Gasolene Air/Fuel Ratio Limits

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west_minist
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Gasolene Air/Fuel Ratio Limits

Post by west_minist »

Air/Fuel Ratio Limits
6.0:1 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
13.2:1 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[
west_minist
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Posts: 1713
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E85 Air/Fuel Ratio Limits

Post by west_minist »

Max Rich Torque of E85 is 7.1:1- 8.5:1

With that being said, here is what i would consider a very safe and conservative fuel tune on E85. *AFR's listed in bold are for widebands o2s that are calibrated for gasoline, AFR's in ( ) are actual E85 AFR:
  • Part Throttle lean (max eco) AFR of 16.5:1(11.0:1) 12.4% leaner than STOICH
    Part Throttle rich AFR of 14.7:1(9.8:1)
    Spool up... AFR of 13.5:1(9.00:1)
    WOT... AFR of 12.1:1(8.06:1) 17.7% richer than STOICH
*If you're using a wideband that is calibrated for gasoline(14.7:1) and cannot change the calibration of the wideband, take your gasoline AFR and divide it by 1.5 to get actual e85 AFR or use the wideband in lambda mode. 1 lambda is 9.8:1

Here are some common AFR conversions(Gas AFR on left, e85 on right):
  • 18.0:1=12.000
    17.5:1=11.666
    17.0:1=11.333
    16.5:1=11.000
    16.0:1=10.666
    15.5:1=10.333
    15.0:1=10.000
    14.5:1=9.666
    14.0:1=9.333
    13.5:1=9.000
    13.0:1=8.666
    12.5:1=8.333
    12.0:1=8.000
    11.5:1=7.666
    11.0:1=7.333
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