AFC base correction: two guides suggest different numbers. Which is it?

[Rice Over Wheat]

Ironically, both guides I'm using suggest different base correction values, and are written by the same guy.

In this guide: http://www.dsmtuners.com/forums/showthread.php?t=103469

...I used the Excel worksheet and put in my data: 650's, stock FPR (43psi), and base correction = -30.77%

But in this guide: http://www.dsmtuners.com/forums/showthread.php?t=58403

...he suggests starting at -18% for 660's as a starting point.

Since 450/650 -1 = -30.8, that should be my base correction after swapping in my 650s in order to flow the same as stock 450's on the stock 43 lbs fuel pressure. I just completed my fmic install and am ready to toss in the 650s, but I won't be tuning for a few weeks. I just want to be ready to tune on a dyno but drive safely in the meantime. So -30.8 is safe right? Or should I run rich at -18%?

Thanks in advance...I'm confused here.

 

[GVR4592]

-18% was a suggestion for a safe starting point, -30% is the actual correction factor. I'd start somewhere between -25% and -28%.

 

[Rice Over Wheat]

Great, I'll set -28% across all rpm points for now, LO and HI. Thanks for the fast response!