I put my wideband in this weekend and have been watching my AF. I have hit a max of 10.6 under WOT which is fine (no tune). But I am more curious about my ratios that are not under WOT. I range from 14.6 to 15.6 when cruising, usually it bounces back in forth between the two. I know 14.7 is closed loop, but is 15.6 too high when not under boost? Also what AF should I be looking for when under partial throttle and boost? Like say 50% throttle?

I also noticed when the car stutters (has done this since the car was stock) at low rpms, the AF meter goes off the chart on the lean side. I have the latest oem flash, I am looking to get tuned after I get my cat back.

 

Your fine.

 

Those are perfectly normal a/f ratios for an untuned evo x. Get that cat back and a tune!

 

Cool thanks for the replies. What kind of AF should you see under partial throttle and boost? Never learned too much on the technical side, trying to learn more. Thanks!

 

lean burn is where the greatest economy is realized. just so long as the car is not under much load, that's where it may go to in some modes of operation. Newer combustion chamber designs work even better with lean mixtures. I hear direct injection makes lean running even more safely possible.

 

Partial throttle you should be around the same, maybe alittle richer. It shouldn't get any leaner then idle while at part throttle.

 

It should be around ~11.5-12 during spool up from what Ive read. That's about what I'm seeing now with my wideband. ~13-15 during cruising is normal. I'm at about 11.5 starting at 2500 then it tapers off to about 11 flat at redline. Sometimes it dips a little lower though like 10.6-10.8 at certain rpms...I need to tweak it a little to fix that but overall its pretty solid now.

 

This caught my attention. Do a boost leak test. When my VIII was doing this, I had a leak on the throttle body that was causing the car to sometimes go lean under vacuum.