octane vs. A/F
*jaw drops with awe*
This is the best question and most responsible answers I have ever seen on any thread on this site!
Good damn question, I never thought about it either, but I can see how it could definitely been an issue (theoretically).
This is the best question and most responsible answers I have ever seen on any thread on this site!

Good damn question, I never thought about it either, but I can see how it could definitely been an issue (theoretically).
in my opinion,its not really a matter of air fuel reading being different because your going to tune whatever octane fuel your using to the desired power and safety range, most tuners stay in the 12:1 range and you can achieve that with whatever octane your using, egt's can vary with octane changes if the rest of your settings stay the same (timing , boost), its all about deferring detonation, if you tune your car on 110, and then go put 93 in the car, its gonna run like ass cakes and will be detonating and knocking all over the place, higher octane allows you a much wider variety of timing settings, super high compression and boost options, you wont make a whole lot of power with 110 as opposed to 93 unless you turn up the boost and changes settings on the car, if you ran the same amount of boost on 93 and 110, truth be told ,youd probably make less power with the 110, higher octane is just a tool to help you make more power and let you have the ability to mess with things that can gain power without having to worry about detonating being a factor, unless your engine management is setup to let you swith back and forth beetween map settings at the flick of a switch( like the u-tec), then i would suggest you tune the car with the fuel that you will use more often, if your driving your car everyday, your prolly not gonna be filling up with 110, but if you can switch maps then i say go for it, just make sure you always have it on the correct fuel map....
Last edited by MORE IMPATIENT; May 19, 2004 at 12:01 PM.
I agree with everything you said impatient.
I do not have the ability to switch between settings. I can only turn the mbc know up and down. The fuel and timing maps have been tuned for 93 and the a/f was around 11:1, but I have increased the airflow since that tune with a few bolt ons and want to see what the a/f looks like now.
I want to turn the boost up while using race gas. On the dyno with race gas, I would like to turn the boost up until the a/f reaches 13:1, as long as the knock link is cool with it.
The main thing is that I make sure my a/f is ok at my current boost setting (19psi). If the gas doesn't make an impact on the a/f then I will be fine using the purple stuff for the whole session. If the gas does impact a/f then I will be resigned to using 93 pump pee pee and just doing some base line runs, possible adjusting boost for the street.
I do not have the ability to switch between settings. I can only turn the mbc know up and down. The fuel and timing maps have been tuned for 93 and the a/f was around 11:1, but I have increased the airflow since that tune with a few bolt ons and want to see what the a/f looks like now.
I want to turn the boost up while using race gas. On the dyno with race gas, I would like to turn the boost up until the a/f reaches 13:1, as long as the knock link is cool with it.
The main thing is that I make sure my a/f is ok at my current boost setting (19psi). If the gas doesn't make an impact on the a/f then I will be fine using the purple stuff for the whole session. If the gas does impact a/f then I will be resigned to using 93 pump pee pee and just doing some base line runs, possible adjusting boost for the street.
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