Tuning Individual Cylinder Fuel Trims
I tried a different method on tuning the individual fuel trims yesterday.
Originally going off the narrow band O2's i'd got the RHS set at 5% richer but the WB AFR bounced all over the place.
So going off a comment i read the other day (Kur4o i think) about tuning them OL I got back from a good run.
Cleared the data log and sat recording idle.
Let it stabilize.
Then every 500 logs cut a cylinder.
Then recorded another 500 logs of idle as a base line.
Loaded the logs into a spread sheet, selected each block of cylinder logs and recorded the average.
If cyl 1 was from log AQ500 to AQ1000, I selected the range AQ525:AQ975 .This just removes cells where the AFR's settle down after swapping cylinders.
Arranged the results Leanest to Richest average. (the leaner the result, the richer that cylinder must have been & vice versa).
Pick one of the center cylinders (Cyl 3 as it's on the leaner side) as base cylinder
Divide the base value by each average result
leanest= 16.116 / 15.801 == 1.0199%
richest= 16.116 / 16.489 == 0.9773%
afr cyl
15.801 2 LEANEST (Richest result) == 1.0199% 14.7 * this == 14.99
15.941 7 == 1.0109
16.113 6 == 1.0001
16.116 3 base == 1.0000
----- ------------------
16.212 5 == 0.9948
16.323 8 == 0.9873
16.332 1 == 0.9867
16.489 4 RICHEST (leanest result) == 0.9773% 14.7 * this == 14.36
These values multiplied by 14.7 shows a comparative spread of AFR ( 0.63) I was getting between cylinders.
After running the car tonight & relogging this again with 1000 logs per cylinder the spread has dropped 14.99-14.36 to 14.97-14.50. (now 0.47)
It doesn't look a massive amount but the cylinders are all within 2% of the base.
The car idled noticeably better and smoother than the previous night.
I'll try this a couple more times and see if the trims settle down any further
Mitch
