Posted by Tim Way on Thursday, April 26, 2001 at 2:06PM :
In Reply to: Re: Don't forget Octane was calculated diffrently back then NTXT posted by Ken in CO on Thursday, April 26, 2001 at 10:18AM :
...of octane to heptane. If it were the percentage of the total volume then yes, max would be 100 (no heptane).
Total Volume Example
1cc octane to 1cc heptane = 2cc total volume = 50% or 50 Octane rating
But if it's a ratio of octane to heptane then you could get over 100.
Ratio Example
1cc octane to 1 cc heptane = ratio 1:1 = 100 Octane rating
1.04cc octane to 1cc heptane = ratio 1.04:1 = 104 Octane rating
The text is a little vague but I interpreted it as a ratio until I found this on the web at http://www.fandl.com/fuel_facts.html
Octane Rating:
This is an anti-knock scale developed in the 1920's to rate the quality of a gasoline's ability to resist knocking or pinging. Samples of any gasoline are placed in a laboratory Knock Engine (this is a small, one cylinder engine with a variable combustion cylinder). While the engine is running, the combustion ratio is increased until the engine begins knocking. Now the gasoline is replaced with N-Heptane with an octane of zero and is mixed with the 100 octane ISO-Octane at various ratios until the motor "knocks." If you end up with 10% N-Heptane and 90% ISO-Octane ratio, your test sample has an octane of 90.
So I was wrong…. Hey, I’ve been wrong before. And I STILL have no idea how you get gasoline with Octane Ratings over 100…sigh.
Tim Way
Albuquerque, NM
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