150hp or 160hp for RV-9?

I'm down to the final stages before ordering the engine. Aerosport will be (re)building me an 0-320. The question I have to decide is will it be 150hp or 160hp. Posing this question right now probably seems ironic since another thread is arguing between 160 and 180 for the -9, but here are my thoughts:

1. With the 150 I can use any autofuel, assuming it's ethanol and water free. While I don't intend to use autofuel all the time, the difference right now between avgas and premium is pushing $2 per gallon. At 8 gal/hr, flying autofuel would save me close to $16 per hour when I do choose to use it.

2. I'm not concerned about 10 extra hp for performance purposes. From Van's specs it appears that I would lose no more than 5-8 mph on the top end. Climb should still be somewhere in the 1700-1800 fpm range. Anyone flying with 150hp to confirm these guestimates? (Regardless of hp, I will be going fixed-pitch Catto.)

3. I have no need for the extra hp so that I can keep up with people in formation. I have absolutely zero interest in flying formation. Never say never, I know, but I don't think that will ever be an issue.

4. Generally I agree that more horsepower is better from a safety standpoint. However, with RV's I take a little different perspective. Even flying from the mountain west where density altitude can be an issue, I tend toward the mindset that if you NEED more power in an RV, you probably should not have been where you were in the first place. Thus, I don't think not having that extra 10hp would significantly limit where and when I would fly.

5. Future resale value? (Only relevant if I ever decide to build again.) I know buyers of -6s, -7s, -8s seem to like higher horsepower. Not sure if the same is true of the -9. Maybe so, but the ability to run autofuel might offset that.

Anyway, given these thoughts, anybody have any additional thoughts that I should be thinking about. As always, help is appreciated. I'll be spending $15K and will have to live with the decision for as long as I own the plane! Thanks.

I would suggest that you go with wherever you get the best deal. You will see VERY little performance difference between the 150 and 160 hp. Another point, if you go with a "Wide Deck" engine, it is very easy to change from 150 to 160 hp at a later time.
As I have said before, I flew my -6 with a very tired (over 2500 hrs.) 150 hp engine out of Leadville, CO when the DA was over 13,000'. No problem. The -9 should do even better with the longer wing.

same initial outlay... get most for your money hehe.. can't 160hp burn mogas?

Radomir said:

same initial outlay... get most for your money hehe.. can't 160hp burn mogas?

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What I understand (and I could be very wrong), is that while the 150hp variants can use any grade autofuel, only some variants of the 160hp can use autofuel and then only premium (high octaine) can be used. If anyone can clarify or correct this, that would be appreciated.

I used regular auto fuel mixed with less than 1/2 100 LL in my 160 hp 0-320, and got detonation on take off. I recognized what was going on and reduced manifold pressure till the engine smoothed out. It was not a happy situation because I had a heavy passenger aboard. When I got back home, I drained the fuel and put it in our Cessna 120. I'll never put regular auto fuel in my RV-6 again. Premium auto fuel works fine.

160 and autogas

I bought an O-320 160 hp off a hurricane Charlie'd 6A. It had 885 hrs TTSN and the owner said he had never used anything except premium auto fuel. I have 70 hours on the engine and have used nothing except 100LL. The engine was very clean when I bought it and had excellent compressions and oil consumption, and it still does. Only difference I can see is that the plugs are dirtier than when I bought it (I have cleaned them twice now.) I believe premium autogas will work in a 160, although here there is little difference in price. Actually, premium was HIGHER than 100LL about 2 months ago. 100LL is $3.86 here now and was $3.68 then, however, and autogas is dropping in price.

Bob Kelly

with a wide bore- cheap upgrade down the road...

I like Mels approach- if fuel cost is your primary concern, get the wide bore 150hp. If you are unsatisfied- you can change out pistons get the higher HP for a slight financial penalty versus having to install a new engine.

My RV7 (bought flying)- he used high test auto from birth. The engine is a 160hp O-320-E2A.

My plans are to use 100LL in the right tank for take offs and landings and high test Auto in the left for cruise. I can always mix the auto with 100ll in the left tank if I need to or run into a good price of Avgas.

PS- there's about a $1 delta between regular auto and the best price Avgas. There's only a $0.69 delta from high test to Avgas. Filling up 20 gal at a time (4-5gal jerry cans hauled in the back of the truck from the local gas station to the airplane) saves approx. $14

That's between 2-2.5 hrs of flying or $6-7 per hour savings.

I was thinking of buying a 50gal transfer tank with pump motor. That's about $300. At a $1/gal savings=300 gals= 37.5hrs of flight= 6,187 miles of flight to recover the cost of the transfer tank. That means if I fly 100hrs a year; I'll spend the first 4 months paying for the transfer tank. Recoup my investment in 4 months- not bad. That means by the end of year one I'll save $500 in fuel costs. That estimate diminishes when you consider you won't always be landing at your home field of course.

