HOWTO: Individual cylinder fuel and spark trim

[Roland@pcmtec]

If you wish to trim individual cylinders due to one cylinder running hotter than the other there are two global fuel and spark modifiers you can change.

auF12418 "Calibration adders to spark angle for development and testing purposes"

This value will be added to the final spark value per cylinder. Eg to remove 1 degree of timing from cylinder 6 you would change this table to the following:

auF10362 "Fuel modifier per cylinder"

This is a simple multiplier for the commanded fuel mass. Eg to run one cylinder 5% leaner you would modify the table by the following amount.

[hymey]

Hey Roland, thanks for this explanation.  What does the "0" cylinder reference too ? Does 0 reference cylinder 1 ? And cyl 5 to be cylinder 6 ? If not, what does changing 0 do ?  . Also in the event of one bank being lean in a fg 5.4 V8 . Ie passenger side bank.  Would it require cylinders 5,6,7,8 to be adjusted ? Regards , Joel .

[Roland@pcmtec]

You'd need to test it to confirm. It would not be safe to trim a cylinder unless you can test the results. It is unlikely all 4 in a bank are lean but rather 1 or 2 cyls only. You need individual egts or widebands to confirm. 

[john.z]

On 1/23/2021 at 10:58 PM, hymey said:

Hey Roland, thanks for this explanation.  What does the "0" cylinder reference too ? Does 0 reference cylinder 1 ? And cyl 5 to be cylinder 6 ? If not, what does changing 0 do ?  . Also in the event of one bank being lean in a fg 5.4 V8 . Ie passenger side bank.  Would it require cylinders 5,6,7,8 to be adjusted ? Regards , Joel .

Can confirm 0-7 is cylinders 1 to 8 in a v8 and yes mine runs slightly leaner on one side, but it's the drivers side that does so since air flow is less obstructed to it, i changed 0-3 to 1.02 to correct.