Quote:
Originally Posted by wparsons
There might be something more to the 91 vs 94 octane up here though. I found that I got a lot of knock on Shell 91 in the midrange (but not WOT) on a 91 octane tune, but with Petro 94 on a 93 octane tune I'm getting no knock in the midrange at all. It was bad enough on the 91 octane tune that I was dropping the IAM down to like 0.5 when I was stuck in traffic.
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Second this...I have to put on my flame suit when I tell people that Shell 91 isn't that great, even on stock tune for knock. Midrange has the most aggressive timing so it's not a surprise for that to happen, particularly under high-load situations. It's mostly when you're in 2500-3500 RPM, especially if there's a bit of a climb.