I went for a drive with an OBD scanner app this morning. I was curious to find out what my knock retard % was.
I'd say 80-90% of the time, it was 0 degrees. Under medium-light acceleration, it read about 2-3 degrees. Under moderate acceleration, it read about 4-5 degrees. I did two near-WOT runs and saw that it read in the 3-6 degrees range with a brief spike to 7-8 degrees (at about 5000 RPM). From what I've read, the 3800 tends to increase timing in some areas, necessitating knock retard sometimes. (Again, from what I've read, the naturally aspirated Series 3 3800 [L22] has the most timing advance of all). It seems to be quite normal, but I'm curious whether anyone who knows the 3800 can confirm this. The owners' manual says to use an octane of 87 or higher, and I've used primarily 87 E10. Premium (91) is 30-50 cents more expensive (30 cents is 91 with ethanol, 50 cents is 91 without ethanol or 93 with ethanol). Any thoughts?
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