This may help.
So you know that a fuel-air mixture, under the right conditions, can spontaneously combust. In order to control this property, all gasolines have chemicals mixed in with them to control how quickly the fuel burns. This is known as the octane rating of the fuel. The higher the rating, the slower and more controlled the fuel burns. Here is a chart that show octane ratings relative to compression ratios.
Compression ratio = Octane
5:1 =72
6:1 =81
7:1=87
8:1=92
9:1=96
10:1=100
11:1=104
12:1=108
How do you convert compression ratio to PSI?
A:
To calculate the pounds per square inch (psi) from the compression ratio, one needs the compression ratio and the atmospheric pressure measurement. Then, the first number in the compression ratio is multiplied by the atmospheric pressure, then divided by the second number in the ratio.
For example, if the atmospheric pressure is 14.7 psi and the compression ratio is 11:1, the equation to solve for the psi is (14.7*11)/1. Therefore, the answer is 161.7 psi. People use this method of calculation to determine the pounds per square a piston produces.
The atmospheric pressure can vary, but the standard atmosphere produces 14.696 psi at sea level. For more exact calculations, the altitude should be considered.
A word on race fuel, there is more in it than meets the eye, some fuel advertised as 100, is actually only 96 octane.
You need to read the fine print, race fuel comes in a variety of octane ratings from 96 to 120+
