EVOlutionary

iTrader: (38)

As you most of you who are running E85 or researching the possibility of running E85 know, the ethanol content in any gallon of "E85" you get from the pump will vary from 70%-85% ethanol depending on the time of year and what part of the country you are from. Here in Michigan it runs around 75% in the winter months, 80% in the late spring and early fall, and 85% for only a couple months during the summer.

If your car has been tuned specifically for 85% ethanol content - during the 10 months of the year that you can't get 85% ethanol from the pump you have to either adjust your tune or mix your own. VP Racing Fuels sells 100% Ethanol (actually only ~ 98%, more on this later) in 55 gallon drums and also probably in smaller sized drums.

So here is a rough quick reference for how much of each grade to mix with 100% ethanol to make 10 gallons of E85:

5gal 70% + 5gal 100% = 10gal 85%
6gal 75% + 4gal 100% = 10gal 85%
7.5gal 80% + 2.5gal 100% = 10gal 85%

Now to discuss about the true percentage of ethanol in E85. E85 is a mixture of 15% gasoline plus 85% "ethanol". BUT - that "ethanol" that is mixed in is not pure. It has additives in it, about 2%, that makes it undrinkable. So, of that 85% ethanol that is being mixed in, only about 83% of it is PURE ETHANOL. If you have an ethanol content gauge and are mixing your own to go get tuned this spring, you want to see it run around 82%-83%. . . . that way when you get the good stuff from the pumps in the summer time it sill be a similar percentage. . .

I have two MS Excel spreadsheets with formulas to calculate how much of different types of fuel to add together to get "E85", but I don't know how to post a spreadsheet with active formulas. If anyone can help me with that it would be much appreciated. . . .

EVOlutionary

Mooseknuckle

iTrader: (4)

Very interesting...thank you!

I am about to get tuned for E85 with a mail in flash from English Racing. Should I just tell them to err on the richer side in case the percentage of ethanol I get from the pump is not quite 85%? How should I go about doing this? I don't want to have to keep changing my tune; I'd like to basically just set it and forget it. I'll be driving the car all the time except for winter so I won't have to worry about the winter blend that comes out in the colder months.

Is it as easy as turning down the boost when the mix isn't quite up to par?

I don't want to be blowing anything up here...so just trying to figure out the best course of action to take to make this a carefree switch over to the good stuff.

E85evo8

iTrader: (21)

best advice would be to tune the car correctly or for how much power you'd like to make on 70% ethanol so when the weather gets warmer and the ethanol content increases in the pumps you will be even more "safe".

In NY right now the pumps have Class 3 Ethanol which is 70%..the months of april and May are Class 2 which is 75% and then for 3-4 months in the summer in is Class 1 or 85%. The fall and winter it drops back down. to Class 3.

EVOlutionary

iTrader: (38)

I would actually recommend the opposite, although I am not a tuner so the *check with you tuner* disclaimer applies.

The reason for this is - if you get tuned on E70, when you put E85 in it you will be running much leaner. You will have more knock resistance from the E85, but I don't know if it will overcome the lean-ness. . .

I would have it tuned for E85 (~83% on an EtOH gauge). That way in the cooler months when you are using Class 2 (75-80%) your car will run a bit richer. You can also turn the boost down a couple PSI if necessary, but that may not even be necessary. . . .

E85evo8

iTrader: (21)

its all about knock resistance.....higher the octane the more timing you can run, the leaner your A/F's can be, more boost you can run. tuning on E70 and then running on E85 is like tuning on 93oct and then filling up with 100oct (just some examples..not specifics). Getting tuned on a lower oct fuel and then running a higher one is "safe"...getting tuned on a higher octane and then running a lower one..."not so safe"

EVOlutionary

iTrader: (38)

Do you know the difference in octane rating between E85 and E80? Those are the only two grades the OP is probably going to encounter if he does not drive the car in the winter. . .

If you tune a car on 93 octane it is completely safe to drive on 87 octane if you turn the boost down a bit. Using the same tune for a little lower octane fuel is OK.

If you tune a car on E70 then run E85, is it going to be safe?? Is going from 11.5@wot to 12.5 or 13 @wot safe (numbers just to show my point - not actual numbers). . .

E85evo8

iTrader: (21)

from what my tuner/friend and myself have agreed upon is that tuning on 70% ethanol and then running anything higher (E75/E80/E85) will increase the safety factor w/out changing anything...ethanol is new to me and my area so maybe someone can chime in and confirm what i'm saying

GRNCT9A

iTrader: (1)

I'm sure a higher oct rating isn't going to adjust the A/F. The fuel maps shouldn't change just because of a higher oct rating. If that were the case, why even tune your fuel maps for different oct ratings?

I'm not saying your wrong. I just don't see that happening. Also, I left out boost and timing because thats not what we are talking about, but of course once you change fuel, those will have to be adjusted in some way, either for safety or better performance.

nothere

iTrader: (23)

Evolutionary makes a good point, that can be lost to some of us.

since ethanol requires a richer mix relative to gasoline, an ethanol ratio of 70 takes less fuel than a mix of 85 to maintain the same afr.

Now as to whether or not the difference is significant given the increased octane, of the 85, I have no idea.

In all likelihood the difference is small enough as to not be worth counting on.


did I get this right?

EVOlutionary

iTrader: (38)

yep, that's what I was trying to say.

I am sure there is a thread on here somewhere where someone has logged AFR's on E70 vs E85 to see just what the difference is. It may or may not be significant. I don't know, because I always just mix up to E85 - that's the easiest solution for me

LV///R

iTrader: (36)

Help me understand this. I'm not saying you're wrong, I just want to fully understand how E85/E70 works...


Why would you run leaner going from E85 (110 oct +/-) "down to" E70 (upper 90's+) make your tune go "leaner"? I always thought it'd be the opposite??? Maybe I shouldn't be looking at the octane rating.

Is it just because of the amount of fuel needed? Now that I think about it, I'm assuming you'd need more fuel, running E85 than E70? Is that correct? That the answer to my question?

I'm in the market to get tuned here this month in South Dakota. I'm sure we're still getting E70ish at the pumps, and my big concern is how the tune will change when the summer months come and what to do!

Thanks guys!

LV///R

iTrader: (36)

Ah, nevermind! "nothere" explained it! I just didn't catch it before I posted!

Thanks!

EVOlutionary

iTrader: (38)

I see you got it figured out. Just to reiterate for others who may have the same question - yes - if you get tuned on E70 you will need more fuel volume (more injector duty cycle) if you run E85 to keep it at the same relative AFR.

Mooseknuckle

iTrader: (4)

So would it be better to get tuned on the highest or lowest possible ethanol rating?

(E70 being lowest and E85 being highest.)

LV///R

iTrader: (36)

Sounds like the best way is to start with E85. Then during the cooler months, when the ethanol blend is lowered, you'll run a bit richer. Probably want to turn the boost down a couple psi as well.

I unfortunately won't have that option being I need to get tuned really soon and we still have E70 according to the blend schedule out there. I think what I'll do is get another refresher tune once we get E85 during the summer months.

Someone correct me if I'm wrong!