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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Mixing 93/91 oct. with E85?



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      03-22-2012, 02:59 PM   #1
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Mixing 93/91 oct. with E85?

So I've seen a few threads about people mentioning that they mix regular gas (91/93 oct) with a few gallons of E85 to achieve a higher octane fuel. But I cannot find much information on this method. Or the few discussions go back and forth whether it's safe or not safe.

So what's the deal, is it a way to get cheaper higher oct. fuel?

Some people say, to use E85, the tune needs to add more fuel, to get the benefits of running it. But there doesn't seem to be any solid info.

Any info would be appreciated.
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      03-22-2012, 03:01 PM   #2
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+1, also curious to know if this works and if its safe, specifically with a cobb
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      03-22-2012, 03:02 PM   #3
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ive been running e85 in my 135 for about a month now and the gains have been incredible. You can read my mods in my sig but i run about 30/70 e85/93 now instead of 50/50 because it was running a little lean with that mixture.
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      03-22-2012, 03:53 PM   #4
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Interesting...
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      03-22-2012, 04:18 PM   #5
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You can add a couple gallons to raise the octane. So if you are stock and can only get 91octane gas, adding a bit of e85 would raise it closer to 93 which is where the 335, or really any performance car, would rather be. If you are adding it to 93 without a tune, I think the gains are minimal/nonexistant.

For those with a tune, particularly one with autotuning, adding e85 will keep resulting in more performance since boost can be raised higher, up to a point. That point is that e85 requires more flow to produce the same energy, which requires special fueling systems.

As for the safety, there have been no long term official studies that I know of. But if you use it within reason most people have had no negative effects.

Anyone can feel free to correct me if I'm wrong somewhere..

Oh also you'll get less mileage out of a tank with e85. But I think it's usually cheaper than normal gas so it probably more or less balances out.
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      03-22-2012, 04:23 PM   #6
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Quote:
Originally Posted by jrsniper12453 View Post
You can add a couple gallons to raise the octane. So if you are stock and can only get 91octane gas, adding a bit of e85 would raise it closer to 93 which is where the 335, or really any performance car, would rather be. If you are adding it to 93 without a tune, I think the gains are minimal/nonexistant.

For those with a tune, particularly one with autotuning, adding e85 will keep resulting in more performance since boost can be raised higher, up to a point. That point is that e85 requires more flow to produce the same energy, which requires special fueling systems.

As for the safety, there have been no long term official studies that I know of. But if you use it within reason most people have had no negative effects.

Anyone can feel free to correct me if I'm wrong somewhere..

Oh also you'll get less mileage out of a tank with e85. But I think it's usually cheaper than normal gas so it probably more or less balances out.
Thanks for this info!
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      03-22-2012, 04:52 PM   #7
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I'm not sure, but my thought is that adding E85 actually raises octane higher then the calculated mass mix due to the extra cooling effects.

When testing different fuel octanes they are run in a test engine and detonation or resistance to it are measured, so both the spontaneous ignition and cooling properties of a fuel determine the octane rating. I just think the cooling aspects would have a stronger effect on a mixes total octane then the typical octane calc when mixing with E85.

I'm curious... any thoughts from someone that's more educated?
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      03-22-2012, 04:56 PM   #8
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If you are running flash tune then there is no point of doing E85 or any other mix without running a map that optimizes for it. With piggies, you can play with boost and timing so you could potentially make your own home brew recipe of gas+e85 blend and optimal settings in your piggy.
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      03-22-2012, 05:15 PM   #9
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Quote:
Originally Posted by vasillalov View Post
If you are running flash tune then there is no point of doing E85 or any other mix without running a map that optimizes for it. With piggies, you can play with boost and timing so you could potentially make your own home brew recipe of gas+e85 blend and optimal settings in your piggy.

I agree if you have 93 octane. But if your running a flash tune and only have 91 and want to run the agressive maps then blending 40% e85 is a great way to bump up your octane. Ive been doing that since stage 2+ came out, only downside is my mpg has gone down. Can't wait till cobb has an e85 map. Then we can really see what the stock fuel system is capable of.
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      03-22-2012, 09:33 PM   #10
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As stated above 30% e85 / 70% 93 oct gas is an awesome performance boost.

I've used it in about 5-6 tank refils or so (Car is F.B.O w' V5 Rev3) and I have got a 5 gallon container of the stuff in my garage

0 problems so far, no misfires, no codes, awesome seat of the pants difference.

However anything over 45% mixture used for a prolonged time and you are pretty much looking for trouble occurring from corrosion from the E85. After all our fuel system is not e85 capable.

Bottom line, tease with it but be careful not to get addicted to it.
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      04-24-2012, 06:12 PM   #11
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I am using 93 octane ( mods in my sig) but onmap 2 & 5 I have a timing drop so it was suggested to use E85 or octane booster to help with this and what I want to know is how do you calculate this? How many gallons of E85 to a tank on a 335i when using 93 octane?
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      04-24-2012, 07:13 PM   #12
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Quote:
Originally Posted by robc1976 View Post
I am using 93 octane ( mods in my sig) but onmap 2 & 5 I have a timing drop so it was suggested to use E85 or octane booster to help with this and what I want to know is how do you calculate this? How many gallons of E85 to a tank on a 335i when using 93 octane?
Yeah it's proven to raise octane however the real question/concern I have is how corrosive is it in the longterm to our fueling system.. I read that Shiv ran an aggressive mix and his low pressure fuel pump went out immediately, which could have been coincidence.. E85 would be good alternative to us CA 91 octane users seeking to raise octane for more boost..
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      04-24-2012, 07:36 PM   #13
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The problem with mixing e85 and pump gas is that the ratio will never be the same. If you measure it precisely (with a calculator) at the pump, that'll get you extremly close, but there is still a margin of ambiguouty that surrounds each of the fuels.

