How lean can you safely take a FI setup in the upper rpm's? I've seen some dyno sheets that show mid 11's at lower rpm, 11.5-11.8 at the "meat", then climb into the low-mid 12's at the last 1000 rpm before redline.

 

You want to be the richest at peak torque. I have never liked the idea of leaning out AFRs above peak torque to redline. It may give you 5 more hp, but ill prefer a cooler engine. But what do I know, I melt pistons

 

They can afford to lean out a little bit in the upper RPMs because the cam is less efficient at drawing air into the cylinders. Dropping cylinder airmass=less boost in the cylinders=you can afford to run a bit leaner for a little more power. Depends on the cam.

 

I am wondering this too. I am now running about 11.4-11.5, and thought I was on the lean side.

 

Safe tune for me, mine goes 11.2 at first wot up to around 4,500 then leans up to 11.8 ish. My truck pulls way harder up top....... could just be that large oil cooler I have up front behind my bumper

 

Good info, mine shows 11.5ish and I was wondering the same.

 

i had my 1998 f-150, procharger 12lbs tuned a couple times and got the a/f that goes in to the o2 to give real time readings and the meter only goes down to 10.14 lol when i mash it it goes right down to it and probably past and stays there the whole time i am at WOT.

 

I'm running around 11.5 at 6000rpm.

 

I've been running mine between 11.7-11.8 all the way to 6400 rpm, and it's working. But I see dyno sheets showing AFR climbing into the low 12's, from say, 5400-ish up to redline.

If leaner AFR is better at these higher rpm, then I might change things up on my tune. I was looking for some input from the experts here first.

 

It also depends on what your setup likes, every one is different. You might not gain anything leaning it out a little bit, while the next guy might see a huge difference. No harm in trying things out, long as you keep a close eye on the scanner