I just installed a Tomei A/F meter yesterday. It gets its signal from its own 02 sensor that I installed on the y-pipe. My OEM 02's were not touched in any way.

When I'm cruising at a steady speed, A/F reading is stoich (around 14.2:1) - no problems there. However, when I go WOT in first and second gear, the reading is only around 12:1 @ 6500rpm. This seems to be too rich. I wish it was leaner to get more power.

I have a N/A 97 with bolt ons and no fuel system mods and over 75000 miles. I have gotten the MIL for rear 02 sensor NUMEROUS times. However, I just ignore it everytime, reset it, & it hasn't come on for a while. Anyway, could a worn 02 sensor cause the ECU to adjust fuel in any way, thereby making the car run rich? Also, is it possible for the OEM fuel pressure regulator to not work as well, also causing the car to run rich? I dunno...

I also installed a fuel pressure gauge but haven't wired everything yet. I want to see how much fuel I'm getting at WOT.

 

Yes the ECU adjust the fuel curve during closed loop operation. However, once it goes into open loop it just uses the fuel curves that were preprogrammed in. If you want to lean out the fuel curve you have 3 alternatives: JWT ECU, G-Force ECU, and Apexi S-AFC. While going leaner might get you a couple horses, bumping the base ignition timing will have far more torque gains. The only way to get that is with an ECU upgrade.

 

Thanks. Well everything seems fine when I'm cruising (closed loop). I'm wondering what's the normal A/F ratio for our N/A cars at WOT (open loop). Better rich than lean, I guess...

 

it's normal for the car to go full rich at WOT (open loop)...mine does it too...pretty much all production cars go rich on WOT...

 

He could adjust the fuel via an adjustable fuel pressure regulator too. Much cheaper than those you mentioned.