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  #1  
Old 02-23-2008, 10:30 PM
Ned R Ned R is offline
 
Join Date: Dec 2006
Location: North Richland Hills, TX
Posts: 12
Default IO 180 HP vs Carborated 180 HP

I'm in the planning stage for an RV-7A and would like to know pros and cons of the 180 hp injected vs carborated engine. I've heard good things and bad about both depending who I talk to. Just need more information to make my decision for me.
Thank you.
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  #2  
Old 02-23-2008, 11:01 PM
Norman CYYJ Norman CYYJ is offline
 
Join Date: Feb 2005
Location: Victoria B.C.
Posts: 1,266
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Both engines have their pros and cons. You will probably get about as many opinions about which engine to use as you would if you asked should I build a tail wheeled or nose wheel plane, or to prime or not to prime.

Both engines will do a fine job of pulling your bird through the sky. But if were you I would definitely go for a .............engine.
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  #3  
Old 02-23-2008, 11:02 PM
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osxuser osxuser is offline
 
Join Date: Aug 2005
Location: Pasadena CA
Posts: 2,484
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Quote:
Originally Posted by Ned R View Post
I'm in the planning stage for an RV-7A and would like to know pros and cons of the 180 hp injected vs carborated engine. I've heard good things and bad about both depending who I talk to. Just need more information to make my decision for me.
Thank you.
Carb:
Cheaper (for now)
Icing
Less balanced mixture = more fuel burned

FI
No ice
Can run LOP
Fwd facing can get a bit more HP
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  #4  
Old 02-23-2008, 11:45 PM
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Bill Wightman Bill Wightman is offline
 
Join Date: Aug 2005
Location: OKC, OK
Posts: 687
Default I prefer injection...

... for several reasons:

1. Better fuel metering to each cylinder
2. Ability to operate lean of peak, if desired (with flow balanced jugs)
3. Not restricted to updraft induction
4. No induction icing problems
5. Cleaner cowl appearance (no snoot on cowl bottom)
6. More induction system design possiblities (locate the servo on front of sump, for instance)
7. System is not attitude sensitive

Drawbacks to FI

1. More expensive components - servo, fuel pump, flow divider, lines, nozzles, etc.
2. Usually harder to start when hot

Either way will yield a dependable engine, but the main advantage to FI in my opinion is the superior fuel metering.

My old RV4 had a 200HP O360 that was converted to injection. Coupled with flowed cylinders and a Light Speed ignition system that advanced the spark to about 38 degrees at 12500 MSL, I routinely saw fuel flows around 7.2 to 7.3 gph at about 50F lean of peak. The engine was totally smooth across the entire range of mixtures right up to cut-off. I don't think you could approach these numbers with a carbureted engine.
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  #5  
Old 02-24-2008, 02:12 PM
BillSchlatterer BillSchlatterer is offline
 
Join Date: Jan 2005
Location: Arkansas
Posts: 571
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All the points above are correct, but they will apply differently to each of us. I chose CARB because it was simple, this was my first build, and it was a little cheaper. It's almost bulletproof and I was not confident with the FI system. I was very reluctant to go FI based on my exisiting experience level.

After listening to all the pros and cons, I just wanted something that would always work, wasn't picky about fuel, easy to maintain, etc. That just means carb to me because I understand them.

Now after going through the build, installing and wiring the panel and engine, and many hours of list research, ... I would do the FI without question. The problem with building is that your confidence level and personal experience affects some of your choices and both change during the build. Wish I had gone FI but don't regret the carb decision.

Just a little .02 not related to the technical side.

Bill S
7a Ark
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  #6  
Old 02-24-2008, 03:26 PM
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Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,687
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I got a carb and don't regret it a bit. The carb is simple, reliable and easily repaired if needed. I run LOP on every flight so balanced injection is not required for this. I do run dual light speed ignition but also ran LOP with just one LSI. One thing I also like about it is the low pressure fuel system, no high pressure pump in the cockpit (which I never really liked that idea but I know it works ok). And as for ice maybe if you live up north or fly IFR that may be an issue but I've never used carb heat except to check to see if it still works during my annual
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  #7  
Old 02-27-2008, 01:30 AM
Ned R Ned R is offline
 
Join Date: Dec 2006
Location: North Richland Hills, TX
Posts: 12
Default IO 180 HP vs Carborated 180 hp

Thanks gentlemen for you comments. Seems that everyone just about says the same thing. I do plan on flying IFR when I have to, IE: takeoff and landing and any clouds that get in the way going from A to B on some trips, but obviously nothing heavy. Lots of VFR flying too. I really appreciate your time and thoughts for your inputs.
Ned
RV-7A Planning Stage
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  #8  
Old 02-27-2008, 11:25 AM
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Mark Castle-Smith Mark Castle-Smith is offline
 
Join Date: Apr 2005
Location: Dorset, England
Posts: 42
Default FADEC Option

I thought I would just throw my 10p (sorry 10c!) into the mix. We went for injection for our RV7 for many of the reasons articulated above and decided on the Aerosance FADEC system. Yes it is more expensive, but not as much as people seem to think when you take away the costs of magnetos etc. I cannot believe how smooth the engine is, no mixture to worry about, always starts within a blade or two, cold or hot, automatically balances the cylinder temperatures etc etc I would recommend you think about this system amongst the many options if you decided to go FI. Whatever you go for - good luck!

Mark Castle-Smith
Finished the RV7: Starting an RV3!
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  #9  
Old 02-27-2008, 11:39 AM
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frankh frankh is offline
 
Join Date: Jul 2006
Location: Corvallis Oregon
Posts: 3,547
Default FI hot starts

If you use the Airflow performance purge valve (and flow divider)...Which can be used with a Bendix servo I understand ...Then hot starts are a non issue.

My hot starts are the same as cold starts after a 10 second or so purge.

Some Carb'd engines can run LOP but it is unusual to have decent enough balancing to achieve this.

Frank
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  #10  
Old 02-27-2008, 11:56 AM
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Jamie Jamie is offline
 
Join Date: Jan 2005
Location: Atlanta, GA
Posts: 2,295
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I have now flown my Superior XP-360 with Precision Airmotive Silverhawk Ex injection through a summer and never, ever even once had a hard time hot starting it -- and this is in the Georgia heat. Crack the throttle, mixture lean, engage starter, wait for it to kick, mixture full rich. Works every time. I have dual impulse coupled mags.

I know that in FI Cessnas I always had a hard time hot starting them but for my RV it's no big deal at all. I think the hot start issue is overblown with FI.

Me? Deal clincher for me was carb ice...you hear so many conflicting things I just decided to avoid the issue entirely.

Just my 2 cents.
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