Hey everyone, new here and love this site. A quick question on the O2 sensors. The one before the cats measure what? and the ones after the cats measure what? I've had both cats on the exhaust go bad. And I'm seeing some turbos at the track with straight pipes (no cats) and bungs with the O2 sensors attached. Are they deleting the CEL's or resetting them or new programs on the ECU?

 

The front O2's measure exhaust gas temp, therefore gas content.
The post cat O2's measure the exhaust temp, therefore gas content.
The pre cat O2 has to do with mixture adjustment. The post cat O2 monitors the increase in temp over the pre cat O2 to determine catalytic efficiency. Hope this makes sense.
Jay.

 

So basically measures the difference and adjust fuel/air to optimum. thanx again for the info.

 

I run streight pipes.... with 100 cel cats.... the cats will go bad eventually ....
but who cares.... as long as they r not clogged up.... its fine.... save ur money and spend it elswhere on mods...

 

I just put my straight pipes on this weekend "tooling around" I got stopped by the polizei and they told me to put my mufflers back on, but they did appriciate the car. But driving around on straight pipes is just too damn loud. I must be getting old.