E85 vs 91 vs 93 vs 100
 

Hi Everyone,

I literally just tried searching "e85" on threads and posts and came up with no results. So I decided to make one, unless someone else can point me in the right direction.

I need to know,

1) Is the OpenFlash tune possible for e85? And what results have been shown?
2) What are the overall benefits of e85 vs. pump gas options.
3) If I have it correct, if you get the right tune, E85 can yield great gains on a stock FRS/BRZ alone vs. pump gas.
4) As a DD, is e85 a realistic option as long as you have enough pumps in your respective surrounding area?
5) Because Flex Fuel is the only way to get e85, I imagine that there is no downside since you can get pump gas when/if needed.

Ill add more if I think of anything. Thanks for now

1) No, none. Maybe in the future.
2) Higher effective knock resistance.
3) +10-15whp N/A, possibly more with FI
4) Sure, the only downsides being greatly reduced distance between fill-ups and increased cost since e85 mpg is ~30% less
5) You'll void your factory warranty covering your engine and fuel system because neither was designed to run flex fuel or e85.

Thanks man, I appreciate the response. With regard to your 4th response, so on e85, if I avg around 26.5 mpg on 91 octane, then I would be averaging around 18 mpg on e85. I guess the benefit is that you can switch between e85 and pump gas which is nice.

Current Fuel Price Averages (excluding reserve tank):

91 octane @ $3.68/gal x 11 gallons = $40
e85 @ 2.75/gal x 11 gallons = $30

Rough numbers of course, but you only save $10 per fill up yet you lose around 8 miles per 1 gallon. Which means you're basically losing 90 miles of distance on a full tank of e85. But people don't typically run a full tank of e85 as their DD right?

If they are running an E85 tune and not a flex-fuel tune (requires extra $$ hardware), then yes - full tanks of E85.

93 octane where I am is $3.28. My only holdbacks from going e85 are:

1. Car wasn't intended with it to begin with
2. Fuel lines withstanding high ethanol
3. Higher fuel consumption with less gas stations to fill up at

e85 seems more for the racing crowd. As it does work with a daily driver, I just wouldn't want to put myself in a situation where I could get stuck on empty with no way to fill it. This car is still new to me, and I do admire all the ballsy people who do e85 and FI options. I just want to see how it handles these long term as I do intend on keeping my FR-S a long time as my daily driver.

Correction:

I typically run a tank full of pure E85. I rarely put gasoline in my car. Why is this?

E85 has a much higher octane rating. Octane rating can vary from area but typically runs 100-110 octane. Also due to increased volume of pressurized fluid & the conductive properties of alcohol this also gives a slight "cooling" effect to the engine. On top of this E85 is typically notably cheaper than gasoline, especially compared to a race gas. 100 octane in my area at a pump ranges from $10-12 a gallon. E85 ranges $2.70-$2.90. 91 octane ranges $3.30-3.60. The cost / decreased fuel economy is nearly balanced out. And when you consider the increase of power obviously it is more desired. And on top of this due to the octane increase it is possible to get power more "effectively" than gasoline due to ignition advance giving you more efficient power delivery that actually slightly offsets the increased fuel requirement for stoich mixture. This for example could ideally require less throttle input to gain the same acceleration. Typically people se 25-30% decreased fuel economy.

E85 however is also more corrosive. Only time will tell how our system will handle E85. Give it a few years for concrete evidence of how our vehicle handles This. We have two fuel systems (DI & Port) and very little has been tested. However there are a number of vehicles that have been running ethanol based fuels for a fair number of miles.

E85 also tends to "clean" the engine. It typically has a slight water content, as well as its corrosive properties tend to keep the internals nice and clean. This however also can damage seals and other components not rated for ethanol. However our cars are regulated by US regulations to handle a specific % of ethanol tolerance. Increasing the ethanol % will just increase corrosion.

So there are ups and downs to E85 compared to other fuels.

Flex fuel is not required. Flex fuel is simply a setup that lets you run a "flexible" amount of ethanol in your car. I would highly recommend doing a flex fuel setup vs a simple E85 switch personally. The reason for this is that if you read the pump it actually typically says "At least 70% ethanol content". Which means that the quantity of ethanol in the blend can vary from time to time.

Also sure OT could run E85! You simply need to have someone who knows what they are doing compensate your fuel map to make up for the ethanol %. If you want a flex fuel setup that is something you would need to discuss with OT to see if they have a system to handle the fuel trim adjustment (and ignition). Also ignition needs to be adjusted, some people just increase a specific amount (canned tuners etc) but this should actually be done on a dyno for peak power as E85 is so resistant to knock due to its octane rating. You will pass the point of increased power due to ignition advance and just push your car closer to a dangerous threshold with no warning.

On a FI car the benefits are amplified quite a bit.

So to recap:
The Good
Higher octane
Better cooling properties
Carbon buildup preventive/cleaning
Lower cost per gallon

The Bad
Increased corrosive properties. This may cause problems down the road
Untested long term in our vehicles
More injection required to run stoich. This means lower fuel economy and more frequent fill ups.
Should technically require a dyno tune for optimal power gains. (There are still some gains that can be generically and or done via remote tuning!)

The Ugly
Don't believe anyone that says it is 100% safe. They are likely trying to sell something to you. This has not been tested long term, however it has been tested on quite a few vehicles.

Also to add to this... True E85 capable vehicles tend to have stainless fuel filters, Ethenol capable fuel lines, ethenol capable fuel pumps... and have lots of R&D testing for long term use. E85 sitting idle over periods of time can become more corrosive. So a car that sits idle will also have more corrosive properties than a car driven more often.

Our engines also sit flat... E85 has an increased water content and leftover water can be stuck in the engine after powering off. There have been reports on subaru forums of corrosion to the sleeves causing extra blow by after extended uses. I personally rev my engine to 2-3k and kill the ignition to help force any moisture out of the engine (who knows if this helps but it cant hurt to try i guess?).

This is why I opted for flex fuel. I travel a lot and drive my car quite a bit. (24k miles in the last 6 months). I never know if I will have access to E85. Switching between fuels is not as ideal as people think to do day to day. I have an ethanol content sensor in my car and when attempting to switch back to pure pump vs pure e85 you have to starve the tank extremely low (well past the E line) and typically burn through a gallon of low blend (say E15 vs E10) to get it to pure. If you are driving a car that is tuned aggressively a 10% swing of ethanol content can give enough swing to be a problem, so switching every week is not ideal. For people who will run E85 90+% of the time switching isn't a huge deal for when going out of town. The closed loop cycle will calibrate the AFR's for you and balance the correct fuel mixture while switching between mixtures (as long as you are keeping off the throttle).

Where are you getting this information from? I can't see a reason why OFT can't support e85. There may not be any tunes for it yet, but there shouldn't be a reason why it's not supported.

Where are you getting 91 for $3.68/gal?! Also, there aren't too many E85 stations in the bay area. I know people who DD on E85, but they also carry a couple of 5 gallon containers of E85 all the time.

To date, the only e85 equipped station I have come across while driving in the central Texas region is Burnet, TX. I am sure there are more, I just don't see them in my areas that I drive in.

We should have and e85 tune for the OpenFlash tablet late next week.

It is just an average number. Doesn't pertain to a specific location.