Need some help with Air/Fuel ratio's..

[C-Kwik]

12:1 is the amount of air to the amount of fuel. It's on an atomic scale and has nothing to do with fuel pressure. 14.7:1 is stoiciometric(no air or fuel atoms/molecules leftover). The only way to truly know how much fuel pressure you are getting is to actually attach a fuel pressure gauge.

[TurboKA37]

u r all mixed up. when the a/f is 12:1 that means there is 12 times the amount of air as there is fuel in the combustion chamber. when u talk about fuel pressure u r talking about the pressure of fuel in the fuel rail. when a FMU is used it will increase the pressure of fuel in the fuel rail by a certain ratio for every pound of boost. so if u r using a 7:1 FMU u will have 7 lbs. of fuel added to the fuel rail for every 1 lb. of boost. (along with the stock fuel rail pressure) so if ur running 7 lbs. of boost with a 7:1 FMU, the FMU will add 49 lbs. of fuel pressure to the fuel rail.

14.1 is rich? 14.1 is richer than 14.7 but u usually dont run that lean.

[C-Kwik]

So that 12:1 is 12lbs of fuel pressure for every 1 lb of air.. right..??So if you say 14.7:1 is stoiciometric, then why does everyone say that 14:1 is WAY TOO rich..??Another, do you know how much pressure the stock ka pump can push..??

No...erase your mind completely of the 12 pounds of fuel pressure per pound of boost. Just let go of it. Think of it on an atomic level. To get a perfect burn where there is no left over fuel or oxygen atoms/molecules, you need 14.7 atoms/molecules of air for every atom/molecule of fuel. This may be different with fuels other than gasoline. The mixture has nothing to do with boost. A normally aspirated car still has an air/fuel ratio.

Now there may be some confusion since FMU ratios can look like A/F ratios. They can have an impact on the A/F ratio, but the FMU ratio has nothing to do with the A/F ratio itself.