Quote from: Brucelinc on October 07, 2015, 09:19:00 AM
Question: Are you guys who mix in some E85 actually testing the fuel to see what the percentage of ethanol really is? There is a sticker on the pumps in my area that say it could be anything over 51% ethanol. If it is only 51%, the octane would obviously be less than if it were 85%. On the other hand, more could be added without potential fuel pressure issues. These variables are why I don't mix it, even though I cannot argue with the track results I have seen from those who do. Thoughts?
When we're looking at such a low blend, I wouldn't worry about the variables as the adaptives will fix it if you're off a bit. My station uses that sticker as well but when I pulled the MSDS they are 70/85 depending on the season. I have never had an unexpected result so I'm pretty sure my station gets theirs from a reputable source. The quality and consistency of E85 has gotten much better over the years when looking at nationwide tests. The last test of 139 stations across the country yielded 3 tat were out of spec and that wasn't alcohol %, it was RVP which really isn't an issue when blending with straight 93. At that level I'm not at all concerned about FRP. I'm still seeing peaks over 2700 PSI on E20.
If you watch your fuel trims you can get close. If you were to go to E20 you'd be looking at around 3% higher.
I'm on a 20% tune right now which Torrie adjusts stoich accordingly. All of my trims are around zero so my blend is very close. If I put more than 20 in the stft and ltft will climb accordingly until the LTFT's are dialed in then the STFT will fall back to zero. Put in less and the same thing will happen in the other direction.
Since you aren't tuned all you will be doing is to help ensure you are getting max performance from your tune under more conditions than straight 93.