Compression and octane rating

[Frédéric CM]

What determin the need for 91 or 93 fuel ?
Is it the Static or Corrected compression ratio ? or the timing ?

Thanks

[dynaglide]

yes to both, sort of - CR will determine actual octane needs, timing is then adjusted for best power.  Retarding timing can compensate for too much compression relative to the fuel, or not enough octane for the compression, but doing so will lose some power.

http://www.daytona-sensors.com/tech_tuning.html

http://www.yellowbullet.com/forum/showthread.php?t=472656