I looked and did not find the exact information I was looking for so I thought a thread dedicated to race fuel alternatives could benefit this section.
I have some experience with e85 coming from the B8 S4 section where many are using either full e85 setups or blends. I am currently running full e85 and it is night and day over 93 in terms of performance (I'm obviously tuned accordingly).
That being said, the B8 S4 and the C7/7.5 S6/S7 are completely different platforms. With the 2010-2016 S4's, those who wanted to protect against any potential knock and/or boost bypass would throw a few gallons of e85 on their 91/93 tunes to lift a few octane points. It was advised to keep that mixture below e30 on stock fueling for safety and to prevent codes. So on average you would see 11-12 gallons of 93/91 and maybe 3-4 gallons of e85.
To run full e85 on the B8 S4, you need to upgrade the high pressure fuel pump, which I did. It's relatively inexpensive ($400) and isn't too terrible to install.
Since I have seen/felt first hand how much of a difference e85 can make performance-wise, I wanted to gauge it's existence with this platform. I fully intend to throw just a few gallons of e85 on top of a nearly full tank of 93 once I get my car and install my stage 1 tune.
Looking forward to hearing feedback with this platform.
Mickey
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