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Just installed jb4 a week ago and have been fooling around between map 2 and 5. anyone know how long i should run map 5 before trying to put a little e85 in the tank? i plan on only doing about 3.5-4 gallons as that should be ~30% of the tank
 

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First of all, BMW says 335i/xDrive needs 89 octane minimum.
Second of all, E85 is 15% ethanol, and BMW says,
"Fuels containing up to and including 10% ethanol or other
oxygenates with up to 2.8% oxygen by weight,
that is, 15% MTBE or 3% methanol plus an
equivalent amount of cosolvent, will not void the
applicable warranties with respect to defects in
materials or workmanship."​

IOW running E85 might be sufficient to cause BMW to deny warranty claims. OTOH, your intention on making 3-4 gal out of a tank of 16 gallons means that the percentage of ethanol is not 15% but some lesser amount (about 5%, if my calculations are correct)
 

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Breaking in the Pony
2019 Mustang GT / 2005 Toyota Tacoma
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First of all, BMW says 335i/xDrive needs 89 octane minimum.
Second of all, E85 is 15% ethanol,
Nope.

E85 is 85% ethanol and only 15% gasoline. Its octane number is up around 100, but there's little gas in it. Mixing 3 - 4 gallons into the tank would give you an EtOH percentage of somewhere in the mid-20s. The octane number will be higher than a mathematical average of the base components (the extra ethanol gives a boost to the octane number of the gasoline), but various components in the fuel system may not be happy at all.
 

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BMW 4 LIFE
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Nope.

E85 is 85% ethanol and only 15% gasoline. It's octane number is up around 100, but there's little gas in it. Mixing 3 - 4 gallons into the tank would give you an EtOH percentage of somethere in the mid-20s. The octane number will be higher than a mathematical average of the base components (the extra ethanol gives a boost to the octane number of the gasoline), but various components in the fuel system may not be happy at all.
So with being said what is the adverse effect on the engine? I presume you shouldn't fill the entire tank up with E85? If so, what happens...eventually? :dunno::dunno:
 

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Breaking in the Pony
2019 Mustang GT / 2005 Toyota Tacoma
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So with being said what is the adverse effect on the engine? I presume you shouldn't fill the entire tank up with E85? If so, what happens...eventually? :dunno::dunno:
If the engine isn't designed for E85, there's no guarantee that all the seals, hoses, diaphragms, etc. in the the fuel system as compatible with the high alcohol content, so there's an unknown effect on the lifetime of different parts. The effects may not be immediately apparent (ie.: "I run E85 all the time, no problem. Oh, has anyone else had to replace their LPFP every 20,000 miles???").

Ethanol also has a significantly lower energy density than gasoline, so you need much larger flows for the same power output. No bets that the fuel pumps and injectors have the capacity to do so, so there may be a reduction in overall engine output as a result.
 

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Nope.

E85 is 85% ethanol and only 15% gasoline. It's octane number is up around 100, but there's little gas in it. Mixing 3 - 4 gallons into the tank would give you an EtOH percentage of somethere in the mid-20s. The octane number will be higher than a mathematical average of the base components (the extra ethanol gives a boost to the octane number of the gasoline), but various components in the fuel system may not be happy at all.
:banghead: Yeah, you're right, I severly misread and inverted the figures!
I computed
  • 22% ethanol, if 4 gal. of E85 mixed into 12 gal. of standard gas, which is higher percentage than the 10% limit which BMW has declared for not voiding warranty.
  • Even 3 gal. of E85 leaves you with 16% content.
  • When you get to 2 gal. E85, you have the 10% content, but then what is the point of the bother of doing that?!
 

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RLTW
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You can run E20-E30 safely on the stock fueling system. The key is logging the low and high pressure fuel pumps and making sure they're keeping up. Can it possibly void your warranty? Sure, but you've already installed a JB4 so who cares.

If you're going to consistently run E85, I would suggest a cheap Ethanol testing kit so you know exactly what the E content of your E85 is so you can accurately calculate the amount of each fuel needed. And don't forget gas in already E10.

I've been running E60-E70 for over 3 yrs in my 335is (with a upgraded lpfp) with zero issues. Mileage takes a hit but the difference in performance is amazing. I can literally walk away from an 335i with the identical bolt ons but on pump gas.
 
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