I was looking at 150 hp also, until Bart told me I can use premium mogas in the 160 hp after break-in with 100LL is complete.

150hp does not run well on 100LL

The 150HP version is designed for 87 octane and tends to foul plugs and stick valves when run on a strict diet of 100LL. Every 25 hours you'll be digging chunks of lead out of your spark plugs. And be darn sure you either use the Lycoming oil additive, or run Aeroshell 100W, Aeroshell 15/150 or Exxon Elite (which you ought to do anyway). You'll also be required to change your oil at least every 25 hours to remove the lead that the engine is not capable of disposing of. How do I know? My first plane was a Cherokee 140.

If you really want to mess with hauling car gas to the airport, the 160HP engine works fine on 93 octane, and it'll give you a little more power.

1967 Cessna 172 same way...

I was part owner (until recently) in a 1956 Cessna 172 that was exactly the same way. It was STC'd for mogas 80 octane. We put the lowest octant we could find. It was GREAT in March because gas was below $2/gal.

It was also fouling with 100ll.

Any issues with the 160hp lycomings fouling form 100ll??

No fouling with EI

I have a 160 HP O-320. With Elect Ignition and aggressive leaning, the plugs stay very clean.

The Continental 0-300 is like a 0-200 with six cylinders. I have thousands of hours behind the four cylinder Continentals. They don't like a straight diet of 100LL. I've had sticking exhaust valves and lead fouled spark plugs several times. I've gone to almost exclusively running auto fuel in the small Continentals. I mix a little Marvel Mystery Oil in. When I need fuel away from home I use 100LL. What I'm doing has worked very well.
The 160 hp 0-320 in my RV-6 runs very clean on 100LL.

I've heard from many the problems with small Continentals running 100LL. However, with around 450 hours (3 airplanes) running C90's and an O300 I've never experienced it. I always ran 100LL exclusively, but added a little MMO and leaned at all times.

I rebuilt a 320 for my 9A and kept the lower compression pistons to extend engine life and fuel options. The Dallas area now has ethanol in autogas, which I refuse to tank, so I am burning 100LL. Proper leaning during taxi as well as flight has left the plugs reasonably clean. Performance with the 150 matches Van's specs- spectacular

Alcohol is required in gas in Dallas, Tarrant, and all adjoining counties. Beyond that you can find non-gasohol.

Mel said:

Alcohol is required in gas in Dallas, Tarrant, and all adjoining counties. Beyond that you can find non-gasohol.

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Last time I checked The Exxon just south of Eagles Nest (Walnut Grove and 287 in Ellis Co.) has no alcohol added.

I have the 160 in my tripacer and would prefer the 150 for the cheaper gas.
I live in the west where the most important advantage for horses is altitude.
I keep a mix of auto and 100ll in my plane and it flies very well. I'm sure it would do well in a 150 with 87 octane, as well.

For resale, the MOGAS option is going to be huge, and getting bigger.

mogas

had pa-28 with 150 hp 320 Ran mogas (80 oct) only, no problems but, used alum fuel tank with filter and h2o seperator for fueling, checked for water always, and tried to buy from busy shell station. 1400 hrs and never a problem--plugs and oil excellent. sold plane with 2300 hrs still running good

150hp or 160hp for RV-9

Installed a freshily overhauled 150hp O-320-E3D (had to change the pistons to get it back to 150hp).

Burn autofuel (regular) almost exclusively and pay about $2.80 per gallon since I buy it 100 gallons at a time in a tank in the back of my PU. 100LL is $4.53 per gallon on the field - saves me $1.70 per gallon! You do the math at 8.5 gph.......

Burned autofuel exclusively in this exact model engine in a 150hp C150 on floats for over 4 years. When I sold the plane (to buy the RV Kit), the engine had 1750 hours on it and was still running strong. Never any problems.

The engine will run just fine on 100LL IF you watch operations on the ground. Lean it aggressively, almost to the point it shuts down, and you won't have any lead fouling. Just make sure to push the mixture control back in before you take off or it will quit on the runway!

I give up a little in cruise speed but it isn't much. I run 158 K (182 mph) TAS at 8000'. I use a Catto fixed pitch 3-blade composite prop. Van's literature for the 160hp says 185 mph so I'm pretty close to their book values.

I've never regretted the decision to go to 150hp especially lately given the rapid increase in 100LL prices which aren't going to come down!



Keith Southard
N355RV

The use of auto gas in Australia (to someone new to all of this) seems to be very limited. When I mentioned the possibility of using autogas to my instructor he commented that fuel vapour lock, and engine warrenty might be a problem. Any comments!!

