This is a site I found on tricking your O2 sensor. It is from a Mustang site but they use the same type on O2 sensor that we use.

http://www.eaton-design.com/mustang/mil/

What he's built is essentially a "first-order low pass filter". I lets low frequencies through while attenuating higher frequencies. The ECU checks to make sure that the cat is working by checking the downstream O2 against the upstream O2. For MT cars, the downstream O2 must have a frequency that is less than 70% of the upstream O2 frequency. For AT cars, the number is 90%. It looks like the eliminator only lets the low frequencies from the downstream O2 pass. The ECU will see that the downstream O2 has a much lower frequency than the upstream and won't trigger a CEL. I was actually planning on building and selling a very similar device. I spent several days this week researching it. Looks like I got beat to the punch. I hope some of you test this out and make sure it works for us.


Corbin

'95 ESI-T
HRC+FMIC+ETC...

I have been running this setup for about two weeks now. It is working great. I just hope it will hold up.

Hey JCurcillo, do I know you? Your name sounds familiar? j/k What's up man?

Hey Kon, don't I know you? ;-)



Eric Madden

ahh, another reason im glad im OBD1, no downstream o2 sensor :)

your kidding? I thought they've been running downstream O2 sensors for alot longer then OBDII has been out... that kinda supprises me.

i have 1 o2 sensor on my car, in the downpipe. even with a test pipe in, i get no CEL. heck, even with no exhaust at all i get no CEL

Odd.

I'm OBD1 and i have 2.

Must be an ASOG thing..

lol, i promise i only have 1 o2 sensor. i installed the turbo and the exhaust myself.

heres the stock exhaust: no o2 sensor:


heres the thermal r&d exhaust, i got it off a 96 car, and had to fill the o2 sensor bung with a spare o2 sensor, but u can see its not hooked up :)

Well.. It looks like you have a second O2, but its not hooked to anything.

What's up Kon. I'll see you at the party tonight.

Later

Well, I just picked up this little unit. Seems to work well, is well made, and does the job. It is more then just a filter, it will actually tell the ECU what it wants to hear.
-=B-=

http://64.119.163.247/catalog/product_info.php/products_id/286

Oh yeah, it was fairly cheap too...

hehe, guess you didnt read anything i typed... lol

once again: stock exhaust is top pic, no o2 sensor. 2nd pic is the thermal R&D exhaust, i got off a 96 car, and had to fill the o2 sensor bung with something, so i just screwed in a spare o2 sensor. my car only has 1 o2 sensor, in the downpipe

that's mean punching a cat :P
That's cruelty to animals