o1geeser

i have heard people use spark plug defoulers but i dont really know what that is?

whiteDCfiver

People use a defouler on the secondary o2 sim to fool it into thinking there is a catalitic converter. The defouler is a part you can buy at autozone for like 4 bucks. You have to bore it out to a 1/2 inch. Its better to use 2 of em. The o2 sim then goes inside the defouler creating more distance btw the sim and exhaust pipe. This distance somehow fools it.

Heres a pic

BarracksSi

I've understood that the O2 sensor is looking for a certain amount of exhaust flow. In a test pipe, the flow is obviously faster than in a catalytic convertor, so the sensor spots the difference and generates an error. Put a couple defoulers in the way, and the sensor sees less flow -- approximately the same as if there were a cat. It doesn't notice anything wrong, so it won't generate an error.

At least, that's what I've been told.

Redline96LX

whats the purpose of it? just to run no cat?

NJslvrtypes

It goes on your race header or test pipe so you don't throw a CEL for not having a catalytic converter. The sensor is not in the direct flow of the exhaust gases so it usually fools the ecu into thinking the cat is doing its job.

o1geeser

thanks for the input! what do i need to bore out?

NJslvrtypes

1/2" Drill Bit

Heres a DIY

http://forums.clubrsx.com/showthread.php?t=296791