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  #1  
Old 10-06-2021, 06:12 PM
Sparrowhwk Sparrowhwk is offline
 
Join Date: Mar 2019
Location: Prescott Az
Posts: 45
Default (I)O-320 powered RV4 questions

I understand the recommendation of the 320 motor for lighter weight and that makes sense. But I have questions:
- How does a 320 equipped RV4 handle high density altitudes? (operations at DA of 7000' and up)
- Could a 320 cruise between 10500' - 15000' comfortably? (mountain flying)
- Are IO-320's available? Guessing this is a rare thing or only converted O-320's out there?
- Does the 320 play well with a CS prop, does that prop make a worthwhile difference, particularly for the higher elevation operations?
- Any other performance considerations or limitations with the 320 engines.

Thanks for any input and wisdom about the 320 versions.

Last edited by Sparrowhwk : 10-06-2021 at 06:14 PM.
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  #2  
Old 10-06-2021, 07:17 PM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 4,994
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A number of RV-3s use an IO-320 with a constant speed prop. Van's sells O and IO-320s.

Dave
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  #3  
Old 10-06-2021, 09:43 PM
blaplante blaplante is offline
 
Join Date: Jan 2010
Location: Southern California
Posts: 292
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Well my io-320 RV6A has been flown often at 13,500 msl - which was way more than that in density altitude. No difficulty getting there. Also, fixed pitch. And the 6A is a heavier plane.

I don't know my actual ceiling, but Van's quotes the 160 HP ceiling for the 6A as 20,500'. I do have one electronic (Lightspeed) ignition, so I'm probably making a few HP more than standard especially at high altitude (due to advance at low MP).

In my case I retrofitted the injection (Bendix RSA-5) to the O-320 (h2ad).
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  #4  
Old 10-07-2021, 04:32 AM
fixnflyguy fixnflyguy is offline
 
Join Date: Jan 2006
Location: Winston-Salem, N.C.
Posts: 1,448
Default My RV-4 O320 does fine

While mine isn't an IO, I have a carbureted O-320H2AD,fixed Sterba toothpick in my -4 and regularly cruise at 10-11K , although I am not in the big mountains (ours are 5K high hills). I like smooth cool air. It gets there quick and easy, even with PAX, and purrs right along. The only thing keeping from going higher is O2(lack of).
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8A7 / Advance NC
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  #5  
Old 10-07-2021, 06:11 AM
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YellerDaisy YellerDaisy is offline
 
Join Date: May 2012
Location: Mountain Southwest
Posts: 190
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To the OP, I'd say 'well' and 'yes' to your first two questions but everything is relative. Better answers might be possible if you could describe your mission and what types of aircraft you are currently flying. I don't know the answer to your other questions.

I have a 160hp O-0320 RV-4, I live in the mountains, and am always flying in the mountains. Home base elevation is 5,000' MSL and I typically operate from airstrips that are 7,500' MSL and higher at density altitudes up to about 12,000' DA during the summer. Prior to January 1, 2020 (ADS-B) I frequently cruised at 12,500' and occasionally higher. Haven't done that since that date unless getting over ridges. The only reason I go that high is for favorable wind on a long cross country. I'm usually MUCH closer to the ground as I love seeing the details of the terrain.

In my opinion and within limits, mountain operation is more about the pilot than the airplane. A 160hp RV-4 is VERY capable but still has its limits. In the mountains, more power is ALWAYS a good thing. The ability to fly slow and maneuver is also a good thing. You can very comfortably cruise around those tight valley's at 70KIAS. The RV-4 slow speed maneuverability is pretty tough to beat and you get incredible visibility to boot. However; airplanes are a compromise. A friend with a Carbon Cub has more fun in the backcountry (able to land at more of the airstrips (short/rough)) than I can but it's six hours for me to get from New Mexico to Johnson Creek, Idaho. It's two days for him. Compromise. If you plan to haul two large people and a ton of camping gear into the backcountry, the RV-4 is not the best airplane. I do pretty well with one (large) person and 'sufficient' camping gear.

Here are a few videos of my RV-4 operating in the mountains. Not sure if they'll help but might give you some insight. Feel free to poke around on my YouTube channel (https://www.youtube.com/channel/UCrY...8piboPjsIuVkA/) as there are takeoff/landing videos of a bunch of backcountry airstrips (Thomas Creek, Upper Loon, Negrito, etc.).

