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Thread: e85 Questions

  1. #1
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    e85 Questions

    I am curious about running e85 on a NA motor. I know most people do it when supercharged or turbo'd to get more power and cooler temps. I was curious about running e85 on a fairly stock 95 M3.

    I would not be doing it for more power, but for the cheaper fuel. I know the mileage would be less, so that's something else to consider. Would it be as much of a decrease as the turbo guys are seeing?

    What would be needed to make the switch over other than injectors and a tune??

    I tried to research it and most post weren't very helpful.

    I'm in the research phase, so please use this as a discussion and bounce ideas instead of a bashing center if at all possible

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    I have an E85 35% mix on my turbo car (not BMW) and I get about 40% less gas mileage even with that little of a mix so for what it’s worth unless it’s a huge savings to run E85 it may not be worth the conversion to get you there.

    Also I’m in Washington state and E85 is about the same price as premium here:/
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    Thankfully I have plenty of e85 here

    91 is currently $2.99 a gallon and e85 is $1.79 a gallon

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    How long will it take to pay off given the cost of the tune, the bigger injectors, and the reduced efficiency?

    E85 adds power in NA motors due to the oxygenation but not much unless tuned to take advantage of the octane. You can find examples of people using it. Gintani has an E85 tune for the E9xM3 though few use it. There are also various flex fuel kits, many universal, that you could look into.

  5. #5
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    Quote Originally Posted by pbonsalb View Post
    How long will it take to pay off given the cost of the tune, the bigger injectors, and the reduced efficiency?
    That's the question I'm trying to answer. I just need educated in the details to be able to come up with the answer

    For example, the cost of a tune? $750 seems reasonable, but could you also get it cheaper? Who tunes for that without power gains being the goal in mind? Can you tune it with gas mileage as a goal? Is that even a thing? What size injectors will do? Pink top 21.5lb injectors big enough or would it require 24lb injectors or even bigger? I don't know. but that one shouldn't be too hard to figure out, I don't think. What would the reduced efficiency be for an NA motor? Would it be less than say a turbo motor? or supercharged motor? or the same regardless?

    Just trying to be educated by the great minds on Bimmerforums

    also open to flex fuel ideas, but I honestly do not understand them that much so I need educated on that too lol

  6. #6
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    I would figure 1/3 more fuel needed, which makes 21 lb injectors risky. So let’s say 93 is $3 and E85 is $2, which is 1/3 less. Since you need 1/3 more fuel, the 1/3 savings are a wash. Even if 1/3 more fuel is a little high, it would take a long time to balance the slight fuel cost savings against the tune and injectors.

    I might spend $1000 to gain 10 rwhp, but I would not spend it to save $250 a year on fuel. Maybe 93 will jump in price. Reconsider then.

  7. #7
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    93 is very limited here, but it's around $3.30. almost every gas station around here has 91 and e85 though

    let's say 24lb injectors and they are around $200? or used around $100? looks like RK Tunes has an obd1 performance tune for $250 (no idea if he that could include tuning for e85) and a fuel filter which I haven't looked into price at all.

    So a 33% lose in mileage is the rule?

    anyone have any experience to verify that on a semi stock e36? Just curious if anyone has done it etc

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    Not sure the E36 fuel system is setup to work with E85...and it's corrosiveness. It'll eat away rubber and other components if not properly designed for it.


    For Reference....

    the NEW silverado base does not allow flex fuel, it's like a $500 upcharge (in fuel lines, and other fuel system components) to allow to run it. (granted, they add a fuel sensor to this as well).


    I'd never run it in my M3...I'd rather give it 87 and not rag on it than risk e85.


    From a 'will it work' scenario...you just need to add more fuel. If you have 17.5lb injectors right now (stock for '95/S50), you could toss in 24lb injectors, say it's close enough, and drive it (w/o a tune...in theory)
    https://en.wikipedia.org/wiki/Gasoli...lon_equivalent

    Maths:
    Ethanol (E85)[5] 1.3900 71.94%

    So true E85 (which we don't get that often...in the US it's more like E50-80) takes 1.39 as much volume for the same energy as 1 part gasoline.

    So you need 1.39 times your current injector flow.

    You have 17.5lb injectors... times 1.39 = 24.3lb injectors (for TRUE e85).

    Take the account that we have E50-80 (ASTM 5798 that specifies the allowable ethanol content in E85 as ranging from 51% to 83%)

    Say E50 would need 1.229 times as much fuel...or 21.5lb injectors.


    So slap 24lb injectors in, and you're damn close...a little rich. OR...toss in 21.5lb injectors (stock S52) and hope for E50...but you'd be running lean with a heavier corn mix.





    LAST EDIT.

    Regarding cost...because the power density, you can look at E85 prices, multiply by 1.4... IF 91 (or w/e grade you would go with) is less than that...it's not even worth buying the E85 in the first place. (could also divide the 91 price by 1.4...whichever)
    Last edited by Moron95M3; 03-23-2018 at 03:43 PM.
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    Word of advice regarding used 24 pound injectors, don’t waste your time unless they can prove that they’ve been flow tested and if they can’t buy them directly from RK Tunes because he has them ready to go.

