A few weeks back someone asked what the air fuel readings were before and after a supercharger pulley installation. I finally got a chance to hook up my wideband and take my stock 2002 SC Xterra out for a spin. The results were very surprising!
The engine idled at a perfect 14.5:1
Cruising on the highway is stayed right around 14.2:1
At WOT, it looked like this:
2000 - 2500 RPM --> 12.0:1 to 12.2:1
2500 - 3000 RPM --> 11.0:1 to 11.3:1
3000 - 5300 RPM --> 10.0:1

My wideband meter bottoms out at 10.0:1 so there is a good possibility the engine is running a good bit richer than 10:1. This would explain the black soot that keeps accumulating on my exhaust tip and the lack of power from a SC V6. I know Nissan wants to keep the engine safe, but richer than 10:1 is rediculous. I bet with a freer flowing exhaust and some good tuning there's and extra 50 HP to be made.
I still need to install my SC pulley and go back out for another run. My only mod to date is a K&N drop in. (if you even want to call that a mod)

Thanks for the great info! Please do post the results of the post upgrade logging.

One other question. Is it the 2.3 pulley you are installing?

Thanks,
Sean

I believe it's the ASP 2.3 inch pulley. I will definitely post the new numbers when I get the pulley installed. I was even thinking of using some sort of piggy back fuel computer to lean the WOT readings to around 11:1 all the way to readline.