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04-25-2015, 06:01 PM
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Join Date: Apr 2013
Location: Southeast
Posts: 663
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IO 540...8.5 or 9
So I was at Sun N Fun planning my RV's future. Was talking to some engine guys about 8.5 or a 9 to 1 compression. Not really caring about adding more HP or burning mo gas. Just want a good solid engine. I was just planning to go with an 8.5, but I was told that the IO 540 actually prefers a 9-1 ratio. I know it adds some HP, but according to the engine guy, he said its better all around for the 540 series engine. Is there a difference beyond some more ponies.
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04-25-2015, 06:06 PM
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Join Date: Jan 2005
Location: Victoria, Canada
Posts: 2,251
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Quote:
Originally Posted by togaflyer
So I was at Sun N Fun planning my RV's future. Was talking to some engine guys about 8.5 or a 9 to 1 compression. Not really caring about adding more HP or burning mo gas. Just want a good solid engine. I was just planning to go with an 8.5, but I was told that the IO 540 actually prefers a 9-1 ratio. I know it adds some HP, but according to the engine guy, he said its better all around for the 540 series engine. Is there a difference beyond some more ponies.
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Better thermodynamic efficiency.... AKA gas mileage. Either way, fuel injection and an electronic ignition will allow LOP operation for more efficiency.
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V e r n. ====
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RV-9A complete
Harmon Rocket complete
S-21 wings complete
Victoria, BC (Summer)
Chandler, Az (Winter)
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04-25-2015, 06:40 PM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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See Mahlon's comments on this thread regarding compression ratios.
Remember, 100LL doesn't know which engine it is burning in.
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Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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04-27-2015, 05:58 PM
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Join Date: Apr 2013
Location: Southeast
Posts: 663
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Anyone running the IO 540 with 9:1 ratio, any issue with it. Are you running electric mags.
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04-28-2015, 11:17 PM
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Join Date: May 2008
Location: Brisbane Qld. Aust.
Posts: 2,271
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My suggestion if you want 9:1 is to stick with standard magneto's.
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David Brown
DYNON Authorised Dealer and Installer
The two best investments you can make, by any financial test, an EMS and APS!
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04-29-2015, 06:55 AM
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Join Date: Aug 2006
Location: Friendswood, TX
Posts: 82
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9:1
I am running 9:1 cylinders with EFII dual ignition system on 100LL. All working very well together.
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Gaylon Koenning
RV-10 #40468
N815DG, Flying
G3X, GTN750, GTS800
Barrett IO-540, 9:1, Cold Air,
Dual SDS Electronic Fuel/Ignition (EM5, V29.1)
Polly Ranch Airpark (7XS0)
Friendswood, TX
Dues Paid 2019
http://www.TexasRV10.com
Last edited by Gaylon : 04-30-2015 at 08:05 AM.
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04-29-2015, 07:05 AM
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Join Date: Jan 2005
Location: Victoria, Canada
Posts: 2,251
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Quote:
Originally Posted by RV10inOz
My suggestion if you want 9:1 is to stick with standard magneto's.
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... Somewhere in this short recommendation is a deep understanding of Lycoming engine operation. Can you educate us?
__________________
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V e r n. ====
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RV-9A complete
Harmon Rocket complete
S-21 wings complete
Victoria, BC (Summer)
Chandler, Az (Winter)
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04-29-2015, 07:21 AM
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Join Date: Apr 2008
Location: Tennessee
Posts: 440
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Quote:
Originally Posted by Gaylon
I am running 9:1 cylinders with EFII dual ignition system. Both working very well together.
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So am I. Works great!
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04-29-2015, 01:36 PM
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Join Date: Oct 2014
Location: Cedar Rapids, IA
Posts: 232
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Quote:
Originally Posted by Gaylon
I am running 9:1 cylinders with EFII dual ignition system. Both working very well together.
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You guys running 9:1, are you running MOGAS as well? Or sticking with 100LL?
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04-29-2015, 09:33 PM
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Join Date: Apr 2013
Location: Southeast
Posts: 663
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I checked on the Peterson aviation WEB site. They offer MoGas STCs for many engine. They have STCs for O 540's, but reading their facts and questions, they do not offer MoGas STCs for the I/O 540 version. They said it did not meet their testing requirements. Since they spent money and time to test and obtain approval for the STCs, its a good indicator that if you want Mogas, maybe you need to run a version of the O-540 engine. Just a messenger, be gentle.
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