OK this first scenario is for an exhaust system...

Say i'm at 11.0:1 right now and i upgrade my stock cat plus piping to full 2.25 inch straight to the back, how much would i lean out by and what would you estimate my new a/f ratio to be?

 

every setup is different, predicting that ---- is like trying to predict how long your next turd is gonna be.

 

lol

 

Lmao, I can predict if its going to be a juicy ---- or not.

 

if you're at 11afr and this isn't hypothetical
then you don't need to worry because thats pretty darned rich..

 

you make it sound like i'm telling you to give me my new exact a/f ratio.

 

11.5312196876321 1/2 :1

 

Correct me if im wrong. usualy the disired AFR is usally anywhere from 14.0 to 14.63.

 

yes you're wrong.

rough'ed up version:

at an idle anywhere in the 14-15:1 range is fine.
cruising at part throttle down the road in your mid to low rpm range, that 14 range is fine.
at wide open throttle, naturally aspirated, you want to be as rich as 13:1 or so on the top end.
turbocharged you're gonna want that WOT number to be more like 11-12:1 range.

 

/\ wot he said. the ecu desires an a/f ratio of 14.7 in idle/partial throttle, when you aren't getting on the gas the closed loop setup likes to lean it out this much in an effort to extend gas mileage. run 15:1 on WOT and you won't be seeing much other than 4 piston cannons and a road covered in oil.