A is for… Air/fuel ratio
The amount of fuel being sent into your Ford engine’s combustion chambers is measured as an air/fuel ratio (AFR), whichright conditions, all of the fuel and all of the oxygen can burn leaving nothing except for the combustion products — this is called the stochiometric ratio. However, a stoichiometric mixture burns very hot and can damage engine components, as well as limit maximum power, and most engines are tuned to run richer, giving a lower AFR number. On most naturally-aspirated engines, maximum power is usually reached at AFRs ranging from 12.5 to 13.3:1.
