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Been doing a considerable amount of tune testing lately and I found a way to get E85 to knock in conditions you would not normally expect knock. Something to look at is dynamic changes in either AFR or timing during a pull. I can cause knock by RAPIDLY changing afr from say 11.4 to 11.9 under load. In addition to the absolute value, rate of change in afr or timing is also very important. Something to look at if you are getting knock when it is not expected.
Thanks. My car is down right now for some updates, but I can report that with additional tuning I was able to do fairly well with the E85 (E70 in CA right now). I'm still 2 degrees less advanced on E85 with water/meth compared to 100 with water/meth, but at 1/5th the price, I'm good. Your post is well received. My initial results were based on maps designed for the 100 octane, with more fuel added across the board. After smoothing things out for the E85, to eliminate the rapid changes you mention, the E85 (E70) did pretty well. I still get a knock or two sometimes on 20psi WOT runs, but no worse than with the 100 octane. Looking forward to the switch to the summer blend...
02-07-2015, 11:01 PM
