Mr. P.
May 31st, 2011, 07:01 AM
I switched widebands this last week, going from a PLX to a NGK AFX (sweet unit, love it) and when I looked closely in EFILive at the wide band PIDs, I discovered that all these are assuming the fuel in the vehicle is 14.7:1 stoich, and that assumption will give incorrect results/logging for most users - the reason why is the increased sale/distribution of E10 in place of 'real' gasoline E0; by 2012 all US gasoline pumps will be E10 due to laws passed by the Obama administration several years ago.
In detail - take a look at the "Wide Band AFR 1 - NGK AFX" PID (CALC.AFR_NGK1), the formula/expression for it is revealed as: AFR = {EXT.AD1} * 1.4 + 9; this math will return the correct AFR if the motor happens to be consuming/exhausting E0 gasoline - this is only accurate for a decreasingly small part of the US population because most heavily populated areas are required to sell E6, E8, or E10 in place of gasoline. In the case you are using E10, the equation for this PID will be {EXT.AD1} * .735 + 8.79 (approximately, assuming stoich of 14.17:1).
I am suggesting to the EFILive developers, either:
1) update the AFR PIDs so that they use some user-input variable stoich value (the same way you have a user give the assumed charge temp for VE grams/cyl calculations in EFILive Tune V7.5 -> Edit -> Properties -> Display folder tab)
- or -
2) remove these PIDs completely, as they are often increasingly incorrect, and unreliable for tuning -plus- best practice now is to monitor EQR or Lambda and determine BENs from the Lambda reported by the wideband device.
Personally I suggest option #2, and get away from using or promoting AFR all-together, and force users to make a calculated PID if they really want to go to the effort to display AFR.
Mr. P. :)
In detail - take a look at the "Wide Band AFR 1 - NGK AFX" PID (CALC.AFR_NGK1), the formula/expression for it is revealed as: AFR = {EXT.AD1} * 1.4 + 9; this math will return the correct AFR if the motor happens to be consuming/exhausting E0 gasoline - this is only accurate for a decreasingly small part of the US population because most heavily populated areas are required to sell E6, E8, or E10 in place of gasoline. In the case you are using E10, the equation for this PID will be {EXT.AD1} * .735 + 8.79 (approximately, assuming stoich of 14.17:1).
I am suggesting to the EFILive developers, either:
1) update the AFR PIDs so that they use some user-input variable stoich value (the same way you have a user give the assumed charge temp for VE grams/cyl calculations in EFILive Tune V7.5 -> Edit -> Properties -> Display folder tab)
- or -
2) remove these PIDs completely, as they are often increasingly incorrect, and unreliable for tuning -plus- best practice now is to monitor EQR or Lambda and determine BENs from the Lambda reported by the wideband device.
Personally I suggest option #2, and get away from using or promoting AFR all-together, and force users to make a calculated PID if they really want to go to the effort to display AFR.
Mr. P. :)