82UL Fuel

[floater]

82UL was developed several years ago, to be easily produced from
automotive fuel. Instead of being produce by only one or two
manufacturers as 100LL is, 82UL could be made by any oil company. This
should make it cheaper to produce. 82UL is NOT a replacement for 100LL.
It is my understanding that about 30% of the general aviation fleet
requires 100LL to prevent detonation, but the other 70% can use 82UL.
With the cost of fuel these days, if 82UL is significantly cheaper than
100LL, it's availability might save general aviation.

With the new various laws requiring ethanol in automotive fuel, it seems
it would be more important than ever that 82UL be produced for the
aviation market.

Yet after all these years 82UL has yet to show up anywhere. What does it
take to get this fuel produced and available to aviators? Does it have
to come from the demand side, by making pilots aware of it's existence,
so they can start to ask for it? Why isn't EAA doing more to see that
this fuel gets produced and made available?

[Kingfish]

Part of the problem is any replacement or augment for 100LL has to be
usable by the entire fleet. There might not be a big enough market for
a second avgas fuel (?) Phillips has said they'll continue making 100LL
indefinitely to support GA, maybe your query should be directed to them.

[Jim Macklin]

At least now, the refinery capacity is stained to the limit
producing auto fuel for the 99.3% of the non-aviation
market. To build a new refinery or a dozen for cars must
come first. Then, if somebody can build a new refinery for
aviation to cover 0.7% of the market...
Back in the 1950's the airlines and military used avgas in
four grades, 80-87, 91-96, 100-130, and 115-145 and jet
fuel. There was a demand for avgas in large quantities for
fighter planes P51s were still being flown by the ANG, the
USAF was flying the EC 121 and some of the cargo was not yet
in C 130s. Airlines flew DC 3 on all the short routes.

82UL won't work well in engines designed for 100-130 or
using turbochargers unless they are derated. Back in WWII
the manuals for the airplanes listed maximum MAP to be used
with different grades of fuel.


--
James H. Macklin
ATP,CFI,A&P

--
The people think the Constitution protects their rights;
But government sees it as an obstacle to be overcome.
some support
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"Kingfish" > wrote in message
ups.com...
| Part of the problem is any replacement or augment for
100LL has to be
| usable by the entire fleet. There might not be a big
enough market for
| a second avgas fuel (?) Phillips has said they'll continue
making 100LL
| indefinitely to support GA, maybe your query should be
directed to them.
|

[Kingfish]

>>>Back in the 1950's the airlines and military used avgas in
four grades, 80-87, 91-96, 100-130, and 115-145 and jet
fuel.<<<

Jim, what do the number pairs stand for? What changes would have to be
made to run 93 octane mogas in my 300hp N/A Lycoming?

[Jim Macklin]

The lower number was the octane rating when at cruise in
lean condition and the higher number was the rating for a
full power rich mixture. 93 mogas would rate about 80-87,
so your 300 hp Lyc would have to be derated to prevent
detonation. The exact required changes depend on the
dash/model number and what changes can be made. You won't
get 300 hp, maybe 250-270.

The EAA has an STC for smaller engines with low compression
such as the 4 cyl. Lyc and Cont engines used on Cubs and
Champs. I don't think you could use the mogas in the big
engines without major changes to operating procedures and
maybe some hardware.


--
James H. Macklin
ATP,CFI,A&P

"Kingfish" > wrote in message
oups.com...
| >>>Back in the 1950's the airlines and military used avgas
in
| four grades, 80-87, 91-96, 100-130, and 115-145 and jet
| fuel.<<<
|
| Jim, what do the number pairs stand for? What changes
would have to be
| made to run 93 octane mogas in my 300hp N/A Lycoming?
|

[Kingfish]

The fuel's octane rating changed based on mixture setting??

[Bob Moore]

Kingfish wrote

> The fuel's octane rating changed based on mixture setting??

YES

Bob Moore

[Kingfish]

> The fuel's octane rating changed based on mixture setting??

>>>YES

Bob Moore<<<

Uh, Bob, I was looking for a more detailed explanation of how & why
that is... but thanks for your input.

[Jim Macklin]

Yes, all fuels do because it is measured in an engine. The
power output and burning rate determine octane by the engine
method.


--
James H. Macklin
ATP,CFI,A&P

--
The people think the Constitution protects their rights;
But government sees it as an obstacle to be overcome.
some support
http://www.usdoj.gov/olc/secondamendment2.htm
See http://www.fija.org/ more about your rights and duties.


"Kingfish" > wrote in message
oups.com...
| The fuel's octane rating changed based on mixture
setting??
|

[Friedrich Ostertag]

Hi NG,

now it's my time to say something again, after mainly lurking here now
and then :-)

Knock resistance is a pretty complicated matter. The basic idea of
measuring the knock-related quality of a given fuel is to compare it to
a mixture of octane (known to be particularly knock-resistant) and
n-heptane, which will cause knocking already at very low compression
ratios. If your fuel behaves the same with regard to knock as a mixture
of 90% octane and 10% n-heptane, your octane number is 90.

Unfortunately it doesn't work quite as simple as that in the real
world. One fuel can be superior in knock resistance to another in one
engine and worse in another, or even depending on operating points in
an identical engine. A given fuel can behave similar to a 90/10%
micture of octane/n-heptane in one operating point, and like 80/20% in
another. Therefore, a defined octane number can only be attributed to a
fuel in conjunction with a defined procedure of measurement. For
automotive fuels, two measurement procedures are widely used, giving
the "motor octane number" MON and the "research octane number" RON. For
automotive fuels, these numbers typically differ by 8-10 points. In
Europe, the RON is quoted at the pump, while in north america it's the
mean value of the two, MON+RON/2, also called the "anti knock index",
AKI.

Aviation uses yet two more definitions, the "lean" and "rich" octane
number. The measurement procedure for the lean octane number is very
similar to the motor octane number and can in fact be derived from it
using a conversion table. The rich octane number is obtained in a very
different way. Instead of increasing the (n/a) test engine's
compression ratio up to the onset of knock, the test engine is boosted
and the boost pressure is increased until knock occurs. The so obtained
rich octane number is typically 30 points higher for high grade fuels
than the lean octane number. It is supposed to describe the fuel
properties particularly under high power, boosted operation.

Avgas 100LL has a lean octane number of 100, at auto pumps it would
therefore be labeled with an AKI of 104 - 105.

Yet another point: As octane is not the most knock resistant fuel in
the world, numbers for knock resistance greater than 100 are required
to describe fuels superior to pure octane. For obvious reasons a direct
comparison to a mixture from octane and n-heptane with equal property
is not possible. Ratings above 100 are derived by extrapolation. In
case of the rich octane number, values above 100 are given by comparing
the power obtained with the fuel to be rated by that obtained with 100%
octane. Fuel with 145 rich octane number allows a 45% higher power
output (obtained by boost increase) than running the same engine on
100% octane. Hence "octane" numbers above 100 should more precisely be
called "power ratings".

Two very good articles about knock and knock resistance can be found
here:

http://www.prime-mover.org/Engines/GArticles/octane.html
http://www.generalaviationnews.com/editorial/articledetail.lasso?-token
..key=11311&-token.src=column&-nothing

Hope that helps clarifying,

regards,
Friedrich

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