[Diesel_Dave]

Okay, I realize I'm a diesel guy and I'm not super familiar with tuning gasoline engines, but something doesn't make sense to me.

The soichiometric air-fuel ratio for gasoline is 14.7:1. This means that if you combine 14.7 kg of air with 1 kg of fuel in a perfectly mixed mixture and burn, all the fuel and all the oxygen in the air will be consumed. Greater than 14.7:1 means there will be oxygen left over, lower than 14.7:1 means that there will be unburned fuel left over. 9 to 1 air fuel ratio is equivalent to 14.7 to 1.64. That means 64% extra fuel! Of the 1.64 kgs of fuel sent in only 1 kg has the possibility of burning--even in a perfectly mixed mixture. So a minimum of 40% of the fuel will go unburned.

Now, I realize that sometimes the AFR will go just a little under 14.7:1 under high power situations, because the mixing isn't perfect. I also realize that ethanol and some other fuels have stoich AFR's down close to 9:1, but I don't see how 9:1 with gasoline can be anything but bad.

What am I missing here?