Help me understand E85

[GilmourD]

E85 really wakes up the coyote. Easiest extra horsepower you can get. The only con to running it is fuel economy like others have said. But if your car is weekend fun car going E85 is a no brainer. You won't regret it at all. I personally run a flex fuel tune because E85 isn't always convenient to get where I'm at.

So, basically, E85 (if it were even commonly available here in New Jersey) wouldn't be the right option for my dailied GT, huh?

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[NightmareMoon]

So, basically, E85 (if it were even commonly available here in New Jersey) wouldn't be the right option for my dailied GT, huh?

I get like 10mpg city on an E85 tune, and I can only fill up at a couple of gas stations in town, none of which are w/in 3 miles of my house, sooo its a bit of a pain for daily driving, just due to the frequency and inconvenience of getting gas. Running low? Better be able to make it to your intended gas station, because you can't just fill up anywhere anymore.

The cooling effects of E85 are a lot more useful for blown cars than for N/A cars, which generally can handle the heat they generate pretty well. I get max timing on '93, so E85 isn't really giving me any more timing than regular gas. Octane protects against detonation by slowing how easily the charge ignites, but if you have sufficient detonation protection to get the timing you want, you won't benefit from a higher octane rating.

All that said, my motor seems very happy with it's E85 tune.

 

[K4fxd]

E85 by itself will add some power due to it carrying its own oxygen.

If it is readily avalible there is no reason not to run it. Personally I would use a flex tune just in case you run out and can only get gas.

 

[Magnetic Stang]

So, basically, E85 (if it were even commonly available here in New Jersey) wouldn't be the right option for my dailied GT, huh?

Not necessarily. I daily my GT. The flex fuel tune is convenient for me. I don't have to test ethanol percentage out of the pump every time I fill up to make sure it's high enough. The car will automatically adjust after the first 10 minutes or so. If I'm not in an area that has E85 i can just fill up with 93 and it's no issue. If I was trying to get the most power all the time, every time I'd probably go with a dedicated E85 tune.

 

[Cory S]

these vehicles are only able to use the widebands to adjust for ethanol and its just not very accurate compared to having an ethanol sensor in line.

Our on board NTK sensors read in true Lambda. They are far more accurate (within 2%) in reading AFR than the inline sensors systems (3-5% accuracy). that only measure Alcohol content.

Only advantage to the inline sensor is the ability to run a wider range of Ethanol percentage so STFT’s can swing far more than the standard mapping of 25%.

But for a straight E85 calibration, the upstream wideband O2 sensors work perfect for allowing a range of E70-E90.

 

[Stephen@lethal]

Our on board NTK sensors read in true Lambda. They are far more accurate (within 2%) in reading AFR than the inline sensors systems (3-5% accuracy). that only measure Alcohol content.

Only advantage to the inline sensor is the ability to run a wider range of Ethanol percentage so STFT’s can swing far more than the standard mapping of 25%.

But for a straight E85 calibration, the upstream wideband O2 sensors work perfect for allowing a range of E70-E90.

The issue there is that most people that are running flex on these cars, are doing so with less ethanol than that and the widebands just don't work well for boosted applications that do not wish to run full e85. This is why tuners like Lund prefer not to use flex tunes for boosted S550s. I am not disputing that the widebands read fine in true Lambda and I am running full e85 just fine.

 

[Mike Pfeifer]

So, if staying NA, and all stock otherwise (besides maybe a drop in air filter), can you get a flex tune and run any fuel you can get hold of, from 93 octane to E85 or anywhere in between? So long as you let it run for 10-15 minute after each fill up? Is that what I am reading here?

 

[GilmourD]

Not necessarily. I daily my GT. The flex fuel tune is convenient for me. I don't have to test ethanol percentage out of the pump every time I fill up to make sure it's high enough. The car will automatically adjust after the first 10 minutes or so. If I'm not in an area that has E85 i can just fill up with 93 and it's no issue. If I was trying to get the most power all the time, every time I'd probably go with a dedicated E85 tune.

Yeah, I tend to run 93, mainly because I always did with my '12GT, which was all stock, but my '15GT came to me modified, unfortunately without a complete list of all the mods (engine appears stock outside of the CAI, but I honestly haven't had the time to really go over every millimeter of it).

Also, living in north Jersey, I don't recall ever seeing E85 at any gas station around here.

 

[K4fxd]

Yes. Don't need to wait 15 min either. Just drive it. The ECU will compensate with short term fueling until it learns.

EDIT. I wouldn't hammer it until you put about 10 miles on it. Driving normal is fine.

 

[Mike Pfeifer]

Yes. Don't need to wait 15 min either. Just drive it. The ECU will compensate with short term fueling until it learns.

EDIT. I wouldn't hammer it until you put about 10 miles on it. Driving normal is fine.

Interesting. I thought I had read on here before that it had to be in a narrow range of like E30-E70 for the flex tune to auto-adapt (and min E70 for E85 dedicated tune). Maybe I misunderstood what that conversation was about.

 

[K4fxd]

It will learn anything from 0 to 100%

It's the same logic as the flex fuel F150. In the Mustang ECU it is just turned off and a few tables need to be filled in. I have no idea why Ford didn't turn it on and make the Mustang flex from the factory. Maybe they didn't want the 50HP boost or whatever it is.

Or more likely it is due to the small fuel tank.

 

[Ewheels]

Haven't seen it mentioned yet but don't let E85 sit in your car for very long. It will create rust if allowed to sit. If the car sits for extended periods of time, put 91 in the car beforehand.
I have a friend who runs E85 on his race car and he let the car sit and he found rust everywhere in the heads.

 

[Cory S]

Haven't seen it mentioned yet but don't let E85 sit in your car for very long. It will create rust if allowed to sit. If the car sits for extended periods of time, put 91 in the car beforehand.
I have a friend who runs E85 on his race car and he let the car sit and he found rust everywhere in the heads.

It takes a lot longer than people think for this kind of thing to happen. it usually doesn’t happen in todays fuel systems anyway, because every component is either, aluminum, stainless steel or composite.

It’s not E85 that causes rust. It’s when too much water/air is introduced at the same time and then allowed to evaporate.

My bud has been running E85 for 7 years. His car sits every winter for 5 months, and stats up and runs 9’s every season. Car hasn’t seen any fuel less than E70 since he built it.

 

[junits15]

On this topic, how does this car actually learn ethanol without a sensor? Is it just watching the fuel trims required to hit stoich and then extrapolating e content from that? Is that really accurate?

I had heard that this was how ford does it in their normal flex fuel cars, I'm surprised to see the feature dormant in the mustang. My assumption was that the regular cars were such low performance that a coarse ethanol estimate was enough to get them running well enough without impacting performance.

 

[Ewheels]

It takes a lot longer than people think for this kind of thing to happen. it usually doesn’t happen in todays fuel systems anyway, because every component is either, aluminum, stainless steel or composite.

It’s not E85 that causes rust. It’s when too much water/air is introduced at the same time and then allowed to evaporate.

My bud has been running E85 for 7 years. His car sits every winter for 5 months, and stats up and runs 9’s every season. Car hasn’t seen any fuel less than E70 since he built it.

I don't know man, my friend has a 2018 GT and found rust in his heads after just a few months. He also always tests his and it's consistently 85%

I'm only saying b/c OP asked for pros and cons. One of the cons is the potential for rust

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