Quote:
Originally Posted by Shagaliscious
12.5:1 compression ratio.
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This right here is your reason. The higher octane is needed to increase the resistance to knock/pre-detonation in the combustion chamber.
For reference as to why the compression ratio of this motor is unique most factory FI cars run around a 9.0:1 from the manufacurer and for N/A motors around 10:1 or just slightly above that.
Direct injection has allowed compression ratios to be bumped up. The FA20 with a 12.5:1 is a first to me.