The Fuel: Spec AN- F- 28, is Graded as 100/130 using the aircraft PN system. The 130 corresponds to the rich power condition, and the 110 is the lean mixture max power rating.
For those who have never heard of the Aircraft PN system, it is an attempt to rank fuels that exceed the maximum octane of 120 that can be determined using the automotive octane tests. They extrapolate the "effective octane" of the fuels based on how much TEL would be needed to get a conventional gasoline to reach the same performance levels.
The Rich max power setting is the typical condition you would use for max take off power, using a rich mixture to prevent detonation under heavy load .
The lean max power setting would be the condition an aircraft would use for high altitude cruise, with lean fuel mixture to get maximum range.
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"Most californian fuel is oxygenated, it doesn't seem to prodcue the same effect as the chart I wonder what happen to the knock resistance properties?" -- Richard L
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I suspect if you looked at the specs for the California RFG gasolines you would find they are a "high sensitivity" blend. Sensitivity is the difference between the RON and the MON. RON has the most effect on engine run on at shutoff and low rpm knock, MON has most effect on high power high rpm condtion knock ( ie. exactly what most performance situations demand)
The R+M/2 AKI system used in the U.S. is simply the average between those two numbers but there (to my knowledge) is no requirement on how large a spread is allowable between the two. Most gasolines are blended with a sensitivity of 6 -10.
If your target is 91 octane you can get it with many different blends that average to that R+M/2 number. YOu could have a fuel of Ron 95, MON 87 and you would have an AKI of 91, and you could also get the same AKI with a blend that rated as RON 93, MON 89. Obviously the former would not be as suitable to use in a high performance car as the latter.
If your comparing fuels for high performance applications, pay attention to the MON numbers they are the most important.
Larry