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  #1  
Old 07-19-2009, 09:03 PM
Imback_again Imback_again is offline
 
Join Date: Jul 2009
Location: Prosper, Texas
Posts: 40
Default 160hp or 180hp? That is the question.

I am having trouble deciding which to buy. There are several -4's with 160hp but not so many with 180hp. Is there really a big difference? I have flown one with 180hp but not 160hp or even 150hp. What do you guys think? And what about an IO-360. Does the injected make a big difference?
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  #2  
Old 07-19-2009, 09:11 PM
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frankh frankh is offline
 
Join Date: Jul 2006
Location: Corvallis Oregon
Posts: 3,547
Default Depends

FP or Constant speed?

a 180hp FP will not be making 180hp anyway..Assuming its pitched for a reasonable cruise.

A 320 with with a CS prop will have more climb performance than a 180HP with a FP cruise prop.

The IO makes no difference to performance, it does make a difference to economy (assuming you run LOP)

Perssonally I'd have a 180hp regardless (either fp or CS)..then again I'm greedy.

Note the only difference will be in the climb..cruise will be barely noticable.

Frank
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  #3  
Old 07-20-2009, 01:18 AM
Steve Sampson Steve Sampson is offline
 
Join Date: Aug 2005
Location: N. Yorkshire, England
Posts: 1,050
Default Van designed it around a -150

If you want the handling benefits of a -4 put a 160 in. (Van designed it around a -150) If going fast in a straight line is what you want go for a 180 (or 200). But then why build a -4?

To me its all about weight.
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  #4  
Old 07-20-2009, 06:22 AM
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N941WR N941WR is offline
 
Join Date: Jan 2005
Location: SC
Posts: 12,887
Default

Quote:
Originally Posted by Steve Sampson View Post
(Van designed it around a -150)
Actually, I think the first one had an O-290 of 125 HP (Possibly 135 HP).

Quote:
Originally Posted by Steve Sampson View Post
To me its all about weight.
Ditto!

If you want 180 HP, get an O-320 and send the engine off and have the cylinders ported and polished. Even a light port and polish will bump a 160 HP O-320 close to 180 HP without compromising TBO.
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RV-9 (Yes, it's a dragon tail)
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  #5  
Old 07-20-2009, 06:45 AM
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L.Adamson L.Adamson is offline
 
Join Date: Apr 2005
Location: KSLC
Posts: 4,021
Default

Quote:
Originally Posted by Steve Sampson View Post
If you want the handling benefits of a -4 put a 160 in. (Van designed it around a -150) If going fast in a straight line is what you want go for a 180 (or 200). But then why build a -4?

To me its all about weight.
Happily.................I found ..... It's all about POWER!!!

L.Adamson --- RV6A 180HP/CS
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  #6  
Old 07-20-2009, 09:58 AM
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Bill Wightman Bill Wightman is offline
 
Join Date: Aug 2005
Location: OKC, OK
Posts: 687
Default HP? MORE!

More is better, that's the short answer to the question. But, keeping a 4 light and in balance is also important.

For me, the 180HP O360 was a good starting point. For exactly ZERO weight increase, I had 9:1 pistons installed, got it flowed, added injection, LSE Plasma II ignition, and of course the cross over exhaust.

Dynoed at 205. I stayed FP with the prop for balance purposes, and it was excellent.
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  #7  
Old 07-20-2009, 11:48 AM
N999BT N999BT is offline
 
Join Date: May 2005
Posts: 213
Default 180 for me

I have an O-360 and can't imagine why I would want an O-320. In cruise I throttle back and get 200 mph at 8gph. I have a FP prop, so I give up a little in climb. But still, with bags, fuel and two people it will still have an intitial rate of 1800 - 2000 fpm depending on temperature, and still has 1000 fpm at 14000 msl loaded. (I've done that with ice on the plane).

The only thing is, keep it light. Mine weighs 985.
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  #8  
Old 07-20-2009, 11:51 AM
CuriousGeorge CuriousGeorge is offline
 
Join Date: Jun 2009
Location: Lakeview, ME
Posts: 56
Default

Bill, did you consider a light CS prop like the MT? And what kind of numbers do you get with that power and a FP? Also, empty weight? And who did your engine work?

Enough questions?


George
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  #9  
Old 07-20-2009, 11:54 AM
CuriousGeorge CuriousGeorge is offline
 
Join Date: Jun 2009
Location: Lakeview, ME
Posts: 56
Default

Brent - same question for you... MT prop a consideration? And what power setting gives you a 200 mph cruise?

Thanks --


George
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  #10  
Old 07-20-2009, 01:04 PM
Sid Lambert Sid Lambert is offline
 
Join Date: Jul 2005
Location: North Atlanta
Posts: 1,120
Default

Assuming money is not a factor I would have IO-360 parallel with one Rose EI and a MT constant speed prop. You could cruise at 10k feet with 40 BTDC timing getting some great fuel mileage and still get out of a 1800' grass strip in August with a passenger.

Just the engine and prop would cost you around $35k though. Most RV-4's are going for under $50k now. Not sure that is a sound financial decision (not that any airplane is) since that engine and prop would get you the same if not better performance in an RV-8.

Build what you want to build though.
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