Thread: E85????
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Old 09-27-2010, 12:04 AM   #19
AleroB888
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Quote:
Originally Posted by natedawg9640 View Post
a word of caution regarding the octane levels of e85... i read a blurb somewhere not overly long ago that followed a study that took samples and check the octane level of e85 fuel from an array of gas stations across the midwest. they got readings all the way from 110+, to below 85. notice that e85 is not labeled as having a certain octane level. as a generality, yes it's high, but the longer it sits, the worse it gets. so if you are maxed out on timing and tuned for 100 for example, and you get a batch of sub 85, you're engine is going to hate you.

I believe that the "Main Spark, Low Octane" table in the PCM may compensate and pull timing out in that situation, at least in theory. However, some tuners copy the High Octane table onto the Low Octane table as part of their tuning method.
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