MoGas Tips, Tricks, Concerns, How To

Other than its high octane value (which isn't needed in 1:7 compression
engines), 100LL isn't such a good fuel to begin with.

Baloney. 100LL is the best fuel made and can't be duplicated Your problems
sound like "The sky is falling"

That's a good one!

Er, um...that *was* meant to be funny...right?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

"Bela P. Havasreti" wrote in message
news
Perhaps a more useful comparison would be how much
lead is/was in 80/87 vs 100LL?

Those of use with older, low compression engines that were designed
to run on 80/87 may be introducing 4 times the amount of lead into our
combustion chambers by running 100LL than the original designers had
intended for.

80/87 has a maximum of 0.5 grams of lead per US gallon while 100LL has
a maximum of 2.0 grams of lead per US gallon. Unleaded Mogas is...
well... Unleaded!

In reading about this somewhere (AvWeb? EAA?) I recall words to the
effect that the refineries can get up to about 97 octane without any
lead, and they only add as much in to get to (or slightly exceed) the
100 octane rating.

This one: http://www.avweb.com/news/columns/182149-1.html

"Jay Honeck" wrote in message
oups.com...
I wonder about the effect of LOP on muffler life. I used just the
low-power-operate-at-peak philosophy and my 172 went thru the muffler
internal flame tubes every 450 hrs, like it could read the hour meter.

As posted before, the head honcho at Dawley Aviation (the exhaust
system folks in Burlington, WI) told me personally that running lean of
peak has been the best thing that EVER happened to their business.

And has been pointed out in this group previously, he's full of ****.

"MB" == Montblack writes:

MB What would your unleaded fuel of choice be?

Good old 80/87. But that's not coming back.

"Montblack" writes:

Too bad mogas is the only unleaded fuel we can get for our LC engines at
this point.

What would your unleaded fuel of choice be?


#2 Diesel....

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

If you run your car engine on 80 octane mogas, it will usually run fine. If
your car overheats, it will start to knock. If you have 100 octane gas it
will start to knock at a higher CHT than if you ran at 80 octane. This is
not usually a problem in a car that has a radiator and thermostat to
regulate the temperature.

In an airplane the same is true. Run normally both octanes are fine. In an
airplane with a manually adjusted mixture being the only temperature control
( ignoring cowl flaps) it is much easier to overheat an engine. If your CHTs
get to high, it will start to knock. With a higher octane gas it will start
to knock at higher CHTs. Therefore, if you overheat your engine, the lower
octane gas will cause more damage than the higher octane gas. Hopefully I
have drawn a clear enough line between the statements that you said were all
true and the conclusion you said was not.

"Jay Honeck" wrote in message
oups.com...
Let me know which of the above statements you disagree with, and I will
find
a reference for it.
I stand by my statement that an overheated engine will be more damaged if
it
is running lower octane fuel.

None of your statements are incorrect, they are merely irrelevant.

Low-compression aircraft engines were designed to run on 80 octane
fuel. Running fuel of higher octane is not going to hurt anything --
but it won't help, either.

87 octane auto gas is perfect for our low compression engines, and
certainly won't hurt them. Using "premium" (or, for that matter, 100
LL) is neither necessary nor recommended.

(Note: SOME mogas STCs do require using a higher octane car gas, but
those are the exception, not the rule.)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

"soxinbox" wrote in message
...
If you run your car engine on 80 octane mogas, it will usually run fine.
If your car overheats, it will start to knock. If you have 100 octane gas
it will start to knock at a higher CHT than if you ran at 80 octane. This
is not usually a problem in a car that has a radiator and thermostat to
regulate the temperature.

I can't remember seeing anything less than 85 octane car gas since, oh,
maybe the 60's?

Jay Honeck wrote:
87 octane auto gas is perfect for our low compression engines, and
certainly won't hurt them. Using "premium" (or, for that matter, 100
LL) is neither necessary nor recommended.

(Note: SOME mogas STCs do require using a higher octane car gas, but
those are the exception, not the rule.)

Don't forget, MANY planes are not considered low compression, even though
they're not exactly "high performance". For example, all the 160 hp versions
of the O-320 found in many Cherokees, Warriors, C-172s, etc, as well as the
normally aspirated 180 hp O-360 found in Cherokee 180s, REQUIRE higher octane
than 87 octane car gas. I believe, for most of them, they could get by with
less than 100, but would certainly need super unleaded as a minimum.

--- Jay


--

Jay Masino "Home is where the critters are"
http://www.JayMasino.com
http://www.OceanCityAirport.com
http://www.oc-Adolfos.com

: than 87 octane car gas. I believe, for most of them, they could get by with
: less than 100, but would certainly need super unleaded as a minimum.

True. The high-compression (8.5:1) O-360/O-540's were certificated on 91/96 avgas. The Petersen STC (the
only one applicable to high-compression engines) requires mogas with the appropriate ASTM ratings and to have an
anti-knock-index (Average of Research and Motor octane... "R+M/2") of 91 or higher. When I bought my STC, Petersen
said that even in the high-temp, altitude, CHT setup, they were unable to induce knocking or detonation even with 89.
The certificiation folks wanted a bit of safety margin.

It should also be pointed out that the R+M/2 rating does not directly compare to the avgas lean rating (i.e.
the "91" of the 91/96 or the "100" of 100/130 100LL). The avgas lean rating testing setup more closely resembles the
Motor method of the R+M/2. Typical point spread ("sensitivity" IIRC) is +-4 to 5 points on either side. In other
words, 91 AKI is more like 96 Research, 86 Motor... i.e. a bit dicey given the 91/96 rating of the aviation engine.

That said, I haven't experienced any troubles running hundreds of gallons of 93 AKI through my O-360 180hp...
summer, winter, etc.

-Cory


************************************************** ***********************
* Cory Papenfuss, Ph.D., PPSEL-IA *
* Electrical Engineering *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

As posted before, the head honcho at Dawley Aviation (the exhaust
system folks in Burlington, WI) told me personally that running lean of
peak has been the best thing that EVER happened to their business.

And has been pointed out in this group previously, he's full of ****.

Hmmm. Let's see. Shall I believe the guy who runs a multi-million
dollar aircraft exhaust system business (and has no incentive to lie to
me), or shall I believe Usenet?

Golly, what a conundrum...

;-)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"