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  #1  
Old 10-29-2020, 07:31 PM
keith6261 keith6261 is offline
 
Join Date: Sep 2018
Location: sykesville, Md
Posts: 7
Default Engine size Pros and Cons

Guys, I trying to decide what engine size for my 8.
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  #2  
Old 10-30-2020, 01:19 AM
gasman gasman is offline
 
Join Date: Mar 2007
Location: Sonoma County
Posts: 3,849
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Based on Van's latest prices, The O360 is the same price as the O320.

So...... at least get the O360.
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  #3  
Old 10-30-2020, 01:48 AM
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rv8ch rv8ch is online now
 
Join Date: Feb 2005
Location: LSGY
Posts: 3,285
Default Mission?

I guess if we knew more about your "primary" mission it would help. Racing? Aero? Cross Country flying? Assuming you want a "normal" RV-8, get the exact engine/prop Van's recommends and your build and test time will be faster and easier.

Otherwise, anything from an 0-320 to an IO-540 will work, with tradeoffs.
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  #4  
Old 10-30-2020, 06:28 AM
Desert Rat Desert Rat is offline
 
Join Date: Aug 2018
Location: 50-50 Wichita KS & Scottsdale AZ
Posts: 392
Default

I just went through this exercise.

Spent hours online and with the calculator, looking at everything from fuel burn, to expected KTAS, to range profiles, to the price of replacement cylinders, to perceived difficulty of each installation. Carefully reviewed each response to my VAF thread where I asked for opinions.

I finally just said heck with it and bought the Thunderbolt IO390.

Probably can't justify it for my mission, But it's ultimately what I wanted.

Where I'm going with this is that you can ask for internet advice and crunch numbers all day long, but ultimately you have to make a decision you can live with and it may not be the most practical one. Only you can decide.
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Last edited by Desert Rat : 10-30-2020 at 07:03 AM.
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  #5  
Old 10-30-2020, 07:44 AM
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Mel Mel is offline
 
Join Date: Mar 2005
Location: Dallas area
Posts: 10,806
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Desert Rat is exactly right. Unless you have a specific operating purpose, Van's recommended engine is usually the best option. More hp will give you more take-off and climb performance (As if the RV needed this), usually at the cost of money & weight, but very little, if any, cruise speed advantage.

Also, as Desert Rat points out, It's your airplane and it's experimental. If you want something in particular, do it!
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  #6  
Old 10-30-2020, 08:25 AM
PilotjohnS PilotjohnS is offline
 
Join Date: Jan 2016
Location: Southwest
Posts: 1,149
Default Just me

But I chose the injected version of the Lycoming for two reasons: easier lean of peak operation, and no carb icing issues.
It seems the price difference is small. Also, it is amazing how many builders initially fly with a carb engine and than upgrade to fuel injection.
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Last edited by PilotjohnS : 10-30-2020 at 03:18 PM.
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  #7  
Old 10-30-2020, 02:55 PM
abwaldal@gmail.com abwaldal@gmail.com is offline
 
Join Date: Jan 2017
Location: Battle Ground WA
Posts: 51
Default Engine size?

Easy answer. Big as you can afford that the airframe can handle. You can never have enough horses under the hood. Fuel economy is only a small factor. I love the bigger horses and fuel injection is necessary for good life in the air.
I would buy the I0-360 because it will fly and sell faster when the time comes.
Enjoy spending the money cause it is gonna be quite a bit. Art
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  #8  
Old 10-30-2020, 04:47 PM
tjo tjo is offline
 
Join Date: Dec 2009
Location: La Center,wa
Posts: 211
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Just my opinion, of course, but best HP/$ is O360. Injected, if you want. The only reason to go angle valve is to go O390. There is no reason to go O320 unless you find a great deal. Simple formula, direct result

Tim
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  #9  
Old 10-30-2020, 05:10 PM
RYOUNG RYOUNG is offline
 
Join Date: Feb 2010
Location: NC
Posts: 46
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Desert Rat nailed it! I too originally planned an O-360 for my RV-8. Then after Van’s approved the IO-390 for use I was torn. After mulling over pros and cons for about a month, I bounced it off a good friend and his advice was “if you’re going to be a bear, be a grizzly”. That did it, along with the upcoming price increase. Now in the process of swapping out lower cowls with Van’s. Not looking back, full speed ahead. After all, what are friends for?
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  #10  
Old 10-30-2020, 08:35 PM
keith6261 keith6261 is offline
 
Join Date: Sep 2018
Location: sykesville, Md
Posts: 7
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So my mission would be some light aerobatics but mostly cruising. Just wondering what true speeds are seen between an IO360 to a IO390. Thanks for everyone's input.
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