Hi Doug,
The Pits is lots of fun and a great performer. Occassionally, I still
give some "dual" in a S-2B (2-seater, 260 hp., Lycoming 540 cu. in.
"Aerobatic" engine). You are correct, it is like a "Tiger with wings".
100LL is the only AvGas that is still available (in the U.S.) and it is
blue in color. I seem to recall that it also has some Toluene blended
to make-up for the reduction in its Lead content from the older AvGas
Grades [see below] and that the amount has been steadily increased since
1980 (although it is a "parts per million" increase). It has a maximum
of 2.0 milliliters Tetraethly Lead per liter of fuel (I need to recheck
the ratio!).
100LL was the replacement for Grade 100/130 AvGas (Green in color) which
had 4.0 millileters of Lead per Liter and Grade 80/87 (Red in color)
which had significantly less Lead than the current 100LL. You may
recall that one of the characteristics of the AvGas is that when blended
in any amount, the color coding began to neutralize each other,
theoretically at 50/50 blend, the fule was clear (this is correct). At
varying ratios up to 50/50, the tendency was to hav a slight color
favoring the greater percentage.
Some of the other "Famous" AvGas options were 115/145 (Purple) used in
the compounded supercharged large radials of WW II and thru the C-97,
DC-6 and DC-7, etc., (until it was phased out). In Naval Aviation, we
used this fuel in the Douglas AD Skyraider series aircraft (except in
Viet Nam for the A-1 Skyraider - same airplane - when I seem to recall
that we could no longer obtain the blend). The original "Blue AvGas"
was Grade 91/96 which began to be phased out in the late sixties/early
seventies (except in Mexico) and Grade 71/78 which I can barely remember
(I believe it was "straw yellow" in color).
A few of the other important characteristics of Avgas are the
vaporization (not as good as automobile fuel - partly because of having
to control vaporization at high altitude and low temperatures) and the
"inert" ingredients that remain in the fuel (theoretically - zero).
I agree with you 100% that the best way to go is to acquire racing fuel
and blend the regular auto fuel with the least amount of racing fuel
that achieves the desired result (anti-knock quality). I would not
recommend this for the daily street driver because of the hazards of
handling and storing the product (unless the person had all of the
safety equipment used for storage and handling). Also, the blend would
probably not be good for the catalytic converter.
The only thing that matters with auto fuel is its "resistance to knock"
(anti-knock quality). This assumes that all other items are identical
(MTBE, alcohol added, etc.).
I seem to notice that most people buy the "higher" numbered fuel
"believing" that it has a better "quality" even though their engine does
not require the increased knock residtance. Good advertising on the
part of the fule providers!
I am not now a member of SAE but I regularly receive and purchase much
information from the organization. A great source of information! For
the other readers of the Tigers List, the URL for SAE is:
http://www.SAE.ORG/. They are located in Pennsylvania and membership is
not very costly.
Another great information site is the Experimental Aircraft Association
(EAA) which is also famous for bringing the great Oshkosh airshow (now
in progress) in Oshkosh, Wisonsin. The "show" ends tomorrow - bummer!
Their URL is: http://www.eaa.org/.
I enjoyed discoursing about fuel. Perhaps there is a fuel chemist in
the group that could get more technical (and explain in layman's terms)
and clarify some of these questions and beliefs.
Keep in touch.
Best regards,
Don Cordier
Aviation Consultant
Glendale, California, USA
doncordier@earthlink.net
Office & Hangar: (818) 997-7640 (24 hours)
FAX: (818) 553-3667
Member: NBAA, NATA, PHPA, AOPA
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