My LIMITED understanding of gasoline octane rating (87, 89, 91, etc.) is the higher the octane the less volatility and longer the burn time needed when running octane ratings above 87, which is why you need to advance the spark timing. I also understand that higher octane does not mean more power.

My question is - If you don't get more power or efficiency from running a higher octane fuel, then what benefit do you get?

More to the point, why does the Edge Evolution require 91+ Octane on the performance setting? Is it just because the timing has been advanced by 2 degrees? If so, why? What is the benefit.

 

Except for his answer to this question: "Is it better to raise fuel octane or lower the octane requirement of the engine?" (I only disagree because the answer is very much oversimplified, especially refering to pump gas) this is a very informative article and pretty well spot on.

http://www.eric-gorr.com/techarticles/Fuel_Basics.htm

Keep in mind if you really want to understand this subject your going to need more than some articles and replies, you need a few books worth of info.

Higher octane doesn't necessarily (most of the time it doesn't) mean slower burning, it's just less likely to auto ignite.

 

Thanks tdister. I think your right, after looking through the link you attached as well as some other information, this appears to be a really complicated subject.

I guess what I'd really like to know is what programming changes does the Edge make in the Level 3 tune that requires 91+ octane? And, how does that result in better performance than the Level 1 and Level 2 (considering you don't get more power from more octane)?

 

Davis,

I always thought that high octane did contribute to more power and fuel efficiency on higher compression engine. So when advancing the timing with the Evo, it might be increasing the compression there for you need a high octane fuel to reach a greater improved performance.

Dex