Help Me Understand My AFR Readings?

I just installed a URD Y-pipe and a wideband O2 sensor for AFR readings. I have a PLX OBDII scanner and a PLX SM-AFR add-on. The wideband O2 sensor is located downstream of the front right cat and reads the right bank only.

My performance mods are;
TRD S/C
TRD Intake
URD 2.8" S/C pulley
URD Y-pipe (no rear cats)
MBRP turndown exhaust
Stock headers and forward cats

The AFR reads 14.6 most of the time. At WOT in 2nd and 3rd it will peak at 10.9 for a moment, thought it will generally stay in the 11-12 range. The AFR stays at 14.6 unless I exceed about 90% engine load.

It looks like 20 is the lowest AFR that the device can display and it will show this when engine braking. I'm guessing that fuel is cut on decel when the transmission is in gear?

So I have these numbers but don't really know if its good or too lean or what. What do you think?

-Thanks!

 

Sounds like she running just about right.....!!

 

14.6 is the ratio your ECU is constantly striving for in closed loop. It'll bounce around slightly, but not too far out of line. As you said, 20 during engine braking is just showing fuel cutoff. So once you go WOT, the ECU switches from closed loop to open loop right around 4k rpm (not exactly sure of the exact rpm). At open loop, the ECU isn't trying to maintain that stoic 14.6 afr anymore, but it's running off of its predetermined settings. The more air you're moving through that engine, the leaner you'll see that WOT number go. The trd reflash tends to run richer than 10 completely stock, which is not good. You want that number to be around 10.5-12, depending on who you ask. The leaner you're running at WOT, the hotter it gets in the combustion chamber and that's how things break, but you tend to make more power. Contrary, the richer run, the less power youll have and there's also a chance that fuel can wash the cylinder walls causing premature wear between piston rings and cylinder wall.

In short, you're safe where it is, and you even have some room for more power.

 

Ur fine.

I used to pin at 10:1 or lower before the pulley swap.

Now I'm in 11's wot.

Lean is mean but can break shit.

Is this with fpr mod done or not?

 

Thanks for all the replies! Glad to hear that its looking good!

Justus, I haven't done the fpr mod but I did replace the OEM pump with a 340lph.

 

good move!

I just wanted a baseline of the fuel mods, thats all.

 

This article has a section of the AFR topic. Very easy to understand.

http://www.motoiq.com/MagazineArtic...t-3-Compression-Ratio-and-Air-Fuel-Ratio.aspx