Hi all. I'm kinda new to this forum. Just got my 96 St Coupe a couple of weeks ago. Traded my 99 Solara for it....and $3000 >>

Anyway, I am orderin up parts and I wondered if anybody with OBD2 has installed a high-flow cat. If so, does it affect the rear O2 sensor and set the cel? I ordered a corolla high-flow and according to the toyota part numbers, the st and corolla 7afe share the same cat so hopefully it will be a direct bolt on. Let me know if anybody has any info. Thanks.

-96stcoupe+Nov 16, 2003 - 8:36 PM

Nope, it shouldn't mess with the O2 reading at all.

Thanks guys. It should be here this week and if it is a direct fit I will slap it in and see what happens.

You'll probably have to modify the header bracket where the cat fits on.
I had to enlarge the holes for it to fit properly.
Fits up nicely to the Greddy SP though.

(I have the OBX high-flow cat. for the corolla).

BTW: I have no problem with 02 sensor reading.

Got the cat yesterday and installed it. 4 bolts. Pretty easy, except getting the old rusty ones out laying on my back in the garage. It seems to breathe a bit better but I really need to get a more high flow muffler. Does it make a difference if I just get a muffler or is it better to get a complete cat back?

Cat-back. The increase in piping size will increase flow better.

Yup, just don't increase the size too much. 2.25" is perfect for most n/a celicas. 2.5" is better for highly modified n/a cars. If you make the tubing too large for the other mods then you'll lose a lot of scavenging and as a result low end torque (and you won't make any more top end power).

Floored it today and the check engine light came on. Threw a code for catalyst inefficiency or some damn thing. It must not be converting very well. Does anybody know where to get an o2 simulator for our cars? I can't find one anywhere.