Real simple. I am assuming that the optimal A/F ratio (power-wise) would be stoich (14.7:1, right?) but what would be considered the most safe A/F for daily driving?

TIA!

Steve

 

safest is a little rich...

 

stoich is not best for power - it is best for complete combustion of mixture...

(i think)

t..

 

My understanding is that stoichiometric 14.7:1 is best for emissions, i.e. complete combustion. I understand that max power comes closer to 13.1:1 for N/A, and 12.5:1 for FI... Anyone know for sure?

-Andie

 

OK here is a litter primer.......but I hate giving tuning numbers..cause YMMV.

14.7 is mandatory for emissions with a 3-way catalyst. That is the catalyst that oxidizes CO and Hydrocarbons and reduces NOx. It will have an O2 sensor before and after. 14.7 Air/Fuel ratio is what every engine (except the lean burn ones...which are currently rare) runs during closed loop ECM control.

15.2 ish ... which is lean ... is tolerable on a stock motor driven by a little ol person, and will result in the best MPG. Just don't push it or lug it.

12.9 ish to 12.2 ish is where you should find best power NA. To get closer you need a dyno and specific experience with the setup. Richer is safer against detonation. 12.5 ish is probably a good starting place.

If you can let it run closed loop in daily driving at 14.7 A/F with a cat, your kids lungs will appreciate it in the years to come. These engines really dump a lot of smog causing baddies when run rich.

Regards,
BigMoose

 

12.5 is optimal for power, all other things sidelined... if you're running F/I you want richer than this.
14.7 is optimal for power & mileage & emissions, as a tradeoff kinda deal.

That's all I know