Maybe I'm just a confused soul, but I was trying to figure this out today. (See topic.) Say for example, you have a B18C5 setup and you bump compression to 12:1. Change the ECU to fuel cut / rev limit at ~9300... (is that even pertinant?) -- how do you determine the octane rating necessary to keep your engine safe/clean?

My first thoughts were FI applications. They cram the air in the combustion chamber, and typically run on pump gas. Using race gas they can add more boost... but, is there a difference for NA applications? Would 12:1 require a higher octane?

Perhaps I'm not asking the right questions... Assuming the car could run on 93 octane pump gas @ 12:1, would you typically make more power and be more efficient running say 100 octane?

Sorry if its drawn out... just trying to get a better understanding. Thanks in advance for the input.

 

No, you should run the lowest octane that doesn't ping.

 

ttt

 

The proper question would be , " how much more fuel" , and the difference would be minimal. The higher octane could actualy cause more of a problem if the higher compression were to cause a lean condition due to inadequate fuel delivery...tuning is everything.


[Modified by white, 6:47 AM 6/29/2002]