(Harry Andreas) wrote in
:
Something like that...
There are two "Octane" ratings systems, Research amd Motor.
Research octane rating compares the evaporation rate of the test fuel
to iso-octane's by dumping a measured amount from a tower and seeing
how much hits the ground.
In Motor Octane rating, a single cylinder engine with adjustable
compression ratio is run at progressively higher compressions until it
knocks. The result is compared to iso-octane.
Um, no. My memory from college days is that the two methods were both
classically run on the same variable compression engine, just differing
in test conditions (I though it was just the input temperature, but see
below).
So I looked around, and found this, which sounds somewhat authoritative,
and close enough to my vague memory that I think it is about right
(certainly compared to seeing how much hits the ground in a tower drop--
you were joking...right?).
The whole thing is at:
http://www.prime-mover.org/Engines/G...es/octane.html
The key paragraph reads:
"How do the motor and research protocol differ? Mostly in input
parameters. In the motor protocol (ASTM D2700-92), the input air temp is
maintained at 38C, the ignition timing varies with compression ratio
between 14 and 26 degrees BTDC, and the motor is run at 900 RPM. In the
research protocol (ASTM D2699-92) the input air temperature varies
between 20C and 52C (depending on barometric pressure), timing is fixed
at 13 degrees BTDC, and the motor is run at 600RPM."
Peter A. Stoll
retired Electrical Engineer
only qualification to comment on the above is that I took a course in
History of the Automobile as a humanities elective in college (well, it
was MIT...), and wrote a paper on lead additives and the knock problem.
Also my father was a Sohio lifer (Standard Oil of Ohio), and had some of
the Broadway Lab working for him at one time.
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