Originally Posted by
Redline Motorsports
Interesting topic.....
Motors NA motors don't melty down at 14.7 AFR at WOT they just don't make any power. Look at pickup trucks that don't allow PE for 120 seconds plus under WOT.....
Now, FI motors like a richer mixture for the cooling effect a richer mixture provides. This doesn't mean you will make more power. The more power a car makes (higher boost pressures or higher cylinder pressure events) do require richer mixtures to help against knock limits. You take a stock Ford 2V 4.6L with 7 psig and they don't make any power in the low to mid elevens as its just too much cooling for the cylinder event. We run those at 12.0-12.2 all day long.
If you have a real efficient combustion chamber the motor will respond better to a leaner mixture. Of course this is a fine combination with spark advance as well (not to mention fuel types).
It also depends where in the boost curve that peak cylinder filling (highest VE) is taking place. I might run 12.5 off the bottom, bring it to 11.5-11.6 at peak torque and then lean out to 12.0 to redline in some applications.
Run a LSX motor at 12.5 and you won't kill it (unless you have serious knock) but power could be flat.....every combo is different.
Howard