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Switching to e30 tune

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#22
Ok, so tune received. Haven't used it yet but I printed the Stratified guide to maintaining an E30 mix and am feeling better about keeping everything where it should be.

The question is... if I was going to err, would it be better to run more or less ethanol in the tank?
 


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#23
Ok, so tune received. Haven't used it yet but I printed the Stratified guide to maintaining an E30 mix and am feeling better about keeping everything where it should be.

The question is... if I was going to err, would it be better to run more or less ethanol in the tank?
I would rather be over than under. But the ECU can compensate for an off mix to a certain extent. I personally just refill with E30 at a quarter tank or less. Doing so at 3 gallons of e85 and the rest in pump gas will give you the proper mix. If you're scared of the potentially low ethanol quality, either test it yourself (kits are like $20) or run a tad more like 3.25. being a bit above or below the E30 mix won't hurt as the ECU will adjust, so don't worry about it too much.

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Location
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#24
Yeah, I'm planning on refilling at a quarter tank or less for consistency. And in those times, that would be easy.

But let's say I take a little road trip and I've already got a full tank of E30. When I fill up, at a quarter tank, that's a 1/4 tank of E30.

If I fill up the rest of the tank with 91, I'm good going back to the 91 tune, even though I would still have a certain percentage of ethanol, right?
 


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Location
Los Angeles
#25
Yeah, I'm planning on refilling at a quarter tank or less for consistency. And in those times, that would be easy.

But let's say I take a little road trip and I've already got a full tank of E30. When I fill up, at a quarter tank, that's a 1/4 tank of E30.

If I fill up the rest of the tank with 91, I'm good going back to the 91 tune, even though I would still have a certain percentage of ethanol, right?
Correct. At a 1/4 tank, it comes out to roughly e15 or so, depending on the ethanol quality and such. Pump gas is already 10% ethanol, so making it e15 in tank is within the ECU range.

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Spork1569

Active member
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Ventura
#26
Correct. At a 1/4 tank, it comes out to roughly e15 or so, depending on the ethanol quality and such. Pump gas is already 10% ethanol, so making it e15 in tank is within the ECU range.

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Yep. I've found my 91 time ran better with a couple gallons of ethanol thrown in. Ethanol's an octane booster so there was very little to no negative corrections even when pushing the car.

If I get lazy from time to time I fill up at the shell near my work with 91 and flash the tune back, and drop in 3 more gallons whenever they fit to go back to E30.
 


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Location
San Antonio
#27
FWIW every couple months I run a half tank of 93, with the corresponding tune of course, just to restart my ethanol calculations. I run the 93 tune to almost empty (less than 20 miles) and then I test the ethanol and restart my E30 tune. Just in case it starts to creep into E40+ range over multiple tanks. I have to fill up every week so I am always doing the math. I’ve been running an e30 tune for almost a year now and I’ve never ran into any issues. I’d rather run more ethanol than less. When ethanol was out of the way for me I would throw a gallon in with my 93 tune and my corrections were almost never negative. The only negatives I would get were on tip in which is pretty common. Ethanol is liquid gold. I HATE when I have to run 93. Car feels so slow lol
 


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