14.7 is about where you want to be at idle and cruising on NA or boosted cars. It's good for fuel economy and emissions and bad for power. On an NA car best power at WOt is going to be around 13.2:1. On a lightly boosted car you might run a 12.0-12.5:1 A/F on pump gas. On a turbo car you usually want to be in the 11.0-12.0:1 range on pump gas. On race gas you can go a bit leaner for more power, but you want to monitor the knock and make sure you have some good gas. Most DSMs that I tune on pump gas are happiest in the 11.0-11.5 range. On race gas I will bring it up closer to 12.0:1. On Mara's I run it as lean as 12.5:1 on race gas at high boost and like 11.0 on pump, her car hated pump gas with her somewhat crappy sidemount and boost creeping Mutt turbo. Nash's was usually tuned aggressive on race gas also, but I wouldn't push the average persons car that far.
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