Originally posted by geoffct:
They automatically retard the spark (reducing power) if the ecu determines there is predetination (knock). Many modern cars do not audibly or noticably knock. The car can detect in less than 2 revs a knock situation, and correct it in the next spark.
I have been able to hear the knock when I ran 87 octain, so it wasn't able to retard the spark at all.
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