[Calveezzzy]

Hey Guys,

I've been reading a lot about mixing e85 with 91 octane to achieve similar 93 octane ratings so that I can use the aggressive maps with my Cobb AP. I haven't read about many people doing this, and I called Cobb Tuning to confirm. They said that they don't recommend mixing 2 different types of fuel to use with their Off-the-Shelf maps, but I see that a lot of people on the forums are doing this.

So, to anyone using an e85/91 octane mixture in their E90 335i with the Cobb AP running any of the aggressive maps (I'd be using the stage 1+ aggressive map btw), have you run into any issues with timing, AFR, lambda, etc? I really want to know if it's safe or not. My gut instinct is to listen to Cobb, but I also want to read about anyone's real world experiences.

[msp2three35i]

I ran the e30 map with 92, with a higher e85 content to compensate the one octane difference with adjusted fuel scalars and there were a lot of timing corrections. Once I ran 93 the timing corrections were minimum to none. This was my experience fwiw.

[marv85]

Originally Posted by Calveezzzy

Hey Guys,

I've been reading a lot about mixing e85 with 91 octane to achieve similar 93 octane ratings so that I can use the aggressive maps with my Cobb AP. I haven't read about many people doing this, and I called Cobb Tuning to confirm. They said that they don't recommend mixing 2 different types of fuel to use with their Off-the-Shelf maps, but I see that a lot of people on the forums are doing this.

So, to anyone using an e85/91 octane mixture in their E90 335i with the Cobb AP running any of the aggressive maps (I'd be using the stage 1+ aggressive map btw), have you run into any issues with timing, AFR, lambda, etc? I really want to know if it's safe or not. My gut instinct is to listen to Cobb, but I also want to read about anyone's real world experiences.

They meant don't mix and run OTS straight. However you can mix, edit the OTS maps in ATR for the amount of ethanol you mixed in and you should be all set. It's super easy to do. Download ATR, then look into the PDF help file they provide. Scroll down to the end and you can find teh fuel scalars for different ethanol contents. Change that and you're all set

[King mode]

I fill up with 3 gallons e85 and the rest 91 on stage 1 aggressive. No issues to date.

[marv85]

Originally Posted by King mode

I fill up with 3 gallons e85 and the rest 91 on stage 1 aggressive. No issues to date.

The DME can compensate some. How do your trims look?

Clean way of doing it would be to adjust the scalar. Actually at that point, you can also add more timing and make a lot more power

[Ænema]

+1 to everything marv has said.
It's totally possible to add some e85 to 91 and clean up timing corrections without any changes to the maps. However, you NEED to keep an eye on LTFTs and STFTs to be sure your mix isn't maxxing fuel trims.

[King mode]

Originally Posted by marv85

The DME can compensate some. How do your trims look?

Clean way of doing it would be to adjust the scalar. Actually at that point, you can also add more timing and make a lot more power

Logs look good. And true that, I could add timing and make more power but have not got around to it. I plan to dyno tune it for 30% - 40% e85

[VNeBLOB42]

Originally Posted by Calveezzzy

Hey Guys,

I've been reading a lot about mixing e85 with 91 octane to achieve similar 93 octane ratings so that I can use the aggressive maps with my Cobb AP. I haven't read about many people doing this, and I called Cobb Tuning to confirm. They said that they don't recommend mixing 2 different types of fuel to use with their Off-the-Shelf maps, but I see that a lot of people on the forums are doing this.

So, to anyone using an e85/91 octane mixture in their E90 335i with the Cobb AP running any of the aggressive maps (I'd be using the stage 1+ aggressive map btw), have you run into any issues with timing, AFR, lambda, etc? I really want to know if it's safe or not. My gut instinct is to listen to Cobb, but I also want to read about anyone's real world experiences.

@Calveezzzy

We are in a state that likes to think low performance additives are better. Well as ignorant as that statement is, I will say ACN 91 Sucks.

I have been running 20% E85 Pump mixed with ACN 91 from April to August. Which works out to be E24 and 91.9 USA Octane Ron+Mon/2 = USA Octane. To compare apples to apples, E85 Pump is about 96 USA (R+M/2) Octane.

I am now on a pro-E-tune of E50 (E85 pump and 91 blends).

I had no issues and have logged each stage, S1 Sport, S1 Aggressive & S1+ Aggressive. I would not recommend running S1 Sport on just ACN 91, but log it anyways, you may be OK. COBB even approved my S1 Sport v401 20% E85 Logs with a big thumbs up.

rader1 thread "Data Logging with COBB" is a good read, you will see his last update was showing how E85 pump can help timing for aggressive MAPs with blends of ACN 91. The graphs are literally from my logs. See Timing Corrections graphs. I have never adjusted the fuel scalar, with only 20% or 3 gallons, it ran OK. anymore I would consider adjusting the fuel scalars.

http://www.e90post.com/forums/showthread.php?t=696472

EDIT:

+1 to marv, AEnema and King

[marv85]

Originally Posted by King mode

Logs look good. And true that, I could add timing and make more power but have not got around to it. I plan to dyno tune it for 30% - 40% e85

if your log is clean with 30%, you won't make more power with 40% unless you increase timing

[Calveezzzy]

MAN!

All this sounds so confusing right now! Thank you all for all of the information, and I'm in the process of downloading the ATR from Cobb.

Honestly, even with all this information, I am still not sure about running e85 yet, so I think I'll just be running 5gallons of 100 octane with 12gallons of 91 octane for an octane rating of about 93.6, which is good enough to run the aggressive maps on Cobb, unless someone wants to spend some one-on-one time with me (I can provide food and beverages).

[marv85]

one on one time for what ? editing off the shelf maps for a specific ethanol content?

[Calveezzzy]

Basically...

Sorry, I'm not 100% confident in messing with maps or anything, even with tutorials, and I don't want to mess up my engine. If anyone can help me out, I guess through PM or meeting in person, I would appreciate it a lot. If not, then I guess I'll just do race fuel instead of e85.

[marv85]

dude, you will be surprised by how easy it is... PM me once you download ATR

[hp jnkey]

I used an E85/91 mix with the Cobb stage 1 aggressive for a few weeks with no issues.
The car really came to life but the gas mileage really sucked. Even with easy driving, the mileage was way less than with the standard 91 tune.
I tried a JB4 on Auto tune Map 5 and the performance is similar but the gas mileage is much better.
Actually I think that the Cobb pulled harder in 1st and 2nd gears but when I hit 3rd gear in the JB4, say good bye. Pulls like a freight train up top.

[poloace]

I run 4 gallons race fuel w 12 of 91... It's funny- before I had been using 93 til I moved to cali. I run stage2+. After creating my own mix, i dont have that 'gurgle' that I had when I was running 93. My feeling is that 93 isn't enough for aggressive 2+. Anyone else come across this?

[marv85]

Originally Posted by hp jnkey

I used an E85/91 mix with the Cobb stage 1 aggressive for a few weeks with no issues.
The car really came to life but the gas mileage really sucked. Even with easy driving, the mileage was way less than with the standard 91 tune.
I tried a JB4 on Auto tune Map 5 and the performance is similar but the gas mileage is much better.
Actually I think that the Cobb pulled harder in 1st and 2nd gears but when I hit 3rd gear in the JB4, say good bye. Pulls like a freight train up top.

JB4 runs much leaner. Second the reason why JB4 runs stronger in map5 than stage1 agg is because it is running the same if not slightly more boost with at least 4-5 degrees of timing. Equation is simple guys. ATR can help fix that