I've read that some folks are doing this. I have a Works P2r 93 octane flash in my Evo and the number of gas stations with 93 are getting harder to come by in my area, but there are a lot of E85 pumps. I've read that some are mixing a gallon or two of E85 in their cars at fill-ups to add some octane. I've read quite a bit about E85 and know that you need a tune, injex, etc to run it straight.

I'd love to be able to mix in a couple gallons to bring my octane up to 93+ to eliminate knock.

Who's doing it, and how's it working for you?

My current tune is for 21lbs of boost, and it has ~11.5:1 AFR (dyno verified).

 

its very hard to mix e85 with pump gas, unless you know exactly how much e85 is in the tank..

i did a mix of 80/20 of 80 percent e85, and my wot a/fs were running around 11.0ish...

the same tune, i put 100percent e85, wot a/fs went to around 12.0ish

 

Are you sure people are doing that without being tuned for it. It's not the same as adding some high octane (100+) for knock suppression. E85 requires SIGNIFICANTLY more fuel, so I'd be concerned with how a mix of E85 and 91/93 works on an 11.5 AFR tune...

 

Good question, I've been wondering this also. I've heard you
you can run up to 25-30% mix without a problem but have yet
to verify it. I'd like to mix a couple gallons just to offset race gas
cost for a little insurance on track days.

 

I've read you need to flow 30-40% more E85 to equal gasoline if your
running it straight. A local guy has a 1G eclipse running straight E85
with the Bushur twin fuel pump set-up and 1000cc injectors and at the
450whp power level the injectors are about maxed.

 

Yep, that's common knowledge . I'm not talking about running it straight though.

 

yea most people get 1600cc injectors for running e85...

 

Sorry that was more of a responce to some of the other posts. I know what your
asking and am wondering the same thing. I will have my wideband installed
soon, could always put in a couple gallons and see how it effects AFR. Is there
a way to calculate the octane to see if 4 gallons or so on a full tank would actually
raise the octane?

 

Thanks for the response....hope I didn't come off like an ***. Theoretically (according to my calcs which may be wrong) 2 gallons of 105 octane plus 12 gallons of 92 octane (typical fillup on an empty tank) would make the octane about 93.8. Maybe simple math doesn't work in this situation, but who knows. This would end up being about 17% E85 / 83% gasoline. Might lean the car out too much I guess. Hmmmm......

EDIT: (again using simple math, which might not apply here), the above scenario would lean the car out to around 12.2:1 AFR (40% x .17 = 6.8%. 11.5 + 6.8% is around 12.2) Probably not the safest I guess.

 

I wouldnt do that either especially if you have all your stock fuel lines in place. E85 is very corrosive

 

Leans out the car because its E85, yet raises octane. Hmm.... this is an interesting one.

 

Lots of folks running straight E85 with stock lines with no issues.

 

Yeah, my math might be all wrong, but it seems to make sense to me.

 

That is not true. Methanol is very corrosive. Ethanol is moderately corrosive. E85 is slightly corrosive at worst.

-Paul

 

Correct.... Im running stock lines with fullblown dual pump setup. 780cc injectors. I havent turn the boost up yet though.

Im on my 5th tank of gas running E85!

I only get about 14mpg though.. but that was compared to only 18mpg with 93 octane.