TL;DR x2

 

If you've ever used E85 then don't read the post,

its obviously for people who have never used E before or don't realize you can drink ethanol

 

FWIW, all gas I've got available to me is already E10. There's one E85 station close, and on the handle it says something like it could be E50-E75

I'm hoping the Blitz & the 100 cell do the trick

 

That's literally every E85 pump you'll ever find on the street, by law they have to disclaim that the mixture can be anywhere between 51-83% ethanol. That really doesn't matter tho, even E50 has way more octane that you'll ever need on a stock turbo and if you're paranoid about it anyway then buy a test kit, they're a few bucks, or build a content sensor so you always know what content is.

 

I've noticed most tunes are in full kill mode as soon as the gauge reads 72% ethanol. So I can see how any extra could only help. It sure makes me feel better about the occasional tank of <80% that I was getting. I was stressing big time.

 

Anywhere between 65-85% for me and I'm NFG about fuel or octane.

 

I have been lucky with the 2 E85 stations by me. They are consistently between 78-80%. I got 82% once but thats the highest I have seen. For me, boost and timing curves are the same from 70% and up. I play it safe with only 26-27 psi spike though.

 

It's pretty common for random people to ask me why I'm filling up with E85 at the station. My go to is to just tell them its government subsidized 105 octane race gas that's cheaper then regular. If they are driving a prius or something like that I'll tell them its a renewable, conflict free, USA made carbon neutral biofuel. I really think with E85 you can have your cake and eat it.

 

what if you tuned on e80, didn't realize, and get e65 the next time?

 

It will run rich, if it does knock the ecu should pull timing and boost. It's been my experience that my E85 sources have been consistent with the blend. If you are filling up at different places all the time it would probably be more important to keep an eye on blend or if your station is using different suppliers. If you do notice a wide variance tank to tank you could even have a chat with the station owner about their vendors.

If you log STFT you will probably see it instantly, certainly in the LTFT's once they set. You would probably notice a difference in sound/feel of the engine in open loop.

 

15% won't hurt anything at a low power level. Yes the car will be running leaner, but you will still have enough octane and cylinder cooling that it's very unlikely there will be knock.

 

It would run rich with a higher gasoline content. Ethanol is already such a higher volume fuel though that your right in that the cooling effect would still be much greater then that of gasoline. I've run it pretty lean while tuning and have never seen knock in my logs from that. You can tell the engine isn't optimal though, like it wants more fuel. I have knocked from being too rich though.

 

In CA it's not so cost effective. At least in my area. It's 20% cheaper than 91, but it burns 30% faster, so it's a losing proposition for me. I don't mind, though, because my Civic gets 42mpg. I figure that balances or my carbon footprint.

I did notice my car seeing 10.9:1 when I was at a lower ethanol content. I think 68% or so. Makes sense, though. Now that I ran the bit of pump gas out and am back to 78% it looks normal again. I like when my car "fixes" itself

 

From a cost/mile standpoint yah its a net negative, however that's comparing it to 91 pump gasoline. Really you should be comparing it to the cost of pump 100 octane (which still isn't as good but illustrates the point), in which case its a huge savings. Without .gov subsidies a gallon of E85 would cost a whole lot more than 91. We are talking about Evo's though, mpg is almost always an after thought.

If you dig too much into either of the arguments I gave neither is really correct without adding more context, but for a quick couple minute convo at the pumps, I think they are a good enough high level explanation of why to use the fuel.

 

there is someone on this forum using 32psi and 93 octane 10% Ethanol


The danger of low octane fuel is mitigated by using the right equipment, low air intake temperature, chamber tech
I don't think the 'amount' of boost really has anything to do with it. That pressure is far lower/insignificant to what comes just after.

you can detonate and ruin an engine at 5psi with hot enough intake air or other problems