Landing/Takeoff at Big Creek: https://youtu.be/hxBSY4tWHlo
Approach and landing at Johnson Creek: https://youtu.be/xu3XmmIFdLI
2019 Backcountry Trip: https://youtu.be/hdQkRgyw4jc
2021 Backcountry Trip: https://youtu.be/Bt6IOlHAQ1g

The thing that these videos do not show is how capable the airplane is climbing up over the 10,000' MSL ridge and then dropping back down into the next valley to land at another airstrip. Excellent performance.

Another of the compromises is the big hershey bar wing. It works great but can be a bit of a bumpy ride when the mountain air is all stirred up and going fast. I have some mountain flying rules of thumb to help avoid that.

A CS prop is far out of my budget but I did install a Sensenich GA. It is VERY easy to change pitch settings (on the ground). When I really need takeoff/climb performance, I change the setting. Certainly not ideal but it works for me - another compromise.

Hope all that helps...
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RV-4 - 160HP O-320 - Sensenich GA
RV-3B - O-320 - "Daisy" (sold)
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  #6  
Old 10-07-2021, 06:29 AM
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YellerDaisy YellerDaisy is offline
 
Join Date: May 2012
Location: Mountain Southwest
Posts: 190
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Oh... also... I'm not sure of the reason for the IO-320 question but suspect it may be related to running LOP.

Here's a photo of my O-320 (carb) running LOP. I fly LOP on nearly all cross countries (about 2520rpm, 6gph, and 150kts -ish). It required a fair amount of tweaking/tuning and attention to detail.

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RV-4 - 160HP O-320 - Sensenich GA
RV-3B - O-320 - "Daisy" (sold)
http://jdfinley.com
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  #7  
Old 10-07-2021, 06:56 AM
Robert Sailor Robert Sailor is offline
 
Join Date: Nov 2018
Location: Nanaimo BC Canada
Posts: 107
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We have an RV6A with an IO-320 with electronic ignition and constant speed prop. Live on the coast in BC so at least half of our flying is in the mountains. I've owned 5 Mooney's, 2 Bonanzas, 2 Cessna 210's and a Bellanca Super Viking. The RV is in the same league and will out perform several of these aircraft in mountain flying all the while sipping fuel.
We can count on 163-165;knots true between 10 and 12000 feet. Lean of peak is drop dead easy and perfectly smooth..Very happy with this little bug smasher
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  #8  
Old 10-07-2021, 07:01 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 6,538
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I have 6, so very similar but a bit heavier I think and more drag. My 320 (160 HP) has been to 13,500 and climb was still around 250. I am guessing 15 or 16 would be near the limit (patience not necessarily absolute). I have a climb oriented FP prop. A CS may help a bit. I have taken off from Denver numerous times without issue. Suspect I would need/want 4000' or more.

If one of my goals was crossing the rockies on a regular basis, I would want more power. Otherwise, I don't regret the 320 decision.

Larry
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  #9  
Old 10-07-2021, 09:21 AM
Sparrowhwk Sparrowhwk is offline
 
Join Date: Mar 2019
Location: Prescott Az
Posts: 45
Default Thanks

Thank you to everyone for your replies, much appreciated.
To expand a little on the reasons behind the questions: I would prefer the IO engine for aerobatic flying (LOP would be a bonus). I'd prefer the CS prop for the improved performance in all phases.
The mission would be mostly fun flying within about 2 hours, with the occasional longer cross-country. Home base in the Southwest at 5000' elevation with higher hills and high summer temperatures (DA regularly well over 7000'), but decent length runways (4500' & 7500'). Not currently interested in super-cub type back country stuff.

I am researching this as an alternate to the RV-8, simply due to the crazy price hikes of the past 2 years, I may be priced out of the -8 market. (Purchasing, not building). Fortunately I'm small enough to fit the RV-4 as is my partner.

Thanks again for the help.

Last edited by Sparrowhwk : 10-07-2021 at 10:59 AM.
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  #10  
Old 10-07-2021, 10:40 AM
Robert Sailor Robert Sailor is offline
 
Join Date: Nov 2018
Location: Nanaimo BC Canada
Posts: 107
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I know a fellow that sold his 8 after doing aerobatics in a friends 4 and bought a 4 so depending on your use, it may not be much of a step down.
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