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View Poll Results: Opinion -- Which large displacement engine is best for a -7?
IO-390 (Any variation) 0 0%
XP-400 1 5.26%
IO-382 (Wildcat and similar variants) 1 5.26%
IO-375 1 5.26%
None. Just stick with a IO-360. 17 89.47%
Multiple Choice Poll. Voters: 19. You may not vote on this poll

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  #1  
Old 08-13-2017, 06:31 PM
CubedRoot's Avatar
CubedRoot CubedRoot is offline
 
Join Date: Sep 2013
Location: Ooltewah, TN.
Posts: 433
Default PIREPS on RV-7's with IO-390, XP-400, or any large engine

Hey all,
I've been reading a bit on engines, and even though I am a LONG way from needing one, I still find it amazing just how in the last few years the engine options available to RV's has increased with so much "goodness".

I have been tossing the idea around of installing an IO-390 into my RV-7, especially considering that Cirrus will begin using them in their aircraft, which means parts and pricing should turn more favorable in the future.

HOWEVER... I have also been looking at the IO-382, XP-400, IO-375 and all the other variants. There are numerous threads sprinkled on the forums from a few years ago with guys building with these engines, but I was hoping we could get some conversation going on these larger engines (larger than the typical IO-360 that people use) in RV-7's.

For the folks that have built with these large engines, can you please post some performance numbers? Stuff like weights, full power performance, economical cruise performance, climbs, etc.

It would also be great to outline any "gotchas" that you came across with building these larger engines in your -7. Things like firewall forward kit issues, exhaust and cooling challenges, custom work you had to do, etc.

I'll even put a poll up on this thread to get the convesation going.
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RV-7 Slider -
Tail kit Completed - March 2017
Wing Kit Started - June 2017
My Build Log: http://www.theskunkwerx.com

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  #2  
Old 08-13-2017, 11:02 PM
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schristo@mac.com schristo@mac.com is offline
 
Join Date: Sep 2007
Location: WA
Posts: 925
Default Great engine in a -7

The 390 has been a great engine choice. Very glad that I did it
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RV7 powered by a lycoming thunderbolt IO-390
turning a whirlwind HRT prop

flying with more than 1,650 on the hobbs
Race 771
margarita!
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  #3  
Old 08-13-2017, 11:40 PM
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CubedRoot CubedRoot is offline
 
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Default

Quote:
Originally Posted by schristo@mac.com View Post
The 390 has been a great engine choice. Very glad that I did it
What kind of performance are you seeing with this engine? Climb, cruise and fuel burn.

Did the extra weight cause you any W&B issues that you had to plan/build around?
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RV-7 Slider -
Tail kit Completed - March 2017
Wing Kit Started - June 2017
My Build Log: http://www.theskunkwerx.com

VAF Donation paid for 2017
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  #4  
Old 08-14-2017, 07:38 AM
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bret bret is offline
 
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When I started building I too was looking at all that cool high HP engine stuff, then when the airframe was done, the 90% done thing, the real costs started to add up, I wanted a full Dynon suite so that took a big chunk of change, came across a used 200 HP lyc and Hartz prop and saved about 30K.
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  #5  
Old 08-14-2017, 07:54 AM
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jcarne jcarne is offline
 
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Location: Worland, Wyoming
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To echo what Bret said, I know I am going to really have a hard time spending another 6k or more on an engine which is why I have already decided to go with the cheaper IO-360 from Van's. Not to mention that package discount. I have also never heard anyone complain about having 180hp in a -7. I don't plan on getting crazy with acro either.
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  #6  
Old 08-14-2017, 11:15 AM
WA85 WA85 is offline
 
Join Date: Apr 2010
Location: Madison, AL
Posts: 103
Default Weight is your enemy

Weight is your enemy on any RV. Big engine and prop equal high empty weight, which is a constant....which will give you transient performance over a small percentage of your normal flight envelope (take off, climb, vertical maneuvers). Keep it light and simple. Heavy RVs fly like SkyHawks...well may be Hawk XPs....
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  #7  
Old 08-14-2017, 11:48 AM
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schristo@mac.com schristo@mac.com is offline
 
Join Date: Sep 2007
Location: WA
Posts: 925
Default Light is great... watch the CG though

Light is great, horsepower is great

Note that the CG of the -7 was designed to accept an angle valve 360 with a metal constant speed prop. As you lighten the nose up the tail gets heavier... too much and you become restricted on baggage loading. A heavy tail is less fun.

The 390 is only a few pounds more than an angle valve 360 and if you go with a composite prop the combination weighs less than the target design weight.

Without the smoke and oxygen tanks, my empty weight is right at 1100 with 64 on the tail.
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RV7 powered by a lycoming thunderbolt IO-390
turning a whirlwind HRT prop

flying with more than 1,650 on the hobbs
Race 771
margarita!
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  #8  
Old 08-14-2017, 11:49 AM
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Raymo Raymo is offline
 
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Location: Richmond Hill, GA (KLHW)
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A fuel injected Superior parallel valve O-360 with EI and cold air sump probably puts out around 190-195 HP. Send it off to Lycon and get it ported, polished and cryo treated (see the Sept issue of Kit Planes).
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RV-7A - Slider - N495KL - First flt 27 Jan 17
O-360-A4M w/ AFP FM-150 FI, 1 PMag, Vetterman Trombone Exh, SkyTech starter,
PlanePower Alt, Catto 3 blade NLE, FlightLines Interior, James cowl & plenum
All lines by TSFlightLines (AKA Hoser)
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"The object of the game, gentlemen, is not to cheat death: the object is not to let him play."
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  #9  
Old 08-15-2017, 07:48 AM
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bret bret is offline
 
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Are there any before and after dyno reports of a cold air adding this much HP? I understand more dense air being able to burn more fuel and adding HP, but I thought I remember reading a thread here stating that the air does not have enough time to collect the heat from the sump as it passes through? any thoughts?
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  #10  
Old 08-15-2017, 08:26 AM
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Raymo Raymo is offline
 
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Quote:
Originally Posted by bret View Post
Are there any before and after dyno reports of a cold air adding this much HP? I understand more dense air being able to burn more fuel and adding HP, but I thought I remember reading a thread here stating that the air does not have enough time to collect the heat from the sump as it passes through? any thoughts?
Clint at Vetterman and Mahlon both said they saw a 7 HP increase. Not from colder air but from more volume, less restriction and higher pressure at the intake (paraphrasing Clint).
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Ray
RV-7A - Slider - N495KL - First flt 27 Jan 17
O-360-A4M w/ AFP FM-150 FI, 1 PMag, Vetterman Trombone Exh, SkyTech starter,
PlanePower Alt, Catto 3 blade NLE, FlightLines Interior, James cowl & plenum
All lines by TSFlightLines (AKA Hoser)
NSDQ

"The object of the game, gentlemen, is not to cheat death: the object is not to let him play."
Patrick Poteen, Sgt. U.S. Army


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