E85 as a 91 octane booster?

squeedle

Lurker
May 29, 2017
19
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0
SF Bay Area
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2009 135i AT MSport Coupe
I've done some googling and still haven't found anything that seems to answer this clearly. Sorry if it's been hashed out already.

I live in CA. We only have 91 octane fuel. I do have E85 near me.

Without doing ANY mods or tuning, can I add a couple gallons of E85 to each tankful of 91 just to try to get the octane up to the 93 range? Even stock, the car should benefit from the slightly higher octane right? Or would it not really matter on the stock tune?

Sorry again if this is dumb or repetitive.
 

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Lieutenant
Nov 14, 2016
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North Wilkesboro
I've done some googling and still haven't found anything that seems to answer this clearly. Sorry if it's been hashed out already.

I live in CA. We only have 91 octane fuel. I do have E85 near me.

Without doing ANY mods or tuning, can I add a couple gallons of E85 to each tankful of 91 just to try to get the octane up to the 93 range? Even stock, the car should benefit from the slightly higher octane right? Or would it not really matter on the stock tune?

Sorry again if this is dumb or repetitive.

If you're wanting to run E85 then you would highly benefit from a tune for it considering the fuel scaling isn't going to be the same for E85 versus pump gas. Running E85 mixes without a tune will result in fault codes and, check engine lights. It shouldn't cause a significant amount of damage if any if used moderately and for purposes besides WOT.

The best thing to do in your case would be to get either a JB4 with a good backend flash or get a good MHD flash.

If you have any questions about tuning for E85 mixtures. Feel free to PM me.
 

1and1

Specialist
Dec 28, 2016
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Tally, FL
Isn't it safe to run 1 gallon of e85 to a full tank of 91? Just curious, I've never tuned or played with e on the bmw platform.

Understand that there's no real performance gain with onlty a gallon of e and/or no tuning for it, but as a troubleshooting process it's often a good way to determine if knock/timing pulls are tune related or mechanical in nature, providing that you're able to log and compare before/after data.

Basic theory being that the gain from even a single gallon of e is enough to clear up nasty cali 91 octane garbage triggered knock from temp or even very light tuning issues- say a mhd s1 on cali 91 octane causing some timing pulls- add one gallon of e to a fill-up of 91 and if it's just aggressive tune the timing will clean up, but if it's mechanical the knock/timing issues remain...

And, of course, to see performance gains with e you must tune for it specifically to take advantage of the additional play room afforded by the e and to offset the extra o2 brought to the party and corresponding changes to the scaling
 

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Lieutenant
Nov 14, 2016
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North Wilkesboro
Isn't it safe to run 1 gallon of e85 to a full tank of 91? Just curious, I've never tuned or played with e on the bmw platform.

Understand that there's no real performance gain with onlty a gallon of e and/or no tuning for it, but as a troubleshooting process it's often a good way to determine if knock/timing pulls are tune related or mechanical in nature, providing that you're able to log and compare before/after data.

Basic theory being that the gain from even a single gallon of e is enough to clear up nasty cali 91 octane garbage triggered knock from temp or even very light tuning issues- say a mhd s1 on cali 91 octane causing some timing pulls- add one gallon of e to a fill-up of 91 and if it's just aggressive tune the timing will clean up, but if it's mechanical the knock/timing issues remain...

And, of course, to see performance gains with e you must tune for it specifically to take advantage of the additional play room afforded by the e and to offset the extra o2 brought to the party and corresponding changes to the scaling

Correct, in moderation the added E wont cause any issues (in most cases) and, will help with the octane level overall but, the thing to keep in mind is you will need to scale the fueling system to fully support the mixture you have. In the case of one gallon it wont need to be altered due to pump/e85 ratio being very high. But, in the case you were going for 20%+ I'd recommend a new tune for the situation.

At the end of the day if it was me, I'd get a gallon. Test the Ethanol content in it, do a run with it and look over data results to see if everything appears to be fine with the mixture. From there add / subtract E% as needed.

Due to 91 being the only gas around besides E85... I'd definitely look into beefing up the fueling system and getting a good tune for E. E85 is an amazing thing for these motors and, these motors need high octane to support some of the owners wants. Ethanol and Meth is pretty much the only decent solutions to having only 91 octane around
 
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markyb0

Corporal
Jun 17, 2017
106
20
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Hampton, VA
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2009 335i ST
I run E30 mix with jb4 and mhd pump bef. You can really tell the difference with the E mix and tune.
 

squeedle

Lurker
May 29, 2017
19
4
0
SF Bay Area
Ride
2009 135i AT MSport Coupe
I appreciate the replies. Clearly the best solution is to run 100% E85, which requires the right hardware and tune. But I'm just not sure that's in my budget right now. I think I will look into meth injection for starters and then work up to E85 if finances permit, once a true flexfuel system is available via MHD. I don't want to have to switch to different BEF maps, measure E85 at the pump, or have to use E85 when it's not convenient. I heard MHD was working on such a system at one time, no idea if they still are. Fingers crossed.
 

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Lieutenant
Nov 14, 2016
655
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North Wilkesboro
I appreciate the replies. Clearly the best solution is to run 100% E85, which requires the right hardware and tune. But I'm just not sure that's in my budget right now. I think I will look into meth injection for starters and then work up to E85 if finances permit, once a true flexfuel system is available via MHD. I don't want to have to switch to different BEF maps, measure E85 at the pump, or have to use E85 when it's not convenient. I heard MHD was working on such a system at one time, no idea if they still are. Fingers crossed.

Honestly, running E60 would be less straining on your fuel system with virtually the same end results.
 
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R.G.

Lieutenant
Nov 17, 2016
669
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Henderson, NV
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E92 335, F10 M5
The answer to your question is yes. All clear and car will run better as long as you do not over do it. I'd say max 3 gallons mixed with a full 16, so 13-3 MAX
 
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[email protected]

Lieutenant
Nov 14, 2016
655
261
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North Wilkesboro
I believe you, but that would also be a pain in the butt. :( I think I'm far too lazy to do that. :)
It's really not that bad doing E50-E60. 7.8 gallons of E85 (assuming it's 85%) and the rest 93

Plus, going 100% e will require either PI or the double barrel hpfp and, even then the upgraded hpfp is still not that reliable. If you wanted a drag build it would last you longer then if you daily your car. But, that's from what I've collected on the hpfp upgrade according to most that have went that route. I've never personally upgraded mine.
 
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squeedle

Lurker
May 29, 2017
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SF Bay Area
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2009 135i AT MSport Coupe
But I wouldn't even get to the E85 station more than 1 out of 3 or 4 fillups, and even then couldn't be sure what my fuel levels would be at the time of filling up. And I have no way to know the true ethanol content of the E85, etc. Hope MHD comes out with a true flexfuel system at some point, that would be killer.
 

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Lieutenant
Nov 14, 2016
655
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North Wilkesboro
But I wouldn't even get to the E85 station more than 1 out of 3 or 4 fillups, and even then couldn't be sure what my fuel levels would be at the time of filling up. And I have no way to know the true ethanol content of the E85, etc. Hope MHD comes out with a true flexfuel system at some point, that would be killer.

Well, luckily this time of year the Ethanol you get is usually good rating because of corn harvests but, you could technically outsource pure ethanol and add in that amount. Just keep in mind e85 doesn't have a good life span when keeping it.

Alternatively you can get the Fuel-IT Bluetooth system which will tell you your e content.

If it was me.. I'd make maps for E30, E40, E50, E60 and just toggle between them after seeing what percentage my tank is at. (Which is virtually what I do now)
 
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