Thread: using E85 temporarily

on Monday I'm driving to a town that has E85. I don't plan on switching, but what if I put 5 gallons in my gas tank and filled the rest with premium? I could also buy like 5 or 10 gallons to use for the next couple fill up's. If I just did a maf adjustment would it be sufficient for the different blend?

42's, duty cycle hasn't exceeded 70%, and that was with a very rich 10ish afr

Even if I'm only running it at a ratio of 1 to 3, and temporary? I'll have like 5 gallons of e85 per fill up for 2 or 3 fill ups?

I think I understand, but it would be 5 gallons of E85 or whatever it ends up being and 10 gallons of E10, so say it is E70 at 5 gallons, and E10 at 10 gallons, that would convert into E30. am I doing the math right? I would do that ratio because I have at least one empty 5 gallon gas can, and I have another 5 gallon gas can, but I don't remember if it is empty. and my other reasoning is that by only doing a 33% E85 blend, the mass air flow sensor should be able to add enough fuel to compensate. E85 has about 30% less energy, so it needs to flow that much more. so E30 would need to flow about 15% more fuel, which the mass air flow is able to calculate and with an adjustment it should be within 5% of 0. I could richen up stoich as needed.

You have a 25 gal gas tank as part of the calculation

so I have enough gas cans for 15 gallons, so I should be able to run it for a couple months.

should I bother getting an ethanol tester?

Originally Posted by Scottydoggs

your injectors will max out on you running e85. they are not really not big enough if your modded. will this work ok? maybe, but its not worth it to me at all. if they got 93 gas there, get that.

I thought about this, and if I was running actual E85%, then my injectors would be maxed out, but based on estimates, I'll probably just be running E30 or E40. E85 needs to flow about 30% more fuel, so E40 would be about half that and need to flow about 15% more fuel.

One thing I find interesting is that according to a website, blends of fuel with 20%-30% ethanol will get the same gas mileage as fuel with no ethanol.

https://www.intercepteft.com/calc.html

Originally Posted by GTPpower

You should be able to run up to around 50% ethanol without actually making any changes to the tune. But, you are cutting it close at that point. I would shoot for about 40% max.

I was planning on using 5 gallons of the E85 with 10 gallons of E10, which is about 30%. I have a ethanol tester on the way so I will know how much to use to get that ratio. I am going to make a maf adjustment because my fuel trims were lean, but other than that I don't think I will change anything.

we drove to that town because my wife had a job interview, and if she gets the job she will be driving there everyday, with the potential for a move. it's only a part time job so like 6 hours a day at 15/hr, but there is good potential for advancement. I'm hoping she get's it, so I can just run straight E85 when/if we move.

here is an update: without actually testing the E85 it is impossible to pinpoint the actual ethanol content, so I'm estimating I have E34 in my tank now. I made a maf adjustment, will need one more to get it dead on, but it is within 5% of 0 during all driving, I just want to dial in the wot area a little closer to 0, right now it is at 0.8. I took 3 pulls during the drive after the maf adjustment with a maximum of 0.2* of kr. so I'll make another maf adjustment and add 1* of timing for now.

thanks for the help team. and just so you guys know, this car isn't my daily driver, so the 14 gallons of E85 I have left in my assorted gas cans will last a few months. hopefully the variances from fill up to fill up won't be significant.

I got the ethanol tester today, and looks like I bought a bunch of E70. Now that I know this, I can get my ethanol blend calculated to 40%. I'll probably add the amount required later today, then take it out for a maf tune tomorrow.

in my gas tank now, I have E27, so another 13% ethanol should help kr even more.