Christian,
I started over with a new derivation just to check your math:
PCM AFR =
14.7/ (1+ PeRpm/100 +PeCool/100), went with your Tuner Cat
formula since I had no way to prove it different.
PCM AFR New / PCM AFR Old = Desired AFR / Dyno WB AFR,
PCM AFR New = (PCM AFR Old) Desired AFR / Dyno WB AFR,
14.7 /(1+PeRpm New/100 + PeCool New/100) = (PCM AFR Old) Desired AFR / Dyno WB AFR,
1 /(1+PeRpm New/100 + PeCool New/100) = ((PCM AFR Old) Desired AFR / Dyno WB AFR)/14.7,
1+PeRpm New/100 + PeCool New/100 = 14.7/((PCM AFR Old) Desired AFR / Dyno WB AFR),
PeRpm New/100 = [14.7/((PCM AFR Old) Desired AFR / Dyno WB AFR)]-1 - PeCool New/100,
PeRpm
New =
[1470/((PCM AFR Old) Desired AFR / Dyno
WB AFR)]-100 - PeCool
New
Notice our terms for PCM AFR and Dyno AFR are swapped between numerator and denominator.
This has to do with the relationship we started with.
I think if you plug some numbers into:
Corrected AFR= Desired AFR( Dyno AFR/PCM AFR), say 15.6 = 13 (12/10) You will see that for a 20% lean mixture you going to change AFR by over 50%
PCM AFR New = (PCM AFR Old) Desired AFR / Dyno WB AFR, say 10.8 =10(13/12), looks a little more logical ;^)