I think going with 150 HP as opposed to 160 HP in order to burn the lower price 87 octane vs. 91 octane auto fuel may be false economy. My reasoning is that at a given power setting the 160 HP O-320 will use less fuel to more than offset the higher price of higher octane. At least in my case, since 91 octane car gas is 12 to 20 cents higher than 87 octane (Tulsa, OK). I have a Tripacer that I upgraded from 150 HP pistons to 160 HP and burn easily 1/2 gallon less per hour at same power settings as before. (The engine was originally 160HP and had been derated to 150HP by a previous owner.) In addition to better take off/ climb performance, I have extended my range. Both enhancements add a degree of safety, IMHO. Plus my only fuel option when traveling is typically 100LL. I save about $2/ hour at my standard power settings burning 100LL with the higher compression pistons.

Grant Cassady
RV6 N9HJ (sold)

Steve Moore: I sent you a private message.

hiland said:

I think going with 150 HP as opposed to 160 HP in order to burn the lower price 87 octane vs. 91 octane auto fuel may be false economy. My reasoning is that at a given power setting the 160 HP O-320 will use less fuel to more than offset the higher price of higher octane. At least in my case, since 91 octane car gas is 12 to 20 cents higher than 87 octane (Tulsa, OK).

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The 80 octane 150 engine can burn regular unleaded, the lowest octane stuff you can find, as long as it is higher than 80.

There is more energy in lower octane fuel, this should be a wash, I would think. I could be wrong here, so please correct me.

This also changes the price per hour by $10/hr. (9.6 GPH & $3.75/gallon for 100LL vs. 2.71 for regular unleaded.)

Bill,
I'm making a case for 160 HP over 150 HP O-320. My assumption is that 160 HP engine burning 91 octane autofuel will get more miles per gallon than 150 HP burning 87 octane autofuel if both are flown at settings which produce the same power (everything else being equal). This is a result of the higher efficiency of the 8.5:1 compression ratio vs. 7:1. The 12 to 20 cents savings per gallon of 87 octane autofuel as compared to 91 octane autofuel is lost in the less efficient fuel burn.

So from a purely economic point of view for someone who knows he will never burn anything but autofuel, it would be a toss-up whether to go 150 or 160. However, the enhanced performance and range of the higher compression engine would favor the 160 HP version.

If you are saying that both engines get the same fuel efficiency when burning their corresponding octane autogas, and if you are correct, then my argument on economics to this point is wrong.

Now, there is no doubt that 160 HP (higher compression) O-320 will get a more efficient fuel burn than 150 HP will if they are both burning 100LL. My actual experience supports that. So, if one concedes that many of their fuel purchases will be 100LL out of logistical necessity, then the economic scales would also then tip toward 160 HP. The $2 per hour savings I mentioned is the difference between 150 HP on 100LL and 160HP on 100LL based on my experience with equal power output settings.

From what I now understand, a 160 hp O-320 can burn premium autofuel. I wasn't aware of that when I originally posted the question. I had thought that only the 150 hp variant could burn autofuel. Knowing that, I agree that there's really no reason to go 150 hp over 160 hp since the price difference b/w 87 and premium autofuel isn't very significant.

That said, if I came across a 150hp for a screaming deal, you can bet I wouldn't turn it down. As with Bill Repucci's experience, I have no doubt that 150 would power the RV-9 just fine, even for someone here in the mountain west.

alpinelakespilot2000 said:

That said, if I came across a 150hp for a screaming deal, you can bet I wouldn't turn it down. As with Bill Repucci's experience, I have no doubt that 150 would power the RV-9 just fine, even for someone here in the mountain west.

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The 150 does just fine in the mountain west. I have approx. 40 hrs in a 9A with two people, and many flights out of KBTF (Next to KSLC), right up over the mountains to the east, and ducking below Class B airspace. You'd never feel as though you were in a Cessna or Piper at all; when it came to climb and density altitude.

Note: it has a Hartzell C/S, which is beneficial for the mountainwest too!

L.Adamson RV6A

Aussie 9A said:

The use of auto gas in Australia (to someone new to all of this) seems to be very limited. When I mentioned the possibility of using autogas to my instructor he commented that fuel vapour lock, and engine warrenty might be a problem. Any comments!!

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I agree with your instructor on both points. I believe Superior specifically says autofuel is allowed in their experimental engines as long as the compression ratio is 8.5:1 or lower. For certified airplanes, we can buy STC's to legally burn autofuel for airframe/ engine combinations which have been approved, eventhough Lycoming may not honor their warranty if you choose to use autofuel. Of course, once the warranty period is over, that's a moot point. You do have to be cautious and diligent with autofuel. Since we are building airframes/ engines which have not been subjected to the rigorous testing that is required for the aforementioned STC's, then we are indeed experimenting. Vapor lock is a concern even on certified aircraft with autofuel STC's. I owned a Cherokee 140 with an autofuel STC some years ago and experienced vapor lock. Fortunately, it was only temporary and I was able to descend and land under power. I believe that I made the mistake of taking off on an unusually hot day in April. The gas was probably "winter blend" still.