MSP said:
Very interesting thread! I tested this out before, and my car actually seemed to pull less with the higher octane... Anyone know why that may happen? Perhaps mine was more inclined to follow the 87 only rule?
My meager understading of this process is somthing like this:
The octane rating of gasoline tells us how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking or early detonation in the engine and subsequent loss of HP. Lower-octane gas, like 87-octane gasoline, can handle the least amount of compression before igniting.
The compression ratio of the engine determines the octane rating of the gas we use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. Higher compression ratio engines require higher-octane fuel. The advantage of a high compression ratio is that it gives the engine a higher horsepower rating for a given engine weight. The differences in compression ratios on 05 Stangs are relatively small, but the room for the process (our Bore and Stroke specifications are large). Those with the V-8 can handle a change in octane better than the V-6 due to the size of the compression area.
Compression Ratio V-6 9.7:1 9.8:1
Bore and Stroke (in.) V-8 3.95 x 3.32 3.6 X 3.6
Higher compression ratios produce more power, up to a point. The more you compress the air/fuel mixture, however, the more likely it is to spontaneously burst into flame (before the spark plug ignites it). Higher-octane gasoline prevents this sort of early combustion. The higher the compression ratio the higher the octane gasoline needed for proper combustion. However, the other 3 aspects of the reciprocation need to follow the laws of engineering and phyics to perform optimumly.
Given the modulation of the Stang, changes in intake/combustion/compression/exhaust will cause an issue with the proper cycle of reciprocating internal combustion.
So, in a hand basket there is the dissertation on combustion relative to octane ratios in the engine. (God I am such a frekin’ nerd!)
Jenn