Running 91 & E85

[DSGCOBRA03]

Does anyone here run both fuels on separate tunes? When I decide to go twin screw I would like to get a tune on 91 and E85. When switching the tunes do you have to drain the fuel tank completely? Or would it matter if there was a couple gallons of 91 in the tank when filling up with E85 or vise versa.
Thanks.

 

[REX-RACER]

Does anyone here run both fuels on separate tunes? When I decide to go twin screw I would like to get a tune on 91 and E85. When switching the tunes do you have to drain the fuel tank completely? Or would it matter if there was a couple gallons of 91 in the tank when filling up with E85 or vise versa.
Thanks.

The trick is to have a "switchable" tuning solution such as an XCal2/3 flash tuner or even a flip chip. I prefer to run the tank down to near empty, fill up, apply the appropriate tune and off I go. Some folks do figure out what percentage of fuel in the tank they can safely run the high octane tune but that just seems like too much work and unnecessary risk to me.

The thing you need to remember is that since the difference in octane is so great if you really tune for E85 you could never run 91 or even 93 safely on that tune. You can however do it in reverse, i.e; run E85 on a 91/93 tune, heck you could even E85 w/ an 87 tune but you'll be pig rich and get horrible mileage.

 

[LTHL VNM]

I have a Diablo revolution flip chip with toggle switch I'll sell you

 

[DSGCOBRA03]

The trick is to have a "switchable" tuning solution such as an XCal2/3 flash tuner or even a flip chip. I prefer to run the tank down to near empty, fill up, apply the appropriate tune and off I go. Some folks do figure out what percentage of fuel in the tank they can safely run the high octane tune but that just seems like too much work and unnecessary risk to me.

The thing you need to remember is that since the difference in octane is so great if you really tune for E85 you could never run 91 or even 93 safely on that tune. You can however do it in reverse, i.e; run E85 on a 91/93 tune, heck you could even E85 w/ an 87 tune but you'll be pig rich and get horrible mileage.

Ya, I was thinking about doing an xcal when time came. I just thought it would be a pita to have to drain the whole tank every time switching tunes. So I was just curious how much it mattered if there was 13 gallons of e85 and 3 gallons of 91 in the tank. Anyways I would wanna run around 21-23 psi on E85. So if I wanted to switch back to a 91 tune I would have to pulley it back to around 17-18 psi anyways. There's a lot of E85 gas stations from where I'm from but I take my car out of town often and I don't want to have to worry about finding E85. So that's when I would like to put a 91 tune on low boost plus 30% more mpg.

I have a Diablo revolution flip chip with toggle switch I'll sell you

I'm not at the point where I'm going to purchase anything quite yet, but thanks for the offer.

 

[04sleeper]

Ya, I was thinking about doing an xcal when time came. I just thought it would be a pita to have to drain the whole tank every time switching tunes. So I was just curious how much it mattered if there was 13 gallons of e85 and 3 gallons of 91 in the tank.

Ethanol mixes perfectly with gasoline. Almost all gas stations have 10% Ethanol already. E10. A few gallons of regular gasoline will not hurt anything.

If you are wondering what it will do to the percentage of Ethanol, you can use this calculator to help you determine different mixtures of gasoline and E85.
Ethanol Calculators


Anyways I would wanna run around 21-23 psi on E85. So if I wanted to switch

back to a 91 tune I would have to pulley it back to around 17-18 psi anyways. There's a lot of E85 gas stations from where I'm from but I take my car out of town often and I don't want to have to worry about finding E85. So that's when I would like to put a 91 tune on low boost plus 30% more mpg.

You should only see a 10-15% drop in fuel economy if your car is tuned properly on E85. the 30% comes @ WOT only.

Just don't want to misinform anyone.

 

[DSGCOBRA03]

Alright, thanks for the information!

 

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