lol...So just a heads up on this.... another head scratcher trap that I fell into... Definitely the case that the more you modify the more you risk getting burned by "hidden" interactions between various tables and constants...

Going over my data I was noticing that my commanded AFR being reported by the ECM was consistently 1/4 point off from what I programmed into the calibration...

I had that issue before and we fixed it

https://www.thirdgen.org/forums/diy-...drives-pe.html

So I was scratching my head on why the issue was popping up again...

Ended up back in Traxxion's thread on commanded AFR

https://www.thirdgen.org/forums/diy-...t-afr-how.html

When the number 14.7 jumped out at me...

I had forgotten that I moved the factory 14.7 stoich value a while ago to 14.5 after reading some of the blended gas threads. In retrospect that probably wasn't necessary since I'm tuning via WB now anyway...

BUT, the stock equations for calculating the %change to AFR in PE and OL are based on 14.7... doh! When I put in my stoich value of 14.5, I get my 1/4 point back.

i.e., 14.5/14.7 = .98

You calculate a desired commanded AFR of 12.50 based on 14.7 stoich via the equations. But the ECM will end up at 12.50 x .98 = 12.25 for a stoich value of 14.5. Thus the 1/4 point richer commanded AFR being reported by Tunerpro.

Any rate, not sure how many people are calculating commanded AFR's and have modified the stoich value. But just a heads up if you modify the stoich value, your commanded AFR's will be off.

 

Oops... meant to post this in DIY PROM. Mods could you please move it?

 

AND.....On blended fuel you should be richer everywhere. At WOT from 2,000-4,000 I typically target about 12:1 and lean a little to 12.6 by redline. Seems to work best on the 10% ethanol pump fuel we have. 13:1 is usually too lean for me on E10. The difference is usually 2-4° of timing more which has way more effect on power than being slightly leaner. With the stock cast iron 350 TPI heads I generally find 32-34° full in by 4,000 rpm to make the best power. The 10:1 355 Hotcam setup with Dart 180s I am currently tuning on likes 32° on 93 octane.