Air/Fuel Ratio Limits 6.01 Rich run limit 9 0.1 Low power. black smoke 11.5.1 Rich. best torque at WOT 12.5.1 Safe. best power at WOT 13.221 Lean, best torque at WOT 14.7.1 Chemically ideal 15.5:1 Lean light load, part throttle 16 2:1 Best economy, part throttle 18-22'1 Lean run limit