https://www.fordmuscle.com/tech-stor...or-less-money/

given the high combustion chamber pressure and heat of our turbo'd rotaries FUEL is foundational and there are many options.

alcohol should be an important part as we pass 450 rw. i choose to get my alcohol, in my case methanol, through my AI setup.

given my experience w E85 i really like the idea of running a reduced % which delivers most of the benefits while being easier on the internals. i realise this isn't news to most who visit this Section.

the link article is an excellent source of all the numbers needed to do the mixing and calculate octane etc.

the item that jumped out for me is the table that shows that given our typical 93/91 octane fuel has around 10% ethanol our various AFR numbers such as 14.7 Stoic, 13.3 best torque etc aren't accurate. given ethanol at 9.0 to 1 stoic and 10% in our fuel our real stoic is 14.1 not 14.7. best torque around 13.2 on 100% gas is 12.7. big difference.

while most of us just look at knock etc, it is still valuable to adjust our AFR guideposts to the actual reality of our fuel... which is impacted significantly by the 10% slice of ethanol.

lots of good stuff in the article.

 

I find pump fuel in my area has around 7% ethanol content according to my content sensor, "e85" has anywhere from 60-70% ethanol content. I highly recommend an ethanol content sensor and flex fuel tuning to combat the inconsistent ethanol content and target afr that comes with it.

I dug up an article that i read a while ago regarding ethanol content in blended fuels and knock resistance which i think is worth reading. I am not sure if there is a linear increase in knock resistance with a linear increase in R+M/2 or RON rating but this article does indicate that there is a non linear increase in knock resistance compared to ethanol content. it is a long read and if you want to skip over the technical stuff and get to the part we are probably interested in open part 2 and scroll to page 8.

part 1: https://docs.google.com/file/d/0B_jE...xYOHdneUU/edit
part 2: https://docs.google.com/file/d/0B_jE...M1UVhjVUU/edit

 

from the linked study:

"There appears to be no significant improvement in antiknock fuel
performance beyond about 40% ethanol content, unless it is
used in a DI engine that can utilize much more of the charge
cooling effect."

"Thus, the charge cooling benefit is generally comparable in magnitude
to the chemical benefit."

as to avoiding knock.

my underline.

 

I think that sums up the main takeaway nicely.