (except in a dive.)
Now, maybe my engine underperforms (carbureted, fixed pitch prop) and others can go faster. But my own experience doesn’t support the possibility of exceeding Vne in level flight.

About Vno. That is the upper limit of the green arc (or the lower limit of the yellow arc). It’s generally understood to mean only go above that limit when in smooth air. Is that a guarantee of no high loads from unexpected gusts like what you described ? No. Flying in the yellow arc is a matter of judgement and the assumption of risk. However that limit was defined for the RV-9 Just like it was for any other standard category plane. (I have experienced sudden gusts like you described, so caution is advisable). There is no reason to regard that limit as defined differently from other aircraft. For the RV-9 its 180 mph IAS. One should give due caution to that limit as one would with any other plane.

I suspect this hp limit on RV-9s was motivated by Vans fearing that RV pilots would think RV-6 and 7 performance was to be expected or considered safe in the RV-9. No, that wouldn’t be a good idea. It is not stressed for acrobatics, and has lower load limits.

John,
The article was written as applicable to all RV models so it does apply to the RV-9 as well, but don't confuse that article with being the reason for the 160 HP recommendation for the RV-9.

The RV-9 is a slightly different breed of RV and has a lower max. HP limit than the other models for a different reason. I think I have now thoroughly explained the reason.
As you mentioned, Vno should be obeyed while flying any aircraft, to which I agree, but having been present and participated in the static load testing of the RV-9 wing and other major air-frame components, and having direct knowledge of many of its design details, I can stand behind my explanation of why there is a smaller engine recommendation specifically for the RV-9.
 
Surprised, other than the cost, no one talks about running a turbocharged motor at elevations above 10,000, in a RV-9.

No talk about ever running a Rotax 915 IS rated at 141 HP, and it's not losing HP at those elevations.

True, your climb rates won't be as good at lower elevations, but probably past 8000 feet and above, where the RV-9 wing does so well, it's still making good power, where a normally aspirated engine isn't. And it's pretty much FADEC capable. Fuel injection.

And to add some blasphemy, the engine is not a design from 1951 or 1953 when 320's and 360's first came out? Fresh design with current technology, manufacturing techniques and metallurgy. Car engine design, snowmobile engine design, jet ski design and other gasoline powered toys have not stood still. Any fresh new designs out of Lycoming lately? Just asking, for a friend. Wink.

Thoughts?

Sorry I am so simple minded... but if you want a o-360, why don't you build or buy something designed for it, a RV-6 or RV-7? Making something capable of doing something it was never designed for, is lost on me. Get the right tool for the flying mission.
 
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