Mogas

[Ken]

It might be interesting to hear more about Angus's valve problems
because I believe that leaded fuel is about the worst thing you can do
to valve guides. Perhaps the larger radial engines have some
peculiarities that I'm not familiar with.

Any lead deposits on valve stems are extremely abrasive. Last time I
paid attention to this, the Cessna pilots association claimed it would
save more the US$10. per hour maintenance to use mogas in single engine
Cessnas.

Lead is a cheap way to increase octane and it definately lubricates the
valve sealing surface but it is a bad thing for valve guides and living
organisms as far as I know. Personally I'd try hard to run more than 75%
mogas (if available without alcohol in it) through one of these small
Lycosaurs and would ignore what mixture was in the tanks unless flying
high and or in hot conditions. I think even 80/87 was way more lead than
optimum for these engines let alone 100LL.

Liquid cooled engines do run dramatically cooler valve guide
temperatures but I don't recall anything about that in regards to leaded
fuel vs unleaded.

Ken

Mike Kimball wrote:

What's the difference between automobile and airplane valve guides? How
come valve guide lubrication isn't a problem with unleaded in cars?

Also, is there any reason why 100LL and MOGAS shouldn't be mixed? (Other
than unknown octane rating and vapor pressure and the usual rubber parts
incompatibility with one type or the other.)

Mike Kimball
SR #044

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com]On Behalf Of
Angus McKenzie
Sent: Thursday, August 26, 2004 7:06 AM
To: rebel-builders@dcsol.com
Subject: Re: Mogas in the M-14P?


Just my opinion BUT each time I've had an ag-plane engine quit while

working

it was valve-guide/mo-gas issues,I personally would not put car gas in an
airplane unless it was an emergency........Angus

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[mike jones]

Ht all



So can I use mogas with a lyco 0-320b2b-160 hp engine , perhaps the top
grade at Sunoco, and assume it must be erhanol free

Or should I stick to avgas

Cheers









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[Ralph Baker]

Mike,
I don't believe the 160 HP is suitable for mogas. You might check the STC list for certified aircraft to see if any with your engine have been STC'ed. Others here may have a better answer on the engine.

In any case, if you elect to use mogas I suggest you test every load for alchohol. I have found stations here in South Carolina with no "alchohol sticker" that did have alchohol. The best tester I've found is the EAA unit and the test is simple. As an alternate the test can be done with any small relatively tall clear container, and a little water.

Auto fuel composition changes at least twice a year with the weather. Don't use winter grade in the summer as the high temps can lead to vapor lock. Mogas allowable vapor pressure is much higher than 100LL.
Ralph Baker



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