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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IO 540...8.5 or 9
- Thread starter togaflyer
- Start date
vlittle
Well Known Member
Better thermodynamic efficiency.... AKA gas mileage. Either way, fuel injection and an electronic ignition will allow LOP operation for more efficiency.
N941WR
Legacy Member
See Mahlon's comments on this thread regarding compression ratios.
Remember, 100LL doesn't know which engine it is burning in.
Remember, 100LL doesn't know which engine it is burning in.
vlittle
Well Known Member
... Somewhere in this short recommendation is a deep understanding of Lycoming engine operation. Can you educate us?
So am I. Works great!
You guys running 9:1, are you running MOGAS as well? Or sticking with 100LL?
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.
http://www.autofuelstc.com/approved_engines_airfames.phtml
I was curious, so on this page, i selected Lycoming for engine type. Notice that they dont list ANY IO engines. Only O engines. Thus, i dont think its displacement specific. Probably some other reason or marketing reason.
For Continentals, they do list IO-470 and IO-520. My guess is this has more to do with the marketing dominance of C182's and Bonanza's from the 70's maybe???
I was curious, so on this page, i selected Lycoming for engine type. Notice that they dont list ANY IO engines. Only O engines. Thus, i dont think its displacement specific. Probably some other reason or marketing reason.
For Continentals, they do list IO-470 and IO-520. My guess is this has more to do with the marketing dominance of C182's and Bonanza's from the 70's maybe???
We've had this discussion in another thread.
Even 8.5:1 IO-540s are not Mogas approved even though a similar IO-360 is. They have, however, been approved for UL91 or 91/96UL available in Europe.
The bottom line is that under the US experimental category you can run what you like........
To get back to the question, I have standard 8.5:1 @260hp. I really can't see any reason to put in higher compression pistons or increase the power above that.
Even 8.5:1 IO-540s are not Mogas approved even though a similar IO-360 is. They have, however, been approved for UL91 or 91/96UL available in Europe.
The bottom line is that under the US experimental category you can run what you like........
To get back to the question, I have standard 8.5:1 @260hp. I really can't see any reason to put in higher compression pistons or increase the power above that.
The engine shop Im considering recommended 9:1. He said its a great match with the IO 540. Said does not affect the engines longevity, gives a few more HP, fuel burn about the same. He does not charge any more for the higher compression jugs, so its not about making more money. I know the stock 8:5 gives the RV 10 more than enough for that platform, but I dont see a bump to the 9:1 a critical difference. Which was one of my concerns.
Who makes them?
Which companies sell the 9:1 pistons or complete cyl assemblies?
Do you have to install cyl and pistons (complete assembly) from the manufacturer, or can you use pistons from one manufacturer and cyls from another?
Does Lycoming produce the 9:1 cyl assemblies?
Which manufacturers of cyl assemblies do you recommend?
Thanks.
Johan
Which companies sell the 9:1 pistons or complete cyl assemblies?
Do you have to install cyl and pistons (complete assembly) from the manufacturer, or can you use pistons from one manufacturer and cyls from another?
Does Lycoming produce the 9:1 cyl assemblies?
Which manufacturers of cyl assemblies do you recommend?
Thanks.
Johan
ColoRv
Well Known Member
Come to Denver. There is no such thing as to much power and many of us are running 10:1 including a buddy's rocket with a 540. No issues and at this altitude, no TBO reduction. At sea level...your mileage may vary if you run around wide open all the time like I tend to up here. Then again, at sea level I can't leave the big handle forward or I'm climbing the barbers pole.
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Johan,
you can change the cylinders, which includes the pistons et all, to increase HP without much weight penalty. A friend has a -10 with 10:1 jugs and he claims he is in the 290 plus HP range. He calls it a poor mans turbo charge. Higher compression cylinders can also mean more wear and tear on the engine and could impact the longevity of the engine. I settled on the 9:1 because it was recommended by the engine shop that will be doing the engine build. Few more HP without being hard on the engine. If you get the XIO 540 from Vans, its a brand new stock engine vs a rebuilt. There is nothing wrong with a shop doing a rebuild, but make sure they use crank shafts etc that meets new specks. Cylinders etc should be new.
you can change the cylinders, which includes the pistons et all, to increase HP without much weight penalty. A friend has a -10 with 10:1 jugs and he claims he is in the 290 plus HP range. He calls it a poor mans turbo charge. Higher compression cylinders can also mean more wear and tear on the engine and could impact the longevity of the engine. I settled on the 9:1 because it was recommended by the engine shop that will be doing the engine build. Few more HP without being hard on the engine. If you get the XIO 540 from Vans, its a brand new stock engine vs a rebuilt. There is nothing wrong with a shop doing a rebuild, but make sure they use crank shafts etc that meets new specks. Cylinders etc should be new.
This where I need advice
I should explain better. I am replacing all 6 cyls on my engine that is being rebuilt. I am keen to go with 9:1 CR. I know there are different manufactures of cyl assemblies (ECI, Superior etc). In the past I have used Lycoming cyl assemblies exclusively, and have little knowledge about the other options. It seems that Lycoming does not produce 9:1 assemblies, but I might be mistaken. So I am asking for advice regarding choices and your experience with other manufacturers.
Thanks.
Johan
I should explain better. I am replacing all 6 cyls on my engine that is being rebuilt. I am keen to go with 9:1 CR. I know there are different manufactures of cyl assemblies (ECI, Superior etc). In the past I have used Lycoming cyl assemblies exclusively, and have little knowledge about the other options. It seems that Lycoming does not produce 9:1 assemblies, but I might be mistaken. So I am asking for advice regarding choices and your experience with other manufacturers.
Thanks.
Johan