    I tried to save 50 bucks and got eBay verified used Bosch 24 pound injectors and only one of them worked when I got it so it’s another 200 bucks to have them properly fixed before I could even get them to work on my car.
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    Quote Originally Posted by TheJordanWhitte View Post
    Word of advice regarding used 24 pound injectors, don’t waste your time unless they can prove that they’ve been flow tested and if they can’t buy them directly from RK Tunes because he has them ready to go.

    I tried to save 50 bucks and got eBay verified used Bosch 24 pound injectors and only one of them worked when I got it so it’s another 200 bucks to have them properly fixed before I could even get them to work on my car.
    Good call! Shouldn't skimp on injectors! You don't always save money on getting used

    - - - Updated - - -

    Quote Originally Posted by Moron95M3 View Post
    Not sure the E36 fuel system is setup to work with E85...and it's corrosiveness. It'll eat away rubber and other components if not properly designed for it.


    For Reference....

    the NEW silverado base does not allow flex fuel, it's like a $500 upcharge (in fuel lines, and other fuel system components) to allow to run it. (granted, they add a fuel sensor to this as well).


    I'd never run it in my M3...I'd rather give it 87 and not rag on it than risk e85.


    From a 'will it work' scenario...you just need to add more fuel. If you have 17.5lb injectors right now (stock for '95/S50), you could toss in 24lb injectors, say it's close enough, and drive it (w/o a tune...in theory)
    https://en.wikipedia.org/wiki/Gasoli...lon_equivalent

    Maths:
    Ethanol (E85)[5] 1.3900 71.94%

    So true E85 (which we don't get that often...in the US it's more like E50-80) takes 1.39 as much volume for the same energy as 1 part gasoline.

    So you need 1.39 times your current injector flow.

    You have 17.5lb injectors... times 1.39 = 24.3lb injectors (for TRUE e85).

    Take the account that we have E50-80 (ASTM 5798 that specifies the allowable ethanol content in E85 as ranging from 51% to 83%)

    Say E50 would need 1.229 times as much fuel...or 21.5lb injectors.


    So slap 24lb injectors in, and you're damn close...a little rich. OR...toss in 21.5lb injectors (stock S52) and hope for E50...but you'd be running lean with a heavier corn mix.





    LAST EDIT.

    Regarding cost...because the power density, you can look at E85 prices, multiply by 1.4... IF 91 (or w/e grade you would go with) is less than that...it's not even worth buying the E85 in the first place. (could also divide the 91 price by 1.4...whichever)

    I've seen a few e36 turbo guys running it with stock lines and they have seemed to hold up ok so far from what I've seen

    Great information and numbers. I will look into it further!!


    - - - Updated - - -

    Is there much horsepower that could be gained from tuning and switching to e85? Just curious, not the goal of course but wondering since everything is better after being tuned

  11. #11
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    Not really unless you somehow gain compression.

    The advantage is you can run higher compression before it knocks...because it's effectively a 110 octane. which helps more for boost buggies.
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    Quote Originally Posted by Moron95M3 View Post
    Not really unless you somehow gain compression.

    The advantage is you can run higher compression before it knocks...because it's effectively a 110 octane. which helps more for boost buggies.

    That makes allot of sense!! Don't want to open up the motor because that gets expensive really quick.

    Are there any tunes that actually improve fuel economy? I know that's not really the norm

  13. #13
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    Drive it less like an asshat...lol.

    I would get 30mpg stock on my 95. Now after mods and a heavy foot...more like 21.
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    Quote Originally Posted by Moron95M3 View Post
    Drive it less like an asshat...lol.

    I would get 30mpg stock on my 95. Now after mods and a heavy foot...more like 21.
    I get about 18-20 in town and I don't drive it hard, granted my commute to work is only a few minutes so that could contribute some

    Sent from my 831C using Tapatalk

  15. #15
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    This is the same reasoning I used to put in the supercharger, 6 speed transmission, and 3.38 diff. Fuel Economy...lol I worked it out. I'll save the cost of the entire swap in about 110 years.
    No matter where you go, there you are...

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    I went for fuel economy by changing my supercharger for a turbocharger — it gave me so much more torque that I changed from a 3.64 diff to a 3.15 diff. To save even more money, I will be installing a 6 speed in place of the 5 speed. No Toyota Prius for me!

  17. #17
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    hahahaaa problem solved!!! 6 speed swap everything lol

    I am running 3.46 gears which I never thought about it before but that's not helping my fuel economy....shucks

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  18. #18
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    Swap in a cheap open 2.93 from a 328i if you want better mpg.

  19. #19
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    Quote Originally Posted by pbonsalb View Post
    Swap in a cheap open 2.93 from a 328i if you want better mpg.
    open diffs are lame! it would be an easy bolt in though

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