Higher knock than usual lately?
 

Getting some unexpectedly higher knock lately? This might have something to do with it:

"That has led to ethanol - historically about 20 cents less per gallon than gas - becoming more expensive than gas. And that has caused refiners to use less ethanol for blending"

Source:

Inflexible ethanol costs stopping further decrease in gas prices

Hah, funny comment in the comments:

WienerDogArmy
1 Hour Ago
I hope they keep e85 since my 1kwhp trans am runs on the corn sauce. Yep that's right, my ability to drive a racecar on cheap fuel is more important than everyone's disdain for corn based fuels.

So everyone should jump on the Methanol bandwagon. Has anyone had problems yet with Meth in the gas tank? I've been doing it for about a yr now, and with less than half the amount of added meth vs E85 (2 gallons vs. 4.5) I seem to get the same results

What are you paying for a gallon of meth? E85 is about $1.80/gallon out here.

$4 a gallon. Don't think it has changed since E85 was close to that.

I just prefer to get one additional fuel. Add to tank and spray :-)

I'm new to this sort of thing, so I'm going to ask the noob question: How does ethanol content influence our knock threshold without changing the overall octane rating of the fuel? Is it because of the evaporative cooling effect that comes from running a gas with a lower A/F stoich ratio?

Yes.

E85 does increase the octane rating of the fuel in your tank, both the actual and effective rating. E85 itself is greater than 93 octane (I've seen sources that say it's anywhere from 98 to 110 octane), and in a DI engine it has an effective rating of something like 160. Threads on this are scattered throughout the forum.

Edit - just realized the question was about ethanol specifically, not E85, but the overall explanation is the same regarding the effect in a DI engine.

E100 has an effective octane in direct injection motors of 160. Not e85.

Yeah, it's basically the same when you're talking pure E vs E85. I've seen posts on here saying E85 had an effective rating of 160:

http://www.mazdaspeedforums.org/foru...vs-e85-115288/
http://www.mazdaspeedforums.org/foru...estion-138335/

Other posts say E85 is 150 octane:
http://www.mazdaspeedforums.org/foru...ooster-177313/

Others say it's pure E that is 160 octane:
http://www.mazdaspeedforums.org/foru...ecific-138097/

Consensus seems to be that E85 and/or E is essentially 150-160 octane in direct inject engines. And at that point, there's really no difference between E85 and E for our purposes.

I have been noticing higher KR that started a couple weeks ago on pump gas. I'm in southwest FL, has anyone else noticed this? Less incentive now for the refiners to blend gas up to E10. Had to back down to a less aggressive pump gas tune, might test my E85 tune today.

I only get on 93 when I absolutely have to. And even plan my trips to an E station accordingly.

I think summer blend is finally being circulated in California. Like the flip of a switch my knock levels are down to normal (around .60 at the highest). During the entirety of winter I was seeing constant 1-1.7 degrees of knock @ WOT. This is totally gone as of 2 weeks ago.

Time to move back to my stratified tune.