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CloudCraft(at)aol.com
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 Posted: Mon Jun 18, 2007 8:16 am Post subject: MoGas STC & LOP |
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In a message dated 18-Jun-07 09:03:21 Pacific Daylight Time, john(at)vormbaum.com writes:
| Quote: | | ...and it will do fine in the Phillippines since it has a Mogas STC. |
Hi John V, and everyone,
I'm interested in the MoGas STC you mentioned. At one of the early Twin Commander Flight Group Fly-Ins (San Antonio circa 1997) Lycoming had a rep there who said none of the Lycoming engines were allowed to run MoGas due to the high chlorine content of MoGas.
If there is now a MoGas STC for the AC-500, that would be a complete turn-around. If they've done a 180, that's fine ... and I'd be (happily) surprised.
And speaking of Lycoming, somewhere I have a graph that shows a dramatic drop in cylinder head temperatures running LOP and this chart is for the IGSO-540.
If I can find the document, I'll scan and post.
Wing Commander Gordon
See what's free at AOL.com.
[quote][b]
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n395v
Joined: 10 Jan 2006
Posts: 450
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| Posted: Mon Jun 18, 2007 12:27 pm Post subject: Re: MoGas STC & LOP |
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ARRRRRRGGGGGGGHHHHH! LOP
The purpose of LOP operations is to decrease wear and tear on the engine meaning CHT and intracylinder pressures. The purpose is not to save $ by reducing fuel flow. It will take 3 years of fuels savings to return the investment in monitoring equipment.
I have run a GTSIO 520K and J LOP for hundreds of hours with no valve or cylinder problems and an IO 540 for close to a thousand LOP hrs with no issues.
When LOP_CHTs are less, peak intracylinder pressures are less and fuel consumption is down. These are demonstrable facts not hearsay. It is no longer true as espoused in the old wives tales that "fuel is a cheap coolant"
There is no reason you cannot go beyond TBO running LOP.
Now the key to safe effective LOP ops is doing it correctly.
1 You need balanced injectors. They don't have to be GAMI you can do it yourself with quarter sizes. All cylinders need to hit peak EGT near simultaneously.
2. You need to temp monitor all cylinders simultaneousl yes you need an engine monitor. You also need a fuel flow guage that is accurate.
3. You need to quickly establish your numbers and not spend a lot of time leaning through the peak. You need to establish fuel flows for various power settings and altitudes.
ARRRRRRGGGGGGGHHHHH! MOGAS
Lycoming, I doubt, will ever agree MoGas is Okay.
If there is an STC it is not held by LYcoming and it is an STC for a specific engine-aircraft-year designation.
The myths about MoGas are
....Too much Chlorine
....Too much Sulfur
....Alcohol in the fuel
....Not enough Octane
....Less BTUs than AVgas
....You need the lead for valve guide lubricant
The chlorine and sulfur are non issues. Cessna suggest a pint of alcohol per xx gallons in the winter to prevent fuel line freezing. Alcohol can cause problems with some seals and some of the older fuel hoses but most of these are out of the system.
Octane ratings only signify antiknock characteristics and have naught to do with energy levels. The lead is there for antiknock purposes.
The problems with MoGas
Lower vaporization pressure. It will vapor lock a lot easier than 100LL.
Things that predispose to vapor lock are, heat. bends in the fuel line, high points in the fuel line, fuel lines going from smaller to larger. Thus the airframe plays a role in the STC process.
To run MoGas you need a fuel line that is as straight as possible, well insulated, and preferably constantly is going up hill. It should remin the same size throughout or restrict to smaller sizes as it goes towards the engine. Lower compression engines do better than high compression.
MoGas has regional additives for EPA temp and altitude differences. These additives are often seasonal and breakdown rather quickly (months) leaving that nasty residue you see on your mower and your home gas cans. This stuff tend to gunk up carburators and injectors.
O 540s and IO 540s should run well on Mogas if there are no problems in the fuel distribution system and you keep the entire system clean.
High performance turboed engines I am not so sure and probably would not try MoGas.
Most MoGas Stcs are owned by Petersen Aviation http://www.autofuelstc.com/autofuelstc/pa/intro.html
or EAA Experimental Aircraft Association. I do not know of an STC for an Aerocommander Twin.
On Mo Gas however I will defer to the wisdom of our Bill Hamilton who I think discussed this issue at length long ago on the old forum.
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YOURTCFG(at)aol.com
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| Posted: Fri Jun 22, 2007 8:02 pm Post subject: MoGas STC & LOP |
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Great info and accurate jb
See what's free at AOL.com.
[quote][b]
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