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Mixing E85 and 93 octane to produce 100 octane

15K views 35 replies 7 participants last post by  EMF Audio (McMedics) 
#1 ·
To run purely E85 in our cars you must upgrade injectors to 1050's and tune for it. This is a costly venture that is also time consuming (not saying it's not worth it, but a consideration). I have a tune for 100 octane and I have E85 pumps readily available. This got me thinking about mixing at the pump.

Using this calculator Octane Calculator - www.bazellracefuels.com it suggests 11 gallons of E85 and 8 gallons of 93 octane will give a 100 octane formula. Using another calculator somewhere I found it specifically took into account E85 and 93 octane, not just octane ratings. That resulted in a 50/50 mix, which is essentially E50.

So my question for you, or discussion, is have you ever mixed fuels to get a boost? Did you monitor the octane rating? Have you tried doing exactly what I'm thinking on stock injectors? I've seen posts of people doing it in other cars, and some even claiming full E85 in non-flex fuel cars (which I wouldn't do), but I'm also pretty sure none of those people were tuned for higher octanes so it kind of negated the whole experiment.
 
#3 ·
I understand the volume must be increased, hence the fuel injector need at full E85. As long as the pump and injectors can supply the appropriate volume, that shouldn't be an issue. Agreed?
 
#4 ·
A tuner would no better than me but I don't think so, our ecu is programmed to detect octane, when you switch to e85 it has to be "told" to push more volume with each injector pulse. If you run 50% e85 yes the car will detect the octane and therefore run more aggressive timing, however I don't think the car will know to pump more volume of fuel. A car that's fexfuel from the factory can do that.
 
#9 ·
Why would u even want to mix and experiment in a car like this ? Just have map switching and run the proper fuel for the map .

The 2 fuels also have different weights and burn rates and just mixing them and trying to max out that map slot is not advised . If anything it would be something I would do if I was running say a 93 octane map and wanted it to be extra safe so u add a few gallons max of e85 or race gas to keep octane up and knock down.

But to try and mix the right amount of e85 with pump 93 to equal 100 I don't think is a good idea.

I'm sure Jon or someone from Mengineering will chime in soon tho .
 
#11 ·
Why would u even want to mix and experiment in a car like this ? Just have map switching and run the proper fuel for the map .

The 2 fuels also have different weights and burn rates and just mixing them and trying to max out that map slot is not advised . If anything it would be something I would do if I was running say a 93 octane map and wanted it to be extra safe so u add a few gallons max of e85 or race gas to keep octane up and knock down.

But to try and mix the right amount of e85 with pump 93 to equal 100 I don't think is a good idea.

I'm sure Jon or someone from Mengineering will chime in soon tho .
I have map switching, just not for E85, because I haven't done injectors. For what I'm doing I'm not sure I can justify doing all the E85 stuff to run full E85. I've also planned on doing a video with the 93 tune and extra octane vs straight 93 and I was going to wrap that into the 100 octane testing also.

I've contacted Jerry already, no response yet, but it is still lunch time on a Monday for them.
 
#12 ·
The official response from M-Engineering regarding the thoughts is "We don't recommend mixing E85 with 93 octane to get 100 octane. For the 100 octane map, only use fuel with the octane rating of 100 or higher."
 
#16 ·
I don't want to deal with checking another tank manually, forgetting to add some, not having enough, etc.
 
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#17 ·
My 2 cents here is that flex fuel "mixing pump E85 with pump 93" is the most difficult tuning to dial in and very unlikely you would reach the 100 octane consistent goal. The major variable being the exact octane rating of the pump E85. You could test it one week and it may actually be E55 or lower and the next week it could test as E85. Most E85 pumps I have seen will have a range on them. The tuners I have worked with state if you can and want to go E85 do the required fuel system upgrades and run the best/highest octane E85 you can get and test it every time you fill up. I personally run 93 octane with a 93 tune and an octane booster to get closer to 100 octane. (No E85 readily available where I live) This will keep the knock sensors happy but will require more frequent spark plug changes.
 
#18 ·
What octane booster are you using?
 
#20 ·
I've used it in my E55, I was going to try Boostane since it's O2 sensor friendly but someone crashed and shut the track down. Torco I think is the on that fouls plugs.
 
#21 ·
So here's the thing, you can run a mixture, but you'll need a map for it, it'll throw off your A/F ratio and with that much E content, the fuel trims may become maxed out. They made me an e40 map which in my opinion is better than the 100 oct map, and by my opinion i mean it ran better 60-130 and 1/4 mile times 🙂. The cooling effect of the addition ethanol also helps during the summer months to suppress knock.

I think on the stock injectors e40 is the max you can go and still have some IDC(injector duty cycle) left over for safety.

It's ok if you don't get the mixture exactly correct e38 vs e40 vs e42 basically the same, only thing is going to e42 gives you less headroom than being at e38.

One thing to look out for is winter blend e85, which can actually be e70
 
#22 ·
Do you have any data to support the E40 theory?
 
#23 ·
I mean, I've probably ran 8000 miles of e40 already, it's literally all i ever use since there's an e85 pump 2 miles away.

🤔 Think my most recent 60-130 and 1/4 mile pass is enough data yeah?(don't mind the time, the mph indicates power, hopefully it uploads, I'm on mobile)
 
#25 ·
Do you have a comparison of your car on 93? I'm curious to see the difference. This is some solid info, which is what I was wanting. What mods have you done?
 
#27 ·
I'm catless and catback, I agree on the filters. When you're at the pump, how do you mix it? I've got E85 pumps 3 miles away.
 
#32 ·
I was more inquiring on how many gallons of E85 you pump before the 93.
 
#31 ·
I'd recommend it to people that are a little more "involved" with their cars such as EMF, otherwise upgrading injectors isn't a bad route since you can just pump full e85 and go (and you might gain another 10-20whp)

I've had to do a few revisions(i do street tuning, real world conditions), but it's to be expected cause as you can tell, not many people run e40, BUT the take away should be that M-Engineering is very capable and can get you what you want.

I genuinely prefer the e40 over e85 because you get a decent amount of extra milage per tank(i go on long drives)
 
#34 ·
So a 2:3 ratio. 19 gallon tank makes for math. I'm debating if it's worth paying for a retune. It seems like it's substantially more power and results.
 
#35 ·
I would say yes it's worth it, not only for the power, but for me it's the peace of mind, knowing that I'm basically driving around with race gas(think it's better even) and don't need to constantly worry the i don't have the right fuel if i decided to have some fun on the way back home.

Plus e85 is cheaper than 93 where i live so it's kind of a win win situation 🙂
 
#36 ·
E85 is way cheaper than 93 here too, but if you factor in loss of mileage (comparing straight fuel of each) it's not beneficial in that aspect. What model car have you got? I forgot to ask. What tires do you have as well?
 
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