It'd be better to do all or nothing... Even though a couple gallons can be a nice bump in octane
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      04-24-2012, 08:29 PM   #14
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Quote:
Originally Posted by GreekMaverick

However anything over 45% mixture used for a prolonged time and you are pretty much looking for trouble occurring from corrosion from the E85. After all our fuel system is not e85 capable.
How did your 46% mixture tests differ from your 44% tests?

Last edited by The Ghost; 04-24-2012 at 08:53 PM.
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      04-24-2012, 09:39 PM   #15
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Quote:
Originally Posted by The Ghost View Post
How did your 46% mixture tests differ from your 44% tests?
or is it 56% and 54% because the pump gas is already 'up to' 10% ethanol.........

I use 4gal as accurate as the pump and amount left in house can measure. It helps we run 93 + E85 so there are no timing pulls on Stg 1 agg COBB with no mods at all.

T
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      04-24-2012, 10:09 PM   #16
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I run 50/50 on E85/93 and my car feels much better. When I say that I mean it feels to be much more responsive in both D and DS. It definitely makes a difference in performance. I raced a friend from 60-140-we have the same mod's(see sig) and I would say I pulled 2-3 cars on him(consistently). I try not to run it on every tank though, because the long term effects are not known.
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      04-24-2012, 10:34 PM   #17
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So what Im getting from you guys is that I can mix e85 with 91 octane here in AZ to run the aggressive map from cobb(93 oct) instead of mixing 100 oct with 91 octane.
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      04-24-2012, 10:35 PM   #18
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Quote:
Originally Posted by Mangler View Post

I use 4gal as accurate as the pump and amount left in house can measure. It helps we run 93 + E85 so there are no timing pulls on Stg 1 agg COBB with no mods at all.

T
I don't follow you. You put 4 gals of e85 then fill up with 93?

As someone said, the problem with mixing is controlling the ratios. If you have a 30/70 mix (e85/93), use all but 2 gals, then add 3 gals of e85 and the rest 93, the 93 has to be 7 gallons. If you ever fill her up, the ratio will progressively be off.

What system are you guys using to control the ratio? You could calculate the gallons left by resetting the MPG record and use the calculated range.
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      04-25-2012, 08:02 AM   #19
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What I do to make sure my ratio is close to the same every time, is I just wait until its down to a 1/8 tank before I get gas, then I always put in 4 gallons of E85 and 10 gallons of 93 (about 29%) even if it doesn't quite fill the tank all the way, its damn close.

The problem is, if there are times when I need gas and I can't find E85, I just put in some straight 93, and then the next time I try the E85 again that last 1/8 of a tank doesn't have much E85 in it anymore. But it should still be between 25-30% which is where an auto tuning map (like the JB4 map 5) is nice to have. I highly doubt you'd notice a difference between 25% and 30% mixture.

And yes, running 25% to 30% E85 on the auto tuning map 5, is a noticeable difference for sure! I'd say it feels very similar to running meth all the time!
Now I can't wait to try the E85 out on map 3 with the meth, I just need to get my meth tank filled up again asap!
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      04-25-2012, 01:30 PM   #20
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Quote:
Originally Posted by Eracer76 View Post
What I do to make sure my ratio is close to the same every time, is I just wait until its down to a 1/8 tank before I get gas, then I always put in 4 gallons of E85 and 10 gallons of 93 (about 29%) even if it doesn't quite fill the tank all the way, its damn close.

The problem is, if there are times when I need gas and I can't find E85, I just put in some straight 93, and then the next time I try the E85 again that last 1/8 of a tank doesn't have much E85 in it anymore. But it should still be between 25-30% which is where an auto tuning map (like the JB4 map 5) is nice to have. I highly doubt you'd notice a difference between 25% and 30% mixture.

And yes, running 25% to 30% E85 on the auto tuning map 5, is a noticeable difference for sure! I'd say it feels very similar to running meth all the time!
Now I can't wait to try the E85 out on map 3 with the meth, I just need to get my meth tank filled up again asap!
So basically 4 gals of e85 with every tank full of gas, wish shell had this....you could put the E85 in at the same time! Next time you go to fill up see how many miles are left for your tank of gas via the end of the turn signal stick, would be great info for us all. I use the fuel gauge as a boost gauge and go by the miles left per tank in the middle of the cluster.
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      04-25-2012, 03:58 PM   #21
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Quote:
Originally Posted by robc1976 View Post
So basically 4 gals of e85 with every tank full of gas, wish shell had this....you could put the E85 in at the same time! Next time you go to fill up see how many miles are left for your tank of gas via the end of the turn signal stick, would be great info for us all. I use the fuel gauge as a boost gauge and go by the miles left per tank in the middle of the cluster.
The distance will be calculated based on averhe mpg, so he'll need to rest yyhe mpg average before taking this reading (and still take into account what the ave mpg was at the time of the reading).
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      04-25-2012, 04:04 PM   #22
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Quote:
Originally Posted by The Ghost View Post
The distance will be calculated based on averhe mpg, so he'll need to rest yyhe mpg average before taking this reading (and still take into account what the ave mpg was at the time of the reading).
Oops lol!! You are correct
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